Prevent Opus DTX from generating intermittent noise during silence

webrtc/modules/audio_coding/codecs/opus/opus_inst.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_OPUS_OPUS_INST_H_
 #define WEBRTC_MODULES_AUDIO_CODING_CODECS_OPUS_OPUS_INST_H_
 
 #include "opus.h"
 
 struct WebRtcOpusEncInst {
   OpusEncoder* encoder;
+  int channels;
   int in_dtx_mode;
+  // When Opus is in DTX mode, we use |zero_counts| to count consecutive zeros

[the sun, 2015/11/09 12:41:00]

Should you add a TODO to remove this workaround once it has been fixed properly
in Opus?

[minyue-webrtc, 2015/11/09 15:13:00]

Done.

+  // to break long zero segment so as to prevent DTX from going wrong. We use
+  // one counter for each channel. After each encoding, |zero_counts| contain
+  // the remaining zeros from the last frame.
+  size_t* zero_counts;
 };
 
 struct WebRtcOpusDecInst {
   OpusDecoder* decoder;
   int prev_decoded_samples;
   int channels;
   int in_dtx_mode;
 };
 
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_OPUS_OPUS_INST_H_