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avviddec: Enable subframe decoding for H.264

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Enable sending NAL units to the decoder without having to first
group them in a frame (an AU).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-libav/-/merge_requests/66>
This commit is contained in:
Olivier Crête 2020-01-22 12:41:27 -05:00 committed by Stéphane Cerveau
parent 81cbd0deb6
commit 17aca8a8c2
3 changed files with 46 additions and 1 deletions
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2
docs/gst_plugins_cache.json
View file

@ -9436,7 +9436,7 @@
"long-name": "libav H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 decoder",
"pad-templates": {
"sink": {
"caps": "video/x-h264:\n alignment: au\n stream-format: { (string)avc, (string)byte-stream }\n",
"caps": "video/x-h264:\n alignment: au\n stream-format: { (string)avc, (string)byte-stream }\nvideo/x-h264:\n alignment: nal\n stream-format: byte-stream\n",
"direction": "sink",
"presence": "always"
},

5
ext/libav/gstavcodecmap.c
View file

@ -1291,6 +1291,11 @@ gst_ffmpeg_codecid_to_caps (enum AVCodecID codec_id,
g_value_unset (&item);
gst_caps_set_value (caps, "stream-format", &arr);
g_value_unset (&arr);
gst_caps_append (caps, gst_ff_vid_caps_new (context, NULL, codec_id,
encode, "video/x-h264", "alignment", G_TYPE_STRING, "nal",
"stream-format", G_TYPE_STRING, "byte-stream", NULL));
} else if (context) {
/* FIXME: ffmpeg currently assumes AVC if there is extradata and
* byte-stream otherwise. See for example the MOV or MPEG-TS code.

40
ext/libav/gstavviddec.c
View file

@ -362,6 +362,18 @@ gst_ffmpegviddec_context_set_flags (AVCodecContext * context, guint flags,
context->flags &= ~flags;
}
static void
gst_ffmpegviddec_context_set_flags2 (AVCodecContext * context, guint flags,
gboolean enable)
{
g_return_if_fail (context != NULL);
if (enable)
context->flags2 |= flags;
else
context->flags2 &= ~flags;
}
/* with LOCK */
static gboolean
gst_ffmpegviddec_close (GstFFMpegVidDec * ffmpegdec, gboolean reset)
@ -575,6 +587,24 @@ gst_ffmpegviddec_set_format (GstVideoDecoder * decoder,
} else
ffmpegdec->context->thread_count = ffmpegdec->max_threads;
if (oclass->in_plugin->id == AV_CODEC_ID_H264) {
GstStructure *s = gst_caps_get_structure (state->caps, 0);
const char *alignment;
gboolean nal_aligned;
alignment = gst_structure_get_string (s, "alignment");
nal_aligned = !g_strcmp0 (alignment, "nal");
if (nal_aligned) {
if (ffmpegdec->context->thread_type == FF_THREAD_FRAME)
goto nal_only_slice;
ffmpegdec->context->thread_type = FF_THREAD_SLICE;
}
gst_ffmpegviddec_context_set_flags2 (ffmpegdec->context,
AV_CODEC_FLAG2_CHUNKS, nal_aligned);
gst_video_decoder_set_subframe_mode (decoder, nal_aligned);
}
/* open codec - we don't select an output pix_fmt yet,
* simply because we don't know! We only get it
* during playback... */
@ -614,6 +644,12 @@ open_failed:
GST_DEBUG_OBJECT (ffmpegdec, "Failed to open");
goto done;
}
nal_only_slice:
{
GST_ERROR_OBJECT (ffmpegdec,
"Can't do NAL aligned H.264 with frame threading.");
goto done;
}
}
typedef struct
@ -1826,6 +1862,10 @@ gst_ffmpegviddec_video_frame (GstFFMpegVidDec * ffmpegdec,
GST_VIDEO_CODEC_FRAME_FLAG_UNSET (frame,
GST_FFMPEG_VIDEO_CODEC_FRAME_FLAG_ALLOCATED);
if (gst_video_decoder_get_subframe_mode (GST_VIDEO_DECODER (ffmpegdec)))
gst_video_decoder_have_last_subframe (GST_VIDEO_DECODER (ffmpegdec),
out_frame);
/* FIXME: Ideally we would remap the buffer read-only now before pushing but
* libav might still have a reference to it!
*/