[GStreamer][MediaStream] AudioSource triggering critical warnings

https://bugs.webkit.org/show_bug.cgi?id=224180

Patch by Philippe Normand <pnormand@igalia.com> on 2021-04-06
Reviewed by Xabier Rodriguez-Calvar.

Keep track of audio channel offsets and store them as metadata in audio buffers. This is
used by downstream elements such as the audio convert elements.

* Modules/webaudio/MediaStreamAudioSourceGStreamer.cpp:
(WebCore::copyBusData):
(WebCore::MediaStreamAudioSource::consumeAudio):

Canonical link: https://commits.webkit.org/236167@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@275510 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,17 @@
+2021-04-06  Philippe Normand  <pnormand@igalia.com>
+
+        [GStreamer][MediaStream] AudioSource triggering critical warnings
+        https://bugs.webkit.org/show_bug.cgi?id=224180
+
+        Reviewed by Xabier Rodriguez-Calvar.
+
+        Keep track of audio channel offsets and store them as metadata in audio buffers. This is
+        used by downstream elements such as the audio convert elements.
+
+        * Modules/webaudio/MediaStreamAudioSourceGStreamer.cpp:
+        (WebCore::copyBusData):
+        (WebCore::MediaStreamAudioSource::consumeAudio):
+
 2021-04-06  Antti Koivisto  <antti@apple.com>
 
         [LFC][Integration] Disable LFC if paginated context has inline boxes

Source/WebCore/Modules/webaudio/MediaStreamAudioSourceGStreamer.cpp

@@ -29,20 +29,25 @@
 
 namespace WebCore {
 
-static void copyBusData(AudioBus& bus, GstBuffer* buffer, bool isMuted)
+static Vector<size_t> copyBusData(AudioBus& bus, GstBuffer* buffer, bool isMuted)
 {
+    Vector<size_t> offsets;
     GstMappedBuffer mappedBuffer(buffer, GST_MAP_WRITE);
     if (isMuted) {
         memset(mappedBuffer.data(), 0, mappedBuffer.size());
-        return;
+        return offsets;
     }
 
+    DisableMallocRestrictionsForCurrentThreadScope disableMallocRestrictions;
+    offsets.reserveInitialCapacity(sizeof(size_t) * bus.numberOfChannels());
     size_t size = mappedBuffer.size() / bus.numberOfChannels();
     for (size_t channelIndex = 0; channelIndex < bus.numberOfChannels(); ++channelIndex) {
-        AudioChannel& channel = *bus.channel(channelIndex);
-        float* destination = reinterpret_cast<float*>(mappedBuffer.data() + (channelIndex * size));
-        memcpy(destination, channel.data(), size);
+        const auto& channel = *bus.channel(channelIndex);
+        auto offset = reinterpret_cast<size_t>(channelIndex * size);
+        memcpy(reinterpret_cast<float*>(mappedBuffer.data() + offset), channel.data(), sizeof(float) * channel.length());
+        offsets.uncheckedAppend(offset);
     }
+    return offsets;
 }
 
 void MediaStreamAudioSource::consumeAudio(AudioBus& bus, size_t numberOfFrames)
@@ -62,7 +67,12 @@ void MediaStreamAudioSource::consumeAudio(AudioBus& bus, size_t numberOfFrames)
 
     auto caps = adoptGRef(gst_audio_info_to_caps(&info));
     auto buffer = adoptGRef(gst_buffer_new_allocate(nullptr, size, nullptr));
-    copyBusData(bus, buffer.get(), muted());
+    auto offsets = copyBusData(bus, buffer.get(), muted());
+#if GST_CHECK_VERSION(1, 16, 0)
+    gst_buffer_add_audio_meta(buffer.get(), &info, numberOfFrames, offsets.data());
+#else
+    UNUSED_VARIABLE(offsets);
+#endif
     auto sample = adoptGRef(gst_sample_new(buffer.get(), caps.get(), nullptr, nullptr));
     GStreamerAudioData audioBuffer(WTFMove(sample), info);
     GStreamerAudioStreamDescription description(&info);