VP9 wrapper: Adjust speed setting.

webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc

Index: webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
diff --git a/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc b/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
index a44d0f66bfc69869f926ffc4757dd3dbed599654..cd91fa3bdeea5c290dbe2e00fe4e2404f8fb716a 100644
--- a/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
+++ b/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
@@ -42,6 +42,17 @@ static void WrappedI420BufferNoLongerUsedCb(
 
 namespace webrtc {
 
+// Only positive speeds, range for real-time coding currently is: 5 - 8.
+// Lower means slower/better quality, higher means fastest/lower quality.
+int GetCpuSpeed(int width, int height) {

[tommi, 2015/07/08 09:13:39]

Can this be in an anonymous namespace?
Also, I find the function name and parameters to be confusing. :-/
The return value doesn't tell you anything about the speed of the cpu...  where
is the range defined (aside from the comment)?  Would it make sense to call this
GetCompressionQuality or GetEncodingQuality?

+  // For smaller resolutions, use lower speed setting (get some coding gain at
+  // the cost of increased encoding complexity).
+  if (width * height <= 352 * 288)
+    return 5;
+  else
+    return 7;
+}
+
 VP9Encoder* VP9Encoder::Create() {
   return new VP9EncoderImpl();
 }
@@ -194,11 +205,11 @@ int VP9EncoderImpl::InitEncode(const VideoCodec* inst,
   } else {
     config_->kf_mode = VPX_KF_DISABLED;
   }
-
   // Determine number of threads based on the image size and #cores.
   config_->g_threads = NumberOfThreads(config_->g_w,
                                        config_->g_h,
                                        number_of_cores);
+  cpu_speed_ = GetCpuSpeed(config_->g_w, config_->g_h);
   return InitAndSetControlSettings(inst);
 }
 
@@ -221,11 +232,6 @@ int VP9EncoderImpl::InitAndSetControlSettings(const VideoCodec* inst) {
   if (vpx_codec_enc_init(encoder_, vpx_codec_vp9_cx(), config_, 0)) {
     return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
   }
-  // Only positive speeds, currently: 0 - 8.
-  // O means slowest/best quality, 8 means fastest/lower quality.
-  cpu_speed_ = 7;

[tommi, 2015/07/08 09:13:39]

cpu_speed_ is in my opinion not a great variable name. For something that
determines quality of the encoding, I would have liked to use something like
encoding_quality_ and define the range in constants (min/max).  As is, cpu_used_
would at least be better since it matches with the vpx settings constant.

-  // Note: some of these codec controls still use "VP8" in the control name.
-  // TODO(marpan): Update this in the next/future libvpx version.
   vpx_codec_control(encoder_, VP8E_SET_CPUUSED, cpu_speed_);
   vpx_codec_control(encoder_, VP8E_SET_MAX_INTRA_BITRATE_PCT,
                     rc_max_intra_target_);