[FFmpeg-devel] [PATCH v3 2/2] ffmpeg_opt: consider HW acceleration method when selecting decoder

[Xiang, Haihao]

From: Haihao Xiang <haihao.xiang at intel.com>

Usually a HW decoder is expected when user specifies a HW acceleration
method via -hwaccel option, however the current implementation doesn't
take HW acceleration method into account, it is possible to select a SW
decoder.

For example:
$ ffmpeg -hwaccel vaapi -i av1.mp4 -f null -
$ ffmpeg -hwaccel nvdec -i av1.mp4 -f null -
$ ffmpeg -hwaccel vdpau -i av1.mp4 -f null -
[...]
Stream #0:0 -> #0:0 (av1 (libdav1d) -> wrapped_avframe (native))

libdav1d is selected in this case even if vaapi, nvdec or vdpau is
specified.

After applying this patch, the native av1 decoder (with vaapi, nvdec or
vdpau support) is selected for decoding(libdav1d is still used for
probing format).
$ ffmpeg -hwaccel vaapi -i av1.mp4 -f null -
$ ffmpeg -hwaccel nvdec -i av1.mp4 -f null -
$ ffmpeg -hwaccel vdpau -i av1.mp4 -f null -
[...]
Stream #0:0 -> #0:0 (av1 (native) -> wrapped_avframe (native))

Tested-by: Mario Roy <marioeroy at gmail.com>
Signed-off-by: Haihao Xiang <haihao.xiang at intel.com>
---
 fftools/ffmpeg_opt.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 2771c5d993..614bfeea80 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -861,6 +861,48 @@ static const AVCodec *choose_decoder(OptionsContext *o, AVFormatContext *s, AVSt
         return avcodec_find_decoder(st->codecpar->codec_id);
 }
 
+static const AVCodec *choose_decoder2(InputStream *ist, OptionsContext *o, AVFormatContext *s, AVStream *st)
+{
+    char *codec_name = NULL;
+
+    MATCH_PER_STREAM_OPT(codec_names, str, codec_name, s, st);
+    if (codec_name) {
+        const AVCodec *codec = find_codec_or_die(codec_name, st->codecpar->codec_type, 0);
+        st->codecpar->codec_id = codec->id;
+        if (recast_media && st->codecpar->codec_type != codec->type)
+            st->codecpar->codec_type = codec->type;
+        return codec;
+    } else {
+        if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
+            ist->hwaccel_id == HWACCEL_GENERIC &&
+            ist->hwaccel_device_type != AV_HWDEVICE_TYPE_NONE) {
+            const AVCodec *p;
+            void *i = 0;
+
+            while ((p = av_codec_iterate(&i))) {
+                int j;
+
+                if (p->id != st->codecpar->codec_id ||
+                    !av_codec_is_decoder(p) ||
+                    !avcodec_get_hw_config(p, 0))
+                    continue;
+
+                for (j = 0; ;j++) {
+                    const AVCodecHWConfig *config = avcodec_get_hw_config(p, j);
+
+                    if (!config)
+                        break;
+
+                    if (config->device_type == ist->hwaccel_device_type)
+                        return p;
+                }
+            }
+        }
+
+        return avcodec_find_decoder(st->codecpar->codec_id);
+    }
+}
+
 /* Add all the streams from the given input file to the global
  * list of input streams. */
 static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
@@ -973,7 +1015,7 @@ static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
             ist->hwaccel_pix_fmt = AV_PIX_FMT_NONE;
         }
 
-        ist->dec = choose_decoder(o, ic, st);
+        ist->dec = choose_decoder2(ist, o, ic, st);
         ist->decoder_opts = filter_codec_opts(o->g->codec_opts, ist->st->codecpar->codec_id, ic, st, ist->dec);
 
         ist->reinit_filters = -1;
-- 
2.17.1