Android中初始化Codec2的具体流程

Android系统中的MediaCodec架构提供了一种直接操作显卡解码器的方式。在Android 5.0之后，MediaCodec架构提供了更为底层的codec，即Codec2，可以方便地实现硬件加速的解码和编码，从而能够提高媒体文件的处理速度。

在Android中初始化Codec2的具体流程如下：

1.获取Codec2的列表

如下代码所示，可以通过MediaCodecList类获取Codec2的列表。然后通过iterate方法，获取系统中所有支持的codec信息。

MediaCodecList codecList = new MediaCodecList(MediaCodecList.REGULAR_CODECS);
for (MediaCodecInfo codecInfo : codecList.getCodecInfos()) {
    if (!codecInfo.isEncoder()) {
        continue;
    }
    String[] types = codecInfo.getSupportedTypes();
    for (String type : types) {
        if (!type.equals(Mime. VIDEO_H264)) {
            continue;
        }
        // Get the default capabilities for an H.264 encoder
        CodecCapabilities capabilities =
                codecInfo.getCapabilitiesForType(type);
        // Check the resolution supported by hardware codec and your device
        int width = 1280;
        int height = 720;
        if (capabilities.isFormatSupported(new MediaFormat().
                setInteger(MediaFormat.KEY_WIDTH, width).
                setInteger(MediaFormat.KEY_HEIGHT, height).
                setString(MediaFormat.KEY_MIME, type))) {
            Log.i(TAG, "Found " + codecInfo.getName() + " supporting " + type + " for "
                    + width + "x" + height + " with default capabilities: " + capabilities);
        }
    }
}

2.创建Codec2

通过Codec2的名称创建MediaCodec对象，并将其配置为编码器或解码器，如下所示：

MediaCodec codec = MediaCodec.createByCodecName(codecInfo.getName());
MediaFormat inputFormat = MediaFormat.createVideoFormat(Mime.VIDEO_H264,
        1280, 720);
codec.configure(inputFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
codec.start();

3.接收数据并编码

通过configure方法配置设置编码器的输入格式，然后通过MediaCodec中的encoderInputBuffer，从交换数组中获取有效的输入数据进行编码，最后将编码后的数据放入MediaCodec的输出缓冲区中，如下所示：

ByteBuffer[] encoderInputBuffer = codec.getInputBuffers();
ByteBuffer[] encoderOutputBuffer = codec.getOutputBuffers();
int timeoutUs = 10000;
while (true) {
    int inputBufferIndex = codec.dequeueInputBuffer(timeoutUs);
    if (inputBufferIndex >= 0) {
        ByteBuffer inputBuffer = encoderInputBuffer[inputBufferIndex];
        //Fill the ByteBuffer with your raw data
        int rawBytesDataLength = getAudioDataLength();
        inputBuffer.clear();
        byte[] rawBytesData = getRawBytesData();
        inputBuffer.put(rawBytesData, 0, rawBytesDataLength);
        codec.queueInputBuffer(inputBufferIndex, 0, rawBytesDataLength, 0, 0);
    }
    MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
    int outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, timeoutUs);
    if (outputBufferIndex >= 0) {
        ByteBuffer outputBuffer = encoderOutputBuffer[outputBufferIndex];
        // Output the encoded frame here to other sources
        codec.releaseOutputBuffer(outputBufferIndex, false);
    }
}

以上是初始化Codec2的具体流程。其中，第二步和第三步中的核心代码，就是通过configure方法来进行配置，然后在输入数据中获取有效数据，经过编码后输出到输出缓冲区中。

下面是两个示例：

示例一：实现将本地视频转换为h.264编码格式并保存到文件中：

MediaCodec codec = MediaCodec.createEncoderByType("video/avc");
int width = 640;
int height = 480;
int frameRate = 30;
int bitRate = 1024 * 1024;
int colorFormat = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Flexible;
int iFrameInterval = 1;
MediaFormat format = MediaFormat.createVideoFormat("video/avc", width, height);
format.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
format.setInteger(MediaFormat.KEY_FRAME_RATE, frameRate);
format.setInteger(MediaFormat.KEY_COLOR_FORMAT, colorFormat);
format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, iFrameInterval);
codec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
codec.start();

ByteBuffer[] inputBuffers = codec.getInputBuffers();
ByteBuffer[] outputBuffers = codec.getOutputBuffers();
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
// Do video decoding here until we get EOS from the decoder
boolean done = false;
while (done) {
    // Do video encoding here
    //extract data from input buffer
    int inputBufferIndex = codec.dequeueInputBuffer(10000);
    if (inputBufferIndex >= 0) {
        ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
        byte[] newInputData = getInputData();
        inputBuffer.put(newInputData);
        codec.queueInputBuffer(inputBufferIndex, 0, newInputData.length, 0, 0);
    }
    //continue dequeueing and encoding until we get an EOF
    int outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, 10000);
    while (outputBufferIndex != -1) {
        ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
        //output the encoded video data
        outputToFile(outputBuffer);
        codec.releaseOutputBuffer(outputBufferIndex, false);
        outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, 0);
    }
    if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
        done = true;
    }
}
codec.stop();
codec.release();

示例二：实现通过异步线程进行数据的编码：

private static class EncodingTask extends AsyncTask<Void, Void, Void> {
    MediaCodec codec;
    ByteBuffer[] inputBuffers;
    ByteBuffer[] outputBuffers;
    MediaCodec.BufferInfo bufferInfo;

    public EncodingTask() {
        codec = MediaCodec.createEncoderByType("video/avc");
        int width = 640;
        int height = 480;
        int frameRate = 30;
        int bitRate = 1024 * 1024;
        int colorFormat = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Flexible;
        int iFrameInterval = 1;
        MediaFormat format = MediaFormat.createVideoFormat("video/avc", width, height);
        format.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
        format.setInteger(MediaFormat.KEY_FRAME_RATE, frameRate);
        format.setInteger(MediaFormat.KEY_COLOR_FORMAT, colorFormat);
        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, iFrameInterval);
        codec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        codec.start();

        int timeoutUs = 10000;
        inputBuffers = codec.getInputBuffers();
        outputBuffers = codec.getOutputBuffers();
        bufferInfo = new MediaCodec.BufferInfo();

        // Put data into our queue
        offerEncoderInput(bufferInfo, true);
    }

    @Override
    protected Void doInBackground(Void... params) {
        while (true) {
            if (isCancelled()) {
                return null;
            }
            int outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, timeoutUs);
            if (outputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
                continue;
            } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                Log.d(TAG, "encoder output format changed: " + codec.getOutputFormat());
                continue;
            } else if (outputBufferIndex < 0) {
                continue;
            }
            ByteBuffer outputBuffer = codec.getOutputBuffers()[outputBufferIndex];
            // Put data in the buffer

            codec.releaseOutputBuffer(outputBufferIndex, false);
            offerEncoderInput(bufferInfo, false);
        }
    }

    private void offerEncoderInput(MediaCodec.BufferInfo bufferInfo, boolean eos) {
        while (true) {
            int inputBufferIndex = codec.dequeueInputBuffer(timeoutUs);
            if (inputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
                continue;
            }
            if (eos) {
                codec.queueInputBuffer(inputBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                break;
            }
            ByteBuffer inputBuffer = codec.getInputBuffers()[inputBufferIndex];
            // Put data into input buffer

            codec.queueInputBuffer(inputBufferIndex, bufferInfo.offset, bufferInfo.size,
                    bufferInfo.presentationTimeUs, bufferInfo.flags);
            break;
        }
    }
}

以上两个示例，分别实现了将本地视频转换为h.264编码格式及通过异步线程进行数据编码，并通过设置各种参数进行优化处理，显著提高了视频编码效率。其中，初始化Codec2的流程，包括获取Codec2的列表、创建Codec2以及接收数据并进行编码，都是必不可少的步骤。

本站文章如无特殊说明，均为本站原创，如若转载，请注明出处：Android中初始化Codec2的具体流程 - Python技术站

Android中初始化Codec2的具体流程

相关文章