support autofocus / autogain in libv4l2

  Hi!

For focus to be useful, we need autofocus implmented
somewhere. Unfortunately, v4l framework does not seem to provide good
place where to put autofocus. I believe, long-term, we'll need some
kind of "video server" providing this kind of services.

Anyway, we probably don't want autofocus in kernel (even through some
cameras do it in hardware), and we probably don't want autofocus in
each and every user application.

So what remains is libv4l2. Now, this is in no way clean or complete,
and functionality provided by sdl.c and asciicam.c probably _should_
be in application, but... I'd like to get the code out there.

Oh and yes, I've canibalized decode_tm6000.c application instead of
introducing my own. Autotools scare me, sorry.

Regards,
							Pavel
  

Hi Pavel,

Em Mon, 24 Apr 2017 11:30:59 +0200
Pavel Machek <pavel@ucw.cz> escreveu:

> Hi!
> 
> For focus to be useful, we need autofocus implmented
> somewhere. Unfortunately, v4l framework does not seem to provide good
> place where to put autofocus. I believe, long-term, we'll need some
> kind of "video server" providing this kind of services.
> 
> Anyway, we probably don't want autofocus in kernel (even through some
> cameras do it in hardware), and we probably don't want autofocus in
> each and every user application.
> 
> So what remains is libv4l2. 

IMO, the best place for autofocus is at libv4l2. Putting it on a
separate "video server" application looks really weird for me.

Btw, libv4l2 already has some autotools for auto gain and auto
white balance. See the implementation under:
	lib/libv4lconvert/processing

The libv4l internal controls can be seen at:
	lib/libv4lconvert/control/libv4lcontrol.h

The ones implemented by the processing part of the library are:

$ git grep v4lcontrol_get_ctrl lib/libv4lconvert/processing/
lib/libv4lconvert/processing/autogain.c:        autogain = v4lcontrol_get_ctrl(data->control, V4LCONTROL_AUTOGAIN);
lib/libv4lconvert/processing/autogain.c:        target = v4lcontrol_get_ctrl(data->control, V4LCONTROL_AUTOGAIN_TARGET);
lib/libv4lconvert/processing/gamma.c:   int gamma = v4lcontrol_get_ctrl(data->control, V4LCONTROL_GAMMA);
lib/libv4lconvert/processing/gamma.c:   gamma = v4lcontrol_get_ctrl(data->control, V4LCONTROL_GAMMA);
lib/libv4lconvert/processing/whitebalance.c:    wb = v4lcontrol_get_ctrl(data->control, V4LCONTROL_WHITEBALANCE);

I guess it shouldn't be hard to add an extra processing module
there for auto-focus.

> Now, this is in no way clean or complete,
> and functionality provided by sdl.c and asciicam.c probably _should_
> be in application, but... I'd like to get the code out there.
> 
> Oh and yes, I've canibalized decode_tm6000.c application instead of
> introducing my own. Autotools scare me, sorry.

Why replace decode_tm6000.c by something else? If you want to add another
test application, just place it on a new file.

I added a few notes together with the code, pointing the main things
I think it require changes, in order for me to do a better review
at the code. I didn't test nor tried to check the algorithms inside,
as the code, on its current state, requires rework and code cleanup.

> 
> Regards,
> 							Pavel
> 
> diff --git a/lib/libv4l2/asciicam.c b/lib/libv4l2/asciicam.c
> new file mode 100644
> index 0000000..5388967
> --- /dev/null
> +++ b/lib/libv4l2/asciicam.c
> @@ -0,0 +1,63 @@
> +/* gcc asciicam.c /usr/lib/i386-linux-gnu/libv4l2.so.0.0.0 -o asciicam
> +   gcc asciicam.c /usr/lib/arm-linux-gnueabi/libv4l2.so.0 -o asciicam
> +
> +gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../.. -fvisibility=hidden -I../../lib/include -Wall -Wpointer-arith -D_GNU_SOURCE -I../../include -g -O2 asciicam.c libv4l2.c /usr/lib/arm-linux-gnueabi/libv4lconvert.so.0 log.c v4l2convert.c v4l2-plugin.c -o asciicam
> + */
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +
> +#include <linux/videodev2.h>
> +
> +#define SIZE 10*1024*1024
> +
> +char buf[SIZE];
> +
> +void main(void)

Please don't add a new application under lib/. It is fine if you want
some testing application, if the ones there aren't enough, but please
place it under contrib/test/.

You should likely take a look at v4l2grab first, as it could have
almost everything you would need.

> +{
> +  int fd = v4l2_open("/dev/video2", O_RDWR);

Hardcoding /dev/video2 doesn't seem a good idea.

> +  int i;
> +  static struct v4l2_format fmt;
> +
> +#if 1
> +  fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> +  fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
> +  fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
> +  fmt.fmt.pix.width = 640;
> +  fmt.fmt.pix.height = 480;
> +  if (fmt.fmt.pix.pixelformat != 'RGB3') /* v4l2_fourcc('R', 'G', 'B', '3'); */
> +    printf("hmm. strange format?\n");
> +  
> +  printf("ioctl = %d\n", v4l2_ioctl(fd, VIDIOC_S_FMT, &fmt));
> +#endif
> +
> +  for (i=0; i<500; i++) {
> +    int num = v4l2_read(fd, buf, SIZE);
> +    int y,x;
> +    
> +    printf("%d\n", num);
> +#if 0
> +    for (y = 0; y < 25; y++) {
> +      for (x = 0; x < 80; x++) {
> +	int y1 = y * 480/25;
> +	int x1 = x * 640/80;
> +	int c = buf[fmt.fmt.pix.width*3*y1 + 3*x1] +
> +	  buf[fmt.fmt.pix.width*3*y1 + 3*x1 + 1] +
> +	  buf[fmt.fmt.pix.width*3*y1 + 3*x1 + 2];
> +
> +	if (c < 30) c = ' ';
> +	else if (c < 60) c = '.';
> +	else if (c < 120) c = '_';
> +	else if (c < 180) c = 'o';
> +	else if (c < 300) c = 'x';
> +	else if (c < 400) c = 'X';
> +	else c = '#';
> +	  
> +	printf("%c", c);
> +      }
> +      printf("\n");
> +    }

IMHO, it would be better to use aalib. Btw, xawtv3 has a code example
using it, under:
	console/ttv.c

As it already uses libv4l, prhaps you could use it, instead of adding
a new ascii app.

> +#endif    
> +  }
> +}
> diff --git a/lib/libv4l2/libv4l2-priv.h b/lib/libv4l2/libv4l2-priv.h
> index 343db5e..af740a7 100644
> --- a/lib/libv4l2/libv4l2-priv.h
> +++ b/lib/libv4l2/libv4l2-priv.h
> @@ -1,3 +1,4 @@
> +/* -*- c-file-style: "linux" -*- */
>  /*
>  #             (C) 2008 Hans de Goede <hdegoede@redhat.com>
>  
> @@ -70,6 +71,14 @@
>  	} while (0)
>  
>  #define MIN(a, b) (((a) < (b)) ? (a) : (b))
> +#define V4L2_MAX_SUBDEVS 16
> +
> +#define V4L2_MAX_FOCUS 10
> +struct v4l2_focus_step {
> +	int num;
> +	int sharpness[V4L2_MAX_FOCUS];
> +	int position[V4L2_MAX_FOCUS];
> +};
>  
>  struct v4l2_dev_info {
>  	int fd;
> @@ -104,6 +113,14 @@ struct v4l2_dev_info {
>  	void *plugin_library;
>  	void *dev_ops_priv;
>  	const struct libv4l_dev_ops *dev_ops;
> +        int subdev_fds[V4L2_MAX_SUBDEVS];
> +  	int exposure; 
> +  	int frame;
> +  	int focus;
> +
> +	/* Autofocus parameters */
> +	int focus_frame, focus_exposure, focus_step, sh_prev;
> +	struct v4l2_focus_step focus_step_params;
>  };
>  
>  /* From v4l2-plugin.c */
> diff --git a/lib/libv4l2/libv4l2.c b/lib/libv4l2/libv4l2.c
> index 0ba0a88..3b84437 100644
> --- a/lib/libv4l2/libv4l2.c
> +++ b/lib/libv4l2/libv4l2.c
> @@ -1,3 +1,4 @@
> +/* -*- c-file-style: "linux" -*- */

Don't add editor-specific macros inside the code. Not everybody uses emacs.

>  /*
>  #             (C) 2008 Hans de Goede <hdegoede@redhat.com>
>  
> @@ -100,6 +101,13 @@ static struct v4l2_dev_info devices[V4L2_MAX_DEVICES] = {
>  };
>  static int devices_used;
>  
> +#include "sdl.c"
> +
> +static struct sdl sdl;
> +
> +int v4l2_get_index(int fd);
> +void my_main(void);
> +

The above looks really odd. Why do you want to make libv4l2 dependent
on sdl?

>  static int v4l2_ensure_convert_mmap_buf(int index)
>  {
>  	if (devices[index].convert_mmap_buf != MAP_FAILED) {
> @@ -311,7 +319,409 @@ static int v4l2_queue_read_buffer(int index, int buffer_index)
>  	return 0;
>  }
>  
> -static int v4l2_dequeue_and_convert(int index, struct v4l2_buffer *buf,
> +static void v4l2_paint(char *buf, int x1, int y1, const struct v4l2_format *fmt)
> +{
> +  int y, x;
> +  int width = fmt->fmt.pix.width;
> +  printf("width = %d\n", width);
> +    
> +    for (y = 0; y < 25; y++) {
> +      for (x = 0; x < 80; x++) {
> +	int c = buf[width*4*y1 + 4*x1] +
> +	  buf[width*4*y1 + 4*x1 + 1] +
> +	  buf[width*4*y1 + 4*x1 + 2];
> +
> +	if (c < 30) c = ' ';
> +	else if (c < 60) c = '.';
> +	else if (c < 120) c = '_';
> +	else if (c < 180) c = 'o';
> +	else if (c < 300) c = 'x';
> +	else if (c < 400) c = 'X';
> +	else c = '#';
> +	  
> +	printf("%c", c);
> +      }
> +      printf("\n");
> +    }
> +}

Please don't add anything like that inside the library.

> +
> +#define SX 80
> +#define SY 25
> +#define BUCKETS 20
> +
> +static void v4l2_histogram(unsigned char *buf, int cdf[], struct v4l2_format *fmt)
> +{
> +    for (int y = 0; y < fmt->fmt.pix.height; y+=19)
> +      for (int x = 0; x < fmt->fmt.pix.width; x+=19) {
> +	pixel p = buf_pixel(fmt, buf, x, y);
> +	
> +	int b;
> +	/* HACK: we divide green by 2 to have nice picture, undo it here. */
> +	b = p.r + 2*p.g + p.b;
> +	b = (b * BUCKETS)/(256);
> +	cdf[b]++;
> +      }
> +}
> +
> +static long v4l2_sharpness(unsigned char *buf, struct v4l2_format *fmt)
> +{
> +  int h = fmt->fmt.pix.height;
> +  int w = fmt->fmt.pix.width;
> +  long r = 0;
> +
> +    for (int y = h/3; y < h-h/3; y+=h/9)
> +      for (int x = w/3; x < w-w/3; x++) {
> +	pixel p1 = buf_pixel(fmt, buf, x, y);
> +	pixel p2 = buf_pixel(fmt, buf, x+2, y);
> +	
> +	int b1, b2;
> +	/* HACK: we divide green by 2 to have nice picture, undo it here. */
> +	b1 = p1.r + 2*p1.g + p1.b;
> +	b2 = p2.r + 2*p2.g + p2.b;
> +
> +	int v;
> +	v = (b1-b2)*(b1-b2);
> +	if (v > 36)
> +		r+=v;
> +      }
> +
> +    return r;
> +}

IMO, the above belongs to a separate processing module under
	lib/libv4lconvert/processing/

> +
> +int v4l2_set_exposure(int fd, int exposure)
> +{
> +	int index = v4l2_get_index(fd);
> +
> +	if (index == -1 || devices[index].convert == NULL) {
> +		V4L2_LOG_ERR("v4l2_set_exposure called with invalid fd: %d\n", fd);
> +		errno = EBADF;
> +		return -1;
> +	}
> +
> +	struct v4l2_control ctrl;
> +	ctrl.id = V4L2_CID_EXPOSURE;
> +	ctrl.value = exposure;
> +	if (ioctl(devices[index].subdev_fds[0], VIDIOC_S_CTRL, &ctrl) < 0) {
> +	  printf("Could not set exposure\n");
> +	}
> +	return 0;
> +}

Shouldn't it be together with lib/libv4lconvert/processing/autogain.c,
perhaps as an alternative implementation, if what's there is not enough?

> +
> +int v4l2_set_gain(int fd, int gain)
> +{
> +	int index = v4l2_get_index(fd);
> +
> +	if (index == -1 || devices[index].convert == NULL) {
> +		V4L2_LOG_ERR("v4l2_set_exposure called with invalid fd: %d\n", fd);
> +		errno = EBADF;
> +		return -1;
> +	}
> +	
> +	struct v4l2_control ctrl;
> +	ctrl.id = 0x00980913;

Don't hardcode control numbers here.

> +	ctrl.value = gain;
> +	if (ioctl(devices[index].subdev_fds[0], VIDIOC_S_CTRL, &ctrl) < 0) {
> +	  printf("Could not set exposure\n");
> +	}
> +	return 0;
> +}
> +
> +int v4l2_set_focus(int fd, int diopt)
> +{
> +	int index = v4l2_get_index(fd);
> +
> +	if (index == -1 || devices[index].convert == NULL) {
> +		V4L2_LOG_ERR("v4l2_set_focus called with invalid fd: %d\n", fd);
> +		errno = EBADF;
> +		return -1;
> +	}
> +
> +	struct v4l2_control ctrl;
> +	ctrl.id = V4L2_CID_FOCUS_ABSOLUTE;
> +	ctrl.value = diopt;
> +	if (ioctl(devices[index].subdev_fds[1], VIDIOC_S_CTRL, &ctrl) < 0) {
> +		printf("Could not set focus\n");
> +	}
> +	return 0;
> +}
> +
> +#define LESS 1
> +#define MID 0
> +#define MORE 2
> +
> +static void v4l2_start_focus_step(struct v4l2_focus_step *fs, int focus, int step)
> +{
> +	int i;
> +
> +	fs->num = 3;
> +	for (i=0; i<V4L2_MAX_FOCUS; i++) {
> +		fs->sharpness[i] = -1;
> +		fs->position[i] = -1;
> +	}
> +
> +	fs->position[LESS] = focus - step;
> +	fs->position[MID] = focus;
> +	fs->position[MORE] = focus + step;
> +}
> +
> +static int v4l2_focus_get_best(struct v4l2_focus_step *fs)
> +{
> +	int i, max = -1, maxi = -1;
> +	
> +	for (i=0; i<fs->num; i++)
> +		if (max < fs->sharpness[i]) {
> +			max = fs->sharpness[i];
> +			maxi = i;
> +		}
> +
> +	return maxi;
> +}
> +
> +static void v4l2_auto_focus_continuous(struct v4l2_dev_info *m, int sh)
> +{
> +	int f = m->frame - m->focus_frame;
> +	int step;
> +	const int max_step = 300, min_step = 20;
> +	struct v4l2_focus_step *fs = &m->focus_step_params;
> +
> +	if (m->focus_step == 0 || m->focus_step > max_step) {
> +		printf("step reset -- max\n");
> +		m->focus_step = max_step;
> +	}
> +	if (m->focus_step < min_step) {
> +		printf("step reset -- 10 (%d)\n", m->focus_step);
> +		m->focus_step = min_step;
> +		/* It takes cca 5.7 seconds to achieve the focus:
> +		   0.76user 0.30system 5.66 (0m5.661s) elapsed 18.72%CPU
> +		 */

The above note seems hardware dependent. 

> +		printf("Focused at %d\n", m->focus);
> +		exit(0);
> +	}
> +
> +	step = m->focus_step;
> +
> +	if (m->exposure != m->focus_exposure) {
> +		m->focus_frame = m->frame;
> +		m->focus_exposure = m->exposure;
> +		v4l2_start_focus_step(fs, m->focus, m->focus_step);
> +		return;
> +	}
> +	if (m->focus < step) {
> +		m->focus = step;
> +	}
> +
> +	const int every = 3;
> +	if (f%every)
> +		return;
> +
> +	{
> +		int i = f/every;
> +
> +		if (i == 0) {
> +			printf("Can not happen?\n");
> +			return;
> +		}
> +		i--;
> +		if (i < fs->num)
> +			v4l2_set_focus(m->fd, fs->position[i]);
> +		if (i > 0)
> +			fs->sharpness[i-1] = sh;
> +		if (i < fs->num)
> +			return;
> +	}
> +	int i;
> +	for (i=0; i<fs->num; i++) {
> +		printf("%d: %d | ", fs->position[i], fs->sharpness[i]);
> +	}

You should probably print something only if log is enabled. Take a look
at lib/libv4l2/log.c. Same applies to similar printf() calls.

> +	int best = v4l2_focus_get_best(fs);
> +	if ((fs->sharpness[best] < m->sh_prev) && (m->focus_step < max_step)) {
> +		m->focus_step *=2;
> +		m->sh_prev = m->sh_prev * 0.9;
> +		printf("step up %d\n", m->focus_step);
> +	} else if (best == LESS) {
> +		printf("less ");
> +		m->focus -= step;
> +	} else if (best == MORE) {
> +		printf("more ");
> +		m->focus += step;
> +	} else {
> +		m->sh_prev = fs->sharpness[MID];
> +		m->focus_step = m->focus_step / 2;
> +		printf("step %d ", m->focus_step);
> +	}
> +	m->focus_frame = m->frame;
> +	v4l2_start_focus_step(fs, m->focus, m->focus_step);
> +	printf("Focus now %d\n", m->focus);
> +}
> +
> +static void v4l2_start_focus_sweep(struct v4l2_focus_step *fs, int focus, int step)
> +{
> +	int i;
> +
> +	fs->num = V4L2_MAX_FOCUS;
> +	for (i=0; i<V4L2_MAX_FOCUS; i++) {
> +		fs->sharpness[i] = -1;
> +		fs->position[i] = -1;
> +	}
> +
> +	int f = focus;
> +	for (i=0; i<V4L2_MAX_FOCUS; i++) {
> +		fs->position[i] = f;
> +		f += step;
> +	}
> +}
> +
> +static void v4l2_auto_focus_single(struct v4l2_dev_info *m, int sh)
> +{
> +	int f = m->frame - m->focus_frame;
> +	int step;
> +	struct v4l2_focus_step *fs = &m->focus_step_params;
> +
> +	if (m->focus_step == 0) {
> +		printf("step reset -- max\n");
> +		m->focus_step = 1;
> +	}
> +
> +	if (m->exposure != m->focus_exposure) {
> +		m->focus_frame = m->frame;
> +		m->focus_exposure = m->exposure;
> +		v4l2_start_focus_sweep(fs, 0, 100);
> +		return;
> +	}
> +
> +	const int every = 3;
> +	if (f%every)
> +		return;
> +
> +	{
> +		int i = f/every;
> +
> +		if (i == 0) {
> +			printf("Can not happen?\n");
> +			return;
> +		}
> +		i--;
> +		if (i < fs->num)
> +			v4l2_set_focus(m->fd, fs->position[i]);
> +		if (i > 0)
> +			fs->sharpness[i-1] = sh;
> +		if (i < fs->num)
> +			return;
> +	}
> +#if 0
> +	int i;
> +	for (i=0; i<fs->num; i++) {
> +		printf("%d: %d | ", fs->position[i], fs->sharpness[i]);
> +	}
> +#endif
> +	int best = v4l2_focus_get_best(fs);
> +	m->focus_frame = m->frame;
> +	switch (m->focus_step) {
> +	case 1:
> +		printf("Best now %d / %d\n", fs->position[best], fs->sharpness[best]);
> +		v4l2_start_focus_sweep(fs, fs->position[best] - 50, 10);
> +		m->focus_step = 2;
> +		break;
> +	case 2:
> +		printf("Best now %d / %d\n", fs->position[best], fs->sharpness[best]);
> +		v4l2_start_focus_sweep(fs, fs->position[best] - 10, 2);
> +		m->focus_step = 3;
> +		break;
> +	case 3:
> +		printf("Best now %d / %d\n", fs->position[best], fs->sharpness[best]);
> +		printf("done.\n");
> +		exit(0);
> +	}
> +}
> +
> +
> +static void v4l2_auto_exposure(int index, struct v4l2_buffer *buf)
> +{
> +	struct v4l2_format *fmt;
> +	int cdf[BUCKETS] = { 0, };
> +	int i;
> +
> +	fmt = &devices[index].src_fmt;
> +
> +	v4l2_histogram(devices[index].frame_pointers[buf->index], cdf, fmt);
> +
> +#if 0
> +	printf("hist: ");
> +	for (i = 0; i<BUCKETS; i++)
> +		printf("%d ", cdf[i]);
> +	printf("\n");
> +#endif
> +	for (i=1; i<BUCKETS; i++)
> +		cdf[i] += cdf[i-1];
> +
> +	int b = BUCKETS;
> +	int brightPixels = cdf[b-1] - cdf[b-8];
> +	int targetBrightPixels = cdf[b-1]/50;
> +	int maxSaturatedPixels = cdf[b-1]/200;
> +	int saturatedPixels = cdf[b-1] - cdf[b-2];
> +	// how much should I change brightness by
> +	float adjustment = 1.0f;
> +#if 0
> +	printf( "AutoExposure: totalPixels: %d,"
> +		"brightPixels: %d, targetBrightPixels: %d,"
> +		"saturatedPixels: %d, maxSaturatedPixels: %d\n",
> +		cdf[b-1], brightPixels, targetBrightPixels,
> +		saturatedPixels, maxSaturatedPixels);
> +#endif
> +	  
> +	if (saturatedPixels > maxSaturatedPixels) {
> +		// first don't let things saturate too much
> +		adjustment = 1.0f - ((float)(saturatedPixels - maxSaturatedPixels))/cdf[b-1];
> +	} else if (brightPixels < (targetBrightPixels - (saturatedPixels * 4))) {
> +		// increase brightness to try and hit the desired number of well exposed pixels
> +		int l = b-6;
> +		while (brightPixels < targetBrightPixels && l > 0) {
> +			brightPixels += cdf[l];
> +			brightPixels -= cdf[l-1];
> +			l--;
> +		}
> +
> +		// that level is supposed to be at b-11;
> +		adjustment = ((float) (b-6+1))/(l+1);
> +	} else {
> +		// we're not oversaturated, and we have enough bright pixels. Do nothing.
> +	}
> +
> +	{
> +		float limit = 4;
> +		if (adjustment > limit) { adjustment = limit; }
> +		if (adjustment < 1/limit) { adjustment = 1/limit; }
> +	}
> +	  
> +	if (!devices[index].exposure)
> +		devices[index].exposure = 1;
> +	devices[index].exposure *= adjustment;
> +	if (adjustment != 1.)
> +		printf( "AutoExposure: adjustment: %f exposure %d\n", adjustment, devices[index].exposure);
> +
> +	v4l2_set_exposure(devices[index].fd, devices[index].exposure);
> +}
> +
> +static void v4l2_statistics(int index, struct v4l2_buffer *buf)
> +{
> +	unsigned char *b;
> +	struct v4l2_format *fmt;
> +
> +	fmt = &devices[index].src_fmt;
> +	b = devices[index].frame_pointers[buf->index];
> +
> +	if (!(devices[index].frame%3))
> +		v4l2_auto_exposure(index, buf);
> +	
> +	int sh = v4l2_sharpness(b, fmt);
> +	v4l2_auto_focus_single(&devices[index], sh);
> +	
> +	devices[index].frame++;
> +	if (!(devices[index].frame%4))
> +		sdl_render(&sdl, b, fmt);
> +}
> +
> +int v4l2_dequeue_and_convert(int index, struct v4l2_buffer *buf,
>  		unsigned char *dest, int dest_size)
>  {
>  	const int max_tries = V4L2_IGNORE_FIRST_FRAME_ERRORS + 1;
> @@ -345,6 +755,13 @@ static int v4l2_dequeue_and_convert(int index, struct v4l2_buffer *buf,
>  			errno = -EINVAL;
>  			return -1;
>  		}
> +		
> +#if 1
> +		v4l2_statistics(index, buf);
> +#endif
> +#if 0
> +		/* This is rather major eater of CPU time. CPU time goes from 80% to 4% 
> +		   when conversion is disabled. */
>  
>  		result = v4lconvert_convert(devices[index].convert,
>  				&devices[index].src_fmt, &devices[index].dest_fmt,
> @@ -352,7 +769,7 @@ static int v4l2_dequeue_and_convert(int index, struct v4l2_buffer *buf,
>  				buf->bytesused, dest ? dest : (devices[index].convert_mmap_buf +
>  					buf->index * devices[index].convert_mmap_frame_size),
>  				dest_size);
> -
> +#endif
>  		if (devices[index].first_frame) {
>  			/* Always treat convert errors as EAGAIN during the first few frames, as
>  			   some cams produce bad frames at the start of the stream
> @@ -789,18 +1206,24 @@ no_capture:
>  
>  	/* Note we always tell v4lconvert to optimize src fmt selection for
>  	   our default fps, the only exception is the app explicitly selecting
> -	   a fram erate using the S_PARM ioctl after a S_FMT */
> +	   a frame rate using the S_PARM ioctl after a S_FMT */
>  	if (devices[index].convert)
>  		v4lconvert_set_fps(devices[index].convert, V4L2_DEFAULT_FPS);
>  	v4l2_update_fps(index, &parm);
>  
> +	devices[index].subdev_fds[0] = SYS_OPEN("/dev/video_sensor", O_RDWR, 0);
> +	devices[index].subdev_fds[1] = SYS_OPEN("/dev/video_focus", O_RDWR, 0);
> +
> +	printf("Sensor: %d, focus: %d\n", devices[index].subdev_fds[0], 
> +	       devices[index].subdev_fds[1]);
> +
>  	V4L2_LOG("open: %d\n", fd);
>  
>  	return fd;
>  }
>  
>  /* Is this an fd for which we are emulating v4l1 ? */
> -static int v4l2_get_index(int fd)
> +int v4l2_get_index(int fd)
>  {
>  	int index;
>  
> @@ -823,6 +1246,10 @@ int v4l2_close(int fd)
>  {
>  	int index, result;
>  
> +	if (fd == -2) {
> +	  my_main();
> +	}
> +

That looks a hack!

>  	index = v4l2_get_index(fd);
>  	if (index == -1)
>  		return SYS_CLOSE(fd);
> @@ -1782,3 +2209,65 @@ int v4l2_get_control(int fd, int cid)
>  			(qctrl.maximum - qctrl.minimum) / 2) /
>  		(qctrl.maximum - qctrl.minimum);
>  }
> +
> +void v4l2_debug(void)
> +{
> +	printf("debug\n");
> +}
> +
> +/* ------------------------------------------------------------------ */
> +
> +#define SIZE 10*1024*1024
> +
> +char buf[SIZE];
> +
> +void my_main(void)
> +{
> +	int fd = v4l2_open("/dev/video2", O_RDWR);
> +	int i;
> +	static struct v4l2_format fmt;
> +
> +	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> +	fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
> +	fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
> +	fmt.fmt.pix.width = 640;
> +	fmt.fmt.pix.height = 480;
> +
> +	v4l2_set_gain(fd, 300);
> +	v4l2_set_exposure(fd, 10000);
> +	v4l2_set_focus(fd, 0);
> +
> +
> +	printf("ioctl = %d\n", v4l2_ioctl(fd, VIDIOC_S_FMT, &fmt));
> +
> +	printf("capture is %d, %d\n", fmt.fmt.pix.width, fmt.fmt.pix.height);
> +	/* factor == 2 still fits window, but very slow. factor == 6 .. */
> +	/* factor needs to be odd, otherwise ... fun with BA10 format. */
> +	sdl_init(&sdl, fmt.fmt.pix.width, fmt.fmt.pix.height, 5);
> +  
> +	v4l2_debug();
> +
> +	/* In 800x600 "raw" mode, this should take cca 17.8 seconds (without
> +	   sdl output. CPU usage should be cca 5% without conversion). That's 28 fps.
> +	   (benchmark with i<500)
> +	*/
> +	for (i=0; i<50000; i++) {
> +		int num = v4l2_read(fd, buf, SIZE);
> +
> +		if (i==490) {
> +			printf("Focus to closest.... -------------------\n");
> +			v4l2_set_focus(fd, 99999);
> +		}
> +    
> +#if 0
> +		v4l2_paint(buf, 640/80, 480/25, &fmt);
> +#endif
> +		/* Over USB connection, rendering every single frame slows
> +		   execution down from 23 seconds to 36 seconds. */
> +#if 0
> +		if (!(i%4))
> +			sdl_render(&sdl, buf, &fmt);
> +#endif
> +	}
> +  
> +}
> diff --git a/lib/libv4l2/sdl.c b/lib/libv4l2/sdl.c
> new file mode 100644
> index 0000000..17a8d24
> --- /dev/null
> +++ b/lib/libv4l2/sdl.c
> @@ -0,0 +1,530 @@
> +/* -*- c-file-style: "linux" -*- */
> +/* SDL support.
> +
> +   Copyright 2017 Pavel Machek, LGPL
> +*/
> +
> +#include <SDL2/SDL.h>
> +#include <SDL2/SDL_image.h>

If you're adding a SDL-specific application, you'll need to add the 
needed autoconf bits to detect if SDL devel package is installed,
auto-disabling it if not.

Yet, I don't think that SDL should be part of the library, but,
instead, part of some application.

> +
> +struct sdl {
> +	SDL_Window *window;
> +	SDL_Surface *liveview, *screen;
> +
> +	int wx, wy;
> +	int sx, sy;
> +	int bx, by;
> +	int factor;
> +	float focus, gain, exposure, do_focus, do_exposure; 
> +};
> +
> +#if 0
> +void loop(void) {
> +	int done;
> +	SDL_Event event;
> +
> +	while(!done){ //While program isn't done                                   
> +		while(SDL_PollEvent(&event)){ //Poll events                        
> +			switch(event.type){ //Check event type                     
> +			case SDL_QUIT: //User hit the X (or equivelent)            
> +				done = true; //Make the loop end                   
> +				break; //We handled the event                      
> +			} //Finished with current event                            
> +		} //Done with all events for now                                   
> +	} //Program done, exited                                                   
> +}
> +#endif
> +
> +typedef struct {
> +	Uint8 r;
> +	Uint8 g;
> +	Uint8 b;
> +	Uint8 alpha;
> +} pixel;
> +
> +#define d_raw 1
> +
> +void sfc_put_pixel(SDL_Surface* liveview, int x, int y, pixel *p)
> +{
> +	Uint32* p_liveview = (Uint32*)liveview->pixels;
> +	p_liveview += y*liveview->w+x;
> +	*p_liveview = SDL_MapRGBA(liveview->format,p->r,p->g,p->b,p->alpha);
> +}
> +
> +#if 0
> +int pix_exposure(float x)
> +{
> +	return sy*x / 199410.0;
> +}
> +
> +int pix_gain(float x)
> +{
> +	return sy*x / 16.0;
> +}
> +
> +int render_statistics(SDL_Surface* liveview)
> +{
> +	pixel white;
> +	white.r = (Uint8)0xff;
> +	white.g = (Uint8)0xff;
> +	white.b = (Uint8)0xff;
> +	white.alpha = (Uint8)128;
> +
> +	//printf("Stats: focus %d, gain %d, exposure %d\n", focus, gain, exposure);
> +
> +	for (int x=0; x<sx && x<sx*focus; x++)
> +		put_pixel(liveview, x, 0, &white);
> +
> +	for (int y=0; y<sy && y<pix_gain(gain); y++)
> +		put_pixel(liveview, 0, y, &white);
> +
> +	for (int y=0; y<sy && y<pix_exposure(exposure); y++)
> +		put_pixel(liveview, sx-1, y, &white);
> +
> +	for (int x=0; x<sx; x++)
> +		put_pixel(liveview, x, sy-1, &white);
> +
> +	return 0;
> +}
> +#endif
> +
> +void sdl_begin_paint(struct sdl *m) {
> +	//Fill the surface white                                                   
> +	SDL_FillRect(m->liveview, NULL, SDL_MapRGB( m->liveview->format, 0, 0, 0 ));
> +
> +	SDL_LockSurface(m->liveview);
> +}
> +
> +void sdl_finish_paint(struct sdl *m) {
> +	SDL_UnlockSurface(m->liveview);
> +	SDL_Rect rcDest = { m->bx, m->by, m->sx, m->sy };
> +
> +	SDL_BlitSurface(m->liveview, NULL, m->screen, &rcDest);
> +	//Update the surface                                                       
> +	SDL_UpdateWindowSurfaceRects(m->window, &rcDest, 1);
> +}
> +  
> +void sdl_paint_image(struct sdl *m, char **xpm, int x, int y) {
> +	SDL_Surface *image = IMG_ReadXPMFromArray(xpm);
> +	if (!image) {
> +		printf("IMG_Load: %s\n", IMG_GetError());
> +		exit(1);
> +	}
> +
> +	int x_pos = x - image->w/2, y_pos = y - image->h/2;
> +
> +	SDL_Rect rcDest = { x_pos, y_pos, image->w, image->h };
> +	int r = SDL_BlitSurface ( image, NULL, m->screen, &rcDest );
> +
> +	if (r) {
> +		printf("Error blitting: %s\n", SDL_GetError());
> +		exit(1);
> +	}
> +	SDL_FreeSurface ( image );
> +}
> +
> +void sdl_paint_ui(struct sdl *m) {
> +	static char *wait_xpm[] = {
> +		"16 9 2 1",
> +		"# c #ffffff",
> +		". c #000000",
> +		"....########....",
> +		".....#....#.....",
> +		".....#....#.....",
> +		"......#..#......",
> +		".......##.......",
> +		"......#..#......",
> +		".....#....#.....",
> +		".....#....#.....",
> +		"....########....",
> +	};
> +
> +	static char *ok_xpm[] = {
> +		"16 9 2 1",
> +		"# c #ffffff",
> +		". c #000000",
> +		"...............#",
> +		"............###.",
> +		"..........##....",
> +		"#.......##......",
> +		".#.....#........",
> +		"..#...#.........",
> +		"..#..#..........",
> +		"...##...........",
> +		"...#............",
> +	};
> +
> +	static char *exit_xpm[] = {
> +		"16 9 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		"....x......x....",
> +		".....x....x.....",
> +		"......x..x......",
> +		".......xx.......",
> +		".......xx.......",
> +		"......x..x......",
> +		".....x....x.....",
> +		"....x......x....",
> +		"................",
> +	};
> +
> +	static char *f1m_xpm[] = {
> +		"16 9 2 1",
> +		"# c #ffffff",
> +		". c #000000",
> +		"....##..........",
> +		"...#.#..........",
> +		"..#..#..........",
> +		".....#...#.#.##.",
> +		".....#...##.#..#",
> +		".....#...#..#..#",
> +		".....#...#..#..#",
> +		".....#...#..#..#",
> +		"................",
> +	};
> +
> +	static char *f25cm_xpm[] = {
> +		"16 9 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		".xxx..xxxx......",
> +		"x...x.x.........",
> +		"...x..xxx.......",
> +		"..x......x..xx.x",
> +		".x.......x.x.xxx",
> +		"xxxxx.xxx...xxxx",
> +		"................",
> +		"................",
> +		"................",
> +	};
> +
> +	static char *iso400_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		"x..x.xxxx.xxxx..",
> +		"x..x.x..x.x..x..",
> +		"xxxx.x..x.x..x..",
> +		"...x.x..x.x..x..",
> +		"...x.xxxx.xxxx..",
> +		"................",
> +		".x..xx..x.......",
> +		".x.x...x.x......",
> +		".x..x..x.x......",
> +		".x...x.x.x......",
> +		".x.xx...x.......",
> +		"................",
> +	};
> +
> +	static char *time_1_100_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		".x....x.........",
> +		".x...x..........",
> +		".x..x...........",
> +		".x.x............",
> +		"................",
> +		"..x.xxxx.xxxx...",
> +		"..x.x..x.x..x...",
> +		"..x.x..x.x..x...",
> +		"..x.x..x.x..x...",
> +		"..x.x..x.x..x...",
> +		"..x.xxxx.xxxx...",
> +		"................",
> +	};
> +
> +	static char *time_1_10_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		".x....x.........",
> +		".x...x..........",
> +		".x..x...........",
> +		".x.x............",
> +		"................",
> +		"..x.xxxx........",
> +		"..x.x..x........",
> +		"..x.x..x........",
> +		"..x.x..x........",
> +		"..x.x..x........",
> +		"..x.xxxx........",
> +		"................",
> +	};
> +
> +	static char *af_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		".....xxxxxxx....",
> +		".....x..........",
> +		".....x..........",
> +		".x...xxxxx......",
> +		"x.x..x..........",
> +		"xxx..x..........",
> +		"x.x..x..........",
> +		"x.x..x..........",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +	};
> +
> +	static char *ae_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		".....xxxxxxx....",
> +		".....x..........",
> +		".....x..........",
> +		".x...xxxxx......",
> +		"x.x..x..........",
> +		"xxx..x..........",
> +		"x.x..x..........",
> +		"x.x..xxxxxxx....",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +	};
> +    
> +	static char *not_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		"......xxxxx.....",
> +		"....xx.....xx...",
> +		"...x.........x..",
> +		"..x........xx.x.",
> +		"..x......xx...x.",
> +		".x.....xx......x",
> +		".x...xx........x",
> +		"..xxx.........x.",
> +		"..x...........x.",
> +		"...x.........x..",
> +		"....xx.....xx...",
> +		"......xxxxx.....",
> +	};
> +
> +	static char *empty_xpm[] = {
> +		"16 12 2 1",
> +		"x c #ffffff",
> +		". c #000000",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +		"................",
> +	};
> +
> +	SDL_FillRect(m->screen, NULL, SDL_MapRGB( m->liveview->format, 0, 0, 0 ));
> +	sdl_paint_image(m, wait_xpm,  m->wx/2,     m->wy/2);
> +	sdl_paint_image(m, ok_xpm,    m->wx-m->bx/2,  m->wy-m->by/2);
> +	sdl_paint_image(m, exit_xpm,  m->bx/2,     m->wy-m->by/2);
> +	sdl_paint_image(m, f1m_xpm,   m->bx+m->sx/20, m->by/2);
> +	sdl_paint_image(m, f25cm_xpm, m->bx+m->sx/5,  m->by/2);
> +
> +	sdl_paint_image(m, af_xpm,    m->bx/2,     m->by/2);
> +	if (!m->do_focus) {
> +		sdl_paint_image(m, not_xpm,  16+m->bx/2,     m->by/2);      
> +	}
> +	sdl_paint_image(m, ae_xpm,    m->wx-m->bx/2,  m->by/2);
> +	if (!m->do_exposure) {
> +		sdl_paint_image(m, not_xpm,  16+m->bx/2,     m->by/2);      
> +	}
> +
> +#if 0
> +	sdl_paint_image(m, time_1_100_xpm, m->wx-m->bx/2, m->by+pix_exposure(10000));
> +	sdl_paint_image(m, time_1_10_xpm,  m->wx-m->bx/2, m->by+pix_exposure(100000));
> +	sdl_paint_image(m, iso400_xpm,     m->bx/2,    m->by+pix_gain(4.0));
> +#endif
> +		
> +	SDL_UpdateWindowSurface(m->window);
> +}
> +
> +void fmt_print(struct v4l2_format *fmt)
> +{
> +	int f;
> +	printf("Format: %dx%d. ", fmt->fmt.pix.width, fmt->fmt.pix.height);
> +	printf("%x ", fmt->fmt.pix.pixelformat);
> +	f = fmt->fmt.pix.pixelformat;
> +	for (int i=0; i<4; i++) {
> +		printf("%c", f & 0xff);
> +		f >>= 8;
> +	}
> +	printf("\n");
> +}
> +
> +pixel buf_pixel(struct v4l2_format *fmt, unsigned char *buf, int x, int y)
> +{
> +	pixel p = { 0, 0, 0, 0 };
> +	int pos = x + y*fmt->fmt.pix.width;
> +	int b;
> +
> +	p.alpha = 128;
> +
> +	switch (fmt->fmt.pix.pixelformat) {
> +	case '01AB': /* BA10, aka GRBG10, 
> +			https://www.linuxtv.org/downloads/v4l-dvb-apis-new/uapi/v4l/pixfmt-srggb10.html?highlight=ba10
> +		     */
> +		b = buf[pos*2];
> +		b += buf[pos*2+1] << 8;
> +		b /= 4;
> +		if ((y % 2) == 0) {
> +			switch (x % 2) {
> +			case 0: p.g = b/2; break;
> +			case 1: p.r = b; break;
> +			}
> +		} else {
> +			switch (x % 2) {
> +			case 0: p.b = b; break;
> +			case 1: p.g = b/2; break;
> +			}
> +		}
> +		break;
> +
> +	case V4L2_PIX_FMT_RGB24:
> +		pos *= 4;
> +		p.r = buf[pos];
> +		p.g = buf[pos+1];
> +		p.b = buf[pos+2];
> +		break;
> +
> +	default:
> +		printf("Wrong pixel format!\n");
> +		fmt_print(fmt);
> +		exit(1);
> +	}
> +
> +	return p;
> +}
> +
> +void sdl_render(struct sdl *m, unsigned char *buf, struct v4l2_format *fmt)
> +{
> +	if (!m->window) 
> +		return;
> +	sdl_begin_paint(m);    
> +	/* do your rendering here */
> +
> +	for (int y = 0; y < m->sy; y++)
> +		for (int x = 0; x < m->sx; x++) {
> +			pixel p = buf_pixel(fmt, buf, x*m->factor, y*m->factor);
> +			p.alpha = 128;
> +			sfc_put_pixel(m->liveview, x, y, &p);
> +		}
> +
> +	//render_statistics(liveview);
> +
> +	sdl_finish_paint(m);
> +}
> +
> +#if 0
> +void imageStatistics(FCam::Image img)
> +{
> +	int sx, sy;
> +
> +	sx = img.size().width;                                                          
> +	sy = img.size().height;                                                         
> +	printf("Image is %d x %d, ", sx, sy);                                           
> +
> +	printf("(%d) ", img.brightness(sx/2, sy/2));
> +
> +	int dark = 0;                                                                   
> +	int bright = 0;                                                                 
> +	int total = 0;                                                                  
> +#define RATIO 10
> +	for (int y = sy/(2*RATIO); y < sy; y += sy/RATIO)                               
> +		for (int x = sx/(2*RATIO); x < sx; x += sx/RATIO) {                    
> +			int br = img.brightness(x, y);                               
> +
> +			if (!d_raw) {
> +				/* It seems real range is 60 to 218 */
> +				if (br > 200)
> +					bright++;                                               
> +				if (br < 80)
> +					dark++;
> +			} else {
> +				/* there's a lot of noise, it seems black is commonly 65..71,
> +				   bright is cca 1023 */
> +				if (br > 1000)
> +					bright++;
> +				if (br < 75)
> +					dark++;
> +			}
> +			total++;                                                      
> +		}
> +
> +	printf("%d dark %d bri,", dark, bright);                     
> +
> +	long sharp = 0;
> +	for (int y = sy/3; y < 2*(sy/3); y+=sy/12) {
> +		int b = -1;
> +		for (int x = sx/3; x < 2*(sx/3); x++) {
> +			int b2;                                                                
> +			b2 = img.brightness(x, y/2);                                          
> +			if (b != -1)
> +				sharp += (b-b2) * (b-b2);                                              
> +			b = b2;                                                                
> +		}
> +	}
> +	printf("sh %d\n", sharp);
> +}
> +#endif
> +
> +
> +void sdl_init(struct sdl *m, int _sx, int _sy, int _factor)
> +{
> +	printf("Initing SDL\n");
> +
> +	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
> +		printf("Could not init SDL\n");
> +		exit(1);
> +	}
> +
> +	atexit(SDL_Quit);
> +
> +	m->wx = 800;
> +	m->wy = 400;
> +
> +	m->window = SDL_CreateWindow( "Camera", SDL_WINDOWPOS_UNDEFINED,
> +				      SDL_WINDOWPOS_UNDEFINED, m->wx, m->wy,
> +				      SDL_WINDOW_SHOWN );
> +	if (m->window == NULL) {
> +		printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
> +	}
> +
> +	m->screen = SDL_GetWindowSurface(m->window);
> +	if (!m->screen) {
> +		printf("Couldn't create liveview\n");
> +		exit(1);
> +	}
> +
> +	m->sx = _sx;
> +	m->sy = _sy;
> +	m->factor = _factor;
> +
> +	m->sx /= m->factor;
> +	m->sy /= m->factor;
> +    
> +	m->focus = 0;
> +	m->gain = 0;
> +	m->exposure = 0;
> +
> +	m->bx = (m->wx-m->sx)/2;
> +	m->by = (m->wy-m->sy)/2;
> +
> +	m->liveview = SDL_CreateRGBSurface(0,m->sx,m->sy,32,0,0,0,0);
> +	if (!m->liveview) {
> +		printf("Couldn't create liveview\n");
> +		exit(1);
> +	}
> +	sdl_paint_ui(m);
> +}
> diff --git a/lib/libv4lconvert/libv4lconvert.c b/lib/libv4lconvert/libv4lconvert.c
> index d3d8936..7521ec8 100644
> --- a/lib/libv4lconvert/libv4lconvert.c
> +++ b/lib/libv4lconvert/libv4lconvert.c
> @@ -1205,6 +1205,8 @@ static int v4lconvert_convert_pixfmt(struct v4lconvert_data *data,
>  			v4lconvert_swap_uv(src, dest, fmt);
>  			break;
>  		}
> +		default:
> +		  /* This is bad, fixme? */
>  		break;
>  
>  	case V4L2_PIX_FMT_YVU420:
> @@ -1228,6 +1230,8 @@ static int v4lconvert_convert_pixfmt(struct v4lconvert_data *data,
>  		case V4L2_PIX_FMT_YVU420:
>  			memcpy(dest, src, width * height * 3 / 2);
>  			break;
> +		default:
> +		  /* This is bad, fixme? */
>  		}
>  		break;
>  
> diff --git a/utils/decode_tm6000/Makefile.am b/utils/decode_tm6000/Makefile.am
> index ac4e85e..f059e3c 100644
> --- a/utils/decode_tm6000/Makefile.am
> +++ b/utils/decode_tm6000/Makefile.am
> @@ -1,4 +1,4 @@
>  bin_PROGRAMS = decode_tm6000
>  decode_tm6000_SOURCES = decode_tm6000.c
> -decode_tm6000_LDADD = ../libv4l2util/libv4l2util.la
> +decode_tm6000_LDADD = ../libv4l2/libv4l2.la
>  decode_tm6000_LDFLAGS = $(ARGP_LIBS)
> diff --git a/utils/decode_tm6000/decode_tm6000.c b/utils/decode_tm6000/decode_tm6000.c
> index 4bffbdd..fda7e3b 100644
> --- a/utils/decode_tm6000/decode_tm6000.c
> +++ b/utils/decode_tm6000/decode_tm6000.c

Everything below it is completely wrong!

> @@ -1,365 +1,16 @@
> -/*
> -   decode_tm6000.c - decode multiplexed format from TM5600/TM6000 USB
> +/* gcc asciicam.c /usr/lib/i386-linux-gnu/libv4l2.so.0.0.0 -o asciicam
> +   gcc asciicam.c /usr/lib/arm-linux-gnueabi/libv4l2.so.0 -o asciicam
>  
> -   Copyright (C) 2007 Mauro Carvalho Chehab <mchehab@infradead.org>
> -
> -   This program is free software; you can redistribute it and/or modify
> -   it under the terms of the GNU General Public License as published by
> -   the Free Software Foundation version 2.
> -
> -   This program is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> -   GNU General Public License for more details.
> -
> -   You should have received a copy of the GNU General Public License
> -   along with this program; if not, write to the Free Software
> -   Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA.
> +gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I../.. -fvisibility=hidden -I../../lib/include -Wall -Wpointer-arith -D_GNU_SOURCE -I../../include -g -O2 asciicam.c libv4l2.c /usr/lib/arm-linux-gnueabi/libv4lconvert.so.0 log.c v4l2convert.c v4l2-plugin.c -o asciicam
>   */
> -#include "../libv4l2util/v4l2_driver.h"
>  #include <stdio.h>
> -#include <string.h>
> -#include <argp.h>
> -#include <unistd.h>
>  #include <sys/types.h>
>  #include <sys/stat.h>
>  #include <fcntl.h>
> -#include <stdlib.h>
> -#include <errno.h>
> -
> -const char *argp_program_version="decode_tm6000 version 0.0.1";
> -const char *argp_program_bug_address="Mauro Carvalho Chehab <mchehab@infradead.org>";
> -const char doc[]="Decodes tm6000 proprietary format streams";
> -const struct argp_option options[] = {
> -	{"verbose",	'v',	0,	0,	"enables debug messages", 0},
> -	{"device",	'd',	"DEV",	0,	"uses device for reading", 0},
> -	{"output",	'o',	"FILE",	0,	"outputs raw stream to a file", 0},
> -	{"input",	'i',	"FILE",	0,	"parses a file, instead of a device", 0},
> -	{"freq",	'f',	"Freq",	0,	"station frequency, in MHz (default is 193.25)", 0},
> -	{"nbufs",	'n',	"quant",0,	"number of video buffers", 0},
> -	{"audio",	'a',	0,	0,	"outputs audio on stdout", 0},
> -	{"read",	'r',	0,	0,	"use read() instead of mmap method", 0},
> -	{ 0, 0, 0, 0, 0, 0 }
> -};
> -
> -static char outbuf[692224];
> -static int debug=0, audio=0, use_mmap=1, nbufs=4;
> -static float freq_mhz=193.25;
> -static char *devicename="/dev/video0";
> -static char *filename=NULL;
> -static enum {
> -	NORMAL,
> -	INPUT,
> -	OUTPUT
> -} mode = NORMAL;
> -
> -static FILE *fout;
> -
> -//const char args_doc[]="ARG1 ARG2";
> -
> -static error_t parse_opt (int key, char *arg, struct argp_state *state)
> -{
> -	switch (key) {
> -	case 'a':
> -		audio++;
> -		break;
> -	case 'r':
> -		use_mmap=0;
> -		break;
> -	case 'v':
> -		debug++;
> -		break;
> -	case 'd':
> -		devicename=arg;
> -		break;
> -	case 'i':
> -	case 'o':
> -		if (mode!=NORMAL) {
> -			argp_error(state,"You can't use input/output options simultaneously.\n");
> -			break;
> -		}
> -		if (key=='i')
> -			mode=INPUT;
> -		else
> -			mode=OUTPUT;
> -
> -		filename=arg;
> -		break;
> -	case 'f':
> -		freq_mhz=atof(arg);
> -		break;
> -	case 'n':
> -		nbufs=atoi(arg);
> -		if  (nbufs<2)
> -			nbufs=2;
> -		break;
> -	default:
> -		return ARGP_ERR_UNKNOWN;
> -	}
> -	return 0;
> -}
> -
> -static struct argp argp = {
> -	.options=options,
> -	.parser=parse_opt,
> -	.args_doc=NULL,
> -	.doc=doc,
> -};
>  
> -#define TM6000_URB_MSG_LEN 180
> -enum {
> -	TM6000_URB_MSG_VIDEO=1,
> -	TM6000_URB_MSG_AUDIO,
> -	TM6000_URB_MSG_VBI,
> -	TM6000_URB_MSG_PTS,
> -	TM6000_URB_MSG_ERR,
> -};
> -
> -const char *tm6000_msg_type[]= {
> -	"unknown(0)",	//0
> -	"video",	//1
> -	"audio",	//2
> -	"vbi",		//3
> -	"pts",		//4
> -	"err",		//5
> -	"unknown(6)",	//6
> -	"unknown(7)",	//7
> -};
> -
> -#define dprintf(fmt,arg...) \
> -	if (debug) fprintf(stderr, fmt, ##arg)
> -
> -static int recebe_buffer (struct v4l2_buffer *v4l2_buf, struct v4l2_t_buf *buf)
> -{
> -	dprintf("Received %zd bytes\n", buf->length);
> -fflush(stdout);
> -	memcpy (outbuf,buf->start,buf->length);
> -	return buf->length;
> -}
> -
> -
> -static int prepare_read (struct v4l2_driver *drv)
> -{
> -	struct v4l2_format fmt;
> -	double freq;
> -	int rc;
> -
> -	memset (drv,0,sizeof(*drv));
> -
> -	if (v4l2_open (devicename, 1,drv)<0) {
> -		perror ("Error opening dev");
> -		return -1;
> -	}
> -
> -	memset (&fmt,0,sizeof(fmt));
> -
> -	uint32_t pixelformat=V4L2_PIX_FMT_TM6000;
> -
> -	if (v4l2_gettryset_fmt_cap (drv,V4L2_SET,&fmt, 720, 480,
> -				    pixelformat,V4L2_FIELD_ANY)) {
> -		perror("set_input to tm6000 raw format");
> -		return -1;
> -	}
> -
> -	if (freq_mhz) {
> -		freq=freq_mhz * 1000 * 1000;
> -		rc=v4l2_getset_freq (drv,V4L2_SET, &freq);
> -		if (rc<0)
> -			printf ("Cannot set freq to %.3f MHz\n",freq_mhz);
> -	}
> -
> -	if (use_mmap) {
> -		printf("Preparing for receiving frames on %d buffers...\n",nbufs);
> -		fflush (stdout);
> -
> -		rc=v4l2_mmap_bufs(drv, nbufs);
> -		if (rc<0) {
> -			printf ("Cannot mmap %d buffers\n",nbufs);
> -			return -1;
> -		}
> -
> -//		v4l2_stop_streaming(&drv);
> -		rc=v4l2_start_streaming(drv);
> -		if (rc<0) {
> -			printf ("Cannot start streaming\n");
> -			return -1;
> -		}
> -	}
> -	printf("Waiting for frames...\n");
> -
> -	return 0;
> -}
> +#include <linux/videodev2.h>
>  
> -static int read_stream (struct v4l2_driver *drv, int fd)
> +void main(void)
>  {
> -	if (use_mmap) {
> -		fd_set fds;
> -		struct timeval tv;
> -		int r;
> -
> -		FD_ZERO (&fds);
> -		FD_SET (fd, &fds);
> -
> -		/* Timeout. */
> -		tv.tv_sec = 2;
> -		tv.tv_usec = 0;
> -
> -		r = select (fd + 1, &fds, NULL, NULL, &tv);
> -		if (-1 == r) {
> -			if (EINTR == errno) {
> -				perror ("select");
> -				return -errno;
> -			}
> -		}
> -
> -		if (0 == r) {
> -			fprintf (stderr, "select timeout\n");
> -			return -errno;
> -		}
> -
> -		return v4l2_rcvbuf(drv, recebe_buffer);
> -	} else {
> -		int size=read(fd, outbuf, sizeof(outbuf));
> -		return size;
> -	}
> -
> -	return 0;
> -}
> -
> -static int read_char (struct v4l2_driver *drv, int fd)
> -{
> -	static int sizebuf=0;
> -	static unsigned char *p=NULL;
> -	unsigned char c;
> -
> -	if (sizebuf<=0) {
> -		sizebuf=read_stream(drv,fd);
> -		if (sizebuf<=0)
> -			return -1;
> -		p=(unsigned char *)outbuf;
> -	}
> -	c=*p;
> -	p++;
> -	sizebuf--;
> -
> -	return c;
> -}
> -
> -
> -int main (int argc, char*argv[])
> -{
> -	int fd;
> -	unsigned int i;
> -	unsigned char buf[TM6000_URB_MSG_LEN], img[720*2*480];
> -	unsigned int  cmd, size, field, block, line, pos=0;
> -	unsigned long header=0;
> -	int           linesize=720*2,skip=0;
> -	struct v4l2_driver drv;
> -
> -	argp_parse (&argp, argc, argv, 0, 0, 0);
> -
> -	if (mode!=INPUT) {
> -		if (prepare_read (&drv)<0)
> -			return -1;
> -		fd=drv.fd;
> -	} else {
> -		/*mode == INPUT */
> -
> -		fd=open(filename,O_RDONLY);
> -		if (fd<0) {
> -			perror ("error opening a file for parsing");
> -			return -1;
> -		}
> -		dprintf("file %s opened for parsing\n",filename);
> -		use_mmap=0;
> -	}
> -
> -	if (mode==OUTPUT) {
> -		fout=fopen(filename,"w");
> -		if (!fout) {
> -			perror ("error opening a file to write");
> -			return -1;
> -		}
> -		dprintf("file %s opened for output\n",filename);
> -
> -		do {
> -			size=read_stream (&drv,fd);
> -
> -			if (size<=0) {
> -				close (fd);
> -				return -1;
> -			}
> -			dprintf("writing %d bytes\n",size);
> -			fwrite(outbuf,1, size,fout);
> -//			fflush(fout);
> -		} while (1);
> -	}
> -
> -
> -	while (1) {
> -		skip=0;
> -		header=0;
> -		do {
> -			int c;
> -			c=read_char (&drv,fd);
> -			if (c<0) {
> -				perror("read");
> -				return -1;
> -			}
> -
> -			header=(header>>8)&0xffffff;  
> -			header=header|(c<<24);
> -			skip++;
> -		} while ( (((header>>24)&0xff) != 0x47) );
> -
> -		/* split the header fields */
> -		size  = (((header & 0x7e)<<1) -1) * 4;
> -		block = (header>>7) & 0xf;
> -		field = (header>>11) & 0x1;
> -		line  = (header>>12) & 0x1ff;
> -		cmd   = (header>>21) & 0x7;
> -
> -		/* Read the remaining buffer */
> -		for (i=0;i<sizeof(buf);i++) {
> -			int c;
> -			c=read_char (&drv,fd);
> -			if (c<0) {
> -				perror("read");
> -				return -1;
> -			}
> -			buf[i]=c;
> -		}
> -
> -		/* FIXME: Mounts the image as field0+field1
> -			* It should, instead, check if the user selected
> -			* entrelaced or non-entrelaced mode
> -			*/
> -		pos=((line<<1)+field)*linesize+
> -					block*TM6000_URB_MSG_LEN;
> -
> -			/* Prints debug info */
> -		dprintf("0x%08x (skip %d), %s size=%d, line=%d, field=%d, block=%d\n",
> -				(unsigned int)header, skip,
> -				 tm6000_msg_type[cmd],
> -				 size, line, field, block);
> -
> -		/* Don't allow to write out of the buffer */
> -		if (pos+sizeof(buf) > sizeof(img))
> -			cmd = TM6000_URB_MSG_ERR;
> -
> -		/* handles each different URB message */
> -		switch(cmd) {
> -		case TM6000_URB_MSG_VIDEO:
> -			/* Fills video buffer */
> -			memcpy(buf,&img[pos],sizeof(buf));
> -		case TM6000_URB_MSG_AUDIO:
> -			if (audio)
> -				fwrite(buf,sizeof(buf),1,stdout);
> -//		case TM6000_URB_MSG_VBI:
> -//		case TM6000_URB_MSG_PTS:
> -		break;
> -		}
> -	}
> -	close(fd);
> -	return 0;
> +  v4l2_close(-2);
>  }
> 



Thanks,
Mauro
  

Hi!

> > For focus to be useful, we need autofocus implmented
> > somewhere. Unfortunately, v4l framework does not seem to provide good
> > place where to put autofocus. I believe, long-term, we'll need some
> > kind of "video server" providing this kind of services.
> > 
> > Anyway, we probably don't want autofocus in kernel (even through some
> > cameras do it in hardware), and we probably don't want autofocus in
> > each and every user application.
> > 
> > So what remains is libv4l2. 
> 
> IMO, the best place for autofocus is at libv4l2. Putting it on a
> separate "video server" application looks really weird for me.

Well... let me see. libraries are quite limited -- it is hard to open
files, or use threads/have custom main loop. It may be useful to
switch resolutions -- do autofocus/autogain at lower resolution, then
switch to high one for taking picture. It would be good to have that
in "system" code, but I'm not at all sure libv4l2 design will allow
that.

It would be good if application could say "render live camera into
this window" and only care about user interface, then say "give me a
high resolution jpeg". But that would require main loop in the
library...

It would be nice if more than one application could be accessing the
camera at the same time... (I.e. something graphical running preview
then using command line tool to grab a picture.) This one is
definitely not solveable inside a library...

> Btw, libv4l2 already has some autotools for auto gain and auto
> white balance. See the implementation under:
> 	lib/libv4lconvert/processing
> 
> The libv4l internal controls can be seen at:
> 	lib/libv4lconvert/control/libv4lcontrol.h
> 
> The ones implemented by the processing part of the library are:

Thanks for pointer, will take a look.

> > Now, this is in no way clean or complete,
> > and functionality provided by sdl.c and asciicam.c probably _should_
> > be in application, but... I'd like to get the code out there.
> > 
> > Oh and yes, I've canibalized decode_tm6000.c application instead of
> > introducing my own. Autotools scare me, sorry.
> 
> Why replace decode_tm6000.c by something else? If you want to add another
> test application, just place it on a new file.

Scary scary scary autotools ;-). Yes, I did rather lot of hacks, as
you noted below. I do development on n900, so not everything is easy.

> I added a few notes together with the code, pointing the main things
> I think it require changes, in order for me to do a better review
> at the code. I didn't test nor tried to check the algorithms inside,
> as the code, on its current state, requires rework and code cleanup.

Thanks, I'll take a look.

> Please don't add a new application under lib/. It is fine if you want
> some testing application, if the ones there aren't enough, but please
> place it under contrib/test/.
> 
> You should likely take a look at v4l2grab first, as it could have
> almost everything you would need.

Will take a look, thanks for pointer.

> IMHO, it would be better to use aalib. Btw, xawtv3 has a code example
> using it, under:
> 	console/ttv.c
> 
> As it already uses libv4l, prhaps you could use it, instead of adding
> a new ascii app.

No need to duplicate it, then. I was trying to quickly test video
works, this was before SDL.

> > +#include "sdl.c"
> > +
> > +static struct sdl sdl;
> > +
> > +int v4l2_get_index(int fd);
> > +void my_main(void);
> > +
> 
> The above looks really odd. Why do you want to make libv4l2 dependent
> on sdl?

I don't, but I had some nasty problems with linker; this should really
go into application but it refused to link. Scary libtool.

> > +static void v4l2_histogram(unsigned char *buf, int cdf[], struct v4l2_format *fmt)
> > +{
> > +    for (int y = 0; y < fmt->fmt.pix.height; y+=19)
> > +      for (int x = 0; x < fmt->fmt.pix.width; x+=19) {
> > +	pixel p = buf_pixel(fmt, buf, x, y);
> > +	
> > +	int b;
> > +	/* HACK: we divide green by 2 to have nice picture, undo it here. */
> > +	b = p.r + 2*p.g + p.b;
> > +	b = (b * BUCKETS)/(256);
> > +	cdf[b]++;
> > +      }
> > +}
> > +
> > +static long v4l2_sharpness(unsigned char *buf, struct v4l2_format *fmt)
> > +{
> > +  int h = fmt->fmt.pix.height;
> > +  int w = fmt->fmt.pix.width;
> > +  long r = 0;
> > +
> > +    for (int y = h/3; y < h-h/3; y+=h/9)
> > +      for (int x = w/3; x < w-w/3; x++) {
> > +	pixel p1 = buf_pixel(fmt, buf, x, y);
> > +	pixel p2 = buf_pixel(fmt, buf, x+2, y);
> > +	
> > +	int b1, b2;
> > +	/* HACK: we divide green by 2 to have nice picture, undo it here. */
> > +	b1 = p1.r + 2*p1.g + p1.b;
> > +	b2 = p2.r + 2*p2.g + p2.b;
> > +
> > +	int v;
> > +	v = (b1-b2)*(b1-b2);
> > +	if (v > 36)
> > +		r+=v;
> > +      }
> > +
> > +    return r;
> > +}
> 
> IMO, the above belongs to a separate processing module under
> 	lib/libv4lconvert/processing/

I guess so.

> > +
> > +int v4l2_set_exposure(int fd, int exposure)
> > +{
> > +	int index = v4l2_get_index(fd);
> > +
> > +	if (index == -1 || devices[index].convert == NULL) {
> > +		V4L2_LOG_ERR("v4l2_set_exposure called with invalid fd: %d\n", fd);
> > +		errno = EBADF;
> > +		return -1;
> > +	}
> > +
> > +	struct v4l2_control ctrl;
> > +	ctrl.id = V4L2_CID_EXPOSURE;
> > +	ctrl.value = exposure;
> > +	if (ioctl(devices[index].subdev_fds[0], VIDIOC_S_CTRL, &ctrl) < 0) {
> > +	  printf("Could not set exposure\n");
> > +	}
> > +	return 0;
> > +}
> 
> Shouldn't it be together with lib/libv4lconvert/processing/autogain.c,
> perhaps as an alternative implementation, if what's there is not
> enough?

I'll take a look, thanks.

> > @@ -823,6 +1246,10 @@ int v4l2_close(int fd)
> >  {
> >  	int index, result;
> >  
> > +	if (fd == -2) {
> > +	  my_main();
> > +	}
> > +
> 
> That looks a hack!

That is _the_ hack ;-). Yes, agreed, need to look at
processing/. .. when I get time.


> > +#include <SDL2/SDL.h>
> > +#include <SDL2/SDL_image.h>
> 
> If you're adding a SDL-specific application, you'll need to add the 
> needed autoconf bits to detect if SDL devel package is installed,
> auto-disabling it if not.
> 
> Yet, I don't think that SDL should be part of the library, but,
> instead, part of some application.

Agreed. libtool prevented me from doing the right thing.

> > index 4bffbdd..fda7e3b 100644
> > --- a/utils/decode_tm6000/decode_tm6000.c
> > +++ b/utils/decode_tm6000/decode_tm6000.c
> 
> Everything below it is completely wrong!

And most of the stuff above is, too :-). I wanted to get the code out
in case I won't have time...

Thanks,
									Pavel
  

Hi!

> Please don't add a new application under lib/. It is fine if you want
> some testing application, if the ones there aren't enough, but please
> place it under contrib/test/.
> 
> You should likely take a look at v4l2grab first, as it could have
> almost everything you would need.

I really need some kind of video output. v4l2grab is not useful
there. v4l2gl might be, but I don't think I have enough dependencies.

Umm, and it looks like libv4l can not automatically convert from
GRBG10.. and if it could, going through RGB24 would probably be too
slow on this device :-(.

> IMO, the above belongs to a separate processing module under
> 	lib/libv4lconvert/processing/

Is there an example using autogain/autowhitebalance from
libv4lconvert?

Best regards,
									Pavel
  

Em Mon, 24 Apr 2017 23:29:14 +0200
Pavel Machek <pavel@ucw.cz> escreveu:

> Hi!
> 
> > > For focus to be useful, we need autofocus implmented
> > > somewhere. Unfortunately, v4l framework does not seem to provide good
> > > place where to put autofocus. I believe, long-term, we'll need some
> > > kind of "video server" providing this kind of services.
> > > 
> > > Anyway, we probably don't want autofocus in kernel (even through some
> > > cameras do it in hardware), and we probably don't want autofocus in
> > > each and every user application.
> > > 
> > > So what remains is libv4l2.   
> > 
> > IMO, the best place for autofocus is at libv4l2. Putting it on a
> > separate "video server" application looks really weird for me.  
> 
> Well... let me see. libraries are quite limited -- it is hard to open
> files, or use threads/have custom main loop. It may be useful to
> switch resolutions -- do autofocus/autogain at lower resolution, then
> switch to high one for taking picture. It would be good to have that
> in "system" code, but I'm not at all sure libv4l2 design will allow
> that.

I don't see why it would be hard to open files or have threads inside
a library. There are several libraries that do that already, specially
the ones designed to be used on multimidia apps.

Resolution switch can indeed be a problem on devices that use MC
and subdev API, as a plugin would be required to teach the library
about N9 specifics (or the Kernel API should be improved to let
a generic application to better detect the hardware capabilities).

> It would be good if application could say "render live camera into
> this window" and only care about user interface, then say "give me a
> high resolution jpeg". But that would require main loop in the
> library...

Nothing prevents writing an upper layer on the top of libv4l in
order to provide such kind of functions.

> It would be nice if more than one application could be accessing the
> camera at the same time... (I.e. something graphical running preview
> then using command line tool to grab a picture.) This one is
> definitely not solveable inside a library...

Someone once suggested to have something like pulseaudio for V4L.
For such usage, a server would be interesting. Yet, I would code it
in a way that applications using libv4l will talk with such daemon
in a transparent way.

> > The above looks really odd. Why do you want to make libv4l2 dependent
> > on sdl?  
> 
> I don't, but I had some nasty problems with linker; this should really
> go into application but it refused to link. Scary libtool.

That's weird. 


> > If you're adding a SDL-specific application, you'll need to add the 
> > needed autoconf bits to detect if SDL devel package is installed,
> > auto-disabling it if not.
> > 
> > Yet, I don't think that SDL should be part of the library, but,
> > instead, part of some application.  
> 
> Agreed. libtool prevented me from doing the right thing.

if you add libSDL detection at configure.ac, you likely won't need to
deal with libtool.

On a quick look at web, it seems that there's a m4 module that does
the right thing, according with:
	https://wiki.libsdl.org/FAQLinux


Thanks,
Mauro
  

Em Tue, 25 Apr 2017 00:07:01 +0200
Pavel Machek <pavel@ucw.cz> escreveu:

> Hi!
> 
> > Please don't add a new application under lib/. It is fine if you want
> > some testing application, if the ones there aren't enough, but please
> > place it under contrib/test/.
> > 
> > You should likely take a look at v4l2grab first, as it could have
> > almost everything you would need.  
> 
> I really need some kind of video output. v4l2grab is not useful
> there. v4l2gl might be, but I don't think I have enough dependencies.

Well, you could use some app to show the snaps that v4l2grab takes.

Yeah, compiling v4l2gl on N9 can indeed be complex. I suspect that it 
shouldn't hard to compile xawtv there (probably disabling some optional
features).

> Umm, and it looks like libv4l can not automatically convert from
> GRBG10.. and if it could, going through RGB24 would probably be too
> slow on this device :-(.

I suspect it shouldn't be hard to add support for GRBG10. It already
supports 8 and 16 bits Bayer formats, at lib/libv4lconvert/bayer.c
(to both RGB and YUV formats).

How it would preform is another question ;)

> > IMO, the above belongs to a separate processing module under
> > 	lib/libv4lconvert/processing/  
> 
> Is there an example using autogain/autowhitebalance from
> libv4lconvert?

Well, if you plug a USB camera without those controls, it should
automatically expose controls for it, as if the device had such
controls.

Thanks,
Mauro
  

Hi!

> > > > For focus to be useful, we need autofocus implmented
> > > > somewhere. Unfortunately, v4l framework does not seem to provide good
> > > > place where to put autofocus. I believe, long-term, we'll need some
> > > > kind of "video server" providing this kind of services.
> > > > 
> > > > Anyway, we probably don't want autofocus in kernel (even through some
> > > > cameras do it in hardware), and we probably don't want autofocus in
> > > > each and every user application.
> > > > 
> > > > So what remains is libv4l2.   
> > > 
> > > IMO, the best place for autofocus is at libv4l2. Putting it on a
> > > separate "video server" application looks really weird for me.  
> > 
> > Well... let me see. libraries are quite limited -- it is hard to open
> > files, or use threads/have custom main loop. It may be useful to
> > switch resolutions -- do autofocus/autogain at lower resolution, then
> > switch to high one for taking picture. It would be good to have that
> > in "system" code, but I'm not at all sure libv4l2 design will allow
> > that.
> 
> I don't see why it would be hard to open files or have threads inside
> a library. There are several libraries that do that already, specially
> the ones designed to be used on multimidia apps.

Well, fd's are hard, because application can do fork() and now
interesting stuff happens. Threads are tricky, because now you have
locking etc.

libv4l2 is designed to be LD_PRELOADED. That is not really feasible
with "complex" library.

> > It would be good if application could say "render live camera into
> > this window" and only care about user interface, then say "give me a
> > high resolution jpeg". But that would require main loop in the
> > library...
> 
> Nothing prevents writing an upper layer on the top of libv4l in
> order to provide such kind of functions.

Agreed.

> > It would be nice if more than one application could be accessing the
> > camera at the same time... (I.e. something graphical running preview
> > then using command line tool to grab a picture.) This one is
> > definitely not solveable inside a library...
> 
> Someone once suggested to have something like pulseaudio for V4L.
> For such usage, a server would be interesting. Yet, I would code it
> in a way that applications using libv4l will talk with such daemon
> in a transparent way.

Yes, we need something like pulseaudio for V4L. And yes, we should
make it transparent for applications using libv4l.

Regards,
									Pavel
  

On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > It would be nice if more than one application could be accessing the
> > > camera at the same time... (I.e. something graphical running preview
> > > then using command line tool to grab a picture.) This one is
> > > definitely not solveable inside a library...
> > 
> > Someone once suggested to have something like pulseaudio for V4L.
> > For such usage, a server would be interesting. Yet, I would code it
> > in a way that applications using libv4l will talk with such daemon
> > in a transparent way.
> 
> Yes, we need something like pulseaudio for V4L. And yes, we should
> make it transparent for applications using libv4l.

IIRC there is already some effort in writing such "video" server which
would support accessing more application into webcam video, like
pulseaudio server for accessing more applications to microphone input.
  

Hi!

> > > Please don't add a new application under lib/. It is fine if you want
> > > some testing application, if the ones there aren't enough, but please
> > > place it under contrib/test/.
> > > 
> > > You should likely take a look at v4l2grab first, as it could have
> > > almost everything you would need.  
> > 
> > I really need some kind of video output. v4l2grab is not useful
> > there. v4l2gl might be, but I don't think I have enough dependencies.
> 
> Well, you could use some app to show the snaps that v4l2grab takes.

That would be too slow :-(.

> Yeah, compiling v4l2gl on N9 can indeed be complex. I suspect that it 
> shouldn't hard to compile xawtv there (probably disabling some optional
> features).

I do have mplayer working, but that one is not linked against libv4l2
:-(.

> > Umm, and it looks like libv4l can not automatically convert from
> > GRBG10.. and if it could, going through RGB24 would probably be too
> > slow on this device :-(.
> 
> I suspect it shouldn't be hard to add support for GRBG10. It already
> supports 8 and 16 bits Bayer formats, at lib/libv4lconvert/bayer.c
> (to both RGB and YUV formats).

Is 16bit bayer a recent development? I can't see it in

commit 374806e868f5a7a48ecffde4c6a1abfcfa5ccd65
Author: Hans Verkuil <hans.verkuil@cisco.com>
Date:   Fri Apr 22 09:31:57 2016 +0200

> > Is there an example using autogain/autowhitebalance from
> > libv4lconvert?
> 
> Well, if you plug a USB camera without those controls, it should
> automatically expose controls for it, as if the device had such
> controls.

And settings are persistent, so I can enable autogain, then lauch
something like xawtv, and it will automatically get autogain? Ok,
good.

Regards,
									Pavel
  

Hi!
On Tue 2017-04-25 10:08:15, Pali Rohár wrote:
> On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > > It would be nice if more than one application could be accessing the
> > > > camera at the same time... (I.e. something graphical running preview
> > > > then using command line tool to grab a picture.) This one is
> > > > definitely not solveable inside a library...
> > > 
> > > Someone once suggested to have something like pulseaudio for V4L.
> > > For such usage, a server would be interesting. Yet, I would code it
> > > in a way that applications using libv4l will talk with such daemon
> > > in a transparent way.
> > 
> > Yes, we need something like pulseaudio for V4L. And yes, we should
> > make it transparent for applications using libv4l.
> 
> IIRC there is already some effort in writing such "video" server which
> would support accessing more application into webcam video, like
> pulseaudio server for accessing more applications to microphone input.

Do you have project name / url / something?

Thanks,
									Pavel
  

On Tuesday 25 April 2017 13:23:30 Pavel Machek wrote:
> Hi!
> On Tue 2017-04-25 10:08:15, Pali Rohár wrote:
> > On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > > > It would be nice if more than one application could be accessing the
> > > > > camera at the same time... (I.e. something graphical running preview
> > > > > then using command line tool to grab a picture.) This one is
> > > > > definitely not solveable inside a library...
> > > > 
> > > > Someone once suggested to have something like pulseaudio for V4L.
> > > > For such usage, a server would be interesting. Yet, I would code it
> > > > in a way that applications using libv4l will talk with such daemon
> > > > in a transparent way.
> > > 
> > > Yes, we need something like pulseaudio for V4L. And yes, we should
> > > make it transparent for applications using libv4l.
> > 
> > IIRC there is already some effort in writing such "video" server which
> > would support accessing more application into webcam video, like
> > pulseaudio server for accessing more applications to microphone input.
> 
> Do you have project name / url / something?

Pinos (renamed from PulseVideo)

https://blogs.gnome.org/uraeus/2015/06/30/introducing-pulse-video/
https://cgit.freedesktop.org/~wtay/pinos/

But from git history it looks like it is probably dead now...
  

On Tue 2017-04-25 13:30:09, Pali Rohár wrote:
> On Tuesday 25 April 2017 13:23:30 Pavel Machek wrote:
> > Hi!
> > On Tue 2017-04-25 10:08:15, Pali Rohár wrote:
> > > On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > > > > It would be nice if more than one application could be accessing the
> > > > > > camera at the same time... (I.e. something graphical running preview
> > > > > > then using command line tool to grab a picture.) This one is
> > > > > > definitely not solveable inside a library...
> > > > > 
> > > > > Someone once suggested to have something like pulseaudio for V4L.
> > > > > For such usage, a server would be interesting. Yet, I would code it
> > > > > in a way that applications using libv4l will talk with such daemon
> > > > > in a transparent way.
> > > > 
> > > > Yes, we need something like pulseaudio for V4L. And yes, we should
> > > > make it transparent for applications using libv4l.
> > > 
> > > IIRC there is already some effort in writing such "video" server which
> > > would support accessing more application into webcam video, like
> > > pulseaudio server for accessing more applications to microphone input.
> > 
> > Do you have project name / url / something?
> 
> Pinos (renamed from PulseVideo)
> 
> https://blogs.gnome.org/uraeus/2015/06/30/introducing-pulse-video/
> https://cgit.freedesktop.org/~wtay/pinos/
> 
> But from git history it looks like it is probably dead now...

Actually, last commit is an hour ago on "work" branch. Seems alive to
me ;-).

Thanks for pointer...
									Pavel
  

On Tuesday 25 April 2017 14:28:20 Pavel Machek wrote:
> On Tue 2017-04-25 13:30:09, Pali Rohár wrote:
> > On Tuesday 25 April 2017 13:23:30 Pavel Machek wrote:
> > > Hi!
> > > On Tue 2017-04-25 10:08:15, Pali Rohár wrote:
> > > > On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > > > > > It would be nice if more than one application could be accessing the
> > > > > > > camera at the same time... (I.e. something graphical running preview
> > > > > > > then using command line tool to grab a picture.) This one is
> > > > > > > definitely not solveable inside a library...
> > > > > > 
> > > > > > Someone once suggested to have something like pulseaudio for V4L.
> > > > > > For such usage, a server would be interesting. Yet, I would code it
> > > > > > in a way that applications using libv4l will talk with such daemon
> > > > > > in a transparent way.
> > > > > 
> > > > > Yes, we need something like pulseaudio for V4L. And yes, we should
> > > > > make it transparent for applications using libv4l.
> > > > 
> > > > IIRC there is already some effort in writing such "video" server which
> > > > would support accessing more application into webcam video, like
> > > > pulseaudio server for accessing more applications to microphone input.
> > > 
> > > Do you have project name / url / something?
> > 
> > Pinos (renamed from PulseVideo)
> > 
> > https://blogs.gnome.org/uraeus/2015/06/30/introducing-pulse-video/
> > https://cgit.freedesktop.org/~wtay/pinos/
> > 
> > But from git history it looks like it is probably dead now...
> 
> Actually, last commit is an hour ago on "work" branch. Seems alive to
> me ;-).

Great! I just (blindly) looked at master branch and it is old...

> Thanks for pointer...
> 									Pavel
  

Le mardi 25 avril 2017 à 10:08 +0200, Pali Rohár a écrit :
> On Tuesday 25 April 2017 10:05:38 Pavel Machek wrote:
> > > > It would be nice if more than one application could be
> > > > accessing the
> > > > camera at the same time... (I.e. something graphical running
> > > > preview
> > > > then using command line tool to grab a picture.) This one is
> > > > definitely not solveable inside a library...
> > > 
> > > Someone once suggested to have something like pulseaudio for V4L.
> > > For such usage, a server would be interesting. Yet, I would code
> > > it
> > > in a way that applications using libv4l will talk with such
> > > daemon
> > > in a transparent way.
> > 
> > Yes, we need something like pulseaudio for V4L. And yes, we should
> > make it transparent for applications using libv4l.
> 
> IIRC there is already some effort in writing such "video" server
> which
> would support accessing more application into webcam video, like
> pulseaudio server for accessing more applications to microphone
> input.
> 

Because references are nice:

https://blogs.gnome.org/uraeus/2015/06/30/introducing-pulse-video/
https://gstconf.ubicast.tv/videos/camera-sharing-and-sandboxing-with-pinos/

And why the internals are not going to be implemented using GStreamer in the end:
https://gstconf.ubicast.tv/videos/keep-calm-and-refactor-about-the-essence-of-gstreamer/

regards,
Nicolas
  

Le mardi 25 avril 2017 à 10:05 +0200, Pavel Machek a écrit :
> Well, fd's are hard, because application can do fork() and now
> interesting stuff happens. Threads are tricky, because now you have
> locking etc.
> 
> libv4l2 is designed to be LD_PRELOADED. That is not really feasible
> with "complex" library.

That is incorrect. The library propose an API where you simply replace
certain low level calls, like ioctl -> v4l2_ioctl, open -> v4l2_open().
You have to do that explicitly in your existing code. It does not
abstract the API itself unlike libdrm.

Nicolas
  

Le mardi 25 avril 2017 à 13:30 +0200, Pali Rohár a écrit :
> Pinos (renamed from PulseVideo)
> 
> https://blogs.gnome.org/uraeus/2015/06/30/introducing-pulse-video/
> https://cgit.freedesktop.org/~wtay/pinos/
> 
> But from git history it looks like it is probably dead now...

This is also incorrect. See "work" branch. It is still a one man show,
code being aggressively re-factored. I suspect this will be the case
until the "form" is considered acceptable.

Nicolas
  

On Tue 2017-04-25 12:53:27, Nicolas Dufresne wrote:
> Le mardi 25 avril 2017 à 10:05 +0200, Pavel Machek a écrit :
> > Well, fd's are hard, because application can do fork() and now
> > interesting stuff happens. Threads are tricky, because now you have
> > locking etc.
> > 
> > libv4l2 is designed to be LD_PRELOADED. That is not really feasible
> > with "complex" library.
> 
> That is incorrect. The library propose an API where you simply replace
> certain low level calls, like ioctl -> v4l2_ioctl, open -> v4l2_open().
> You have to do that explicitly in your existing code. It does not
> abstract the API itself unlike libdrm.

You are right, no LD_PRELOAD. But same API as kernel, which is really
limiting -- see my other mail.

									Pavel