[FFmpeg-cvslog] r19091 - trunk/libavcodec/4xm.c

[Baptiste Coudurier]

On 6/5/2009 2:25 PM, Michael Niedermayer wrote:
> On Fri, Jun 05, 2009 at 02:09:05PM -0700, Baptiste Coudurier wrote:
>> On 6/5/2009 1:10 PM, Michael Niedermayer wrote:
>>> On Fri, Jun 05, 2009 at 10:12:14AM +0200, bcoudurier wrote:
>>>> Author: bcoudurier
>>>> Date: Fri Jun  5 10:12:14 2009
>>>> New Revision: 19091
>>>>
>>>> Log:
>>>> 4xm decoder uses get_buffer, set CODEC_CAP_DR1
>>> i think you broke several decoders with these changes, no i dont
>>> know which but
>>> CODEC_CAP_DR1 does not just mean the codec uses get_buffer()
>>> but it means it works with any get_buffer() implementation while
>>> lack of CODEC_CAP_DR1 means it requires the libavcodec internal get_buffer()
>> Interesting, I did misunderstand the Doxygen then:
>> /**
>>  * Codec uses get_buffer() for allocating buffers.
>>  * direct rendering method 1
>>  */
>> #define CODEC_CAP_DR1             0x0002
>>
>>> one case (that applies to 4xm IIRC) is that linesize == width*bpp is required
>>> by some decoders
>> Well, user can override the function in any case, so decoder must not
>> use get_buffer in AVCodecContext IMHO.
> 
> hmm, the original idea i think was that the user would not override
> get_buffer when CODEC_CAP_DR1 is not set but it seems not documented
> anywhere, this is of course not good
> 
> we either could fix the docs and call everyone who overrides get_buffer
> without a CODEC_CAP_DR1 buggy
> or
> change decoders to not use (re)get_buffer/release_buffer but the default
> code directly
> 
> IMHO, because overriding get_buffer without a set CODEC_CAP_DR1 always was
> buggy i think user apps should be fixed that do this

> I mean even if we change codecs to use default_*buffer() directly, user apps
> would still fail to work with old libavcodec
> thus IMHO this is a bug in the docs not the code

IMHO, codecs should be updated to use avcodec_default_get_buffer
directly which will avoid confusion.

Ideally users would not have to worry about setting or not get_buffer,
depending on codecs or CODEC_CAP_DR1, same for draw_horiz_band.

I think we should avoid bothering users more because of our lack for
documentation :)

I recognize that checking for AVCodecContext->codec->capabilities &
CODEC_CAP_DR1 is not so complicated either, if you insist.

I'll check decoders and revert/modify them on a per case basis once we
settled this.

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
FFmpeg maintainer                                  http://www.ffmpeg.org