Android 用MediaCodec实现视频硬解码(转)

本文向你讲述如何用android标准的API （MediaCodec）实现视频的硬件编解码。例程将从摄像头采集视频开始，然后进行H264编码，再解码，然后显示。我将尽量讲得简短而清晰，不展示 那些不相关的代码。但是，我不建议你读这篇文章，也不建议你开发这类应用，而应该转而开发一些戳鱼、打鸟、其乐融融的程序。好吧，下面的内容是写给那些执 迷不悟的人的，看完之后也许你会同意我的说法：Android只是一个玩具，很难指望它来做靠谱的应用。

1、从摄像头采集视频

可以通过摄像头Preview的回调，来获取视频数据。

首先创建摄像头，并设置参数：

宽度和高度必须是摄像头支持的尺寸，否则会报错。要获得所有支持的尺寸，可用getSupportedPreviewSizes，这里不再累述。据说所有的参数必须设全，漏掉一个就可能报错，不过只是据说，我只设了几个属性也没出错。    然后就开始Preview了：

            buf = new byte[camWidth * camHeight * 3 / 2];
            cam.addCallbackBuffer(buf);
            cam.setPreviewCallbackWithBuffer(this);
            cam.startPreview(); 

setPreviewCallbackWithBuffer是很有必要的，不然每次回调系统都重新分配缓冲区，效率会很低。

在onPreviewFrame中就可以获得原始的图片了（当然，this 肯定要 implements PreviewCallback了）。这里我们是把它传给编码器：

    public void onPreviewFrame(byte[] data, Camera camera) {
        if (frameListener != null) {
            frameListener.onFrame(data, 0, data.length, 0);
        }
        cam.addCallbackBuffer(buf);
    }

2、编码

首先要初始化编码器：

           mediaCodec = MediaCodec.createEncoderByType("Video/AVC");
        MediaFormat mediaFormat = MediaFormat.createVideoFormat(type, width, height);
        mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, 125000);
        mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, 15);
        mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Planar);
        mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 5);
        mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mediaCodec.start();

然后就是给他喂数据了，这里的数据是来自摄像头的：

 public void onFrame(byte[] buf, int offset, int length, int flag) {
    ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
    ByteBuffer[] outputBuffers = mediaCodec.getOutputBuffers();
    int inputBufferIndex = mediaCodec.dequeueInputBuffer(-1);
    if (inputBufferIndex >= 0)
        ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
        inputBuffer.clear();
        inputBuffer.put(buf, offset, length);
        mediaCodec.queueInputBuffer(inputBufferIndex, 0, length, 0, 0);
    }
    MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
    int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo,0);
    while (outputBufferIndex >= 0) {
        ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
        if (frameListener != null)
            frameListener.onFrame(outputBuffer, 0, length, flag);
        mediaCodec.releaseOutputBuffer(outputBufferIndex, false);
        outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
    } 

先把来自摄像头的数据喂给它，然后从它里面取压缩好的数据喂给解码器。

3、解码和显示

首先初始化解码器：

            mediaCodec = MediaCodec.createDecoderByType("Video/AVC");
            MediaFormat mediaFormat = MediaFormat.createVideoFormat(mime, width, height);
            mediaCodec.configure(mediaFormat, surface, null, 0);
            mediaCodec.start();

这里通过给解码器一个surface，解码器就能直接显示画面。

然后就是处理数据了：

    public void onFrame(byte[] buf, int offset, int length, int flag) {
            ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
                int inputBufferIndex = mediaCodec.dequeueInputBuffer(-1);
            if (inputBufferIndex >= 0) {
                ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                inputBuffer.clear();
                inputBuffer.put(buf, offset, length);
                mediaCodec.queueInputBuffer(inputBufferIndex, 0, length, mCount * 1000000 / FRAME_RATE, 0);
                    mCount++;
            }

        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
        int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo,0);
        while (outputBufferIndex >= 0) {
            mediaCodec.releaseOutputBuffer(outputBufferIndex, true);
            outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
        }
    }

queueInputBuffer第三个参数是时间戳，其实怎么写都无所谓，只要是按时间线性增加的就可以，这里就随便弄一个了。后面一段的代码就是把缓 冲区给释放掉，因为我们直接让解码器显示，就不需要解码出来的数据了，但是必须要这么释放一下，否则解码器始终给你留着，内存就该不够用了。

好了，到现在，基本上就可以了。如果你运气够好，现在就能看到视频了，比如在我的三星手机上这样就可以了。但是，我试过几个其他平台，多数都不可以，总是有各种各样的问题，如果要开发一个不依赖平台的应用，还有很多的问题要解决。说说我遇到的一些情况：

1、视频尺寸

一般都能支持176X144/352X288这种尺寸，但是大一些的，640X480就有很多机子不行了，至于为什么，我也不知道。当然，这个尺寸必须和摄像头预览的尺寸一致，预览的尺寸可以枚举一下。

2、颜色空间

根据ANdroid SDK文档，确保所有硬件平台都支持的颜色，在摄像头预览输出是YUV12，在编码器输入是COLOR_FormatYUV420Planar，也就是前面代码中设置的那样。       不过，文档终究是文档，否则安卓就不是安卓。

在有的平台上，这两个颜色格式是一样的，摄像头的输出可以直接作为编码器的输入。也有的平台，两个是不一样的，前者就是YUV12，后者等于I420，需要把前者的UV分量颠倒一下。下面的代码效率不高，可供参考。

    byte[] i420bytes = null;
    private byte[] swapYV12toI420(byte[] yv12bytes, int width, int height) {
        if (i420bytes == null)
            i420bytes = new byte[yv12bytes.length];
        for (int i = 0; i < width*height; i++)
            i420bytes[i] = yv12bytes[i];
        for (int i = width*height; i < width*height + (width/2*height/2); i++)
            i420bytes[i] = yv12bytes[i + (width/2*height/2)];
        for (int i = width*height + (width/2*height/2); i < width*height + 2*(width/2*height/2); i++)
            i420bytes[i] = yv12bytes[i - (width/2*height/2)];
        return i420bytes;
    }

这里的困难是，我不知道怎样去判断是否需要这个转换。据说，Android 4.3不用再从摄像头的PreView里面取图像，避开了这个问题。这里有个例子，虽然我没读，但看起来挺厉害的样子，应该不会有错吧（觉厉应然）。http://bigflake.com/mediacodec/CameraToMpegTest.java.txt，这个文件的代码附在本文最后。

3、输入输出缓冲区的格式

SDK里并没有规定格式，但是，这种情况H264的格式基本上就是附录B。但是，也有比较有特色的，它就是不带那个StartCode，就是那个0x000001，搞得把他编码器编出来的东西送给他的解码器，他自己都解不出来。还好，我们可以自己加。

                ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                byte[] outData = new byte[bufferInfo.size + 3];
                    outputBuffer.get(outData, 3, bufferInfo.size);
                if (frameListener != null) {
                    if ((outData[3]==0 && outData[4]==0 && outData[5]==1)
                    || (outData[3]==0 && outData[4]==0 && outData[5]==0 && outData[6]==1))
                    {
                        frameListener.onFrame(outData, 3, outData.length-3, bufferInfo.flags);
                    }
                    else
                    {
                        outData[0] = 0;
                        outData[1] = 0;
                        outData[2] = 1;
                        frameListener.onFrame(outData, 0, outData.length, bufferInfo.flags);
                    }
                }

4、有时候会死在dequeueInputBuffer(-1)上面

根据SDK文档，dequeueInputBuffer 的参数表示等待的时间（毫秒），-1表示一直等，0表示不等。按常理传-1就行，但实际上在很多机子上会挂掉，没办法，还是传0吧，丢帧总比挂掉好。当然也可以传一个具体的毫秒数，不过没什么大意思吧。

在遇到上述的问题之后，我给出了我的感慨：Android是一个玩具。

/*
 * Copyright 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.media.cts;

import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.opengl.EGL14;
import android.opengl.EGLConfig;
import android.opengl.EGLContext;
import android.opengl.EGLDisplay;
import android.opengl.EGLExt;
import android.opengl.EGLSurface;
import android.opengl.GLES11Ext;
import android.opengl.GLES20;
import android.opengl.Matrix;
import android.os.Environment;
import android.test.AndroidTestCase;
import android.util.Log;
import android.view.Surface;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

//20131106: removed unnecessary glFinish(), removed hard-coded "/sdcard"
//20131205: added alpha to EGLConfig
//20131210: demonstrate un-bind and re-bind of texture, for apps with shared EGL contexts
//20140123: correct error checks on glGet*Location() and program creation (they don't set error)

/**
 * Record video from the camera preview and encode it as an MP4 file.  Demonstrates the use
 * of MediaMuxer and MediaCodec with Camera input.  Does not record audio.
 * <p>
 * Generally speaking, it's better to use MediaRecorder for this sort of thing.  This example
 * demonstrates one possible advantage: editing of video as it's being encoded.  A GLES 2.0
 * fragment shader is used to perform a silly color tweak every 15 frames.
 * <p>
 * This uses various features first available in Android "Jellybean" 4.3 (API 18).  There is
 * no equivalent functionality in previous releases.  (You can send the Camera preview to a
 * byte buffer with a fully-specified format, but MediaCodec encoders want different input
 * formats on different devices, and this use case wasn't well exercised in CTS pre-4.3.)
 * <p>
 * The output file will be something like "/sdcard/test.640x480.mp4".
 * <p>
 * (This was derived from bits and pieces of CTS tests, and is packaged as such, but is not
 * currently part of CTS.)
 */
public class CameraToMpegTest extends AndroidTestCase {
    private static final String TAG = "CameraToMpegTest";
    private static final boolean VERBOSE = false;           // lots of logging

    // where to put the output file (note: /sdcard requires WRITE_EXTERNAL_STORAGE permission)
    private static final File OUTPUT_DIR = Environment.getExternalStorageDirectory();

    // parameters for the encoder
    private static final String MIME_TYPE = "video/avc";    // H.264 Advanced Video Coding
    private static final int FRAME_RATE = 30;               // 30fps
    private static final int IFRAME_INTERVAL = 5;           // 5 seconds between I-frames
    private static final long DURATION_SEC = 8;             // 8 seconds of video

    // Fragment shader that swaps color channels around.
    private static final String SWAPPED_FRAGMENT_SHADER =
            "#extension GL_OES_EGL_image_external : require\n" +
            "precision mediump float;\n" +
            "varying vec2 vTextureCoord;\n" +
            "uniform samplerExternalOES sTexture;\n" +
            "void main() {\n" +
            "  gl_FragColor = texture2D(sTexture, vTextureCoord).gbra;\n" +
            "}\n";

    // encoder / muxer state
    private MediaCodec mEncoder;
    private CodecInputSurface mInputSurface;
    private MediaMuxer mMuxer;
    private int mTrackIndex;
    private boolean mMuxerStarted;

    // camera state
    private Camera mCamera;
    private SurfaceTextureManager mStManager;

    // allocate one of these up front so we don't need to do it every time
    private MediaCodec.BufferInfo mBufferInfo;

    /** test entry point */
    public void testEncodeCameraToMp4() throws Throwable {
        CameraToMpegWrapper.runTest(this);
    }

    /**
     * Wraps encodeCameraToMpeg().  This is necessary because SurfaceTexture will try to use
     * the looper in the current thread if one exists, and the CTS tests create one on the
     * test thread.
     *
     * The wrapper propagates exceptions thrown by the worker thread back to the caller.
     */
    private static class CameraToMpegWrapper implements Runnable {
        private Throwable mThrowable;
        private CameraToMpegTest mTest;

        private CameraToMpegWrapper(CameraToMpegTest test) {
            mTest = test;
        }

        @Override
        public void run() {
            try {
                mTest.encodeCameraToMpeg();
            } catch (Throwable th) {
                mThrowable = th;
            }
        }

        /** Entry point. */
        public static void runTest(CameraToMpegTest obj) throws Throwable {
            CameraToMpegWrapper wrapper = new CameraToMpegWrapper(obj);
            Thread th = new Thread(wrapper, "codec test");
            th.start();
            th.join();
            if (wrapper.mThrowable != null) {
                throw wrapper.mThrowable;
            }
        }
    }

    /**
     * Tests encoding of AVC video from Camera input.  The output is saved as an MP4 file.
     */
    private void encodeCameraToMpeg() {
        // arbitrary but popular values
        int encWidth = 640;
        int encHeight = 480;
        int encBitRate = 6000000;      // Mbps
        Log.d(TAG, MIME_TYPE + " output " + encWidth + "x" + encHeight + " @" + encBitRate);

        try {
            prepareCamera(encWidth, encHeight);
            prepareEncoder(encWidth, encHeight, encBitRate);
            mInputSurface.makeCurrent();
            prepareSurfaceTexture();

            mCamera.startPreview();

            long startWhen = System.nanoTime();
            long desiredEnd = startWhen + DURATION_SEC * 1000000000L;
            SurfaceTexture st = mStManager.getSurfaceTexture();
            int frameCount = 0;

            while (System.nanoTime() < desiredEnd) {
                // Feed any pending encoder output into the muxer.
                drainEncoder(false);

                // Switch up the colors every 15 frames.  Besides demonstrating the use of
                // fragment shaders for video editing, this provides a visual indication of
                // the frame rate: if the camera is capturing at 15fps, the colors will change
                // once per second.
                if ((frameCount % 15) == 0) {
                    String fragmentShader = null;
                    if ((frameCount & 0x01) != 0) {
                        fragmentShader = SWAPPED_FRAGMENT_SHADER;
                    }
                    mStManager.changeFragmentShader(fragmentShader);
                }
                frameCount++;

                // Acquire a new frame of input, and render it to the Surface.  If we had a
                // GLSurfaceView we could switch EGL contexts and call drawImage() a second
                // time to render it on screen.  The texture can be shared between contexts by
                // passing the GLSurfaceView's EGLContext as eglCreateContext()'s share_context
                // argument.
                mStManager.awaitNewImage();
                mStManager.drawImage();

                // Set the presentation time stamp from the SurfaceTexture's time stamp.  This
                // will be used by MediaMuxer to set the PTS in the video.
                if (VERBOSE) {
                    Log.d(TAG, "present: " +
                            ((st.getTimestamp() - startWhen) / 1000000.0) + "ms");
                }
                mInputSurface.setPresentationTime(st.getTimestamp());

                // Submit it to the encoder.  The eglSwapBuffers call will block if the input
                // is full, which would be bad if it stayed full until we dequeued an output
                // buffer (which we can't do, since we're stuck here).  So long as we fully drain
                // the encoder before supplying additional input, the system guarantees that we
                // can supply another frame without blocking.
                if (VERBOSE) Log.d(TAG, "sending frame to encoder");
                mInputSurface.swapBuffers();
            }

            // send end-of-stream to encoder, and drain remaining output
            drainEncoder(true);
        } finally {
            // release everything we grabbed
            releaseCamera();
            releaseEncoder();
            releaseSurfaceTexture();
        }
    }

    /**
     * Configures Camera for video capture.  Sets mCamera.
     * <p>
     * Opens a Camera and sets parameters.  Does not start preview.
     */
    private void prepareCamera(int encWidth, int encHeight) {
        if (mCamera != null) {
            throw new RuntimeException("camera already initialized");
        }

        Camera.CameraInfo info = new Camera.CameraInfo();

        // Try to find a front-facing camera (e.g. for videoconferencing).
        int numCameras = Camera.getNumberOfCameras();
        for (int i = 0; i < numCameras; i++) {
            Camera.getCameraInfo(i, info);
            if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
                mCamera = Camera.open(i);
                break;
            }
        }
        if (mCamera == null) {
            Log.d(TAG, "No front-facing camera found; opening default");
            mCamera = Camera.open();    // opens first back-facing camera
        }
        if (mCamera == null) {
            throw new RuntimeException("Unable to open camera");
        }

        Camera.Parameters parms = mCamera.getParameters();

        choosePreviewSize(parms, encWidth, encHeight);
        // leave the frame rate set to default
        mCamera.setParameters(parms);

        Camera.Size size = parms.getPreviewSize();
        Log.d(TAG, "Camera preview size is " + size.width + "x" + size.height);
    }

    /**
     * Attempts to find a preview size that matches the provided width and height (which
     * specify the dimensions of the encoded video).  If it fails to find a match it just
     * uses the default preview size.
     * <p>
     * TODO: should do a best-fit match.
     */
    private static void choosePreviewSize(Camera.Parameters parms, int width, int height) {
        // We should make sure that the requested MPEG size is less than the preferred
        // size, and has the same aspect ratio.
        Camera.Size ppsfv = parms.getPreferredPreviewSizeForVideo();
        if (VERBOSE && ppsfv != null) {
            Log.d(TAG, "Camera preferred preview size for video is " +
                    ppsfv.width + "x" + ppsfv.height);
        }

        for (Camera.Size size : parms.getSupportedPreviewSizes()) {
            if (size.width == width && size.height == height) {
                parms.setPreviewSize(width, height);
                return;
            }
        }

        Log.w(TAG, "Unable to set preview size to " + width + "x" + height);
        if (ppsfv != null) {
            parms.setPreviewSize(ppsfv.width, ppsfv.height);
        }
    }

    /**
     * Stops camera preview, and releases the camera to the system.
     */
    private void releaseCamera() {
        if (VERBOSE) Log.d(TAG, "releasing camera");
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }

    /**
     * Configures SurfaceTexture for camera preview.  Initializes mStManager, and sets the
     * associated SurfaceTexture as the Camera's "preview texture".
     * <p>
     * Configure the EGL surface that will be used for output before calling here.
     */
    private void prepareSurfaceTexture() {
        mStManager = new SurfaceTextureManager();
        SurfaceTexture st = mStManager.getSurfaceTexture();
        try {
            mCamera.setPreviewTexture(st);
        } catch (IOException ioe) {
            throw new RuntimeException("setPreviewTexture failed", ioe);
        }
    }

    /**
     * Releases the SurfaceTexture.
     */
    private void releaseSurfaceTexture() {
        if (mStManager != null) {
            mStManager.release();
            mStManager = null;
        }
    }

    /**
     * Configures encoder and muxer state, and prepares the input Surface.  Initializes
     * mEncoder, mMuxer, mInputSurface, mBufferInfo, mTrackIndex, and mMuxerStarted.
     */
    private void prepareEncoder(int width, int height, int bitRate) {
        mBufferInfo = new MediaCodec.BufferInfo();

        MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, width, height);

        // Set some properties.  Failing to specify some of these can cause the MediaCodec
        // configure() call to throw an unhelpful exception.
        format.setInteger(MediaFormat.KEY_COLOR_FORMAT,
                MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
        format.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
        format.setInteger(MediaFormat.KEY_FRAME_RATE, FRAME_RATE);
        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, IFRAME_INTERVAL);
        if (VERBOSE) Log.d(TAG, "format: " + format);

        // Create a MediaCodec encoder, and configure it with our format.  Get a Surface
        // we can use for input and wrap it with a class that handles the EGL work.
        //
        // If you want to have two EGL contexts -- one for display, one for recording --
        // you will likely want to defer instantiation of CodecInputSurface until after the
        // "display" EGL context is created, then modify the eglCreateContext call to
        // take eglGetCurrentContext() as the share_context argument.
        mEncoder = MediaCodec.createEncoderByType(MIME_TYPE);
        mEncoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mInputSurface = new CodecInputSurface(mEncoder.createInputSurface());
        mEncoder.start();

        // Output filename.  Ideally this would use Context.getFilesDir() rather than a
        // hard-coded output directory.
        String outputPath = new File(OUTPUT_DIR,
                "test." + width + "x" + height + ".mp4").toString();
        Log.i(TAG, "Output file is " + outputPath);

        // Create a MediaMuxer.  We can't add the video track and start() the muxer here,
        // because our MediaFormat doesn't have the Magic Goodies.  These can only be
        // obtained from the encoder after it has started processing data.
        //
        // We're not actually interested in multiplexing audio.  We just want to convert
        // the raw H.264 elementary stream we get from MediaCodec into a .mp4 file.
        try {
            mMuxer = new MediaMuxer(outputPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
        } catch (IOException ioe) {
            throw new RuntimeException("MediaMuxer creation failed", ioe);
        }

        mTrackIndex = -1;
        mMuxerStarted = false;
    }

    /**
     * Releases encoder resources.
     */
    private void releaseEncoder() {
        if (VERBOSE) Log.d(TAG, "releasing encoder objects");
        if (mEncoder != null) {
            mEncoder.stop();
            mEncoder.release();
            mEncoder = null;
        }
        if (mInputSurface != null) {
            mInputSurface.release();
            mInputSurface = null;
        }
        if (mMuxer != null) {
            mMuxer.stop();
            mMuxer.release();
            mMuxer = null;
        }
    }

    /**
     * Extracts all pending data from the encoder and forwards it to the muxer.
     * <p>
     * If endOfStream is not set, this returns when there is no more data to drain.  If it
     * is set, we send EOS to the encoder, and then iterate until we see EOS on the output.
     * Calling this with endOfStream set should be done once, right before stopping the muxer.
     * <p>
     * We're just using the muxer to get a .mp4 file (instead of a raw H.264 stream).  We're
     * not recording audio.
     */
    private void drainEncoder(boolean endOfStream) {
        final int TIMEOUT_USEC = 10000;
        if (VERBOSE) Log.d(TAG, "drainEncoder(" + endOfStream + ")");

        if (endOfStream) {
            if (VERBOSE) Log.d(TAG, "sending EOS to encoder");
            mEncoder.signalEndOfInputStream();
        }

        ByteBuffer[] encoderOutputBuffers = mEncoder.getOutputBuffers();
        while (true) {
            int encoderStatus = mEncoder.dequeueOutputBuffer(mBufferInfo, TIMEOUT_USEC);
            if (encoderStatus == MediaCodec.INFO_TRY_AGAIN_LATER) {
                // no output available yet
                if (!endOfStream) {
                    break;      // out of while
                } else {
                    if (VERBOSE) Log.d(TAG, "no output available, spinning to await EOS");
                }
            } else if (encoderStatus == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
                // not expected for an encoder
                encoderOutputBuffers = mEncoder.getOutputBuffers();
            } else if (encoderStatus == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                // should happen before receiving buffers, and should only happen once
                if (mMuxerStarted) {
                    throw new RuntimeException("format changed twice");
                }
                MediaFormat newFormat = mEncoder.getOutputFormat();
                Log.d(TAG, "encoder output format changed: " + newFormat);

                // now that we have the Magic Goodies, start the muxer
                mTrackIndex = mMuxer.addTrack(newFormat);
                mMuxer.start();
                mMuxerStarted = true;
            } else if (encoderStatus < 0) {
                Log.w(TAG, "unexpected result from encoder.dequeueOutputBuffer: " +
                        encoderStatus);
                // let's ignore it
            } else {
                ByteBuffer encodedData = encoderOutputBuffers[encoderStatus];
                if (encodedData == null) {
                    throw new RuntimeException("encoderOutputBuffer " + encoderStatus +
                            " was null");
                }

                if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                    // The codec config data was pulled out and fed to the muxer when we got
                    // the INFO_OUTPUT_FORMAT_CHANGED status.  Ignore it.
                    if (VERBOSE) Log.d(TAG, "ignoring BUFFER_FLAG_CODEC_CONFIG");
                    mBufferInfo.size = 0;
                }

                if (mBufferInfo.size != 0) {
                    if (!mMuxerStarted) {
                        throw new RuntimeException("muxer hasn't started");
                    }

                    // adjust the ByteBuffer values to match BufferInfo (not needed?)
                    encodedData.position(mBufferInfo.offset);
                    encodedData.limit(mBufferInfo.offset + mBufferInfo.size);

                    mMuxer.writeSampleData(mTrackIndex, encodedData, mBufferInfo);
                    if (VERBOSE) Log.d(TAG, "sent " + mBufferInfo.size + " bytes to muxer");
                }

                mEncoder.releaseOutputBuffer(encoderStatus, false);

                if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    if (!endOfStream) {
                        Log.w(TAG, "reached end of stream unexpectedly");
                    } else {
                        if (VERBOSE) Log.d(TAG, "end of stream reached");
                    }
                    break;      // out of while
                }
            }
        }
    }

    /**
     * Holds state associated with a Surface used for MediaCodec encoder input.
     * <p>
     * The constructor takes a Surface obtained from MediaCodec.createInputSurface(), and uses
     * that to create an EGL window surface.  Calls to eglSwapBuffers() cause a frame of data to
     * be sent to the video encoder.
     * <p>
     * This object owns the Surface -- releasing this will release the Surface too.
     */
    private static class CodecInputSurface {
        private static final int EGL_RECORDABLE_ANDROID = 0x3142;

        private EGLDisplay mEGLDisplay = EGL14.EGL_NO_DISPLAY;
        private EGLContext mEGLContext = EGL14.EGL_NO_CONTEXT;
        private EGLSurface mEGLSurface = EGL14.EGL_NO_SURFACE;

        private Surface mSurface;

        /**
         * Creates a CodecInputSurface from a Surface.
         */
        public CodecInputSurface(Surface surface) {
            if (surface == null) {
                throw new NullPointerException();
            }
            mSurface = surface;

            eglSetup();
        }

        /**
         * Prepares EGL.  We want a GLES 2.0 context and a surface that supports recording.
         */
        private void eglSetup() {
            mEGLDisplay = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY);
            if (mEGLDisplay == EGL14.EGL_NO_DISPLAY) {
                throw new RuntimeException("unable to get EGL14 display");
            }
            int[] version = new int[2];
            if (!EGL14.eglInitialize(mEGLDisplay, version, 0, version, 1)) {
                throw new RuntimeException("unable to initialize EGL14");
            }

            // Configure EGL for recording and OpenGL ES 2.0.
            int[] attribList = {
                    EGL14.EGL_RED_SIZE, 8,
                    EGL14.EGL_GREEN_SIZE, 8,
                    EGL14.EGL_BLUE_SIZE, 8,
                    EGL14.EGL_ALPHA_SIZE, 8,
                    EGL14.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
                    EGL_RECORDABLE_ANDROID, 1,
                    EGL14.EGL_NONE
            };
            EGLConfig[] configs = new EGLConfig[1];
            int[] numConfigs = new int[1];
            EGL14.eglChooseConfig(mEGLDisplay, attribList, 0, configs, 0, configs.length,
                    numConfigs, 0);
            checkEglError("eglCreateContext RGB888+recordable ES2");

            // Configure context for OpenGL ES 2.0.
            int[] attrib_list = {
                    EGL14.EGL_CONTEXT_CLIENT_VERSION, 2,
                    EGL14.EGL_NONE
            };
            mEGLContext = EGL14.eglCreateContext(mEGLDisplay, configs[0], EGL14.EGL_NO_CONTEXT,
                    attrib_list, 0);
            checkEglError("eglCreateContext");

            // Create a window surface, and attach it to the Surface we received.
            int[] surfaceAttribs = {
                    EGL14.EGL_NONE
            };
            mEGLSurface = EGL14.eglCreateWindowSurface(mEGLDisplay, configs[0], mSurface,
                    surfaceAttribs, 0);
            checkEglError("eglCreateWindowSurface");
        }

        /**
         * Discards all resources held by this class, notably the EGL context.  Also releases the
         * Surface that was passed to our constructor.
         */
        public void release() {
            if (mEGLDisplay != EGL14.EGL_NO_DISPLAY) {
                EGL14.eglMakeCurrent(mEGLDisplay, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE,
                        EGL14.EGL_NO_CONTEXT);
                EGL14.eglDestroySurface(mEGLDisplay, mEGLSurface);
                EGL14.eglDestroyContext(mEGLDisplay, mEGLContext);
                EGL14.eglReleaseThread();
                EGL14.eglTerminate(mEGLDisplay);
            }
            mSurface.release();

            mEGLDisplay = EGL14.EGL_NO_DISPLAY;
            mEGLContext = EGL14.EGL_NO_CONTEXT;
            mEGLSurface = EGL14.EGL_NO_SURFACE;

            mSurface = null;
        }

        /**
         * Makes our EGL context and surface current.
         */
        public void makeCurrent() {
            EGL14.eglMakeCurrent(mEGLDisplay, mEGLSurface, mEGLSurface, mEGLContext);
            checkEglError("eglMakeCurrent");
        }

        /**
         * Calls eglSwapBuffers.  Use this to "publish" the current frame.
         */
        public boolean swapBuffers() {
            boolean result = EGL14.eglSwapBuffers(mEGLDisplay, mEGLSurface);
            checkEglError("eglSwapBuffers");
            return result;
        }

        /**
         * Sends the presentation time stamp to EGL.  Time is expressed in nanoseconds.
         */
        public void setPresentationTime(long nsecs) {
            EGLExt.eglPresentationTimeANDROID(mEGLDisplay, mEGLSurface, nsecs);
            checkEglError("eglPresentationTimeANDROID");
        }

        /**
         * Checks for EGL errors.  Throws an exception if one is found.
         */
        private void checkEglError(String msg) {
            int error;
            if ((error = EGL14.eglGetError()) != EGL14.EGL_SUCCESS) {
                throw new RuntimeException(msg + ": EGL error: 0x" + Integer.toHexString(error));
            }
        }
    }

    /**
     * Manages a SurfaceTexture.  Creates SurfaceTexture and TextureRender objects, and provides
     * functions that wait for frames and render them to the current EGL surface.
     * <p>
     * The SurfaceTexture can be passed to Camera.setPreviewTexture() to receive camera output.
     */
    private static class SurfaceTextureManager
            implements SurfaceTexture.OnFrameAvailableListener {
        private SurfaceTexture mSurfaceTexture;
        private CameraToMpegTest.STextureRender mTextureRender;

        private Object mFrameSyncObject = new Object();     // guards mFrameAvailable
        private boolean mFrameAvailable;

        /**
         * Creates instances of TextureRender and SurfaceTexture.
         */
        public SurfaceTextureManager() {
            mTextureRender = new CameraToMpegTest.STextureRender();
            mTextureRender.surfaceCreated();

            if (VERBOSE) Log.d(TAG, "textureID=" + mTextureRender.getTextureId());
            mSurfaceTexture = new SurfaceTexture(mTextureRender.getTextureId());

            // This doesn't work if this object is created on the thread that CTS started for
            // these test cases.
            //
            // The CTS-created thread has a Looper, and the SurfaceTexture constructor will
            // create a Handler that uses it.  The "frame available" message is delivered
            // there, but since we're not a Looper-based thread we'll never see it.  For
            // this to do anything useful, OutputSurface must be created on a thread without
            // a Looper, so that SurfaceTexture uses the main application Looper instead.
            //
            // Java language note: passing "this" out of a constructor is generally unwise,
            // but we should be able to get away with it here.
            mSurfaceTexture.setOnFrameAvailableListener(this);
        }

        public void release() {
            // this causes a bunch of warnings that appear harmless but might confuse someone:
            //  W BufferQueue: [unnamed-3997-2] cancelBuffer: BufferQueue has been abandoned!
            //mSurfaceTexture.release();

            mTextureRender = null;
            mSurfaceTexture = null;
        }

        /**
         * Returns the SurfaceTexture.
         */
        public SurfaceTexture getSurfaceTexture() {
            return mSurfaceTexture;
        }

        /**
         * Replaces the fragment shader.
         */
        public void changeFragmentShader(String fragmentShader) {
            mTextureRender.changeFragmentShader(fragmentShader);
        }

        /**
         * Latches the next buffer into the texture.  Must be called from the thread that created
         * the OutputSurface object.
         */
        public void awaitNewImage() {
            final int TIMEOUT_MS = 2500;

            synchronized (mFrameSyncObject) {
                while (!mFrameAvailable) {
                    try {
                        // Wait for onFrameAvailable() to signal us.  Use a timeout to avoid
                        // stalling the test if it doesn't arrive.
                        mFrameSyncObject.wait(TIMEOUT_MS);
                        if (!mFrameAvailable) {
                            // TODO: if "spurious wakeup", continue while loop
                            throw new RuntimeException("Camera frame wait timed out");
                        }
                    } catch (InterruptedException ie) {
                        // shouldn't happen
                        throw new RuntimeException(ie);
                    }
                }
                mFrameAvailable = false;
            }

            // Latch the data.
            mTextureRender.checkGlError("before updateTexImage");
            mSurfaceTexture.updateTexImage();
        }

        /**
         * Draws the data from SurfaceTexture onto the current EGL surface.
         */
        public void drawImage() {
            mTextureRender.drawFrame(mSurfaceTexture);
        }

        @Override
        public void onFrameAvailable(SurfaceTexture st) {
            if (VERBOSE) Log.d(TAG, "new frame available");
            synchronized (mFrameSyncObject) {
                if (mFrameAvailable) {
                    throw new RuntimeException("mFrameAvailable already set, frame could be dropped");
                }
                mFrameAvailable = true;
                mFrameSyncObject.notifyAll();
            }
        }
    }

    /**
     * Code for rendering a texture onto a surface using OpenGL ES 2.0.
     */
    private static class STextureRender {
        private static final int FLOAT_SIZE_BYTES = 4;
        private static final int TRIANGLE_VERTICES_DATA_STRIDE_BYTES = 5 * FLOAT_SIZE_BYTES;
        private static final int TRIANGLE_VERTICES_DATA_POS_OFFSET = 0;
        private static final int TRIANGLE_VERTICES_DATA_UV_OFFSET = 3;
        private final float[] mTriangleVerticesData = {
                // X, Y, Z, U, V
                -1.0f, -1.0f, 0, 0.f, 0.f,
                 1.0f, -1.0f, 0, 1.f, 0.f,
                -1.0f,  1.0f, 0, 0.f, 1.f,
                 1.0f,  1.0f, 0, 1.f, 1.f,
        };

        private FloatBuffer mTriangleVertices;

        private static final String VERTEX_SHADER =
                "uniform mat4 uMVPMatrix;\n" +
                "uniform mat4 uSTMatrix;\n" +
                "attribute vec4 aPosition;\n" +
                "attribute vec4 aTextureCoord;\n" +
                "varying vec2 vTextureCoord;\n" +
                "void main() {\n" +
                "    gl_Position = uMVPMatrix * aPosition;\n" +
                "    vTextureCoord = (uSTMatrix * aTextureCoord).xy;\n" +
                "}\n";

        private static final String FRAGMENT_SHADER =
                "#extension GL_OES_EGL_image_external : require\n" +
                "precision mediump float;\n" +      // highp here doesn't seem to matter
                "varying vec2 vTextureCoord;\n" +
                "uniform samplerExternalOES sTexture;\n" +
                "void main() {\n" +
                "    gl_FragColor = texture2D(sTexture, vTextureCoord);\n" +
                "}\n";

        private float[] mMVPMatrix = new float[16];
        private float[] mSTMatrix = new float[16];

        private int mProgram;
        private int mTextureID = -12345;
        private int muMVPMatrixHandle;
        private int muSTMatrixHandle;
        private int maPositionHandle;
        private int maTextureHandle;

        public STextureRender() {
            mTriangleVertices = ByteBuffer.allocateDirect(
                    mTriangleVerticesData.length * FLOAT_SIZE_BYTES)
                    .order(ByteOrder.nativeOrder()).asFloatBuffer();
            mTriangleVertices.put(mTriangleVerticesData).position(0);

            Matrix.setIdentityM(mSTMatrix, 0);
        }

        public int getTextureId() {
            return mTextureID;
        }

        public void drawFrame(SurfaceTexture st) {
            checkGlError("onDrawFrame start");
            st.getTransformMatrix(mSTMatrix);

            // (optional) clear to green so we can see if we're failing to set pixels
            GLES20.glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
            GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);

            GLES20.glUseProgram(mProgram);
            checkGlError("glUseProgram");

            GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
            GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, mTextureID);

            mTriangleVertices.position(TRIANGLE_VERTICES_DATA_POS_OFFSET);
            GLES20.glVertexAttribPointer(maPositionHandle, 3, GLES20.GL_FLOAT, false,
                    TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mTriangleVertices);
            checkGlError("glVertexAttribPointer maPosition");
            GLES20.glEnableVertexAttribArray(maPositionHandle);
            checkGlError("glEnableVertexAttribArray maPositionHandle");

            mTriangleVertices.position(TRIANGLE_VERTICES_DATA_UV_OFFSET);
            GLES20.glVertexAttribPointer(maTextureHandle, 2, GLES20.GL_FLOAT, false,
                    TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mTriangleVertices);
            checkGlError("glVertexAttribPointer maTextureHandle");
            GLES20.glEnableVertexAttribArray(maTextureHandle);
            checkGlError("glEnableVertexAttribArray maTextureHandle");

            Matrix.setIdentityM(mMVPMatrix, 0);
            GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, mMVPMatrix, 0);
            GLES20.glUniformMatrix4fv(muSTMatrixHandle, 1, false, mSTMatrix, 0);

            GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
            checkGlError("glDrawArrays");

            // IMPORTANT: on some devices, if you are sharing the external texture between two
            // contexts, one context may not see updates to the texture unless you un-bind and
            // re-bind it.  If you're not using shared EGL contexts, you don't need to bind
            // texture 0 here.
            GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, 0);
        }

        /**
         * Initializes GL state.  Call this after the EGL surface has been created and made current.
         */
        public void surfaceCreated() {
            mProgram = createProgram(VERTEX_SHADER, FRAGMENT_SHADER);
            if (mProgram == 0) {
                throw new RuntimeException("failed creating program");
            }
            maPositionHandle = GLES20.glGetAttribLocation(mProgram, "aPosition");
            checkLocation(maPositionHandle, "aPosition");
            maTextureHandle = GLES20.glGetAttribLocation(mProgram, "aTextureCoord");
            checkLocation(maTextureHandle, "aTextureCoord");

            muMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
            checkLocation(muMVPMatrixHandle, "uMVPMatrix");
            muSTMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uSTMatrix");
            checkLocation(muSTMatrixHandle, "uSTMatrix");

            int[] textures = new int[1];
            GLES20.glGenTextures(1, textures, 0);

            mTextureID = textures[0];
            GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, mTextureID);
            checkGlError("glBindTexture mTextureID");

            GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MIN_FILTER,
                    GLES20.GL_NEAREST);
            GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MAG_FILTER,
                    GLES20.GL_LINEAR);
            GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_S,
                    GLES20.GL_CLAMP_TO_EDGE);
            GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_T,
                    GLES20.GL_CLAMP_TO_EDGE);
            checkGlError("glTexParameter");
        }

        /**
         * Replaces the fragment shader.  Pass in null to reset to default.
         */
        public void changeFragmentShader(String fragmentShader) {
            if (fragmentShader == null) {
                fragmentShader = FRAGMENT_SHADER;
            }
            GLES20.glDeleteProgram(mProgram);
            mProgram = createProgram(VERTEX_SHADER, fragmentShader);
            if (mProgram == 0) {
                throw new RuntimeException("failed creating program");
            }
        }

        private int loadShader(int shaderType, String source) {
            int shader = GLES20.glCreateShader(shaderType);
            checkGlError("glCreateShader type=" + shaderType);
            GLES20.glShaderSource(shader, source);
            GLES20.glCompileShader(shader);
            int[] compiled = new int[1];
            GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compiled, 0);
            if (compiled[0] == 0) {
                Log.e(TAG, "Could not compile shader " + shaderType + ":");
                Log.e(TAG, " " + GLES20.glGetShaderInfoLog(shader));
                GLES20.glDeleteShader(shader);
                shader = 0;
            }
            return shader;
        }

        private int createProgram(String vertexSource, String fragmentSource) {
            int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexSource);
            if (vertexShader == 0) {
                return 0;
            }
            int pixelShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentSource);
            if (pixelShader == 0) {
                return 0;
            }

            int program = GLES20.glCreateProgram();
            if (program == 0) {
                Log.e(TAG, "Could not create program");
            }
            GLES20.glAttachShader(program, vertexShader);
            checkGlError("glAttachShader");
            GLES20.glAttachShader(program, pixelShader);
            checkGlError("glAttachShader");
            GLES20.glLinkProgram(program);
            int[] linkStatus = new int[1];
            GLES20.glGetProgramiv(program, GLES20.GL_LINK_STATUS, linkStatus, 0);
            if (linkStatus[0] != GLES20.GL_TRUE) {
                Log.e(TAG, "Could not link program: ");
                Log.e(TAG, GLES20.glGetProgramInfoLog(program));
                GLES20.glDeleteProgram(program);
                program = 0;
            }
            return program;
        }

        public void checkGlError(String op) {
            int error;
            while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
                Log.e(TAG, op + ": glError " + error);
                throw new RuntimeException(op + ": glError " + error);
            }
        }

        public static void checkLocation(int location, String label) {
            if (location < 0) {
                throw new RuntimeException("Unable to locate '" + label + "' in program");
            }
        }
    }
}