[FFmpeg-devel] [PATCH v5 1/2] lavc: add HWACCEL_CAP_RESET_WITHOUT_UNINIT capacity for hwaccel

[Xiang, Haihao]

On Mon, 2022-11-14 at 09:16 +0800, Fei Wang wrote:
> The capacity can avoid hwaccel being uninited when do the reset. It
> provides the method for hwaccel if it still want to use the previous
> initialized configuration after reset. And the configuration can be
> updated in AVHWAccel.init() if needed.
> 
> For example, when use vaapi vp9 decode dynamic resolution clips, need
> to avoid changing vaContext in avctx->internal->hwaccel_priv_data if
> current frame resolution change and it reference a pervious frame with
> different resolution. Otherwise reference frame's information bound
> in vaContext will be lost, then corrupt current frame.
> 
> Signed-off-by: Fei Wang <fei.w.wang at intel.com>
> ---
> update:
> 1. consider the case of va_config/va_context equal to 0.
> 
>  libavcodec/decode.c   | 10 ++++++----
>  libavcodec/hwconfig.h |  7 +++++++
>  2 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index 6be2d3d6ed..cfada048e8 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -1109,7 +1109,7 @@ 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)
> @@ -1134,10 +1134,12 @@ static int hwaccel_init(AVCodecContext *avctx,
>  
>  static void hwaccel_uninit(AVCodecContext *avctx)
>  {
> -    if (avctx->hwaccel && avctx->hwaccel->uninit)
> -        avctx->hwaccel->uninit(avctx);
> +    if (avctx->hwaccel && !(avctx->hwaccel->caps_internal &
> HWACCEL_CAP_RESET_WITHOUT_UNINIT)) {
> +        if (avctx->hwaccel->uninit)
> +            avctx->hwaccel->uninit(avctx);
>  
> -    av_freep(&avctx->internal->hwaccel_priv_data);
> +        av_freep(&avctx->internal->hwaccel_priv_data);
> +    }
>  
>      avctx->hwaccel = NULL;
>  
> diff --git a/libavcodec/hwconfig.h b/libavcodec/hwconfig.h
> index 721424912c..5fb4e06d5f 100644
> --- a/libavcodec/hwconfig.h
> +++ b/libavcodec/hwconfig.h
> @@ -25,6 +25,13 @@
>  
>  #define HWACCEL_CAP_ASYNC_SAFE      (1 << 0)
>  
> +/**
> + * The hwaccel supports reset without calling back AVHWAccel.uninit()
> + * and realloc avctx->internal->hwaccel_priv_data.
> + *
> + * New configuration can set up through AVHWAccel.init().
> + */
> +#define HWACCEL_CAP_RESET_WITHOUT_UNINIT     (1 << 1)
>  
>  typedef struct AVCodecHWConfigInternal {
>      /**

Patchset LGTM and works well for me. After applying this patchset, I can get the
same md5 values when running the commands below for vp9 clips with resolution
change.

$ ffmpeg -c:v libvpx-vp9 -i input.webm -autoscale 0 -f md5 -
$ ffmpeg -hwaccel vaapi -i input.webm -pix_fmt yuv420p -f md5 -

Thanks
Haihao