Fix Linux audio playback for short files

media/audio/linux/alsa_output.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // THREAD SAFETY
 //
 // The AlsaPcmOutputStream object's internal state is accessed by two threads:
 //
 //   client thread - creates the object and calls the public APIs.
 //   message loop thread - executes all the internal tasks including querying
@@ skipping 377 matching lines @@
   }
 }
 
 void AlsaPcmOutputStream::StartTask() {
   DCHECK_EQ(message_loop_, MessageLoop::current());
 
   if (stop_stream_) {
     return;
   }
 
+  if (shared_data_.state() != kIsPlaying) {
+    return;
+  }
+
+  // Before starting, the buffer might have audio from previous user of this
+  // device.
+  buffer_->Clear();
+
   // When starting again, drop all packets in the device and prepare it again
   // incase we are restarting from a pause state and need to flush old data.
   int error = wrapper_->PcmDrop(playback_handle_);
   if (error < 0 && error != -EAGAIN) {
     LOG(ERROR) << "Failure clearing playback device ("
                << wrapper_->PcmName(playback_handle_) << "): "
                << wrapper_->StrError(error);
     stop_stream_ = true;
     return;
   }
@@ skipping 123 matching lines @@
 
 void AlsaPcmOutputStream::WritePacket() {
   DCHECK_EQ(message_loop_, MessageLoop::current());
 
   // If the device is in error, just eat the bytes.
   if (stop_stream_) {
     buffer_->Clear();
     return;
   }
 
+  if (shared_data_.state() == kIsStopped) {
+    return;
+  }
+
   CHECK_EQ(buffer_->forward_bytes() % bytes_per_output_frame_, 0u);
 
   const uint8* buffer_data;
   size_t buffer_size;
   if (buffer_->GetCurrentChunk(&buffer_data, &buffer_size)) {
     buffer_size = buffer_size - (buffer_size % bytes_per_output_frame_);
     snd_pcm_sframes_t frames = buffer_size / bytes_per_output_frame_;
 
     DCHECK_GT(frames, 0);
 
@@ skipping 21 matching lines @@
     } else {
       if (frames_written > frames) {
         LOG(WARNING)
             << "snd_pcm_writei() has written more frame that we asked.";
         frames_written = frames;
       }
 
       // Seek forward in the buffer after we've written some data to ALSA.
       buffer_->Seek(frames_written * bytes_per_output_frame_);
     }
+  } else {
+    // If nothing left to write and playback hasn't started yet, start it now.
+    // This ensures that shorter sounds will still play.
+    if (playback_handle_ &&
+        (wrapper_->PcmState(playback_handle_) == SND_PCM_STATE_PREPARED) &&
+        GetCurrentDelay() > 0) {
+      wrapper_->PcmStart(playback_handle_);
+    }
   }
 }
 
 void AlsaPcmOutputStream::WriteTask() {
   DCHECK_EQ(message_loop_, MessageLoop::current());
 
   if (stop_stream_) {
     return;
   }
 
+  if (shared_data_.state() == kIsStopped) {
+    return;
+  }
+
   bool source_exhausted;
   BufferPacket(&source_exhausted);
   WritePacket();
 
   ScheduleNextWrite(source_exhausted);
 }
 
 void AlsaPcmOutputStream::ScheduleNextWrite(bool source_exhausted) {
   DCHECK_EQ(message_loop_, MessageLoop::current());
 
@@ skipping 311 matching lines @@
 }
 
 // Changes the AudioSourceCallback to proxy calls to.  Pass in NULL to
 // release ownership of the currently registered callback.
 void AlsaPcmOutputStream::SharedData::set_source_callback(
     AudioSourceCallback* callback) {
   DCHECK_EQ(MessageLoop::current(), state_transition_loop_);
   base::AutoLock l(lock_);
   source_callback_ = callback;
 }