diff mbox

Live TV problem with 1.7.15

Message ID 201006082124.40356.vdr@pickles.me.uk
State New
Headers

Commit Message

Dave P June 8, 2010, 8:24 p.m. UTC 
  (I'll start a new thread as my problem may not be the same as the one 
posted earlier).

VDR 1.7.15 will not record or show live TV from my DVB-T card - 1.7.14 was 
fine. On startup I see this message in the log:

Jun  8 16:24:14 vdr: [18819] frontend 0/0 provides DVB-T with unknown 
modulations ("DST DVB-T")

The problem seems to be in the new code in dvbdevice.c. My card returns 
frontendInfo.caps = 0xb0201, ie the FE_CAN_QAM_AUTO bit is set but not any 
of the individual QAM bits. Hence the logic in 
cDvbDevice::ProvidesTransponder() incorrectly decides that the card cannot 
receive any channel.

The simple patch (attached) fixes the problem but I'm not sure that it 
doesn't break something else.

Dave

Comments

VDRU VDRU June 8, 2010, 8:36 p.m. UTC | #1 
I'm not sure what FE_CAN_QAM_AUTO is supposed to represent exactly so
the problem may not be in VDR, but rather your cards driver not
accurately reporting it's capabilities.  In which case, the driver
needs to be fixed of course.
Dave P June 9, 2010, 6:13 p.m. UTC | #2 
On Tuesday 08 Jun 2010, VDR User wrote:
> I'm not sure what FE_CAN_QAM_AUTO is supposed to represent exactly so
> the problem may not be in VDR, but rather your cards driver not
> accurately reporting it's capabilities.  In which case, the driver
> needs to be fixed of course.

The card is a Twinhan DST DVB-T using the bttv driver. I'm not an expert at 
reading kernel source, but in drivers/media/dvb/bt8xx/dst.c it does seem 
that FE_CAN_QAM_AUTO is unconditionally set. The card documentation 
doesn't specify whether the device can in fact handle all possible QAM 
settings.

Dave
Klaus Schmidinger June 11, 2010, 1:08 p.m. UTC | #3 
On 09.06.2010 20:13, Dave P wrote:
> On Tuesday 08 Jun 2010, VDR User wrote:
>> I'm not sure what FE_CAN_QAM_AUTO is supposed to represent exactly so
>> the problem may not be in VDR, but rather your cards driver not
>> accurately reporting it's capabilities.  In which case, the driver
>> needs to be fixed of course.
> 
> The card is a Twinhan DST DVB-T using the bttv driver. I'm not an expert at 
> reading kernel source, but in drivers/media/dvb/bt8xx/dst.c it does seem 
> that FE_CAN_QAM_AUTO is unconditionally set. The card documentation 
> doesn't specify whether the device can in fact handle all possible QAM 
> settings.

My understanding of the FE_CAN_QAM_... flags is that the driver must
tell the application which modulations it can handle. If FE_CAN_QAM_AUTO
is set, the application doesn't need to tell the driver which modulation
to use, because the driver (or better: the device) can detect it automatically.
If a driver only sets FE_CAN_QAM_AUTO, the applications can't know which of the
various modulations the device can actually handle. I don't think that
FE_CAN_QAM_AUTO is a synonym for "can handle *all* modulations".

The simplest fix (if it is unknown which modulations the device can actually
handle) is probably to set all FE_CAN_QAM_... flags in the driver.

Your patch is not a solution, only a workaround. It would prevent drivers
that can actually handle only a subset of modulations, but do have "auto"
capability, from being properly handled by the application.

Klaus
diff mbox

Patch

--- dvbdevice.c.orig    2010-05-01 10:47:13.000000000 +0100
+++ dvbdevice.c 2010-06-08 21:17:08.000000000 +0100
@@ -710,6 +710,7 @@ 
         if (frontendInfo.caps & FE_CAN_QAM_64)  { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(QAM_64, ModulationValues)); }
         if (frontendInfo.caps & FE_CAN_QAM_128) { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(QAM_128, ModulationValues)); }
         if (frontendInfo.caps & FE_CAN_QAM_256) { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(QAM_256, ModulationValues)); }
+        if (frontendInfo.caps & FE_CAN_QAM_AUTO) { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(QAM_AUTO, ModulationValues)); }
         if (frontendInfo.caps & FE_CAN_8VSB)    { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(VSB_8, ModulationValues)); }
         if (frontendInfo.caps & FE_CAN_16VSB)   { numProvidedSystems++; p += sprintf(p, ",%s", MapToUserString(VSB_16, ModulationValues)); }
         if (frontendInfo.caps & FE_CAN_TURBO_FEC){numProvidedSystems++; p += sprintf(p, ",%s", "TURBO_FEC"); }
@@ -914,11 +915,11 @@ 
   cDvbTransponderParameters dtp(Channel->Parameters());
   if (dtp.System() == SYS_DVBS2 && frontendType == SYS_DVBS ||
      dtp.Modulation() == QPSK     && !(frontendInfo.caps & FE_CAN_QPSK) ||
-     dtp.Modulation() == QAM_16   && !(frontendInfo.caps & FE_CAN_QAM_16) ||
-     dtp.Modulation() == QAM_32   && !(frontendInfo.caps & FE_CAN_QAM_32) ||
-     dtp.Modulation() == QAM_64   && !(frontendInfo.caps & FE_CAN_QAM_64) ||
-     dtp.Modulation() == QAM_128  && !(frontendInfo.caps & FE_CAN_QAM_128) ||
-     dtp.Modulation() == QAM_256  && !(frontendInfo.caps & FE_CAN_QAM_256) ||
+     dtp.Modulation() == QAM_16   && !(frontendInfo.caps & (FE_CAN_QAM_16 | FE_CAN_QAM_AUTO)) ||
+     dtp.Modulation() == QAM_32   && !(frontendInfo.caps & (FE_CAN_QAM_32 | FE_CAN_QAM_AUTO)) ||
+     dtp.Modulation() == QAM_64   && !(frontendInfo.caps & (FE_CAN_QAM_64 | FE_CAN_QAM_AUTO)) ||
+     dtp.Modulation() == QAM_128  && !(frontendInfo.caps & (FE_CAN_QAM_128 | FE_CAN_QAM_AUTO)) ||
+     dtp.Modulation() == QAM_256  && !(frontendInfo.caps & (FE_CAN_QAM_256 | FE_CAN_QAM_AUTO)) ||
      dtp.Modulation() == QAM_AUTO && !(frontendInfo.caps & FE_CAN_QAM_AUTO) ||
      dtp.Modulation() == VSB_8    && !(frontendInfo.caps & FE_CAN_8VSB) ||
      dtp.Modulation() == VSB_16   && !(frontendInfo.caps & FE_CAN_16VSB) ||