AudioMixer uses downmix effect for multichannel content
In the AudioMixer structure associated with each track, add an object
that acts as the buffer provider when the track has more than two
channels of input in the mixer. This object, DownmixerBufferProvider,
gets audio from the actual buffer provider of the track, and applies
a downmix effect on it.
The downmix effect is created and configured when the track gets
created in AudioFlinger, which causes AudioMixer::getTrackName()
to be called with the new track's channel mask. It is released
when the track is disabled in the mixer.
Change-Id: I05281ed5f61bef663a8af7ca7d5ceac3517c82db
diff --git a/services/audioflinger/AudioMixer.h b/services/audioflinger/AudioMixer.h
index 856450c..a04fe95 100644
--- a/services/audioflinger/AudioMixer.h
+++ b/services/audioflinger/AudioMixer.h
@@ -21,9 +21,14 @@
#include <stdint.h>
#include <sys/types.h>
+#include <utils/threads.h>
+
#include "AudioBufferProvider.h"
#include "AudioResampler.h"
+#include <audio_effects/effect_downmix.h>
+#include <system/audio.h>
+
namespace android {
// ----------------------------------------------------------------------------
@@ -37,7 +42,10 @@
/*virtual*/ ~AudioMixer(); // non-virtual saves a v-table, restore if sub-classed
static const uint32_t MAX_NUM_TRACKS = 32;
+ // maximum number of channels supported by the mixer
static const uint32_t MAX_NUM_CHANNELS = 2;
+ // maximum number of channels supported for the content
+ static const uint32_t MAX_NUM_CHANNELS_TO_DOWNMIX = 8;
static const uint16_t UNITY_GAIN = 0x1000;
@@ -60,6 +68,7 @@
FORMAT = 0x4001,
MAIN_BUFFER = 0x4002,
AUX_BUFFER = 0x4003,
+ DOWNMIX_TYPE = 0X4004,
// for target RESAMPLE
SAMPLE_RATE = 0x4100,
RESET = 0x4101,
@@ -94,7 +103,7 @@
private:
enum {
- NEEDS_CHANNEL_COUNT__MASK = 0x00000003,
+ NEEDS_CHANNEL_COUNT__MASK = 0x00000007,
NEEDS_FORMAT__MASK = 0x000000F0,
NEEDS_MUTE__MASK = 0x00000100,
NEEDS_RESAMPLE__MASK = 0x00001000,
@@ -119,6 +128,7 @@
struct state_t;
struct track_t;
+ class DownmixerBufferProvider;
typedef void (*hook_t)(track_t* t, int32_t* output, size_t numOutFrames, int32_t* temp, int32_t* aux);
static const int BLOCKSIZE = 16; // 4 cache lines
@@ -147,8 +157,10 @@
uint8_t channelCount; // 1 or 2, redundant with (needs & NEEDS_CHANNEL_COUNT__MASK)
uint8_t format; // always 16
uint16_t enabled; // actually bool
- uint32_t channelMask; // currently under-used
+ audio_channel_mask_t channelMask;
+ // actual buffer provider used by the track hooks, see DownmixerBufferProvider below
+ // for how the Track buffer provider is wrapped by another one when dowmixing is required
AudioBufferProvider* bufferProvider;
// 16-byte boundary
@@ -169,7 +181,9 @@
uint64_t localTimeFreq;
- int64_t padding;
+ DownmixerBufferProvider* downmixerBufferProvider; // 4 bytes
+
+ int32_t padding;
// 16-byte boundary
@@ -194,6 +208,19 @@
track_t tracks[MAX_NUM_TRACKS]; __attribute__((aligned(32)));
};
+ // AudioBufferProvider that wraps a track AudioBufferProvider by a call to a downmix effect
+ class DownmixerBufferProvider : public AudioBufferProvider {
+ public:
+ virtual status_t getNextBuffer(Buffer* buffer, int64_t pts);
+ virtual void releaseBuffer(Buffer* buffer);
+ DownmixerBufferProvider();
+ virtual ~DownmixerBufferProvider();
+
+ AudioBufferProvider* mTrackBufferProvider;
+ effect_handle_t mDownmixHandle;
+ effect_config_t mDownmixConfig;
+ };
+
// bitmask of allocated track names, where bit 0 corresponds to TRACK0 etc.
uint32_t mTrackNames;
@@ -205,7 +232,13 @@
state_t mState __attribute__((aligned(32)));
+ // effect descriptor for the downmixer used by the mixer
+ static effect_descriptor_t dwnmFxDesc;
+ // indicates whether a downmix effect has been found and is usable by this mixer
+ static bool isMultichannelCapable;
+
void invalidateState(uint32_t mask);
+ static status_t prepareTrackForDownmix(track_t* pTrack, int trackNum);
static void track__genericResample(track_t* t, int32_t* out, size_t numFrames, int32_t* temp, int32_t* aux);
static void track__nop(track_t* t, int32_t* out, size_t numFrames, int32_t* temp, int32_t* aux);