Android平台RTMP/RTSP播放器开发系列--解码和绘制

本文主要抛砖引玉，粗略介绍下Android平台RTMP/RTSP播放器中解码和绘制相关的部分(Github)。

解码

提到解码，大家都知道软硬解，甚至一些公司觉得硬解码已经足够通用，慢慢抛弃软解了，如果考虑到设备匹配，软硬解码都支持，是个不错的选择，为此，大牛直播SDK在开发这块的时候，分类是这样的：

1. 软解码：解码后获取到原始数据，可进行后续的原始数据回调和快照等操作；

2. 硬解码：解码后获取到原始数据，可进行后续的原始数据回调和快照等操作；

3. 硬解码：设置surface模式，直接render到设置的surface上，不可进行快照和解码后数据回调操作。

大家可能会疑惑，有了模式2，干嘛要再支持模式3呢？模式2和3分别有什么优势呢？

硬解码直接设置surface模式，相对来说，大多芯片支持更好，解码通用性更好，而且减少了数据拷贝，资源占用更低，缺点是无法获得解码后的原始数据，更像个黑盒操作；模式2兼顾了硬解码资源占用（相对软解）和二次操作原始数据能力（如针对解码后的yuv/rgb数据二次处理），解码通用性相对模式3略差，但数据处理更灵活。

相关接口：

	/**
	 * Set Video H.264 HW decoder(设置H.264硬解码)
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param isHWDecoder: 0: software decoder; 1: hardware decoder.
	 *
	 * @return {0} if successful
	 */
	public native int SetSmartPlayerVideoHWDecoder(long handle, int isHWDecoder);

	/**
	 * Set Video H.265(hevc) HW decoder(设置H.265硬解码)
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param isHevcHWDecoder: 0: software decoder; 1: hardware decoder.
	 *
	 * @return {0} if successful
	 */
	public native int SetSmartPlayerVideoHevcHWDecoder(long handle, int isHevcHWDecoder);

	/**
	 * Set Surface view(设置播放的surfaceview).
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param surface: surface view
	 *
	 * <pre> NOTE: if not set or set surface with null, it will playback audio only. </pre>
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetSurface(long handle, Object surface);

考虑到不是所有设备都支持硬解，大牛直播SDK的设计思路是先做硬解检测，检测到不支持，直接切换到软解模式。

绘制

大牛直播SDK的RTMP和RTSP播放器绘制这块，支持两种模式，普通的SurfaceView和GLSurface，普通的surface兼容性更好，GLSurface绘制相对来说更细腻，此外，普通的surface模式下，还支持了一些抗锯齿参数设置。两种模式下，都设计了视频画面的填充模式设置选项（是否等比例显示），具体接口设计如下：

	/**
	 * 设置视频画面的填充模式，如填充整个view、等比例填充view，如不设置，默认填充整个view
	 * @param handle: return value from SmartPlayerOpen()
	 * @param render_scale_mode 0: 填充整个view; 1: 等比例填充view, 默认值是0
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetRenderScaleMode(long handle, int render_scale_mode);

	/**
	 * 设置SurfaceView模式下(NTRenderer.CreateRenderer第二个参数传false的情况)，render类型
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param format: 0: RGB565格式，如不设置，默认此模式; 1: ARGB8888格式
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetSurfaceRenderFormat(long handle, int format);

	/**
	 * 设置SurfaceView模式下(NTRenderer.CreateRenderer第二个参数传false的情况)，抗锯齿效果，注意：抗锯齿模式开启后，可能会影像性能，请慎用
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param isEnableAntiAlias: 0: 如不设置，默认不开启抗锯齿模式; 1: 开启抗锯齿模式
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetSurfaceAntiAlias(long handle, int isEnableAntiAlias);

音频输出这块，可以考虑audiotrack和opensl es，考虑到通用性，可以选择audiotrack模式，当然最好是设置个选项，用户自行选择：

	/**
	 * Set AudioOutput Type(设置audio输出类型)
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param use_audiotrack:
	 *
	 * <pre> NOTE: if use_audiotrack with 0: it will use auto-select output devices; if with 1: will use audio-track mode. </pre>
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetAudioOutputType(long handle, int use_audiotrack);

视频view反转/旋转

	/**
	 * 设置视频垂直反转
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param is_flip： 0: 不反转, 1: 反转
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetFlipVertical(long handle, int is_flip);

	/**
	 * 设置视频水平反转
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param is_flip： 0: 不反转, 1: 反转
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetFlipHorizontal(long handle, int is_flip);

	/**
	 * 设置顺时针旋转, 注意除了0度之外， 其他角度都会额外消耗性能
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param degress： 当前支持 0度，90度, 180度, 270度 旋转
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetRotation(long handle, int degress);

解码后原始数据回调

在有些场景下，开发者需要针对解码后的YUV/RGB或者PCM数据进行处理，这个时候，需要设计针对解码后数据回调的接口模型：

	/**
	 * Set External Render(设置回调YUV/RGB数据)
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param external_render: External Render
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetExternalRender(long handle, Object external_render);

	/**
	 * Set External Audio Output(设置回调PCM数据)
	 *
	 * @param handle: return value from SmartPlayerOpen()
	 *
	 * @param external_audio_output:  External Audio Output
	 *
	 * @return {0} if successful
	 */
	public native int SmartPlayerSetExternalAudioOutput(long handle, Object external_audio_output);

具体调用实例：

//libPlayer.SmartPlayerSetExternalRender(playerHandle, new RGBAExternalRender());
//libPlayer.SmartPlayerSetExternalRender(playerHandle, new I420ExternalRender());

拿到原始数据，进行二次操作（如人脸识别等）：

    class RGBAExternalRender implements NTExternalRender {
        // public static final int NT_FRAME_FORMAT_RGBA = 1;
        // public static final int NT_FRAME_FORMAT_ABGR = 2;
        // public static final int NT_FRAME_FORMAT_I420 = 3;

        private int width_ = 0;
        private int height_ = 0;
        private int row_bytes_ = 0;
        private ByteBuffer rgba_buffer_ = null;

        @Override
        public int getNTFrameFormat() {
            Log.i(TAG, "RGBAExternalRender::getNTFrameFormat return "
                    + NT_FRAME_FORMAT_RGBA);
            return NT_FRAME_FORMAT_RGBA;
        }

        @Override
        public void onNTFrameSizeChanged(int width, int height) {
            width_ = width;
            height_ = height;

            row_bytes_ = width_ * 4;

            Log.i(TAG, "RGBAExternalRender::onNTFrameSizeChanged width_:"
                    + width_ + " height_:" + height_);

            rgba_buffer_ = ByteBuffer.allocateDirect(row_bytes_ * height_);
        }

        @Override
        public ByteBuffer getNTPlaneByteBuffer(int index) {
            if (index == 0) {
                return rgba_buffer_;
            } else {
                Log.e(TAG,
                        "RGBAExternalRender::getNTPlaneByteBuffer index error:"
                                + index);
                return null;
            }
        }

        @Override
        public int getNTPlanePerRowBytes(int index) {
            if (index == 0) {
                return row_bytes_;
            } else {
                Log.e(TAG,
                        "RGBAExternalRender::getNTPlanePerRowBytes index error:"
                                + index);
                return 0;
            }
        }

        public void onNTRenderFrame(int width, int height, long timestamp) {
            if (rgba_buffer_ == null)
                return;

            rgba_buffer_.rewind();

            // copy buffer

            // test
            // byte[] test_buffer = new byte[16];
            // rgba_buffer_.get(test_buffer);

            Log.i(TAG, "RGBAExternalRender:onNTRenderFrame w=" + width + " h="
                    + height + " timestamp=" + timestamp);

            // Log.i(TAG, "RGBAExternalRender:onNTRenderFrame rgba:" +
            // bytesToHexString(test_buffer));
        }
    }

    class I420ExternalRender implements NTExternalRender {
        // public static final int NT_FRAME_FORMAT_RGBA = 1;
        // public static final int NT_FRAME_FORMAT_ABGR = 2;
        // public static final int NT_FRAME_FORMAT_I420 = 3;

        private int width_ = 0;
        private int height_ = 0;

        private int y_row_bytes_ = 0;
        private int u_row_bytes_ = 0;
        private int v_row_bytes_ = 0;

        private ByteBuffer y_buffer_ = null;
        private ByteBuffer u_buffer_ = null;
        private ByteBuffer v_buffer_ = null;

        @Override
        public int getNTFrameFormat() {
            Log.i(TAG, "I420ExternalRender::getNTFrameFormat return "
                    + NT_FRAME_FORMAT_I420);
            return NT_FRAME_FORMAT_I420;
        }

        @Override
        public void onNTFrameSizeChanged(int width, int height) {
            width_ = width;
            height_ = height;

            y_row_bytes_ = (width_ + 15) & (~15);
            u_row_bytes_ = ((width_ + 1) / 2 + 15) & (~15);
            v_row_bytes_ = ((width_ + 1) / 2 + 15) & (~15);

            y_buffer_ = ByteBuffer.allocateDirect(y_row_bytes_ * height_);
            u_buffer_ = ByteBuffer.allocateDirect(u_row_bytes_
                    * ((height_ + 1) / 2));
            v_buffer_ = ByteBuffer.allocateDirect(v_row_bytes_
                    * ((height_ + 1) / 2));

            Log.i(TAG, "I420ExternalRender::onNTFrameSizeChanged width_="
                    + width_ + " height_=" + height_ + " y_row_bytes_="
                    + y_row_bytes_ + " u_row_bytes_=" + u_row_bytes_
                    + " v_row_bytes_=" + v_row_bytes_);
        }

        @Override
        public ByteBuffer getNTPlaneByteBuffer(int index) {
            if (index == 0) {
                return y_buffer_;
            } else if (index == 1) {
                return u_buffer_;
            } else if (index == 2) {
                return v_buffer_;
            } else {
                Log.e(TAG, "I420ExternalRender::getNTPlaneByteBuffer index error:" + index);
                return null;
            }
        }

        @Override
        public int getNTPlanePerRowBytes(int index) {
            if (index == 0) {
                return y_row_bytes_;
            } else if (index == 1) {
                return u_row_bytes_;
            } else if (index == 2) {
                return v_row_bytes_;
            } else {
                Log.e(TAG, "I420ExternalRender::getNTPlanePerRowBytes index error:" + index);
                return 0;
            }
        }

        public void onNTRenderFrame(int width, int height, long timestamp) {
            if (y_buffer_ == null)
                return;

            if (u_buffer_ == null)
                return;

            if (v_buffer_ == null)
                return;

            y_buffer_.rewind();

            u_buffer_.rewind();

            v_buffer_.rewind();

    		/*
    		if ( !is_saved_image )
    		{
    			is_saved_image = true;

    			int y_len = y_row_bytes_*height_;

    			int u_len = u_row_bytes_*((height_+1)/2);
    			int v_len = v_row_bytes_*((height_+1)/2);

    			int data_len = y_len + (y_row_bytes_*((height_+1)/2));

    			byte[] nv21_data = new byte[data_len];

    			byte[] u_data = new byte[u_len];
    			byte[] v_data = new byte[v_len];

    			y_buffer_.get(nv21_data, 0, y_len);
    			u_buffer_.get(u_data, 0, u_len);
    			v_buffer_.get(v_data, 0, v_len);

    			int[] strides = new int[2];
    			strides[0] = y_row_bytes_;
    			strides[1] = y_row_bytes_;

    			int loop_row_c = ((height_+1)/2);
    			int loop_c = ((width_+1)/2);

    			int dst_row = y_len;
    			int src_v_row = 0;
    			int src_u_row = 0;

    			for ( int i = 0; i < loop_row_c; ++i)
    			{
    				int dst_pos = dst_row;

    				for ( int j = 0; j <loop_c; ++j )
    				{
    					nv21_data[dst_pos++] = v_data[src_v_row + j];
    					nv21_data[dst_pos++] = u_data[src_u_row + j];
    				}

    				dst_row   += y_row_bytes_;
    				src_v_row += v_row_bytes_;
    				src_u_row += u_row_bytes_;
    			}

    			String imagePath = "/sdcard" + "/" + "testonv21" + ".jpeg";

    			Log.e(TAG, "I420ExternalRender::begin test save iamge++ image_path:" + imagePath);

    			try
    			{
    				File file = new File(imagePath);

        			FileOutputStream image_os = new FileOutputStream(file);

        			YuvImage image = new YuvImage(nv21_data, ImageFormat.NV21, width_, height_, strides);

        			image.compressToJpeg(new android.graphics.Rect(0, 0, width_, height_), 50, image_os);

        			image_os.flush();
        			image_os.close();
    			}
    			catch(IOException e)
    			{
    				e.printStackTrace();
    			}

    			Log.e(TAG, "I420ExternalRender::begin test save iamge--");
    		}

    		*/

            Log.i(TAG, "I420ExternalRender::onNTRenderFrame w=" + width + " h=" + height + " timestamp=" + timestamp);

            // copy buffer

            // test
            // byte[] test_buffer = new byte[16];
            // y_buffer_.get(test_buffer);

            // Log.i(TAG, "I420ExternalRender::onNTRenderFrame y data:" + bytesToHexString(test_buffer));

            // u_buffer_.get(test_buffer);
            // Log.i(TAG, "I420ExternalRender::onNTRenderFrame u data:" + bytesToHexString(test_buffer));

            // v_buffer_.get(test_buffer);
            // Log.i(TAG, "I420ExternalRender::onNTRenderFrame v data:" + bytesToHexString(test_buffer));
        }
    }

总结

以上就是Android平台开发RTMP/RTSP播放器时，针对解码和绘制部分的一点考量，算是抛砖引玉，感兴趣的开发者可酌情参考。