[FFmpeg-devel] [PATCH v1] avcodec/av1dec: check if hwaccel is specificed

[Wang, Fei W]

On Fri, 2021-08-27 at 19:09 +0200, Hendrik Leppkes wrote:
> On Fri, Aug 27, 2021 at 1:54 PM Fei Wang <fei.w.wang at intel.com>
> wrote:
> > 
> > Since av1 decoder is only available for hw acceleration. This will
> > gives out more accurate information if this decoder used but
> > doesn't
> > specificed a hwaccel.
> > 
> > For example:
> > ffmpeg -c:v av1 -i INPUT OUTPUT
> > 
> > Signed-off-by: Fei Wang <fei.w.wang at intel.com>
> > ---
> > 1. This is improvement of patch for:
> > https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=4660
> > 
> >  libavcodec/av1dec.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> > index a69808f7b6..58a9deeb4e 100644
> > --- a/libavcodec/av1dec.c
> > +++ b/libavcodec/av1dec.c
> > @@ -452,15 +452,22 @@ static int get_pixel_format(AVCodecContext
> > *avctx)
> >      *fmtp++ = s->pix_fmt;
> >      *fmtp = AV_PIX_FMT_NONE;
> > 
> > -    ret = ff_thread_get_format(avctx, pix_fmts);
> > -    if (ret < 0)
> > -        return ret;
> > -
> >      /**
> > -     * check if the HW accel is inited correctly. If not, return
> > un-implemented.
> > +     * check if the HW accel is specificed. If not, return un-
> > implemented.
> >       * Since now the av1 decoder doesn't support native decode, if
> > it will be
> >       * implemented in the future, need remove this check.
> >       */
> > +    if (!avctx->hw_device_ctx) {
> > +        av_log(avctx, AV_LOG_ERROR, "The AV1 decoder requires a hw
> > acceleration"
> > +              " to be specified.\n");
> > +        return AVERROR(ENOSYS);
> > +    }
> > +
> 
> Not every hwaccel uses a hw_device_ctx. Its still perfectly valid and
> supported to use the old setup which overrides get_format/get_buffer2
> and sets avctx->hwaccel_context directly.
> You will not know if this is the case before get_format was called,
> so
> you cannot pre-detect it.

If so, the only way to fix is keep previous check with avctx->hwaccel
but change its log context like "The AV1 decoder requires a hw acceleration to be specified or the specified hw doesn't support AV1 decoding."

Btw, just for curious, which hwaccel are you using that doesn't set up
the hw_device_ctx?

> 
> Or in other words, this patch breaks my application, so its not a
> valid solution.
> 
> - Hendrik
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