[FFmpeg-devel] [PATCH v4 2/2] ffmpeg_opt: consider HW acceleration method when selecting decoder

[Anton Khirnov]

Quoting Xiang, Haihao (2022-08-02 09:56:01)
> From: Haihao Xiang <haihao.xiang at intel.com>
> 
> Usually a HW decoder is expected when user specifies a HW acceleration
> method via -hwaccel option, however the current implementation doesn't
> take HW acceleration method into account, it is possible to select a SW
> decoder.
> 
> For example:
> $ ffmpeg -hwaccel vaapi -i av1.mp4 -f null -
> $ ffmpeg -hwaccel nvdec -i av1.mp4 -f null -
> $ ffmpeg -hwaccel vdpau -i av1.mp4 -f null -
> [...]
> Stream #0:0 -> #0:0 (av1 (libdav1d) -> wrapped_avframe (native))
> 
> libdav1d is selected in this case even if vaapi, nvdec or vdpau is
> specified.
> 
> After applying this patch, the native av1 decoder (with vaapi, nvdec or
> vdpau support) is selected for decoding(libdav1d is still used for
> probing format).
> $ ffmpeg -hwaccel vaapi -i av1.mp4 -f null -
> $ ffmpeg -hwaccel nvdec -i av1.mp4 -f null -
> $ ffmpeg -hwaccel vdpau -i av1.mp4 -f null -
> [...]
> Stream #0:0 -> #0:0 (av1 (native) -> wrapped_avframe (native))
> 
> Tested-by: Mario Roy <marioeroy at gmail.com>
> Signed-off-by: Haihao Xiang <haihao.xiang at intel.com>
> ---
>  fftools/ffmpeg_opt.c | 31 +++++++++++++++++++++++++++----
>  1 file changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index cf0c31bdc2..db51cca66d 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -857,7 +857,9 @@ static const AVCodec *find_codec_or_die(const char *name, enum AVMediaType type,
>      return codec;
>  }
>  
> -static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVStream *st)
> +static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVStream *st,
> +                                     enum HWAccelID hwaccel_id, enum AVHWDeviceType hwaccel_device_type)
> +
>  {
>      char *codec_name = NULL;
>  
> @@ -868,8 +870,29 @@ static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVSt
>          if (recast_media && st->codecpar->codec_type != codec->type)
>              st->codecpar->codec_type = codec->type;
>          return codec;
> -    } else
> +    } else {
> +        if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
> +            hwaccel_id == HWACCEL_GENERIC &&
> +            hwaccel_device_type != AV_HWDEVICE_TYPE_NONE) {
> +            const AVCodec *c;
> +            void *i = NULL;
> +
> +            while ((c = av_codec_iterate(&i))) {
> +                const AVCodecHWConfig *config;
> +
> +                if (c->id != st->codecpar->codec_id ||
> +                    !av_codec_is_decoder(c))
> +                    continue;
> +
> +                for (int j = 0; config = avcodec_get_hw_config(c, j); j++) {
> +                    if (config->device_type == hwaccel_device_type)
> +                        return c;

Maybe a verbose-level log message like

"Selecting decoder '%s' because of requested hwaccel method %s\n",
c->name, av_hwdevice_get_type_name(hwaccel_device_type)

would be appropriate. No need to send a new patch, just add it (or not,
as you like) and push.

-- 
Anton Khirnov