pixfmt: add a CUDA hwaccelled format

doc/APIchanges

@@ -19,6 +19,7 @@ API changes, most recent first:
                         for handling hwaccel frames.
   xxxxxxx hwcontext_vdpau.h - Add a new installed header hwcontext_vdpau.h with
                               VDPAU-specific hwcontext definitions.
+  xxxxxxx pixfmt.h - Add AV_PIX_FMT_CUDA.
 
 2016-xx-xx - xxxxxxx - lavf 57.3.0 - avformat.h
   Add AVFormatContext.opaque, io_open and io_close, allowing custom IO

libavutil/pixdesc.c

@@ -1577,6 +1577,10 @@ static const AVPixFmtDescriptor av_pix_fmt_descriptors[AV_PIX_FMT_NB] = {
         .name = "mmal",
         .flags = AV_PIX_FMT_FLAG_HWACCEL,
     },
+    [AV_PIX_FMT_CUDA] = {
+        .name = "cuda",
+        .flags = AV_PIX_FMT_FLAG_HWACCEL,
+    },
 };
 #if FF_API_PLUS1_MINUS1
 FF_ENABLE_DEPRECATION_WARNINGS

libavutil/pixfmt.h

@@ -217,6 +217,12 @@ enum AVPixelFormat {
 
     AV_PIX_FMT_D3D11VA_VLD,  ///< HW decoding through Direct3D11, Picture.data[3] contains a ID3D11VideoDecoderOutputView pointer
 
+    /**
+     * HW acceleration through CUDA. data[i] contain CUdeviceptr pointers
+     * exactly as for system memory frames.
+     */
+    AV_PIX_FMT_CUDA,
+
     AV_PIX_FMT_NB,        ///< number of pixel formats, DO NOT USE THIS if you want to link with shared libav* because the number of formats might differ between versions
 };