(OBSOLETE) Increasing audio buffer on Iphone 4S.

webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.mm

Index: webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.mm
diff --git a/webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.m b/webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.mm
similarity index 91%
rename from webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.m
rename to webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.mm
index d2d04835499fe9ee990f546ddda01cc787d5cf39..ea6200270ce0dc56387b6f1b0f6115c4a63568f6 100644
--- a/webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.m
+++ b/webrtc/modules/audio_device/ios/objc/RTCAudioSessionConfiguration.mm
@@ -13,6 +13,7 @@
 #import "WebRTC/RTCDispatcher.h"
 
 #import "webrtc/modules/audio_device/ios/objc/RTCAudioSession.h"
+#include "webrtc/modules/utility/include/helpers_ios.h"

[tkchin_webrtc, 2016/06/24 00:30:48]

Let's avoid using this file. I want to move helpers away to sdk/objc.

 
 // Try to use mono to save resources. Also avoids channel format conversion
 // in the I/O audio unit. Initial tests have shown that it is possible to use
@@ -44,6 +45,10 @@ const double kRTCAudioSessionLowComplexitySampleRate = 16000.0;
 // sequence without bursts of callbacks back to back.
 const double kRTCAudioSessionHighPerformanceIOBufferDuration = 0.01;
 
+// Use a larger buffer size on iphone 4S to allow it running complex tasks
+// e.g., encoding large frames with Opus codec.
+const double kRTCAudioSessionHighPerformanceIOBufferDurationIphone4s = 0.02;
+
 // Use a larger buffer size on devices with only one core (e.g. iPhone 4).
 // It will result in a lower CPU consumption at the cost of a larger latency.
 // The size of 60ms is based on instrumentation that shows a significant
@@ -84,7 +89,12 @@ static RTCAudioSessionConfiguration *gWebRTCConfiguration = nil;
     // core.
     if (processorCount > 1) {
       _sampleRate = kRTCAudioSessionHighPerformanceSampleRate;
-      _ioBufferDuration = kRTCAudioSessionHighPerformanceIOBufferDuration;
+      if (webrtc::ios::GetDeviceName() == "iPhone 4S") {

[tkchin_webrtc, 2016/06/24 00:30:48]

Wouldn't use strings like this. We should enumerate devices elsewhere.

I think the better things to do is to add a category to UIDevice, e.g.
UIDevice+WebRTC.h, define an enum for all the known device types, and then have
a method that does GetDeviceName() except it returns the type instead of the
string.

It should go into webrtc/sdk/objc/Framework/Headers/WebRTC/

+        _ioBufferDuration =
+            kRTCAudioSessionHighPerformanceIOBufferDurationIphone4s;
+      } else {
+        _ioBufferDuration = kRTCAudioSessionHighPerformanceIOBufferDuration;
+      }
     } else {
       _sampleRate = kRTCAudioSessionLowComplexitySampleRate;
       _ioBufferDuration = kRTCAudioSessionLowComplexityIOBufferDuration;