ffmpeg: Switch cuvid to generic hwaccel

With generic hwaccel, it is additionally necessary to specify the
output format. If this is not done, we'll end up downloading the
frames back and then re-uploading them.

For example:

ffmpeg -y -hwaccel cuvid -hwaccel_output_format cuda \
       -c:v h264_cuvid -i sample.mp4 \
       -c:v h264_nvenc -f rawvideo /dev/null

Makefile

@@ -37,7 +37,6 @@ OBJS-ffmpeg-$(CONFIG_LIBMFX)  += ffmpeg_qsv.o
 ifndef CONFIG_VIDEOTOOLBOX
 OBJS-ffmpeg-$(CONFIG_VDA)     += ffmpeg_videotoolbox.o
 endif
-OBJS-ffmpeg-$(CONFIG_CUVID)   += ffmpeg_cuvid.o
 OBJS-ffmpeg-$(HAVE_DXVA2_LIB) += ffmpeg_dxva2.o
 OBJS-ffserver                 += ffserver_config.o
 

ffmpeg.h

@@ -665,7 +665,6 @@ int dxva2_init(AVCodecContext *s);
 int vda_init(AVCodecContext *s);
 int videotoolbox_init(AVCodecContext *s);
 int qsv_init(AVCodecContext *s);
-int cuvid_init(AVCodecContext *s);
 
 HWDevice *hw_device_get_by_name(const char *name);
 int hw_device_init_from_string(const char *arg, HWDevice **dev);

ffmpeg_opt.c

@@ -91,8 +91,8 @@ const HWAccel hwaccels[] = {
       AV_HWDEVICE_TYPE_VAAPI },
 #endif
 #if CONFIG_CUVID
-    { "cuvid", cuvid_init, HWACCEL_CUVID, AV_PIX_FMT_CUDA,
-      AV_HWDEVICE_TYPE_NONE },
+    { "cuvid", hwaccel_decode_init, HWACCEL_CUVID, AV_PIX_FMT_CUDA,
+      AV_HWDEVICE_TYPE_CUDA },
 #endif
     { 0 },
 };