Not streaming packets of silence.

remoting/host/audio_capturer.cc

Index: remoting/host/audio_capturer.cc
diff --git a/remoting/host/audio_capturer.cc b/remoting/host/audio_capturer.cc
index 8828475de5f1be97c1334da6b4bd8310757b023e..28ec1b19a0b287a735a790a5517fe9f8b9165f46 100644
--- a/remoting/host/audio_capturer.cc
+++ b/remoting/host/audio_capturer.cc
@@ -4,10 +4,19 @@
 
 #include "remoting/host/audio_capturer.h"
 
+#include <math.h>

[Sergey Ulanov, 2012/07/27 22:46:51]

abs() is in stdlib.h

[kxing, 2012/07/30 16:55:18]

Done.

+
+#include "base/basictypes.h"
 #include "remoting/proto/audio.pb.h"
 
+namespace {
+const int kBytesPerSample = 2;
+const int kSilenceThreshold = 2;
+}  // namespace
+
 namespace remoting {
 
+// static
 bool AudioCapturer::IsValidSampleRate(int sample_rate) {
   switch (sample_rate) {
     case AudioPacket::SAMPLING_RATE_44100:
@@ -18,4 +27,16 @@ bool AudioCapturer::IsValidSampleRate(int sample_rate) {
   }
 }
 
+// static
+bool AudioCapturer::IsPacketOfSilence(const AudioPacket* packet) {
+  const int16* data = reinterpret_cast<const int16*>(packet->data().data());
+  int number_of_samples = packet->data().size() / kBytesPerSample;
+
+  for (int i = 0; i < number_of_samples; i++) {
+    if (std::abs(data[i]) > kSilenceThreshold)

[Sergey Ulanov, 2012/07/27 22:46:51]

I think using memchr() to verify that the data is all zeroes would be good
enough here.
If there is really a need to filter low-volume noise then we probably need a
fancier algorithm here. E.g. the buffer can contain the same value different
from 0 for all samples - that's still silence.

[Sergey Ulanov, 2012/07/27 22:46:51]

abs() without std::

[kxing, 2012/07/30 16:55:18]

Done.

[kxing, 2012/07/30 16:55:18]

Windows can give samples such as [0, 0, 0, 1, -1, 0, 0, 0, ..., 0, 1, 0, -1, 0]
even when nothing is playing. I'm not sure if memchr would be the right solution
for that.
For this CL, I'll stick to low volume noise centered around 0. Perhaps in the
future, I'll turn it into an algorithm detecting low-volume noise centered
around an arbitrary value.

[Sergey Ulanov, 2012/07/30 17:53:48]

Hm. that is strange. Then it looks like this particular implementation should be
windows-specific. I doubt that we will see the same behavior on other platforms.
Move this function to audio_capturer_win.cc? and then you can revert changes for
audio_capturer_util.cc.

[kxing, 2012/07/30 20:21:36]

Done.

+      return false;
+  }
+  return true;
+}
+
 } // namespace remoting