[FFmpeg-devel] [RFC] be more kind with wrong psm in mpeg ps

Måns Rullgård mans
Mon Apr 21 14:06:11 CEST 2008

Baptiste Coudurier wrote:
> Baptiste Coudurier wrote:
>> Hi,
>> M?ns Rullg?rd wrote:
>>> Michael Niedermayer wrote:
>>>> On Mon, Apr 07, 2008 at 04:36:41PM +0200, Baptiste Coudurier wrote:
>>>>> M?ns Rullg?rd wrote:
>>>>>> Baptiste Coudurier wrote:
>>>>>>> Hi,
>>>>>>> Attached patch make ps demuxer correctly detects lpcm files with wrong
>>>>>>> psm (mplayer and vlc plays them correctly).
>>>>>>> Should fix wrong_psm_lpcm.mpg on mplayerhq.
>>>>>>> I think those checks are reasonable. Comments ?
>>>>>> I don't like it.  It can break valid files.
>>>>> Question is does it ?
>>>>> I'd like some real measures of the effects of the psm considering vlc
>>>>> and mplayer ignore it and play many files.
>>>>> if psm says AC3 or DTS then fine, but if psm says private data or mpeg1
>>>>> audio, it's reasonable to guess that it is not what psm says.
>>>>> I think I'll ask for a vote on this, since I would really like being
>>>>> able to play those files.
>>>> I am in favor of having as many files as possible supported. So if this patch
>>>> makes files playable that arent currently and we have none that it breaks
>>>> then, iam in favor of the patch.
>>>> Maybe a compromise would be printing a "This file specifies an invalid codec
>>>> in the PSM"?
>>>> Also without checking the spec, what is invalid if a AC3/DTS/MP3/LPCM is
>>>> "private data"? IMHO if something else indicates a more specific type that
>>>> should override "private data". But maybe i misunderstood something?
>>> If the PSM says private data (stream_type == 6), there is no telling what
>>> it is, unless some descriptor or other identifies it.  AC3, DTS, and PCM
>>> are not supported by the ISO spec at all, and several incompatible
>>> extensions to handle these codecs exist, the most common being that found
>>> on DVDs.
>> Atm, if psm says private data, track is just ignored by lavf, however,
>> if track uses dvd private data mechanism, it is IMHO easy to support it.
>> Do we need a vote for this ? I'd really like lavf to support those files
>> like mplayer and vlc do.
> Ping

I still don't like it.  Idiots that create invalid files can blame

M?ns Rullg?rd
mans at mansr.com

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