[vlc-devel] [PATCH] switcher: Fix compilation with ffmpeg-0.10.2

[Rafaël Carré]

Le 2012-03-21 05:01, Richard Grenville a écrit :
> On Wed, Mar 21, 2012 at 03:41:33AM -0400, Rafaël Carré wrote:
>>> ---
>>> #define LIBAVCODEC_VERSION_MAJOR 53
>>> /* ... */
>>> #define FF_API_OLD_FF_PICT_TYPES (LIBAVCODEC_VERSION_MAJOR < 54)
>>> ---
>>>
>>> So ffmpeg should already have replaced FF_*_TYPE with the correct
>>> AV_PICTURE_TYPE_*, why this is not happening? Eventually I found these
>>> things in vlc's git tree, ./modules/codec/avcodec.h, which switch.c
>>> includes, too:
>>
>> Perhaps because your headers are too recent (LIBAVCODEC_VERSION_MAJOR >= 54)
> 
> Hmm? "#define LIBAVCODEC_VERSION_MAJOR 53", it's clearly written there.
> I use ffmpeg-0.10.2.
> 
> I did a test just now:
> ---
> $ cd /var/tmp/portage/media-video/vlc-2.0.1/work/vlc-2.0.1/modules/stream_out
> $ gcc -E -dD -I/usr/include/libavcodec -I../../include switcher.c | grep FF_P_TYPE
> #define FF_P_TYPE AV_PICTURE_TYPE_P
> #define AV_PICTURE_TYPE_P FF_P_TYPE
>         id->p_frame->pict_type = FF_P_TYPE;
>     case FF_P_TYPE:
> ---
> 
> Two circular macro definitions are there, and FF_P_TYPE is not replaced
> correctly. After I commented out the 3 "#define AV_PICTURE_TYPE_*
> FF_*_TYPE" lines in ./modules/codec/avcodec/avcodec.h, it worked as
> expected:
> 
> ---
> $ gcc -E -dD -I/usr/include/libavcodec -I../../include switcher.c | grep FF_P_TYPE
> #define FF_P_TYPE AV_PICTURE_TYPE_P
> ---
> 
> Obviously it's a VLC bug related to these 3 lines.
> 
>>
>>> ---
>>> #if LIBAVCODEC_VERSION_MAJOR < 54
>>> #   define AV_PICTURE_TYPE_B        FF_B_TYPE
>>> #   define AV_PICTURE_TYPE_I        FF_I_TYPE
>>> #   define AV_PICTURE_TYPE_P        FF_P_TYPE
>>> ---
>>>
>>> They are introduced in commit 8f24e725ff9945975f6d7232477cff7f7a8e2cff
>>> "avcodec: update to libavcodec 54", by Rafaël Carré, aka, you. Together
>>> with ffmpeg-0.10's code in avcodec.h and version.h, they generated a
>>> circular macro definition, replace A with B, then replace B with A...
>>
>> Weird, perhaps we need to add some ifdef.
>> I thought the code has been tested with different (old and new) versions
>> though.
>>
> 
> Perhaps the gcc version you use to test vlc handles circular macro
> definitions in a different fashion? Like, your gcc is smarter than mine.
> :-)
> 
>>> However I didn't pay attention to the compatiblity with older ffmpeg
>>> versions. I always use a fully updated system and don't quite understand
>>> what "older versions" mean. :-)
>>
>> It means 2 or 3 years old, perhaps more.
>>
>> e.g. try last Ubuntu LTS and VLC should continue to build (and run), or
>> error out at configure stage.
> 
> Thanks for the explanation. Looks like developing a software is truly
> much harder than submitting patches, so many things to consider. :-)

I pushed a patch based on yours (66da497b204), thanks