[FFmpeg-devel] [PATCH 1/6] doc/v4l2_m2m: Add documentation

[Gyan]

On 13-01-2020 09:41 am, Andriy Gelman wrote:
> From: Andriy Gelman <andriy.gelman at gmail.com>
>
> Signed-off-by: Andriy Gelman <andriy.gelman at gmail.com>
> ---
>   doc/decoders.texi | 12 ++++++++++++
>   doc/encoders.texi | 27 +++++++++++++++++++++++++++
>   2 files changed, 39 insertions(+)
>
> diff --git a/doc/decoders.texi b/doc/decoders.texi
> index f18226b3504..222f681810b 100644
> --- a/doc/decoders.texi
> +++ b/doc/decoders.texi
> @@ -86,6 +86,18 @@ AVS2-P2/IEEE1857.4 video decoder wrapper.
>   
>   This decoder allows libavcodec to decode AVS2 streams with davs2 library.
>   
> + at section v4l2m2m
> +
> + at command{ffmpeg} supports a set of v4l2m2m wrappers for interfacing with
> +hardware decoders. Depending on the hardware's capabilties the following decoders may be selected:
> +h264, hevc, mpeg1, mpeg2, mpeg4, h263, vc1, vp8, and vp9.

If these decoders are available through lavc API then replace ffmpeg 
with libavcodec. Is there a command for a user to identify which 
decoder/encoders are available?

Also,  s/capabilties/capabilities

> +
> +To use a specifix decoder append a  _v4l2m2m suffix. For example to select h264
s/specifix/specific

> +decoder use:
> + at example
> +ffmpeg -codec:v h264_v4l2m2m -i INPUT OUTPUT
> + at end example
> +
>   @c man end VIDEO DECODERS
>   
>   @chapter Audio Decoders
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 61e674cf968..6cb43aedbce 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -3117,6 +3117,33 @@ required to produce a stream usable with all decoders.
>   
>   @end table
>   
> + at section v4l2m2m
> +
> + at command{ffmpeg} supports a set of v4l2m2m wrappers for interfacing with hardware encoders.
> +Depending on the hardware's capabilties the following encoders may be selected:
> +mpeg4, h263, h264, hevc, and vp8.

Same notes as for decoders.

> +
> +To use a specific encoder append _v4l2m2m suffix. For example to select h264 use:
> + at example
> +ffmpeg -i INPUT [-pix_fmt pixfmt] -codec:v h264_v4l2m2m OUTPUT
> + at end example
> +In some cases, it may be necessary to insert a pixel format conversion with
> + at code{-pix_fmt} option. This is required if the pixel format of the input does not
> +match the format of the encoder. If there is a mismatch, @command{ffmpeg} will
> +exit and specify the required pixfmt to use.
> +
> +The following standard libavcodec options are supported:
> + at itemize
> + at item
> + at option{g} / @option{gop_size}
> + at item
> + at option{qpel}
> + at item
> + at option{qmin}
> + at item
> + at option{qmax}
> + at end itemize
> +

I see both the decoder and encoder wrappers have options for nb of 
capture and output buffers. Should document these with description, 
range and default values.

>   @section vc2
>   
>   SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed at

Thanks,
Gyan