[mythtv-users] Varying data formats during digital reception

John Pilkington J.Pilk at tesco.net
Tue Nov 6 12:20:05 UTC 2012


On 06/11/12 10:38, Jose Paulo Moitinho de Almeida wrote:
> On Tuesday 06 November 2012, John Pilkington wrote:
>> On 05/11/12 23:26, JP Moitinho de Almeida wrote:
>>> On Monday 05 November 2012 18:40:21 John Pilkington wrote:
>>>> On 05/11/12 17:46, Jose Paulo Moitinho de Almeida wrote:
>>>>>> ...problem is, he has to get the program started before he can use the
>>>>>> editor to set the cutpoints...
>>>>>>
>>>>>> possible if you have sufficient padding before the actual content
>>>>>> starts, I suppose. But will the editor fail be
>>>>>> cause the format changed, even so?
>>>>>
>>>>> I am not at home but, effectively, using the editor is not possible.
>>>>> Editing those files past that point also hangs the frontend.
>>>>>
>>>>> But I can work with "tail/head -c" by iteration/bisection of the file,
>>>>> until I just capture the zone of the relevant point.
>>>>>
>>>>> I'll post that tonight.
>>>>>
>>>>> Regards
>>>>>
>>>>> ZP
>>>>
>>>> Or:  mv infile.mpg infile.mpg0
>>>>
>>>> dd bs=1M skip=35  count=40 if=infile.mpg0 of=infile.mpg
>>>>
>>>> adjust the skip number and see if it plays in Myth, then omit the count.
>>>
>>> The link has a 10 Mb clip where the format changes. With this short
>>> version the frontend gives up without hanging, but the problem is
>>> clearly there.
>>>
>>> http://dl.dropbox.com/u/20086953/myth_samples/12002_20121104214000.mpg
>>>
>>> (thanks for the dd, I was missing the skip option)
>>>
>>> Regards
>>>
>>> ZP
>>
>> For me vlc plays for 35 sec, mythtv as a recording (overwriting a short
>> recording made here) or as a video for about 30 sec until the presenter
>> walks on, then returns to the Watch Recordings screen.  If that's where
>> you see the problem it might be better to have more data after it.
>>
>> There's a change in aspect ratio just after the yellow countdown, but
>> that doesn't seem to be a problem.  I didn't notice it initially.
>>
>> You might find the vlc  'Tools > Codec info' informative.
>>
>> All in MythTV 0.25.3.
>>
>> John
>>
>
>
> The problem happens with the aspect ratio change, which played without
> problems in 0.25.
>
> After updating to 0.26 the video stops there and then the frontend player
> stops. With a longer sample the frontend player takes (much) longer to give
> up.
>
> The log is full of "AFD: Unknown decoding error" messages (text written from
> memory).
>
> Regards
>
> ZP

I've run ffmpeg -i from the start and from the middle of this file, 
which has been renamed to look like a local recording:
------------------
ffmpeg -i 1001_20121106090300.mpg 2>&1 | grep -C 4 stereo
   Duration: 00:00:35.96, start: 67743.186556, bitrate: 2332 kb/s
   Program 1
     Stream #0:0[0x21](por): Subtitle: dvb_teletext ([6][0][0][0] / 0x0006)
     Stream #0:1[0x200]: Video: h264 (Main) ([27][0][0][0] / 0x001B), 
yuv420p, 720x576 [SAR 16:11 DAR 20:11], 53.85 fps, 50 tbr, 90k tbn, 50 tbc
     Stream #0:2[0x201](por): Audio: aac_latm ([17][0][0][0] / 0x0011), 
48000 Hz, stereo, s16

-----------------------
dd bs=1M skip=5   if=1001_20121106090300.mpg of=tmp.mpg

ffmpeg -i tmp.mpg  2>&1 | grep -C 4 stereo
   Duration: 00:00:12.92, start: 67766.226556, bitrate: 3246 kb/s
   Program 1
     Stream #0:0[0x21](por): Subtitle: dvb_teletext ([6][0][0][0] / 0x0006)
     Stream #0:1[0x200]: Video: h264 (Main) ([27][0][0][0] / 0x001B), 
yuv420p, 720x576 [SAR 12:11 DAR 15:11], 61.14 fps, 50 tbr, 90k tbn, 50 tbc
     Stream #0:2[0x201](por): Audio: aac_latm ([17][0][0][0] / 0x0011), 
48000 Hz, stereo, s16
---------------

This email format make it difficult to see, but the main changes appear 
to be the aspect ratio and fps, which looks strange.

Without the grep, ffmpeg complains a lot and reports an audio format change.

[aac_latm @ 0x12aca00] audio config changed

[h264 @ 0x12ac040] non-existing PPS referenced
[h264 @ 0x12ac040] non-existing PPS 0 referenced
[h264 @ 0x12ac040] decode_slice_header error
[h264 @ 0x12ac040] no frame!

I tried it via UPnP on my Panasonic tv, too.  As a recording it played 
straight through to the end with no apparent aspect ratio change.  As a 
Video I get 'Cannot read file'.  It would be nice to understand this!

John P











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