[移动开发]Webrtc创建Android端编码器流程

1.根据info创建对应的硬软编码器（vp8还是H264），优先选择硬编码

public VideoEncoder createEncoder(VideoCodecInfo info) {
  final VideoEncoder softwareEncoder = softwareVideoEncoderFactory.createEncoder(info);
  final VideoEncoder hardwareEncoder = hardwareVideoEncoderFactory.createEncoder(info);
  if (hardwareEncoder != null && softwareEncoder != null) {
    // Both hardware and software supported, wrap it in a software fallback
    return new VideoEncoderFallback(
        /* fallback= */ softwareEncoder, /* primary= */ hardwareEncoder);
  }
  return hardwareEncoder != null ? hardwareEncoder : softwareEncoder;
}

public VideoEncoder createEncoder(VideoCodecInfo input) {
  // HW encoding is not supported below Android Kitkat.
  if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
    return null;
  }

  VideoCodecMimeType type = VideoCodecMimeType.valueOf(input.getName());
  MediaCodecInfo info = findCodecForType(type);

  if (info == null) {
    return null;
  }
 }

2.判断是否VideoCodecMimeType type类型的编码器

enum VideoCodecMimeType {
  VP8("video/x-vnd.on2.vp8"),
  VP9("video/x-vnd.on2.vp9"),
  H264("video/avc"),
  AV1("video/av01");
}

private MediaCodecInfo findCodecForType(VideoCodecMimeType type) {
  for (int i = 0; i < MediaCodecList.getCodecCount(); ++i) {
    MediaCodecInfo info = null;
    try {
      info = MediaCodecList.getCodecInfoAt(i);
    } catch (IllegalArgumentException e) {
      Logging.e(TAG, "Cannot retrieve encoder codec info", e);
    }

    if (info == null || !info.isEncoder()) {
      continue;
    }

    if (isSupportedCodec(info, type)) {
      return info;
    }
  }
  return null; // No support for this type.
}

private boolean isSupportedCodec(MediaCodecInfo info, VideoCodecMimeType type) {
  if (!MediaCodecUtils.codecSupportsType(info, type)) {
    return false;
  }
  // Check for a supported color format.
  if (MediaCodecUtils.selectColorFormat(
          MediaCodecUtils.ENCODER_COLOR_FORMATS, info.getCapabilitiesForType(type.mimeType()))
      == null) {
    return false;
  }
  return isHardwareSupportedInCurrentSdk(info, type) && isMediaCodecAllowed(info);
}

3.根据supportedH264HwCodecPrefixes里面的型号判断当前设备是否支持硬编码

static final String[] supportedH264HwCodecPrefixes = new String[]{"OMX.qcom.", 
"OMX.Exynos.", "OMX.MTK.", "OMX.IMG.TOPAZ.",  "OMX.k3.", "OMX.amlogic.", 
"OMX.rk.", "OMX.MS."};

private boolean isHardwareSupportedInCurrentSdkH264(MediaCodecInfo info) {
  // First, H264 hardware might perform poorly on this model.
  if (H264_HW_EXCEPTION_MODELS.contains(Build.MODEL)) {
      Logging.e("Log","isHardwareSupportedInCurrentSdkH264 HardwareSupported false");
      return false;
  }
  String name = info.getName();
  Logging.i("Log","isHardwareSupportedInCurrentSdkH264 HardwareSupported:" + name);
  for (int i =0;i<MediaCodecUtils.supportedH264HwCodecPrefixes.length;i++){
    if (name.startsWith(MediaCodecUtils.supportedH264HwCodecPrefixes[i])){
        Logging.i("_Log","isHardwareSupportedInCurrentSdkH264 HardwareSupported true");
        return true;
    }
  }

  Logging.i("Log","isHardwareSupportedInCurrentSdkH264 HardwareSupported false");
  return false;
}