message: AV1: set superblock to 64x64 for 720p 4 threads.
  Multithreading is more effective.
  Cr-Commit-Position: refs/heads/master@{#33306}
diff: @@ -64,6 +64,14 @@ int GetCpuSpeed(int width, int height, int number_of_cores) {
  return 7;
  }
  +aom_superblock_size_t GetSuperblockSize(int width, int height, int threads) {
  + int resolution = width * height;
  + if (threads >= 4 && resolution >= 960 * 540 && resolution < 1920 * 1080)
  + return AOM_SUPERBLOCK_SIZE_64X64;
  + else
  + return AOM_SUPERBLOCK_SIZE_DYNAMIC;
  +}
  +
  class LibaomAv1Encoder final : public VideoEncoder {
  public:
  LibaomAv1Encoder();
  @@ -353,6 +361,15 @@ int LibaomAv1Encoder::InitEncode(const VideoCodec* codec_settings,
  return WEBRTC_VIDEO_CODEC_ERROR;
  }
  + ret =
  + aom_codec_control(&ctx_, AV1E_SET_SUPERBLOCK_SIZE,
  + GetSuperblockSize(cfg_.g_w, cfg_.g_h, cfg_.g_threads));
  + if (ret != AOM_CODEC_OK) {
  + RTC_LOG(LS_WARNING) << "LibaomAv1Encoder::EncodeInit returned " << ret
  + << " on control AV1E_SET_SUPERBLOCK_SIZE.";
  + return WEBRTC_VIDEO_CODEC_ERROR;
  + }
  +
  return WEBRTC_VIDEO_CODEC_OK;
  }
  