From b2e857efc67c474862c8ce3c5aa2dffbfec31015 Mon Sep 17 00:00:00 2001
From: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Mon, 22 Mar 2021 16:58:26 -0400
Subject: [PATCH] matroskademux: Store alpha stream in VideoCodecAlphaMeta

This generalize the feature over using mini object quark data. If
that feature was Matroska specifc, using the new CustomMeta would have
been enough and arguably cleaner then QData, though it seems that
similar technique is use with AV1 Image Format (AVIF).

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/968>
---
 gst/matroska/matroska-demux.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/gst/matroska/matroska-demux.c b/gst/matroska/matroska-demux.c
index 05266a11b4..a1e5d1c9e4 100644
--- a/gst/matroska/matroska-demux.c
+++ b/gst/matroska/matroska-demux.c
@@ -64,6 +64,7 @@
 #include <gst/audio/audio.h>
 #include <gst/tag/tag.h>
 #include <gst/pbutils/pbutils.h>
+#include <gst/video/gstvideocodecalphameta.h>
 #include <gst/video/video.h>
 
 #include "gstmatroskaelements.h"
@@ -4982,14 +4983,20 @@ gst_matroska_demux_parse_blockgroup_or_simpleblock (GstMatroskaDemux * demux,
 
         while ((blockadd = g_queue_pop_head (&additions))) {
           if (blockadd->id == 1
-              && !strcmp (stream->codec_id, GST_MATROSKA_CODEC_ID_VIDEO_VP8)) {
-            GST_TRACE_OBJECT (demux, "adding block addition %u as VP8 alpha "
-                "qdata to buffer %p, %u bytes", (guint) blockadd->id, buf,
+              && (!strcmp (stream->codec_id, GST_MATROSKA_CODEC_ID_VIDEO_VP8)
+                  || !strcmp (stream->codec_id,
+                      GST_MATROSKA_CODEC_ID_VIDEO_VP9))) {
+            GstBuffer *alpha_buffer;
+
+            GST_TRACE_OBJECT (demux, "adding block addition %u as VP8/VP9 "
+                "alpha meta to buffer %p, %u bytes", (guint) blockadd->id, buf,
                 (guint) blockadd->size);
-            gst_mini_object_set_qdata (GST_MINI_OBJECT (sub),
-                matroska_block_additional_quark,
-                g_bytes_new_take (blockadd->data, blockadd->size),
-                (GDestroyNotify) g_bytes_unref);
+
+            alpha_buffer = gst_buffer_new_wrapped (blockadd->data,
+                blockadd->size);
+            gst_buffer_copy_into (alpha_buffer, sub,
+                GST_BUFFER_COPY_FLAGS | GST_BUFFER_COPY_TIMESTAMPS, 0, -1);
+            gst_buffer_add_video_codec_alpha_meta (sub, alpha_buffer);
           } else {
             g_free (blockadd->data);
           }