[vlc] Re: Mainconcept encode play error

[Måns Rullgård]

Vaclav Koldus <vaclav.koldus at avpark.cz> writes:

> Måns Rullgård napsal(a):
>
>>Vaclav Koldus <vaclav.koldus at avpark.cz> writes:
>>
>>>>>Hi Pete!
>>>>>
>>>>>The problem with main concept H.264 encoded videos is indeed that
>>>>>these are mpeg files. Vlc can't recognize if the .mpeg file contains
>>>>>mpeg2 or h.264 stream. It just assumes it is a mpeg2 stream. Only
>>>>>solution I came with is to give up playing mpeg2 and consider all
>>>>>mpegs to be h264s. I don't know whether this stream can be decoded
>>>>>with ffmpeg.
>>>>>
>>>>>
>>>>The H.264 video is decoded correctly by ffmpeg.  The problem is
>>>>identifying it as being H.264 in the first place.  Normally a Program
>>>>Stream Map is included in MPEG-PS streams with non-MPEG2 video for
>>>>precisely this purpose.
>>>>
>>>>
>>>>
>>>Well, then there's only one thing to do. To patch ps/ts demuxer
>>>modules to corretly identify h264 streams. When you look
>>>into the source files ts.c and ps.c, you'll find out that this is
>>>implemented well. It seems that MC signs the stream incorrectly
>>>(or with their own id.) I'll have a look at it, it shouldn't be a big
>>>prob.
>>>
>>>
>>
>>The PS demuxer parses the PSM to determine the codecs for each stream.
>>If there is no PSM it defaults to MPEG video and audio.  As I said,
>>the file from Pete has no PSM.
>>
>>I haven't seen a sample from you, so I can't say what might be the
>>problem there.
>>
>>
>>
> I see it now too. MC H264 mpegs has no PSM indeed. However, this can be
> "hacked" like this:
>
>         else if( (i_id&0xf0) == 0xe0 && i_type == 0x00 )
>         {
>             es_format_Init( &tk->fmt, VIDEO_ES,
>             VLC_FOURCC('h','2','6','4') );
>         }
>
> Obviously, this isn't clean, but it forces vlc to use H264 decoder for
> these files.

Yes, that would make it play files with H.264 video.  Anything else,
like the more common MPEG2 files, would become unplayable.

> I'm affraid it can't be done cleanly, cause they have no PSM so
> there isn't any way how to recognize h264 from mpeg2 without PSM.
> This is arguable, because mpeg2 streams should have PSM, so it could
> be safe to assume that the file is h264 when there's no PSM.

Normally MPEG PS files without a PSM have MPEG2 video.  Assuming
anything else would probably cause more problems than it solved.

> Anyway, there's another prob. ffmpeg fails decoding this stream like
> this:
>
> [h264 @ 0xb7eae5b0]concealing 1620 DC, 1620 AC, 1620 MV errors
> [h264 @ 0xb7eae5b0]left block unavailable for requested intra4x4 mode
> -1
> at 0 2
> [h264 @ 0xb7eae5b0]error while decoding MB 0 2
> [h264 @ 0xb7eae5b0]concealing 1579 DC, 1579 AC, 1579 MV errors
> [h264 @ 0xb7eae5b0]left block unavailable for requested intra mode at 0 3
> [h264 @ 0xb7eae5b0]error while decoding MB 0 3
> [h264 @ 0xb7eae5b0]illegal short term buffer state detected
> [h264 @ 0xb7eae5b0]concealing 1534 DC, 1534 AC, 1534 MV errors
> vlc: h264.c:2584: mc_dir_part: Assertion `pic->data[0]' failed.
>
> I don't know anything about h264, so I can't see why is this happening.
> Please someone has an idea??

Is your file damaged in some way?  Is it cut from a longer file?  Can
you provide a sample showing this problem?

> Here comes the possibility to implement MC H.264 decoder (SDK). But this
> one isn't free.

FFmpeg should be able to decode almost all correct H.264 streams.  If
it fails, either ffmpeg or the file is broken.

-- 
Måns Rullgård
mru at inprovide.com

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