Compute sleep time when AudioTrack client callback returns no PCM data
Callbacks can go into a sleep-wait cycle if the client/app is unable to
deliver data. This can happen if the buffer is large, or if
the client/app cannot keep the buffer filled, or upon a stream end condition.
We improve the sleep time computation for AudioTrack PCM callbacks.
This minimizes the number of callbacks to NuPlayerRenderer.
Bug: 21198655
Change-Id: I4247798a6638def2f0d8f1b46f60323482065cb2
diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 070baa1..e2889b1 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -38,11 +38,23 @@
namespace android {
// ---------------------------------------------------------------------------
+// TODO: Move to a separate .h
+
template <typename T>
-const T &min(const T &x, const T &y) {
+static inline const T &min(const T &x, const T &y) {
return x < y ? x : y;
}
+template <typename T>
+static inline const T &max(const T &x, const T &y) {
+ return x > y ? x : y;
+}
+
+static inline nsecs_t framesToNanoseconds(ssize_t frames, uint32_t sampleRate, float speed)
+{
+ return ((double)frames * 1000000000) / ((double)sampleRate * speed);
+}
+
static int64_t convertTimespecToUs(const struct timespec &tv)
{
return tv.tv_sec * 1000000ll + tv.tv_nsec / 1000;
@@ -1759,7 +1771,7 @@
// Cache other fields that will be needed soon
uint32_t sampleRate = mSampleRate;
float speed = mPlaybackRate.mSpeed;
- uint32_t notificationFrames = mNotificationFramesAct;
+ const uint32_t notificationFrames = mNotificationFramesAct;
if (mRefreshRemaining) {
mRefreshRemaining = false;
mRemainingFrames = notificationFrames;
@@ -1797,7 +1809,14 @@
mLock.unlock();
+ // get anchor time to account for callbacks.
+ const nsecs_t timeBeforeCallbacks = systemTime();
+
if (waitStreamEnd) {
+ // FIXME: Instead of blocking in proxy->waitStreamEndDone(), Callback thread
+ // should wait on proxy futex and handle CBLK_STREAM_END_DONE within this function
+ // (and make sure we don't callback for more data while we're stopping).
+ // This helps with position, marker notifications, and track invalidation.
struct timespec timeout;
timeout.tv_sec = WAIT_STREAM_END_TIMEOUT_SEC;
timeout.tv_nsec = 0;
@@ -1882,12 +1901,17 @@
minFrames = kPoll * notificationFrames;
}
+ // This "fudge factor" avoids soaking CPU, and compensates for late progress by server
+ static const nsecs_t kWaitPeriodNs = WAIT_PERIOD_MS * 1000000LL;
+ const nsecs_t timeAfterCallbacks = systemTime();
+
// Convert frame units to time units
nsecs_t ns = NS_WHENEVER;
if (minFrames != (uint32_t) ~0) {
- // This "fudge factor" avoids soaking CPU, and compensates for late progress by server
- static const nsecs_t kFudgeNs = 10000000LL; // 10 ms
- ns = ((double)minFrames * 1000000000) / ((double)sampleRate * speed) + kFudgeNs;
+ ns = framesToNanoseconds(minFrames, sampleRate, speed) + kWaitPeriodNs;
+ ns -= (timeAfterCallbacks - timeBeforeCallbacks); // account for callback time
+ // TODO: Should we warn if the callback time is too long?
+ if (ns < 0) ns = 0;
}
// If not supplying data by EVENT_MORE_DATA, then we're done
@@ -1895,6 +1919,13 @@
return ns;
}
+ // EVENT_MORE_DATA callback handling.
+ // Timing for linear pcm audio data formats can be derived directly from the
+ // buffer fill level.
+ // Timing for compressed data is not directly available from the buffer fill level,
+ // rather indirectly from waiting for blocking mode callbacks or waiting for obtain()
+ // to return a certain fill level.
+
struct timespec timeout;
const struct timespec *requested = &ClientProxy::kForever;
if (ns != NS_WHENEVER) {
@@ -1925,12 +1956,15 @@
return NS_NEVER;
}
- if (mRetryOnPartialBuffer && !isOffloaded()) {
+ if (mRetryOnPartialBuffer && audio_is_linear_pcm(mFormat)) {
mRetryOnPartialBuffer = false;
if (avail < mRemainingFrames) {
- int64_t myns = ((double)(mRemainingFrames - avail) * 1100000000)
- / ((double)sampleRate * speed);
- if (ns < 0 || myns < ns) {
+ if (ns > 0) { // account for obtain time
+ const nsecs_t timeNow = systemTime();
+ ns = max((nsecs_t)0, ns - (timeNow - timeAfterCallbacks));
+ }
+ nsecs_t myns = framesToNanoseconds(mRemainingFrames - avail, sampleRate, speed);
+ if (ns < 0 /* NS_WHENEVER */ || myns < ns) {
ns = myns;
}
return ns;
@@ -1953,7 +1987,42 @@
// Keep this thread going to handle timed events and
// still try to get more data in intervals of WAIT_PERIOD_MS
// but don't just loop and block the CPU, so wait
- return WAIT_PERIOD_MS * 1000000LL;
+
+ // mCbf(EVENT_MORE_DATA, ...) might either
+ // (1) Block until it can fill the buffer, returning 0 size on EOS.
+ // (2) Block until it can fill the buffer, returning 0 data (silence) on EOS.
+ // (3) Return 0 size when no data is available, does not wait for more data.
+ //
+ // (1) and (2) occurs with AudioPlayer/AwesomePlayer; (3) occurs with NuPlayer.
+ // We try to compute the wait time to avoid a tight sleep-wait cycle,
+ // especially for case (3).
+ //
+ // The decision to support (1) and (2) affect the sizing of mRemainingFrames
+ // and this loop; whereas for case (3) we could simply check once with the full
+ // buffer size and skip the loop entirely.
+
+ nsecs_t myns;
+ if (audio_is_linear_pcm(mFormat)) {
+ // time to wait based on buffer occupancy
+ const nsecs_t datans = mRemainingFrames <= avail ? 0 :
+ framesToNanoseconds(mRemainingFrames - avail, sampleRate, speed);
+ // audio flinger thread buffer size (TODO: adjust for fast tracks)
+ const nsecs_t afns = framesToNanoseconds(mAfFrameCount, mAfSampleRate, speed);
+ // add a half the AudioFlinger buffer time to avoid soaking CPU if datans is 0.
+ myns = datans + (afns / 2);
+ } else {
+ // FIXME: This could ping quite a bit if the buffer isn't full.
+ // Note that when mState is stopping we waitStreamEnd, so it never gets here.
+ myns = kWaitPeriodNs;
+ }
+ if (ns > 0) { // account for obtain and callback time
+ const nsecs_t timeNow = systemTime();
+ ns = max((nsecs_t)0, ns - (timeNow - timeAfterCallbacks));
+ }
+ if (ns < 0 /* NS_WHENEVER */ || myns < ns) {
+ ns = myns;
+ }
+ return ns;
}
size_t releasedFrames = writtenSize / mFrameSize;