[FFmpeg-user] VAAPI Decoding/Encoding with C code

[Victor dMdB]

Thanks for the response Mark!

I might be misreading the source code, but for decoding, doesn't
vaapi_decode_init
do all the heavy lifting? 
It seems to already call the functions and sets the variables you
mentioned.

So might the code be just:

avcodec_open2(codecCtx, codec,NULL);
vaapi_decode_init(codecCtx); 

On Fri, 2 Dec 2016, at 09:03 PM, Mark Thompson wrote:
> On 02/12/16 10:57, Victor dMdB wrote:
> > I was wondering if there were any examples of implementations with
> > avformatcontext?
> > 
> > I've looked at the source of ffmpeg vaapi implementation:
> > https://www.ffmpeg.org/doxygen/trunk/ffmpeg__vaapi_8c_source.html
> > 
> > and there is a reference to the cli values here
> > https://ffmpeg.org/pipermail/ffmpeg-user/2016-May/032153.html
> > 
> > But I'm not really sure how one actually implements the it within either
> > decoding or encoding pipeline?
> 
> Start by making an hwdevice.  This can be done with
> av_hwdevice_ctx_create(), or if you already have a VADisplay (for
> example, to do stuff in X via DRI[23]) you can use
> av_hwdevice_ctx_alloc() followed by av_hwdevice_ctx_init().
> 
> For a decoder:
> 
> Make the decoder as you normally would for software.  You must set an
> AVCodecContext.get_format callback.
> Start feeding data to the decoder.
> Once enough there is enough data to determine the output format, the
> get_format callback will be called (this will always happen before any
> output is generated).
> The callback has a set of possible formats to use, this will contain
> AV_PIX_FMT_VAAPI if your stream is supported (note that not all streams
> are supported for a given decoder - for H.264 the hwaccel only supports
> YUV 4:2:0 in 8-bit depth).
> Make an hwframe context for the output frames and a struct vaapi_context
> containing a decode context*.  See ffmpeg_vaapi.c:vaapi_decode_init() and
> its callees for this part.
> Attach your new hwframe context (AVCodecContext.hw_frames_ctx) and decode
> context (AVCodecContext.hwaccel_context) to the decoder.
> Once you return from the callback, decoding continues and will give you
> AV_PIX_FMT_VAAPI frames.
> If you need the output frames in normal memory rather than GPU memory,
> you can copy them back with av_hwframe_transfer_data().
> 
> For an encoder:
> 
> Find an hwframe context to use as the encoder input.  For a transcode
> case this can be the one from the decoder above, or it could be output
> from a filter like scale_vaapi.  If only have frames in normal memory,
> you need to make a new one here.
> Make the encoder as you normally would (you'll need to get the codec by
> name (like "h264_vaapi"), because it will not choose it by default with
> just the ID), and set AVCodecContext.hw_frames_ctx with your hwframe
> context.
> Now feed the encoder with the AV_PIX_FMT_VAAPI frames from your hwframe
> context.
> If you only have input frames in normal memory, you will need to upload
> them to GPU memory in the hwframe context with av_hwframe_transfer_data()
> before giving them to the encoder.
> 
> 
> - Mark
> 
> 
> * It is intended that struct vaapi_context will be deprecated completely
> soon, and this part will not be required (lavc will handle that context
> creation).
> 
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