[cast] Allow audio encoder implementations to specify the frame length.

media/cast/sender/audio_sender.cc

 // Copyright 2014 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/cast/sender/audio_sender.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "media/cast/cast_defines.h"
 #include "media/cast/net/cast_transport_config.h"
 #include "media/cast/sender/audio_encoder.h"
 
 namespace media {
 namespace cast {
-namespace {
-
-// TODO(miu): This should be specified in AudioSenderConfig, but currently it is
-// fixed to 100 FPS (i.e., 10 ms per frame), and AudioEncoder assumes this as
-// well.
-const int kAudioFrameRate = 100;
-
-}  // namespace
 
 AudioSender::AudioSender(scoped_refptr<CastEnvironment> cast_environment,
                          const AudioSenderConfig& audio_config,
                          CastTransportSender* const transport_sender)
-    : FrameSender(
-        cast_environment,
-        true,
-        transport_sender,
-        base::TimeDelta::FromMilliseconds(audio_config.rtcp_interval),
-        audio_config.frequency,
-        audio_config.ssrc,
-        kAudioFrameRate,
-        audio_config.min_playout_delay,
-        audio_config.max_playout_delay,
-        NewFixedCongestionControl(audio_config.bitrate)),
+    : FrameSender(cast_environment,
+                  true,
+                  transport_sender,
+                  base::TimeDelta::FromMilliseconds(audio_config.rtcp_interval),
+                  audio_config.frequency,
+                  audio_config.ssrc,
+                  0,  // |max_frame_rate_| is set after encoder initialization.
+                  audio_config.min_playout_delay,
+                  audio_config.max_playout_delay,
+                  NewFixedCongestionControl(audio_config.bitrate)),
       samples_in_encoder_(0),
       weak_factory_(this) {
   cast_initialization_status_ = STATUS_AUDIO_UNINITIALIZED;
 
   if (!audio_config.use_external_encoder) {
     audio_encoder_.reset(
         new AudioEncoder(cast_environment,
                          audio_config.channels,
                          audio_config.frequency,
                          audio_config.bitrate,
                          audio_config.codec,
                          base::Bind(&AudioSender::OnEncodedAudioFrame,
                                     weak_factory_.GetWeakPtr(),
                                     audio_config.bitrate)));
     cast_initialization_status_ = audio_encoder_->InitializationResult();
   } else {
     NOTREACHED();  // No support for external audio encoding.
     cast_initialization_status_ = STATUS_AUDIO_UNINITIALIZED;
   }
 
+  // The number of samples per encoded audio frame depends on the codec and its
+  // initialization parameters. Now that we have an encoder, we can calculate
+  // the maximum frame rate.
+  max_frame_rate_ =
+      audio_config.frequency / audio_encoder_->GetSamplesPerFrame();
+
   media::cast::CastTransportRtpConfig transport_config;
   transport_config.ssrc = audio_config.ssrc;
   transport_config.feedback_ssrc = audio_config.incoming_feedback_ssrc;
   transport_config.rtp_payload_type = audio_config.rtp_payload_type;
   transport_config.aes_key = audio_config.aes_key;
   transport_config.aes_iv_mask = audio_config.aes_iv_mask;
 
   transport_sender->InitializeAudio(
       transport_config,
       base::Bind(&AudioSender::OnReceivedCastFeedback,
@@ skipping 45 matching lines @@
   DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::MAIN));
 
   samples_in_encoder_ -= audio_encoder_->GetSamplesPerFrame() + samples_skipped;
   DCHECK_GE(samples_in_encoder_, 0);
 
   SendEncodedFrame(encoder_bitrate, encoded_frame.Pass());
 }
 
 }  // namespace cast
 }  // namespace media