[FFmpeg-devel] [PATCH] libavcodec/vp9: Fix VP9 dynamic resolution changing decoding on VAAPI.

Hendrik Leppkes h.leppkes at gmail.com
Tue May 28 11:43:05 EEST 2019


On Tue, May 28, 2019 at 9:46 AM Yan Wang <yan.wang at linux.intel.com> wrote:
>
>
> On 5/28/2019 3:16 PM, Hendrik Leppkes wrote:
> > On Tue, May 28, 2019 at 8:57 AM Yan Wang <yan.wang at linux.intel.com> wrote:
> >> When the format change, the VAAPI context cannot be destroyed.
> >> Otherwise, the reference frame surface will lost.
> >>
> >> Signed-off-by: Yan Wang <yan.wang at linux.intel.com>
> >> ---
> >>   libavcodec/decode.c | 6 ++++++
> >>   1 file changed, 6 insertions(+)
> >>
> >> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> >> index 6c31166ec2..3eda1dc42c 100644
> >> --- a/libavcodec/decode.c
> >> +++ b/libavcodec/decode.c
> >> @@ -1397,7 +1397,9 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
> >>
> >>       for (;;) {
> >>           // Remove the previous hwaccel, if there was one.
> >> +#if !CONFIG_VP9_VAAPI_HWACCEL
> >>           hwaccel_uninit(avctx);
> >> +#endif
> >>
> >>           user_choice = avctx->get_format(avctx, choices);
> >>           if (user_choice == AV_PIX_FMT_NONE) {
> >> @@ -1479,7 +1481,11 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
> >>                      "missing configuration.\n", desc->name);
> >>               goto try_again;
> >>           }
> >> +#if CONFIG_VP9_VAAPI_HWACCEL
> >> +        if (hw_config->hwaccel && !avctx->hwaccel) {
> >> +#else
> >>           if (hw_config->hwaccel) {
> >> +#endif
> >>               av_log(avctx, AV_LOG_DEBUG, "Format %s requires hwaccel "
> >>                      "initialisation.\n", desc->name);
> >>               err = hwaccel_init(avctx, hw_config);
> >> --
> >> 2.17.2
> >>
> > This change feels just wrong. First of all, preprocessors are
> > absolutely the wrong way to go about this.
>
> Sorry for this. I am new guy for ffmpeg development. What way should be
>
> better? I can refine it.
>
> > Secondly, if the frames need to change size, or surface format, then
> > this absolutely needs to be called, doesn't it?
>
> Based on VP9 spec, the frame resolution can be changed per frame. But
> current
>
> frame will need refer to previous frame still. So if destroy the VAAPI
> context, it
>
> will cause reference frame surface in VAAPI driver lost.
>
> In fact, this patch is for the issue:
>
> https://github.com/intel/media-driver/issues/629
>
> its 2nd frame (128x128) will refer to the 1st frame (256x256).
>

This may work if the frame size decreases, but what if it increases?
Then the frame buffers in the pool are too small, and anything could
go wrong.
This won't be an easy issue to solve, and needs very careful design.

- Hendrik


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