android - 如何使用 MediaCodec 将位图编码为视频？

Question

我想将我拥有的一组位图编码为 h264。这可以通过 MediaEncoder 实现吗？为了做到这一点，我编写了一些代码，但输出无法在我尝试过的任何媒体播放器中播放。以下是我主要从 Stackoverflow 上找到的其他来源借用的一些代码。

mMediaCodec = MediaCodec.createEncoderByType("video/avc");
mMediaFormat = MediaFormat.createVideoFormat("video/avc", 320, 240);
mMediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, 125000);
mMediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, 15);
mMediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Planar);
mMediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 5);
mMediaCodec.configure(mMediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
mMediaCodec.start();
mInputBuffers = mMediaCodec.getInputBuffers();

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream); // image is the bitmap
byte[] input = byteArrayOutputStream.toByteArray();

int inputBufferIndex = mMediaCodec.dequeueInputBuffer(-1);
if (inputBufferIndex >= 0) {
    ByteBuffer inputBuffer = mInputBuffers[inputBufferIndex];
    inputBuffer.clear();
    inputBuffer.put(input);
    mMediaCodec.queueInputBuffer(inputBufferIndex, 0, input.length, 0, 0);
}

我应该调整什么？

Answer 1

我已修改 abalta 提供的代码以实时接受位图(即您不需要将位图保存到光盘)。它还具有性能改进，因为您不需要从磁盘写入然后读取位图。我还增加了原始示例中的 TIMEOUT_USEC，它修复了我遇到的一些与超时相关的错误。

希望这对某人有所帮助。我花了很长时间尝试做到这一点，而不必将大型第三方库打包到我的应用程序(例如 ffmpeg)中，所以我非常感谢 abalta 的回答。

我正在使用 rxjava，所以你需要在应用的 build.gradle 依赖项中使用它:

implementation 'io.reactivex.rxjava2:rxandroid:2.0.2'

如果您尝试写入外部存储，则需要 list 中定义的外部存储权限:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

并在系统设置应用中为您的应用手动切换权限，或将权限请求处理添加到您的 Activity 中。

这是类(class):

import android.graphics.Bitmap;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaCodecList;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.util.Log;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;

import io.reactivex.Completable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;

public class BitmapToVideoEncoder {
    private static final String TAG = BitmapToVideoEncoder.class.getSimpleName();

    private IBitmapToVideoEncoderCallback mCallback;
    private File mOutputFile;
    private Queue<Bitmap> mEncodeQueue = new ConcurrentLinkedQueue();
    private MediaCodec mediaCodec;
    private MediaMuxer mediaMuxer;

    private Object mFrameSync = new Object();
    private CountDownLatch mNewFrameLatch;

    private static final String MIME_TYPE = "video/avc"; // H.264 Advanced Video Coding
    private static int mWidth;
    private static int mHeight;
    private static final int BIT_RATE = 16000000;
    private static final int FRAME_RATE = 30; // Frames per second

    private static final int I_FRAME_INTERVAL = 1;

    private int mGenerateIndex = 0;
    private int mTrackIndex;
    private boolean mNoMoreFrames = false;
    private boolean mAbort = false;

    public interface IBitmapToVideoEncoderCallback {
        void onEncodingComplete(File outputFile);
    }

    public BitmapToVideoEncoder(IBitmapToVideoEncoderCallback callback) {
        mCallback = callback;
    }

    public boolean isEncodingStarted() {
        return (mediaCodec != null) && (mediaMuxer != null) && !mNoMoreFrames && !mAbort;
    }

    public int getActiveBitmaps() {
        return mEncodeQueue.size();
    }

    public void startEncoding(int width, int height, File outputFile) {
        mWidth = width;
        mHeight = height;
        mOutputFile = outputFile;

        String outputFileString;
        try {
            outputFileString = outputFile.getCanonicalPath();
        } catch (IOException e) {
            Log.e(TAG, "Unable to get path for " + outputFile);
            return;
        }

        MediaCodecInfo codecInfo = selectCodec(MIME_TYPE);
        if (codecInfo == null) {
            Log.e(TAG, "Unable to find an appropriate codec for " + MIME_TYPE);
            return;
        }
        Log.d(TAG, "found codec: " + codecInfo.getName());
        int colorFormat;
        try {
            colorFormat = selectColorFormat(codecInfo, MIME_TYPE);
        } catch (Exception e) {
            colorFormat = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar;
        }

        try {
            mediaCodec = MediaCodec.createByCodecName(codecInfo.getName());
        } catch (IOException e) {
            Log.e(TAG, "Unable to create MediaCodec " + e.getMessage());
            return;
        }

        MediaFormat mediaFormat = MediaFormat.createVideoFormat(MIME_TYPE, mWidth, mHeight);
        mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);
        mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, FRAME_RATE);
        mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, colorFormat);
        mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, I_FRAME_INTERVAL);
        mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mediaCodec.start();
        try {
            mediaMuxer = new MediaMuxer(outputFileString, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
        } catch (IOException e) {
            Log.e(TAG,"MediaMuxer creation failed. " + e.getMessage());
            return;
        }

        Log.d(TAG, "Initialization complete. Starting encoder...");

        Completable.fromAction(() -> encode())
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe();
    }

    public void stopEncoding() {
        if (mediaCodec == null || mediaMuxer == null) {
            Log.d(TAG, "Failed to stop encoding since it never started");
            return;
        }
        Log.d(TAG, "Stopping encoding");

        mNoMoreFrames = true;

        synchronized (mFrameSync) {
            if ((mNewFrameLatch != null) && (mNewFrameLatch.getCount() > 0)) {
                mNewFrameLatch.countDown();
            }
        }
    }

    public void abortEncoding() {
        if (mediaCodec == null || mediaMuxer == null) {
            Log.d(TAG, "Failed to abort encoding since it never started");
            return;
        }
        Log.d(TAG, "Aborting encoding");

        mNoMoreFrames = true;
        mAbort = true;
        mEncodeQueue = new ConcurrentLinkedQueue(); // Drop all frames

        synchronized (mFrameSync) {
            if ((mNewFrameLatch != null) && (mNewFrameLatch.getCount() > 0)) {
                mNewFrameLatch.countDown();
            }
        }
    }

    public void queueFrame(Bitmap bitmap) {
        if (mediaCodec == null || mediaMuxer == null) {
            Log.d(TAG, "Failed to queue frame. Encoding not started");
            return;
        }

        Log.d(TAG, "Queueing frame");
        mEncodeQueue.add(bitmap);

        synchronized (mFrameSync) {
            if ((mNewFrameLatch != null) && (mNewFrameLatch.getCount() > 0)) {
                mNewFrameLatch.countDown();
            }
        }
    }

    private void encode() {

        Log.d(TAG, "Encoder started");

        while(true) {
            if (mNoMoreFrames && (mEncodeQueue.size() ==  0)) break;

            Bitmap bitmap = mEncodeQueue.poll();
            if (bitmap ==  null) {
                synchronized (mFrameSync) {
                    mNewFrameLatch = new CountDownLatch(1);
                }

                try {
                    mNewFrameLatch.await();
                } catch (InterruptedException e) {}

                bitmap = mEncodeQueue.poll();
            }

            if (bitmap == null) continue;

            byte[] byteConvertFrame = getNV21(bitmap.getWidth(), bitmap.getHeight(), bitmap);

            long TIMEOUT_USEC = 500000;
            int inputBufIndex = mediaCodec.dequeueInputBuffer(TIMEOUT_USEC);
            long ptsUsec = computePresentationTime(mGenerateIndex, FRAME_RATE);
            if (inputBufIndex >= 0) {
                final ByteBuffer inputBuffer = mediaCodec.getInputBuffer(inputBufIndex);
                inputBuffer.clear();
                inputBuffer.put(byteConvertFrame);
                mediaCodec.queueInputBuffer(inputBufIndex, 0, byteConvertFrame.length, ptsUsec, 0);
                mGenerateIndex++;
            }
            MediaCodec.BufferInfo mBufferInfo = new MediaCodec.BufferInfo();
            int encoderStatus = mediaCodec.dequeueOutputBuffer(mBufferInfo, TIMEOUT_USEC);
            if (encoderStatus == MediaCodec.INFO_TRY_AGAIN_LATER) {
                // no output available yet
                Log.e(TAG, "No output from encoder available");
            } else if (encoderStatus == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                // not expected for an encoder
                MediaFormat newFormat = mediaCodec.getOutputFormat();
                mTrackIndex = mediaMuxer.addTrack(newFormat);
                mediaMuxer.start();
            } else if (encoderStatus < 0) {
                Log.e(TAG, "unexpected result from encoder.dequeueOutputBuffer: " + encoderStatus);
            } else if (mBufferInfo.size != 0) {
                ByteBuffer encodedData = mediaCodec.getOutputBuffer(encoderStatus);
                if (encodedData == null) {
                    Log.e(TAG, "encoderOutputBuffer " + encoderStatus + " was null");
                } else {
                    encodedData.position(mBufferInfo.offset);
                    encodedData.limit(mBufferInfo.offset + mBufferInfo.size);
                    mediaMuxer.writeSampleData(mTrackIndex, encodedData, mBufferInfo);
                    mediaCodec.releaseOutputBuffer(encoderStatus, false);
                }
            }
        }

        release();

        if (mAbort) {
            mOutputFile.delete();
        } else {
            mCallback.onEncodingComplete(mOutputFile);
        }
    }

    private void release() {
        if (mediaCodec != null) {
            mediaCodec.stop();
            mediaCodec.release();
            mediaCodec = null;
            Log.d(TAG,"RELEASE CODEC");
        }
        if (mediaMuxer != null) {
            mediaMuxer.stop();
            mediaMuxer.release();
            mediaMuxer = null;
            Log.d(TAG,"RELEASE MUXER");
        }
    }

    private static MediaCodecInfo selectCodec(String mimeType) {
        int numCodecs = MediaCodecList.getCodecCount();
        for (int i = 0; i < numCodecs; i++) {
            MediaCodecInfo codecInfo = MediaCodecList.getCodecInfoAt(i);
            if (!codecInfo.isEncoder()) {
                continue;
            }
            String[] types = codecInfo.getSupportedTypes();
            for (int j = 0; j < types.length; j++) {
                if (types[j].equalsIgnoreCase(mimeType)) {
                    return codecInfo;
                }
            }
        }
        return null;
    }

    private static int selectColorFormat(MediaCodecInfo codecInfo,
                                         String mimeType) {
        MediaCodecInfo.CodecCapabilities capabilities = codecInfo
                .getCapabilitiesForType(mimeType);
        for (int i = 0; i < capabilities.colorFormats.length; i++) {
            int colorFormat = capabilities.colorFormats[i];
            if (isRecognizedFormat(colorFormat)) {
                return colorFormat;
            }
        }
        return 0; // not reached
    }

    private static boolean isRecognizedFormat(int colorFormat) {
        switch (colorFormat) {
            // these are the formats we know how to handle for
            case MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420Planar:
            case MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420PackedPlanar:
            case MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar:
            case MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420PackedSemiPlanar:
            case MediaCodecInfo.CodecCapabilities.COLOR_TI_FormatYUV420PackedSemiPlanar:
                return true;
            default:
                return false;
        }
    }

    private byte[] getNV21(int inputWidth, int inputHeight, Bitmap scaled) {

        int[] argb = new int[inputWidth * inputHeight];

        scaled.getPixels(argb, 0, inputWidth, 0, 0, inputWidth, inputHeight);

        byte[] yuv = new byte[inputWidth * inputHeight * 3 / 2];
        encodeYUV420SP(yuv, argb, inputWidth, inputHeight);

        scaled.recycle();

        return yuv;
    }

    private void encodeYUV420SP(byte[] yuv420sp, int[] argb, int width, int height) {
        final int frameSize = width * height;

        int yIndex = 0;
        int uvIndex = frameSize;

        int a, R, G, B, Y, U, V;
        int index = 0;
        for (int j = 0; j < height; j++) {
            for (int i = 0; i < width; i++) {

                a = (argb[index] & 0xff000000) >> 24; // a is not used obviously
                R = (argb[index] & 0xff0000) >> 16;
                G = (argb[index] & 0xff00) >> 8;
                B = (argb[index] & 0xff) >> 0;


                Y = ((66 * R + 129 * G + 25 * B + 128) >> 8) + 16;
                U = ((-38 * R - 74 * G + 112 * B + 128) >> 8) + 128;
                V = ((112 * R - 94 * G - 18 * B + 128) >> 8) + 128;


                yuv420sp[yIndex++] = (byte) ((Y < 0) ? 0 : ((Y > 255) ? 255 : Y));
                if (j % 2 == 0 && index % 2 == 0) {
                    yuv420sp[uvIndex++] = (byte) ((U < 0) ? 0 : ((U > 255) ? 255 : U));
                    yuv420sp[uvIndex++] = (byte) ((V < 0) ? 0 : ((V > 255) ? 255 : V));

                }

                index++;
            }
        }
    }

    private long computePresentationTime(long frameIndex, int framerate) {
        return 132 + frameIndex * 1000000 / framerate;
    }
}

用法类似于:

BitmapToVideoEncoder bitmapToVideoEncoder = new BitmapToVideoEncoder(new IBitmapToVideoEncoderCallback() {
    @Override
    public void onEncodingComplete(File outputFile) {
        Toast.makeText(this,  "Encoding complete!", Toast.LENGTH_LONG).show();
    }
});

bitmapToVideoEncoder.startEncoding(getWidth(), getHeight(), new File("some_path"));
bitmapToVideoEncoder.queueFrame(bitmap1);
bitmapToVideoEncoder.queueFrame(bitmap2);
bitmapToVideoEncoder.queueFrame(bitmap3);
bitmapToVideoEncoder.queueFrame(bitmap4);
bitmapToVideoEncoder.queueFrame(bitmap5);
bitmapToVideoEncoder.stopEncoding();

如果您的录制被中断(例如 Activity 正在暂停)，您可以中止，它会删除文件(因为无论如何它都会损坏)。或者，只需调用 stopEncoding ，它就会正确关闭文件，以免损坏:

bitmapToVideoEncoder.abortEncoding();

还有一个 getActiveBitmaps() 函数可以查看队列有多大(如果队列变大，您可能会耗尽内存)。这里还有一些代码可以有效地从 View 中创建位图，以便您可以将其排队(我的应用程序会定期截取屏幕截图并将它们编码成视频):

View view = some_view;
final Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(),
        Bitmap.Config.ARGB_8888);

// Create a handler thread to offload the processing of the image.
final HandlerThread handlerThread = new HandlerThread("PixelCopier");
handlerThread.start();

PixelCopy.request(view, bitmap, (copyResult) -> {
    bitmapToVideoEncoder.queueFrame(bitmap);
}, new Handler(handlerThread.getLooper()));