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

webrtc/common_audio/channel_buffer.h

Index: webrtc/common_audio/channel_buffer.h
diff --git a/webrtc/common_audio/channel_buffer.h b/webrtc/common_audio/channel_buffer.h
index faecec9194ceb86be1d37104e24e7ad0a6915048..d6661de4ff7ee8629e432f3f915cb99fe919e403 100644
--- a/webrtc/common_audio/channel_buffer.h
+++ b/webrtc/common_audio/channel_buffer.h
@@ -48,13 +48,14 @@ class ChannelBuffer {
         bands_(new T*[num_channels * num_bands]),
         num_frames_(num_frames),
         num_frames_per_band_(num_frames / num_bands),
+        num_allocated_channels_(num_channels),
         num_channels_(num_channels),
         num_bands_(num_bands) {
-    for (size_t i = 0; i < num_channels_; ++i) {
+    for (size_t i = 0; i < num_allocated_channels_; ++i) {
       for (size_t j = 0; j < num_bands_; ++j) {
-        channels_[j * num_channels_ + i] =
+        channels_[j * num_allocated_channels_ + i] =
             &data_[i * num_frames_ + j * num_frames_per_band_];
-        bands_[i * num_bands_ + j] = channels_[j * num_channels_ + i];
+        bands_[i * num_bands_ + j] = channels_[j * num_allocated_channels_ + i];
       }
     }
   }
@@ -63,7 +64,7 @@ class ChannelBuffer {
   // Usage:
   // channels()[channel][sample].
   // Where:
-  // 0 <= channel < |num_channels_|
+  // 0 <= channel < |num_allocated_channels_|
   // 0 <= sample < |num_frames_|
   T* const* channels() { return channels(0); }
   const T* const* channels() const { return channels(0); }
@@ -73,11 +74,11 @@ class ChannelBuffer {
   // channels(band)[channel][sample].
   // Where:
   // 0 <= band < |num_bands_|
-  // 0 <= channel < |num_channels_|
+  // 0 <= channel < |num_allocated_channels_|
   // 0 <= sample < |num_frames_per_band_|
   const T* const* channels(size_t band) const {
     RTC_DCHECK_LT(band, num_bands_);
-    return &channels_[band * num_channels_];
+    return &channels_[band * num_allocated_channels_];
   }
   T* const* channels(size_t band) {
     const ChannelBuffer<T>* t = this;
@@ -118,7 +119,12 @@ class ChannelBuffer {
   size_t num_frames_per_band() const { return num_frames_per_band_; }
   size_t num_channels() const { return num_channels_; }
   size_t num_bands() const { return num_bands_; }
-  size_t size() const {return num_frames_ * num_channels_; }
+  size_t size() const {return num_frames_ * num_allocated_channels_; }
+
+  void set_num_channels(size_t num_channels) {
+    RTC_DCHECK_LE(num_channels, num_allocated_channels_);
+    num_channels_ = num_channels;
+  }
 
   void SetDataForTesting(const T* data, size_t size) {
     RTC_CHECK_EQ(size, this->size());
@@ -131,7 +137,10 @@ class ChannelBuffer {
   std::unique_ptr<T* []> bands_;
   const size_t num_frames_;
   const size_t num_frames_per_band_;
-  const size_t num_channels_;
+  // Number of channels the internal buffer holds.
+  const size_t num_allocated_channels_;
+  // Number of channels the user sees.
+  size_t num_channels_;
   const size_t num_bands_;
 };
 
@@ -152,7 +161,13 @@ class IFChannelBuffer {
 
   size_t num_frames() const { return ibuf_.num_frames(); }
   size_t num_frames_per_band() const { return ibuf_.num_frames_per_band(); }
-  size_t num_channels() const { return ibuf_.num_channels(); }
+  size_t num_channels() const {
+    return ivalid_ ? ibuf_.num_channels() : fbuf_.num_channels();
+  }
+  void set_num_channels(size_t num_channels) {
+    ibuf_.set_num_channels(num_channels);
+    fbuf_.set_num_channels(num_channels);
+  }
   size_t num_bands() const { return ibuf_.num_bands(); }
 
  private: