Keep track of the user-facing number of channels in a ChannelBuffer

webrtc/common_audio/channel_buffer.cc

 /*
  *  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.
  */
 
@@ skipping 36 matching lines @@
 void IFChannelBuffer::RefreshF() const {
   if (!fvalid_) {
     RTC_DCHECK(ivalid_);
     const int16_t* const* int_channels = ibuf_.channels();
     float* const* float_channels = fbuf_.channels();
     for (size_t i = 0; i < ibuf_.num_channels(); ++i) {
       for (size_t j = 0; j < ibuf_.num_frames(); ++j) {
         float_channels[i][j] = int_channels[i][j];
       }
     }
+    fbuf_.set_num_channels(ibuf_.num_channels());

[peah-webrtc, 2016/06/23 13:32:21]

Would it be possible to move this before the copy? As it is now, the DCHECK for
the valid number of channels that occurs inside set_num_channels will happen
after the sample copy, which means that the DCHECK does not properly protect
agains incorrect buffer usage.

[aluebs-webrtc, 2016/06/24 02:49:16]

Good point, although it should never happen. Done.

     fvalid_ = true;
   }
 }
 
 void IFChannelBuffer::RefreshI() const {
   if (!ivalid_) {
     RTC_DCHECK(fvalid_);
     int16_t* const* int_channels = ibuf_.channels();
     const float* const* float_channels = fbuf_.channels();
-    for (size_t i = 0; i < ibuf_.num_channels(); ++i) {
+    for (size_t i = 0; i < fbuf_.num_channels(); ++i) {
       FloatS16ToS16(float_channels[i],
                     ibuf_.num_frames(),
                     int_channels[i]);
     }
+    ibuf_.set_num_channels(fbuf_.num_channels());

[peah-webrtc, 2016/06/23 13:32:21]

Would it be possible to move this before the copy? As it is now, the DCHECK for
the valid number of channels that occurs inside set_num_channels will happen
after the sample copy, which means that the DCHECK does not properly protect
agains incorrect buffer usage.

[aluebs-webrtc, 2016/06/24 02:49:16]

Good point, although it should never happen. Done.

     ivalid_ = true;
   }
 }
 
 }  // namespace webrtc