media: add AudioTrack::getMinFrameCount().
Change-Id: If15162583d1d16d89f59be0793106afe77417f35
diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index c46df1e..ef537f4 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -102,6 +102,17 @@
typedef void (*callback_t)(int event, void* user, void *info);
+ /* Returns the minimum frame count required for the successful creation of
+ * an AudioTrack object.
+ * Returned status (from utils/Errors.h) can be:
+ * - NO_ERROR: successful operation
+ * - NO_INIT: audio server or audio hardware not initialized
+ */
+
+ static status_t getMinFrameCount(int* frameCount,
+ int streamType =-1,
+ uint32_t sampleRate = 0);
+
/* Constructs an uninitialized AudioTrack. No connection with
* AudioFlinger takes place.
*/
diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 4b61131..2118f8f 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -41,6 +41,35 @@
#define UNLIKELY( exp ) (__builtin_expect( (exp) != 0, false ))
namespace android {
+// ---------------------------------------------------------------------------
+
+// static
+status_t AudioTrack::getMinFrameCount(
+ int* frameCount,
+ int streamType,
+ uint32_t sampleRate)
+{
+ int afSampleRate;
+ if (AudioSystem::getOutputSamplingRate(&afSampleRate, streamType) != NO_ERROR) {
+ return NO_INIT;
+ }
+ int afFrameCount;
+ if (AudioSystem::getOutputFrameCount(&afFrameCount, streamType) != NO_ERROR) {
+ return NO_INIT;
+ }
+ uint32_t afLatency;
+ if (AudioSystem::getOutputLatency(&afLatency, streamType) != NO_ERROR) {
+ return NO_INIT;
+ }
+
+ // Ensure that buffer depth covers at least audio hardware latency
+ uint32_t minBufCount = afLatency / ((1000 * afFrameCount) / afSampleRate);
+ if (minBufCount < 2) minBufCount = 2;
+
+ *frameCount = (sampleRate == 0) ? afFrameCount * minBufCount :
+ afFrameCount * minBufCount * sampleRate / afSampleRate;
+ return NO_ERROR;
+}
// ---------------------------------------------------------------------------