Weird recording problem

  Hi,

It's the same problem I had in France with the channel TNT "France 4". I 
proposed this dirty patch in May 2010, without understanding why :


I use it since without problem.

Senufo

> Date: Fri, 03 Jun 2011 22:33:53 +0200
> From: Johan Andersson<jna@jna.pp.se>
> Subject: Re: [vdr] Weird recording problem
> To: vdr@linuxtv.org
> Message-ID:<4DE94531.2010103@jna.pp.se>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> Klaus,
>
> I got a new reply from Teracom, where they had looked into this and
> could not see any problem on their end. They did say they had recently
> changed coding platform for TV6 though but it produced correct codes.
>
> So, I did some further analysis of this, and I believe now the error is
> in vdr/remux.c.
>
> It seems the 'new coding platform', before an I-frame, always puts the
> picture startcode, ie '00000100' at the end of the TS packet. This means
> that the code:
>
>       independentFrame = ((Data[i + 2]>>  3)&  0x07) == 1; // I-Frame
>
> looks at the wrong byte, as i+2>  TS_SIZE
>
> For non-I frames it can appear anywhere in the packet. The idea seems to
> be that an I-frame is always at the start of a TS-packet, do not ask me why.
>
> So, your instinct of rejecting my suggestion for a patch was correct.
>
> I have sample TS data of this stream, or dvbsnoop output of the relevant
> PID, if you are interested.
>
> /Johan
>
>
> Johan Andersson skrev 2011-05-29 19:14:
>> [...]
>> I got a very positive sounding response from Teracom. I got the
>> impression they are really going to fix this. For anyone else interested
>> I simply mailed their support address on their homepage
>> http://www.teracom.se, ie: kundtjanst@teracom.se
>>
>>
>> /Johan
>>
>>
>> Klaus Schmidinger skrev 2011-05-28 23:55:
>>> On 28.05.2011 10:57, Johan Andersson wrote:
>>>>
>>>> I sent off a question to customer support at Teracom and got a reply
>>>> indicating that they do have an error relating to these channels in
>>>> their 'coding platform'.
>>>
>>> Thanks for actually doing this - finally a broadcaster who at
>>> least admits *they* have a problem ;-)
>>>
>>>> 'Your problem seems to relate to the error we have', was their
>>>> statement. They had no due date for fixing it though.
>>>
>>> Maybe they would give this more priority if more people contacted
>>> them about this. Once replying to inquiries takes up a considerable
>>> amount of their time, they might consider doing something about it.
>>> Perhaps you should post here how to contact them, so other viewers
>>> of their channels could also bother them ;-)
>>>
>>> Klaus
>>>
>
>
  

Yes, I have a similar patch and it works nicely too.
It's just that it does not work for the reason I thought,
namely that the stream held an illegal code.

I think it works because it detects that the starting code is at the end 
of a packet and this stream always starts an I-frame in the next
packet when the '00000100' is at the end of this packet.

That is 'i+2 > TS_SIZE' meaning Data[i+2] is before the payload of the 
next packet. This is what I currently believe.

/Johan



Senufo skrev 2011-06-06 15:23:
> Hi,
>
> It's the same problem I had in France with the channel TNT "France 4". I
> proposed this dirty patch in May 2010, without understanding why :
>
> --- remux.c 2010-05-04 14:55:50.000000000 +0200
> +++ remux.c.orig 2010-05-04 21:57:38.000000000 +0200
> @@ -960,6 +960,7 @@
> return Processed; // flush everything before this new frame
> newFrame = true;
> independentFrame = ((Data[i + 2] >> 3) & 0x07) == 1; // I-Frame
> + if (((Data[i + 2] >> 3) & 0x07) == 0) { independentFrame = 1;}
> if (synced) {
> if (framesPerPayloadUnit <= 1)
> scanning = false;
>
> I use it since without problem.
>
> Senufo
>
>> Date: Fri, 03 Jun 2011 22:33:53 +0200
>> From: Johan Andersson<jna@jna.pp.se>
>> Subject: Re: [vdr] Weird recording problem
>> To: vdr@linuxtv.org
>> Message-ID:<4DE94531.2010103@jna.pp.se>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>>
>> Klaus,
>>
>> I got a new reply from Teracom, where they had looked into this and
>> could not see any problem on their end. They did say they had recently
>> changed coding platform for TV6 though but it produced correct codes.
>>
>> So, I did some further analysis of this, and I believe now the error is
>> in vdr/remux.c.
>>
>> It seems the 'new coding platform', before an I-frame, always puts the
>> picture startcode, ie '00000100' at the end of the TS packet. This means
>> that the code:
>>
>> independentFrame = ((Data[i + 2]>> 3)& 0x07) == 1; // I-Frame
>>
>> looks at the wrong byte, as i+2> TS_SIZE
>>
>> For non-I frames it can appear anywhere in the packet. The idea seems to
>> be that an I-frame is always at the start of a TS-packet, do not ask
>> me why.
>>
>> So, your instinct of rejecting my suggestion for a patch was correct.
>>
>> I have sample TS data of this stream, or dvbsnoop output of the relevant
>> PID, if you are interested.
>>
>> /Johan
>>
>>
>> Johan Andersson skrev 2011-05-29 19:14:
>>> [...]
>>> I got a very positive sounding response from Teracom. I got the
>>> impression they are really going to fix this. For anyone else interested
>>> I simply mailed their support address on their homepage
>>> http://www.teracom.se, ie: kundtjanst@teracom.se
>>>
>>>
>>> /Johan
>>>
>>>
>>> Klaus Schmidinger skrev 2011-05-28 23:55:
>>>> On 28.05.2011 10:57, Johan Andersson wrote:
>>>>>
>>>>> I sent off a question to customer support at Teracom and got a reply
>>>>> indicating that they do have an error relating to these channels in
>>>>> their 'coding platform'.
>>>>
>>>> Thanks for actually doing this - finally a broadcaster who at
>>>> least admits *they* have a problem ;-)
>>>>
>>>>> 'Your problem seems to relate to the error we have', was their
>>>>> statement. They had no due date for fixing it though.
>>>>
>>>> Maybe they would give this more priority if more people contacted
>>>> them about this. Once replying to inquiries takes up a considerable
>>>> amount of their time, they might consider doing something about it.
>>>> Perhaps you should post here how to contact them, so other viewers
>>>> of their channels could also bother them ;-)
>>>>
>>>> Klaus
>>>>
>>
>>
>
>
> _______________________________________________
> vdr mailing list
> vdr@linuxtv.org
> http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
>
> .
>