Fix for dropped output audio frames

On every standby, some audio frames were being dropped causing the
presentation frame count to slowly drift from the written frames.

Test: Run CtsMedia module repeatedly
Bug: 31648354
Change-Id: I1075ffaad4e1baec7fdc7ebdcc9391fbb6945d28
(cherry picked from commit 818cfde6a65e7a212486092dbbcbb6f0b8de8cce)

1 files changed, 17 insertions, 1 deletions

diff --git a/audio/audio_hw.c b/audio/audio_hw.c
index ed136d82..fd3826bd 100644
--- a/audio/audio_hw.c
+++ b/audio/audio_hw.c
@@ -586,9 +586,25 @@ static int out_get_render_position(const struct audio_stream_out *stream,
 
 static void do_out_standby(struct generic_stream_out *out)
 {
+    int frames_sleep = 0;
+    uint64_t sleep_time_us = 0;
     pthread_mutex_lock(&out->lock);
+    while (true) {
+        get_current_output_position(out, &out->underrun_position, NULL);
+        frames_sleep = out->frames_written - out->underrun_position;
+
+        if (frames_sleep == 0) {
+            break;
+        }
+
+        sleep_time_us = frames_sleep * 1000000LL /
+                        out_get_sample_rate(&out->stream.common);
+
+        pthread_mutex_unlock(&out->lock);
+        usleep(sleep_time_us);
+        pthread_mutex_lock(&out->lock);
+    }
     out->worker_standby = true;
-    get_current_output_position(out, &out->underrun_position, NULL);
     out->standby = true;
     pthread_mutex_unlock(&out->lock);
 }