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

Andriy Gelman andriy.gelman at gmail.com
Mon Jan 13 18:32:08 EET 2020


On Mon, 13. Jan 10:56, Gyan wrote:
> 
> 
> 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. 

Thanks, will update.

> Is there a command for a user to identify which decoder/encoders
> are available?

At the moment this doesn't exist. 
But I do have a patch that lists the supported encoders/decoders. 
I'll send this in the next version.

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

will update both. 

> 
> > +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.

yep, will add this. 

Thanks, 
-- 
Andriy


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