avcodec: allow multiple hwaccels for the same codec/pixfmt

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.

1 files changed, 8 insertions, 4 deletions

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 44b874d..9fdc7bb 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -1090,15 +1090,19 @@ 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->codec->priv_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;
 }
 
@@ -1106,7 +1110,7 @@ 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) {