[FFmpeg-devel] [PATCH 2/2] lavc/vaapi_decode: recreate hw_frames_ctx without destroy va_context

[Hendrik Leppkes]

On Sun, Jul 7, 2019 at 6:41 AM Linjie Fu <linjie.fu at intel.com> wrote:
>
> VP9 allows resolution changes per frame. Currently in VAAPI, resolution
> changes leads to va context destroy and reinit. This will cause
> reference frame surface lost and produce garbage.
>
> As libva allows re-create surface separately without changing the
> context, this issue could be handled by only recreating hw_frames_ctx.
>
> Could be verified by:
> ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -i
> ./resolutions.ivf
> -pix_fmt p010le -f rawvideo -vframes 20 -y vaapi.yuv
>
> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> ---
>  libavcodec/decode.c       |  8 ++++----
>  libavcodec/vaapi_decode.c | 40 ++++++++++++++++++++++------------------
>  2 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index 0863b82..a81b857 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -1254,7 +1254,6 @@ int ff_decode_get_hw_frames_ctx(AVCodecContext *avctx,
>
>      frames_ctx = (AVHWFramesContext*)avctx->hw_frames_ctx->data;
>
> -
>      if (frames_ctx->initial_pool_size) {
>          // We guarantee 4 base work surfaces. The function above guarantees 1
>          // (the absolute minimum), so add the missing count.
> @@ -1333,7 +1332,7 @@ static int hwaccel_init(AVCodecContext *avctx,
>          return AVERROR_PATCHWELCOME;
>      }
>
> -    if (hwaccel->priv_data_size) {
> +    if (hwaccel->priv_data_size && !avctx->internal->hwaccel_priv_data) {
>          avctx->internal->hwaccel_priv_data =
>              av_mallocz(hwaccel->priv_data_size);
>          if (!avctx->internal->hwaccel_priv_data)
> @@ -1397,8 +1396,9 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
>
>      for (;;) {
>          // Remove the previous hwaccel, if there was one.
> -        hwaccel_uninit(avctx);
> -
> +        // VAAPI allows reinit hw_frames_ctx only
> +        if (choices[0] != AV_PIX_FMT_VAAPI_VLD)
> +            hwaccel_uninit(avctx);
>          user_choice = avctx->get_format(avctx, choices);

Having VAAPI specific code in this generic code path (or any hwaccel
specific code) seems like a design flaw, and should perhaps be
adressed by a generic improvement, instead of VAAPI specific hacks.

- Hendrik