How To Open Cv::videowriter In Android

I'm using OpenCV 2.4.8 in Android using JNI. I opening the camera with VideoCapture and I want to record it. I have the image in a cv::Mat, it appear in the screen correctly. But,

Solution 1:

As I know OpenCV4adnroid doesn’t support video reading and writing. Try to rebuild your Opencv with an encoder option: (such: WITH_FFMPEG=YES or WITH_VFW=YES )

OR try save a sequence of images then encode a video from this sequence from java code I tried next proposition (ref)

publicvoidimageToMP4(BufferedImage bi) {
    // A transform to convert RGB to YUV colorspaceRgbToYuv420transform=newRgbToYuv420(0, 0);

    // A JCodec native picture that would hold source image in YUV colorspacePicturetoEncode= Picture.create(bi.getWidth(), bi.getHeight(), ColorSpace.YUV420);

    // Perform conversion
    transform.transform(AWTUtil.fromBufferedImage(bi), yuv);

    // Create MP4 muxerMP4Muxermuxer=newMP4Muxer(sink, Brand.MP4);

    // Add a video trackCompressedTrackoutTrack= muxer.addTrackForCompressed(TrackType.VIDEO, 25);

    // Create H.264 encoderH264Encoderencoder=newH264Encoder(rc);

    // Allocate a buffer that would hold an encoded frameByteBuffer_out= ByteBuffer.allocate(ine.getWidth() * ine.getHeight() * 6);

    // Allocate storage for SPS/PPS, they need to be stored separately in a special place of MP4 file
    List<ByteBuffer> spsList = newArrayList<ByteBuffer>();
    List<ByteBuffer> ppsList = newArrayList<ByteBuffer>();

    // Encode image into H.264 frame, the result is stored in '_out' bufferByteBufferresult= encoder.encodeFrame(_out, toEncode);

    // Based on the frame above form correct MP4 packet
    H264Utils.encodeMOVPacket(result, spsList, ppsList);

    // Add packet to video track
    outTrack.addFrame(newMP4Packet(result, 0, 25, 1, 0, true, null, 0, 0));

    // Push saved SPS/PPS to a special storage in MP4
    outTrack.addSampleEntry(H264Utils.createMOVSampleEntry(spsList, ppsList));

    // Write MP4 header and finalize recording
    muxer.writeHeader();
}

You can download JCodec library from a project web site or via Maven, for this add the below snippet to your pom.xml:

<dependency><groupId>org.jcodec</groupId><artifactId>jcodec</artifactId><version>0.1.3</version></dependency>

Android: Android users can use something like below to convert Android Bitmap object to JCodec native format:

publicstatic Picture fromBitmap(Bitmap src) {
    Picturedst= Picture.create((int)src.getWidth(), (int)src.getHeight(), RGB);
    fromBitmap(src, dst);
    return dst;
}

publicstaticvoidfromBitmap(Bitmap src, Picture dst) {
    int[] dstData = dst.getPlaneData(0);
    int[] packed = newint[src.getWidth() * src.getHeight()];

    src.getPixels(packed, 0, src.getWidth(), 0, 0, src.getWidth(), src.getHeight());

    for (inti=0, srcOff = 0, dstOff = 0; i < src.getHeight(); i++) {
        for (intj=0; j < src.getWidth(); j++, srcOff++, dstOff += 3) {
            intrgb= packed[srcOff];
            dstData[dstOff]     = (rgb >> 16) & 0xff;
            dstData[dstOff + 1] = (rgb >> 8) & 0xff;
            dstData[dstOff + 2] = rgb & 0xff;
        }
    }
}

Solution 2:

('M','J','P','G') is the only supported by android while using .avi ext. Most important of all is to #include stdio.h, without this you wont be able to open VideoWriter video

Solution 3:

cv::VideoWriter writer;
writer.open("your_mp4_file_path", cv::VideoWriter::fourcc('H', '2', '6', '4'),
                    15, //framerate
                    cv::Size(720, 1280),
                    true);
writer << mat_frame;

// remember writer.release() when finish

android opencv 4.5.2, opencv with ffmpeg + openh264, work well for me