AudioMixer: Expand mono track to multi-channel
Extend MONO_HACK to multi-channel output.
Mono track will have only one channel output on multi-channel devices.
Since ARC++ exposed a 4-channel output device and downmix track in
ChromeOS, we need to add this feature to support mono track sample
expansion.
Add support for both re-sample and non-resample path.
For resample path, we need to add MIXTYPE_STEREOEXPAND in
AudioMixerOps.h since AudioResampler will upmix mono track to stereo
track.
Bug: 120222604
Bug: 112341269
Bug: 117116052
Bug: crbug.com/890560
Test: Play mono tracks without re-sampling on ARC++
Test: Play mono tracks with re-sampling on ARC++
Test: Play normal stereo tracks on ARC++
(cherry picked from commit 9b79e0752e6536c31430aa31838a9de1b7b56f9f)
Change-Id: I51f5914c41dd0196db9c6a2e1a99b44e5d87c0d6
diff --git a/media/libaudioprocessing/AudioMixer.cpp b/media/libaudioprocessing/AudioMixer.cpp
index c0b11a4..1a31420 100644
--- a/media/libaudioprocessing/AudioMixer.cpp
+++ b/media/libaudioprocessing/AudioMixer.cpp
@@ -162,10 +162,10 @@
// discard the previous downmixer if there was one
unprepareForDownmix();
// MONO_HACK Only remix (upmix or downmix) if the track and mixer/device channel masks
- // are not the same and not handled internally, as mono -> stereo currently is.
+ // are not the same and not handled internally, as mono for channel position masks is.
if (channelMask == mMixerChannelMask
|| (channelMask == AUDIO_CHANNEL_OUT_MONO
- && mMixerChannelMask == AUDIO_CHANNEL_OUT_STEREO)) {
+ && isAudioChannelPositionMask(mMixerChannelMask))) {
return NO_ERROR;
}
// DownmixerBufferProvider is only used for position masks.