[FFmpeg-devel] [PATCH 38/42] fftools/ffmpeg: add support for multiview video

[James Almer]

On 9/3/2024 6:47 AM, Anton Khirnov wrote:
> Quoting James Almer (2024-08-31 15:56:24)
>> On 8/31/2024 4:44 AM, Anton Khirnov wrote:
>>> Quoting James Almer (2024-08-30 02:40:49)
>>>> On 8/29/2024 8:26 PM, Michael Niedermayer wrote:
>>>>> On Tue, Aug 27, 2024 at 05:05:18PM +0200, Anton Khirnov wrote:
>>>>>> This extends the syntax for specifying input streams in -map and complex
>>>>>> filtergraph labels, to allow selecting a view by view ID, index, or
>>>>>> position. The corresponding decoder is then set up to decode the
>>>>>> appropriate view and send frames for that view to the correct
>>>>>> filtergraph input(s).
>>>>>> ---
>>>>>>     doc/ffmpeg.texi           |  30 +++-
>>>>>>     fftools/cmdutils.c        |   2 +-
>>>>>>     fftools/cmdutils.h        |   2 +
>>>>>>     fftools/ffmpeg.h          |  45 ++++-
>>>>>>     fftools/ffmpeg_dec.c      | 355 +++++++++++++++++++++++++++++++++++++-
>>>>>>     fftools/ffmpeg_demux.c    |  24 ++-
>>>>>>     fftools/ffmpeg_filter.c   |  71 +++++---
>>>>>>     fftools/ffmpeg_mux_init.c |  29 +++-
>>>>>>     fftools/ffmpeg_opt.c      |  70 +++++++-
>>>>>>     9 files changed, 575 insertions(+), 53 deletions(-)
>>>>>
>>>>> breaks build on mingw64
>>>>>
>>>>> src/fftools/ffmpeg_dec.c: In function ‘packet_decode’:
>>>>> src/fftools/ffmpeg_dec.c:811:19: error: implicit declaration of function ‘ffs’ [-Werror=implicit-function-declaration]
>>>>>      811 |             pos = ffs(outputs_mask) - 1;
>>>>>          |                   ^~~
>>>>> cc1: some warnings being treated as errors
>>>>> make: *** [src/ffbuild/common.mak:81: fftools/ffmpeg_dec.o] Error 1
>>>>> make: *** Waiting for unfinished jobs....
>>>>>
>>>>> thx
>>>>
>>>> Would ff_clz(outputs_mask) work here?
>>>
>>> In principle yes, but it's private and I'd rather not include a private
>>> header in ffmpeg CLI.
>>>
>>> We could either make it public, or I could add a ffs() implementation
>>> for Windows to compat/. Anyone has a preference?

Also, ffs() is posix. Is Windows the only target that lacks it?

>>
>> I think i prefer making ff_clz public in common.h.
> 
> common.h is the wrong place for anything
> 
>> It has an optimized version not exclusive to Windows using a gcc/clang
>> builtin, and even one specific for riscv.
> 
> Which would not be visible to ffmpeg CLI anyway.

True. We could make it aware of it by setting HAVE_AV_CONFIG_H during 
compilation, but that's kinda dirty.

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