Remove media::AudioRendererImpl::SignalEndOfStream() and some other minor cleanup.

media/filters/audio_renderer_impl.cc

 // Copyright (c) 2012 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.
 
 #include "media/filters/audio_renderer_impl.h"
 
 #include <math.h>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 259 matching lines @@
     case kUnderflow:
     case kRebuffering:
       if (buffer && !buffer->IsEndOfStream())
         algorithm_->EnqueueBuffer(buffer);
       return;
     case kStopped:
       return;
   }
 }
 
-void AudioRendererImpl::SignalEndOfStream() {
-  DCHECK(received_end_of_stream_);
-  if (!rendered_end_of_stream_) {
-    rendered_end_of_stream_ = true;
-    host()->NotifyEnded();
-  }
-}
-
 void AudioRendererImpl::ScheduleRead_Locked() {
   lock_.AssertAcquired();
   if (pending_read_ || state_ == kPaused)
     return;
   pending_read_ = true;
   decoder_->Read(read_cb_);
 }
 
 void AudioRendererImpl::SetPlaybackRate(float playback_rate) {
   DCHECK_LE(0.0f, playback_rate);
@@ skipping 101 matching lines @@
       // the subclass can restart the conversation.
       //
       // This should get handled by the subclass http://crbug.com/106600
       const uint32 kZeroLength = 8192;
       size_t zeros_to_write =
           std::min(kZeroLength, requested_frames * bytes_per_frame_);
       memset(dest, 0, zeros_to_write);
       return zeros_to_write / bytes_per_frame_;
     }
 
-    // Use three conditions to determine the end of playback:
-    // 1. Algorithm needs more audio data.
-    // 2. We've received an end of stream buffer.
-    //    (received_end_of_stream_ == true)
-    // 3. Browser process has no audio data being played.
-    //    There is no way to check that condition that would work for all
-    //    derived classes, so call virtual method that would either render
-    //    end of stream or schedule such rendering.
+    // We use the following conditions to determine end of playback:
+    //   1) Algorithm needs more audio data
+    //   2) We received an end of stream buffer
+    //   3) We haven't already signalled that we've ended
+    //   4) Our estimated earliest end time has expired
     //
-    // Three conditions determine when an underflow occurs:
-    // 1. Algorithm has no audio data.
-    // 2. Currently in the kPlaying state.
-    // 3. Have not received an end of stream buffer.
-    if (algorithm_->NeedsMoreData()) {
-      if (received_end_of_stream_) {
-        // TODO(enal): schedule callback instead of polling.
-        if (base::Time::Now() >= earliest_end_time_)
-          SignalEndOfStream();
-      } else if (state_ == kPlaying) {
-        state_ = kUnderflow;
-        underflow_cb = underflow_cb_;
-      }
+    // TODO(enal): we should replace (4) with a check that the browser has no
+    // more audio data or at least use a delayed callback.
+    //
+    // We use the following conditions to determine underflow:
+    //   1) Algorithm needs more audio data
+    //   2) We have NOT received an end of stream buffer
+    //   3) We are in the kPlaying state
+    //
+    // Otherwise fill the buffer with whatever data we can send to the device.
+    if (algorithm_->NeedsMoreData() && received_end_of_stream_ &&
+        !rendered_end_of_stream_ && base::Time::Now() >= earliest_end_time_) {
+      rendered_end_of_stream_ = true;
+      host()->NotifyEnded();
+    } else if (algorithm_->NeedsMoreData() && !received_end_of_stream_ &&
+               state_ == kPlaying) {
+      state_ = kUnderflow;
+      underflow_cb = underflow_cb_;
+    } else if (!algorithm_->NeedsMoreData()) {
+      frames_written = algorithm_->FillBuffer(dest, requested_frames);
+      DCHECK_GT(frames_written, 0u);
     } else {
-      // Otherwise fill the buffer.
-      frames_written = algorithm_->FillBuffer(dest, requested_frames);
+      // ATTN VRK: What should we do here? I can leave an empty else branch
+      // here, or we can be comfortable calling FillBuffer() + remove DCHECK
+      // even if NeedsMoreData() returns false.

[vrk (LEFT CHROMIUM), 2012/05/17 04:40:52]

Hmmm... 

Since all this code is crazy, I think keeping the empty else statement + comment
is the best thing to do. It's not elegant, but it's explicit -- so that way when
someone tries to rewrite this class (someday!!), they'll understand what was
happening originally.

[scherkus (not reviewing), 2012/05/19 03:13:08]

Done.

+      //
+      // Sample comment:
+      //
+      // We can't write any data this cycle. For example, we may have
+      // sent all available data to the audio device while not reaching
+      // |earliest_end_time_|.
     }
 
     // The |audio_time_buffered_| is the ending timestamp of the last frame
     // buffered at the audio device. |playback_delay| is the amount of time
     // buffered at the audio device. The current time can be computed by their
     // difference.
     if (audio_time_buffered_ != kNoTimestamp()) {
       base::TimeDelta previous_time = current_time_;
       current_time_ = audio_time_buffered_ - playback_delay;
 
@@ skipping 55 matching lines @@
         base::Time::kMicrosecondsPerSecond * bytes / bytes_per_second_);
   }
   return base::TimeDelta();
 }
 
 void AudioRendererImpl::OnRenderError() {
   host()->DisableAudioRenderer();
 }
 
 }  // namespace media