Don't allow AudioTrack frameCount to decrease

This is a workaround for bug that client can cache return value of
frameCount(), and is not notified when this value changes due to automatic
re-recreation of the underlying IAudioTrack.

A better long-term fix would be to notify clients when these kinds of
parameters change, and to fix assumptions in client code that they are
constant (e.g. in SoundPool and maybe obtainBuffer).

Also, once a fast track request is denied, don't request it again.

Bug: 6431187
Change-Id: I55b4ff30bbd9ed3a402e39452a38de52cdea53a9

1 files changed, 11 insertions, 1 deletions

diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index b5b7adc..6189be5 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -269,6 +269,7 @@ status_t AudioTrack::set(
     mNotificationFramesReq = notificationFrames;
     mSessionId = sessionId;
     mAuxEffectId = 0;
+    mFlags = flags;
     mCbf = cbf;
 
     if (cbf != NULL) {
@@ -310,7 +311,6 @@ status_t AudioTrack::set(
     mNewPosition = 0;
     mUpdatePeriod = 0;
     mFlushed = false;
-    mFlags = flags;
     AudioSystem::acquireAudioSessionId(mSessionId);
     mRestoreStatus = NO_ERROR;
     return NO_ERROR;
@@ -770,7 +770,9 @@ status_t AudioTrack::createTrack_l(
             // use case 2: callback handler
             (mCbf != NULL))) {
         ALOGW("AUDIO_OUTPUT_FLAG_FAST denied by client");
+        // once denied, do not request again if IAudioTrack is re-created
         flags = (audio_output_flags_t) (flags & ~AUDIO_OUTPUT_FLAG_FAST);
+        mFlags = flags;
     }
     ALOGV("createTrack_l() output %d afLatency %d", output, afLatency);
 
@@ -899,6 +901,9 @@ status_t AudioTrack::createTrack_l(
             ALOGV("AUDIO_OUTPUT_FLAG_FAST successful; frameCount %u", mCblk->frameCount);
         } else {
             ALOGV("AUDIO_OUTPUT_FLAG_FAST denied by server; frameCount %u", mCblk->frameCount);
+            // once denied, do not request again if IAudioTrack is re-created
+            flags = (audio_output_flags_t) (flags & ~AUDIO_OUTPUT_FLAG_FAST);
+            mFlags = flags;
         }
         if (sharedBuffer == 0) {
             mNotificationFramesAct = mCblk->frameCount/2;
@@ -920,6 +925,11 @@ status_t AudioTrack::createTrack_l(
     mRemainingFrames = mNotificationFramesAct;
     // FIXME don't believe this lie
     mLatency = afLatency + (1000*mCblk->frameCount) / sampleRate;
+    // If IAudioTrack is re-created, don't let the requested frameCount
+    // decrease.  This can confuse clients that cache frameCount().
+    if (mCblk->frameCount > mFrameCount) {
+        mFrameCount = mCblk->frameCount;
+    }
     return NO_ERROR;
 }