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

[Baptiste Coudurier]

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.

-- 
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