[FFmpeg-devel] [PATCH 1/2] lavc/decode: re-allocate surface in ff_decode_get_hw_frames_ctx

[Hendrik Leppkes]

On Fri, Dec 27, 2019 at 9:59 AM Linjie Fu <linjie.fu at intel.com> wrote:
>
> Allow hw_frames_ctx to be recreated instead of just return if it exists.
>
> Move hw_frames_ctx check outside ff_decode_get_hw_frames_ctx, and check
> in relevant code.
>
> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> ---
>  libavcodec/decode.c | 2 +-
>  libavcodec/dxva2.c  | 8 +++++---
>  libavcodec/vdpau.c  | 9 +++++----
>  3 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index cd275ba..ad046d9 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -1229,7 +1229,7 @@ int ff_decode_get_hw_frames_ctx(AVCodecContext *avctx,
>          return AVERROR(ENOSYS);
>
>      if (avctx->hw_frames_ctx)
> -        return 0;
> +        av_buffer_unref(&avctx->hw_frames_ctx);
>      if (!avctx->hw_device_ctx) {
>          av_log(avctx, AV_LOG_ERROR, "A hardware frames or device context is "
>                  "required for hardware accelerated decoding.\n");


As mentioned in the other mail, this is not safe. An externally
provided hw_frames_ctx could be allocated with special requirements,
and shared with a renderer. If a user provides an external
hw_frames_ctx, then avcodec cannot just re-allocate it, instead we
would have to ask the user to do so.

- Hendrik