[FFmpeg-devel] [PATCH 6/7] avcodec: allow multiple hwaccels for the same codec/pixfmt

[Philip Langdale]

On Tue,  3 Oct 2017 15:15:17 +0200
wm4 <nfxjfg at googlemail.com> wrote:

> Currently, AVHWAccels are looked up using a (codec_id, pixfmt) tuple.
> This means it's impossible to have 2 decoders for the same codec and
> using the same opaque hardware pixel format.
> 
> This breaks merging Libav's CUVID hwaccel. FFmpeg has its own CUVID
> support, but it's a full stream decoder, using NVIDIA's codec parser.
> The Libav one is a true hwaccel, which is based on the builtin
> software decoders.
> 
> Fix this by introducing another field to disambiguate AVHWAccels, and
> use it for our CUVID decoders. FF_CODEC_CAP_HWACCEL_REQUIRE_CLASS
> makes this mechanism backwards compatible and optional.
> ---
>  libavcodec/Makefile   |  1 +
>  libavcodec/avcodec.h  |  5 +++++
>  libavcodec/cuviddec.c |  2 ++
>  libavcodec/decode.c   | 12 ++++++++----
>  libavcodec/internal.h |  5 +++++
>  5 files changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index fa3ab8f08a..3e0d654541 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -820,6 +820,7 @@ OBJS-$(CONFIG_ADPCM_YAMAHA_DECODER)       +=
> adpcm.o adpcm_data.o OBJS-$(CONFIG_ADPCM_YAMAHA_ENCODER)       +=
> adpcmenc.o adpcm_data.o 
>  # hardware accelerators
> +OBJS-$(CONFIG_CUVID)                      += cuvid.o
>  OBJS-$(CONFIG_D3D11VA)                    += dxva2.o
>  OBJS-$(CONFIG_DXVA2)                      += dxva2.o
>  OBJS-$(CONFIG_VAAPI)                      += vaapi_decode.o
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index 52cc5b0ca0..ecc49e5643 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -4000,6 +4000,11 @@ typedef struct AVHWAccel {
>       * Internal hwaccel capabilities.
>       */
>      int caps_internal;
> +
> +    /**
> +     * Some hwaccels are ambiguous if only
> +     */
> +    const AVClass *decoder_class;
>  } AVHWAccel;
>  
>  /**
> diff --git a/libavcodec/cuviddec.c b/libavcodec/cuviddec.c
> index 2ba8e00c6a..6370348639 100644
> --- a/libavcodec/cuviddec.c
> +++ b/libavcodec/cuviddec.c
> @@ -1106,6 +1106,7 @@ static const AVOption options[] = {
>          .type           = AVMEDIA_TYPE_VIDEO, \
>          .id             = AV_CODEC_ID_##X, \
>          .pix_fmt        = AV_PIX_FMT_CUDA, \
> +        .decoder_class  = &x##_cuvid_class, \
>      }; \
>      AVCodec ff_##x##_cuvid_decoder = { \
>          .name           = #x "_cuvid", \
> @@ -1120,6 +1121,7 @@ static const AVOption options[] = {
>          .receive_frame  = cuvid_output_frame, \
>          .flush          = cuvid_flush, \
>          .capabilities   = AV_CODEC_CAP_DELAY |
> AV_CODEC_CAP_AVOID_PROBING, \
> +        .caps_internal  = FF_CODEC_CAP_HWACCEL_REQUIRE_CLASS, \
>          .pix_fmts       = (const enum
> AVPixelFormat[]){ AV_PIX_FMT_CUDA, \ AV_PIX_FMT_NV12, \
>                                                          AV_PIX_FMT_P010,
> \ diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index 668ef9667f..7060f6a3b7 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -1152,15 +1152,19 @@ enum AVPixelFormat
> avcodec_default_get_format(struct AVCodecContext *s, const en return
> fmt[0]; }
>  
> -static AVHWAccel *find_hwaccel(enum AVCodecID codec_id,
> +static AVHWAccel *find_hwaccel(AVCodecContext *avctx,
>                                 enum AVPixelFormat pix_fmt)
>  {
>      AVHWAccel *hwaccel = NULL;
> +    const AVClass *av_class =
> +        (avctx->codec->caps_internal &
> FF_CODEC_CAP_HWACCEL_REQUIRE_CLASS)
> +        ? avctx->av_class : NULL;
>  
> -    while ((hwaccel = av_hwaccel_next(hwaccel)))
> -        if (hwaccel->id == codec_id
> +    while ((hwaccel = av_hwaccel_next(hwaccel))) {
> +        if (hwaccel->decoder_class == av_class && hwaccel->id ==
> avctx->codec_id && hwaccel->pix_fmt == pix_fmt)
>              return hwaccel;
> +    }
>      return NULL;
>  }
>  
> @@ -1168,7 +1172,7 @@ static int setup_hwaccel(AVCodecContext *avctx,
>                           const enum AVPixelFormat fmt,
>                           const char *name)
>  {
> -    AVHWAccel *hwa = find_hwaccel(avctx->codec_id, fmt);
> +    AVHWAccel *hwa = find_hwaccel(avctx, fmt);
>      int ret        = 0;
>  
>      if (!hwa) {
> diff --git a/libavcodec/internal.h b/libavcodec/internal.h
> index faa923c11f..0177ea6521 100644
> --- a/libavcodec/internal.h
> +++ b/libavcodec/internal.h
> @@ -69,6 +69,11 @@
>   */
>  #define FF_CODEC_CAP_SLICE_THREAD_HAS_MF    (1 << 5)
>  
> +/**
> + * Allow only AVHWAccels which have a matching decoder_class field.
> + */
> +#define FF_CODEC_CAP_HWACCEL_REQUIRE_CLASS  (1 << 6)
> +
>  #ifdef TRACE
>  #   define ff_tlog(ctx, ...) av_log(ctx, AV_LOG_TRACE, __VA_ARGS__)
>  #else

Looks fine. Nothing beyond what Timo said.


--phil