Adjust the amount of VP8 encoder threads for Android builds.

webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc

 /*
  *  Copyright (c) 2012 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 615 matching lines @@
   // if resolution is below CIF. Otherwise, keep the default/user setting
   // (|cpu_speed_default_|) set on InitEncode via codecSpecific.VP8.complexity.
   if (width * height < 352 * 288)
     return (cpu_speed_default_ < -4) ? -4 : cpu_speed_default_;
   else
     return cpu_speed_default_;
 #endif
 }
 
 int VP8EncoderImpl::NumberOfThreads(int width, int height, int cpus) {
+#if defined(ANDROID)
+  if (width * height >= 320 * 180) {
+    if (cpus >= 4) {
+      // 3 threads for CPUs with 4 and more cores since most of times only 4
+      // cores will be active.
+      return 3;
+    } else if (cpus == 3 || cpus == 2) {
+      return 2;
+    } else {
+      return 1;
+    }
+  }
+  return 1;
+#else
   if (width * height >= 1920 * 1080 && cpus > 8) {
     return 8;  // 8 threads for 1080p on high perf machines.
   } else if (width * height > 1280 * 960 && cpus >= 6) {
     // 3 threads for 1080p.
     return 3;
   } else if (width * height > 640 * 480 && cpus >= 3) {
     // 2 threads for qHD/HD.
     return 2;
   } else {
     // 1 thread for VGA or less.
     return 1;
   }
+#endif
 }
 
 int VP8EncoderImpl::InitAndSetControlSettings() {
   vpx_codec_flags_t flags = 0;
   flags |= VPX_CODEC_USE_OUTPUT_PARTITION;
 
   if (encoders_.size() > 1) {
     int error = vpx_codec_enc_init_multi(&encoders_[0], vpx_codec_vp8_cx(),
                                          &configurations_[0], encoders_.size(),
                                          flags, &downsampling_factors_[0]);
@@ skipping 758 matching lines @@
     return -1;
   }
   if (vpx_codec_control(copy->decoder_, VP8_SET_REFERENCE, ref_frame_) !=
       VPX_CODEC_OK) {
     return -1;
   }
   return 0;
 }
 
 }  // namespace webrtc