[mythtv-users] Playback issue with certain video

Mark Greenwood fatgerman at gmail.com
Sun Oct 21 13:41:33 UTC 2012


On 21 Oct 2012, at 11:40, Martin Moores wrote:

> On 20 October 2012 22:37, Jean-Yves Avenard <jean-yves at avenard.org> wrote:
>> 
>> 
>> On Sunday, 21 October 2012, Mark Greenwood wrote:
>>> 
>>> 
>>> I haven't tried playing it on my myth box, but I can tell you it's MJPEG,
>>> not MPEG2, which might be why your myth box is having trouble with it. File
>>> seems OK for an MJPEG file though, it's 30fps at 640x480 resolution. The
>>> audio is 8-bit PCM, mono, 8KHz, which is unusual and could also be the
>>> source of the problem.
>>> 
>>> 
>> The format of the audio is irrelevant, myth will perform any conversion on
>> the fly as required and is able to play 8, 16, 24, 32 bits integer and float
>> audio
>> 
> 
> Thanks for the replies both.  If Myth doesn't know what it is and
> guesses wrong, then I guess that could be the issue.  I have no idea
> how to tell though.
> 
> Hopefully someone will get chance to take a look

OK I've tried it on my myth box (0.25) and I get similar playback errors to you - it plays but it stutters. 

Mine does recognise it as MJPG :

2012-10-21 14:26:53.641 AFD: Opened codec 0xa3092d10, id(MJPEG) type(Video)
2012-10-21 14:26:53.641 AFD: codec PCM_U8 has 1 channels
2012-10-21 14:26:53.641 AFD: codec PCM_U8 has 1 channels
2012-10-21 14:26:53.641 AFD: Opened codec 0xa3093580, id(PCM_U8) type(Audio)
2012-10-21 14:26:53.923 AO: Resampling from 8 kHz to 32 kHz with quality medium
2012-10-21 14:26:53.951 AO: Opening audio device 'hdmi:CARD=NVidia,DEV=0' ch 2(1) sr 32000 sf signed 32 bit reenc 0
2012-10-21 14:26:53.962 AudioPlayer: Enabling Audio

 After that I get loads of

2012-10-21 14:26:59.551 Player(3): Waited 100ms for video buffers ffffffffffffffffffffffAf
2012-10-21 14:26:59.551 Player(3): Timed out waiting for frames, and
			there are not enough free frames. Discarding buffered frames.
2012-10-21 14:26:59.560 Player(3): Waited 100ms for video buffers AAAAAAAAAAAAAAAAAAAAAAAA
2012-10-21 14:27:00.096 ALSA, Error: WriteAudio: buffer underrun
2012-10-21 14:27:00.823 Player(3): Waited 100ms for video buffers fffffffffffffffffffffAff

etc etc.

As an experiment I bunged it into avidemux and tried two variants:

Copy the video stream but convert the audio to MP3 - same playback problem.
Convert the video to x264 but keep the audio stream the same - plays perfectly.

So it's either something dodgy with your file (avidemux thinks it's fine) or myth has issues with MJPG.

Mark

Mark


> 
> Cheers
> 
> Martin
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