[FFmpeg-devel] [PATCH] lavc/cuvid: fail early if GPU can't handle video parameters

wm4 nfxjfg at googlemail.com
Sun Jan 22 13:09:21 EET 2017


On Sat, 21 Jan 2017 10:35:50 -0700
Pavel Koshevoy <pkoshevoy at gmail.com> wrote:

> On Sat, Jan 21, 2017 at 10:27 AM,  <pkoshevoy at gmail.com> wrote:
> > From: Pavel Koshevoy <pkoshevoy at gmail.com>
> >
> > Evidently CUVID doesn't support decoding 422 or 444 chroma formats,
> > and only a limited set of resolutions per codec are supported.
> >
> > Unfortunately CUVID silently drops packets for video of unsupported
> > resolution.  However, it will error-out at cuvidCreateDecoder call
> > if the indicated video resolution is not supported.
> >
> > Given that stream resolution and pixel format are typically known as
> > a result of probing it is better to use this information during
> > avcodec_open2 call to fail immediately, rather than proceeding to
> > decode and never receiving any frames from the decoder nor receiving
> > any indication of decode failure.
> > ---
> >  libavcodec/cuvid.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 57 insertions(+), 5 deletions(-)
> >
> > diff --git a/libavcodec/cuvid.c b/libavcodec/cuvid.c
> > index 8fc713d..f9c29a1 100644
> > --- a/libavcodec/cuvid.c
> > +++ b/libavcodec/cuvid.c
> > @@ -612,7 +612,11 @@ static av_cold int cuvid_decode_end(AVCodecContext *avctx)
> >      return 0;
> >  }
> >
> > -static int cuvid_test_dummy_decoder(AVCodecContext *avctx, CUVIDPARSERPARAMS *cuparseinfo)
> > +static int cuvid_test_dummy_decoder(AVCodecContext *avctx,
> > +                                    const CUVIDPARSERPARAMS *cuparseinfo,
> > +                                    cudaVideoChromaFormat probed_chroma_format,
> > +                                    int probed_width,
> > +                                    int probed_height)
> >  {
> >      CuvidContext *ctx = avctx->priv_data;
> >      CUVIDDECODECREATEINFO cuinfo;
> > @@ -622,11 +626,11 @@ static int cuvid_test_dummy_decoder(AVCodecContext *avctx, CUVIDPARSERPARAMS *cu
> >      memset(&cuinfo, 0, sizeof(cuinfo));
> >
> >      cuinfo.CodecType = cuparseinfo->CodecType;
> > -    cuinfo.ChromaFormat = cudaVideoChromaFormat_420;
> > +    cuinfo.ChromaFormat = probed_chroma_format;
> >      cuinfo.OutputFormat = cudaVideoSurfaceFormat_NV12;
> >
> > -    cuinfo.ulWidth = 1280;
> > -    cuinfo.ulHeight = 720;
> > +    cuinfo.ulWidth = probed_width;
> > +    cuinfo.ulHeight = probed_height;
> >      cuinfo.ulTargetWidth = cuinfo.ulWidth;
> >      cuinfo.ulTargetHeight = cuinfo.ulHeight;
> >
> > @@ -653,6 +657,36 @@ static int cuvid_test_dummy_decoder(AVCodecContext *avctx, CUVIDPARSERPARAMS *cu
> >      return 0;
> >  }
> >
> > +static int convert_to_cuda_video_chroma_format(enum AVPixelFormat pix_fmt,
> > +                                               cudaVideoChromaFormat *out)
> > +{
> > +    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
> > +    if (!(out && desc &&
> > +          (desc->nb_components == 1 || desc->nb_components == 3) &&
> > +          (desc->log2_chroma_w < 2 && desc->log2_chroma_h < 2)))
> > +    {
> > +        return AVERROR(EINVAL);
> > +    }
> > +
> > +    if (desc->nb_components == 1)
> > +    {
> > +        *out = cudaVideoChromaFormat_Monochrome;
> > +    }
> > +    else if (desc->flags == AV_PIX_FMT_FLAG_PLANAR)
> > +    {
> > +        *out = ((desc->log2_chroma_w == 0) ? cudaVideoChromaFormat_444 :
> > +                (desc->log2_chroma_h == 0) ? cudaVideoChromaFormat_422 :
> > +                cudaVideoChromaFormat_420);
> > +    }
> > +    else
> > +    {
> > +        return AVERROR(EINVAL);
> > +    }
> > +
> > +    // unfortunately, 420 is the only one that works:
> > +    return (*out == cudaVideoChromaFormat_420) ? 0 : AVERROR_EXTERNAL;
> > +}
> > +
> >  static av_cold int cuvid_decode_init(AVCodecContext *avctx)
> >  {
> >      CuvidContext *ctx = avctx->priv_data;
> > @@ -663,12 +697,27 @@ static av_cold int cuvid_decode_init(AVCodecContext *avctx)
> >      CUcontext cuda_ctx = NULL;
> >      CUcontext dummy;
> >      const AVBitStreamFilter *bsf;
> > +    cudaVideoChromaFormat probed_chroma_format;
> > +    int probed_width;
> > +    int probed_height;
> >      int ret = 0;
> >
> >      enum AVPixelFormat pix_fmts[3] = { AV_PIX_FMT_CUDA,
> >                                         AV_PIX_FMT_NV12,
> >                                         AV_PIX_FMT_NONE };
> >
> > +    enum AVPixelFormat probed_pix_fmt = (avctx->pix_fmt <= 0 ?
> > +                                         AV_PIX_FMT_YUV420P :
> > +                                         avctx->pix_fmt);
> > +
> > +    ret = convert_to_cuda_video_chroma_format(probed_pix_fmt, &probed_chroma_format);
> > +    if (ret < 0) {
> > +        // pixel format is not supported:
> > +        return ret;
> > +    }
> > +    probed_width = avctx->coded_width ? avctx->coded_width : 1280;
> > +    probed_height = avctx->coded_height ? avctx->coded_height : 720;
> > +
> >      // Accelerated transcoding scenarios with 'ffmpeg' require that the
> >      // pix_fmt be set to AV_PIX_FMT_CUDA early. The sw_pix_fmt, and the
> >      // pix_fmt for non-accelerated transcoding, do not need to be correct
> > @@ -824,7 +873,10 @@ static av_cold int cuvid_decode_init(AVCodecContext *avctx)
> >      if (ret < 0)
> >          goto error;
> >
> > -    ret = cuvid_test_dummy_decoder(avctx, &ctx->cuparseinfo);
> > +    ret = cuvid_test_dummy_decoder(avctx, &ctx->cuparseinfo,
> > +                                   probed_chroma_format,
> > +                                   probed_width,
> > +                                   probed_height);
> >      if (ret < 0)
> >          goto error;
> >
> > --
> > 2.9.2
> >  
> 
> 
> Despite wm4 objections I am resubmitting this patch, because I can
> find no other reasonable method for rejecting ffmpeg cuvid decoder
> when it can't handle a given video stream.  An unreasonable
> alternative would be to duplicate the work that cuvid.c does
> internally on my application side, and that would be of little benefit
> to me and to ffmpeg -- I might as well use the nvenc APIs directly
> then.  I still see this patch as an improvement.

I'm still against this.

Also, I have the same problem (due to ffmpeg.c being so low level and
essentially unsuitable to support hardware transcoding on arbitrary
hardware). I'm telling you you won't get far with this anyway, because
you need different filter graphs for sw and hw.

I also dislike this because it's complex and requires creating the
decoder twice (which it shouldn't do in the first place).


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