如何在 Android 中打开 cv::VideoWriter [英] How to open cv::VideoWriter in Android
问题描述
我正在使用 JNI 在 Android 中使用 OpenCV 2.4.8.
I'm using OpenCV 2.4.8 in Android using JNI.
我用 VideoCapture 打开相机,我想录制它.我在 cv::Mat 中有图像,它正确显示在屏幕上.
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.
但是,当我尝试打开 VideoCapture 时,它总是返回 false.
But, when I try to open VideoCapture, it returns false always.
// Camera resolution is 640x480 and its fine.
_camera_resolution = calc_optimal_camera_resolution(u.name, 640, 480);
// Store in sdcard, I have permission in AndroidManifest.xml
const char * videoName = "/sdcard/videoTest.avi";
// Segmentation fault 11! this method doesnt work in Android? so commented
//const int ex = static_cast<int>(_reader.get(CV_CAP_PROP_FOURCC));
// Segmentation fault 11! too!!! so commented
//const double fps = _reader.get(CV_CAP_PROP_FPS);
// Try to open
_isRecording = _writer.open(videoName, -1, 30, _camera_resolution, true);
// Return FALSE always
if(!_writer.isOpened())
{
LOGE("rec - Error opening video writer");
}
else
{
LOGD("rec - Video writer opened in startRecording");
}
我曾尝试用作 FOURCC:
I have tried to use as FOURCC:
CV_FOURCC('M', 'J', 'P', 'G') 和 CV_FOURCC('M', 'P', '4', 'V')//不起作用!
CV_FOURCC('M', 'J', 'P', 'G') and CV_FOURCC('M', 'P', '4', 'V') // It doesn't works!
我尝试过不同的 fps 比率,15.0、30.0...
I have tried with different fps ratios, 15.0, 30.0...
相机分辨率似乎有效,因为当我打印时值是正确的.
Camera resolution seems work because when I print the value is correct.
为什么不能正确打开?
推荐答案
据我所知 OpenCV4adnroid 不支持视频读写.尝试使用编码器选项重建您的 Opencv:(例如: WITH_FFMPEG=YES 或 WITH_VFW=YES )
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 )
或者尝试保存一个图像序列,然后用 java 代码从这个序列中编码一个视频我尝试了下一个命题(ref)
OR try save a sequence of images then encode a video from this sequence from java code I tried next proposition (ref)
public void imageToMP4(BufferedImage bi) {
// A transform to convert RGB to YUV colorspace
RgbToYuv420 transform = new RgbToYuv420(0, 0);
// A JCodec native picture that would hold source image in YUV colorspace
Picture toEncode = Picture.create(bi.getWidth(), bi.getHeight(), ColorSpace.YUV420);
// Perform conversion
transform.transform(AWTUtil.fromBufferedImage(bi), yuv);
// Create MP4 muxer
MP4Muxer muxer = new MP4Muxer(sink, Brand.MP4);
// Add a video track
CompressedTrack outTrack = muxer.addTrackForCompressed(TrackType.VIDEO, 25);
// Create H.264 encoder
H264Encoder encoder = new H264Encoder(rc);
// Allocate a buffer that would hold an encoded frame
ByteBuffer _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 = new ArrayList<ByteBuffer>();
List<ByteBuffer> ppsList = new ArrayList<ByteBuffer>();
// Encode image into H.264 frame, the result is stored in '_out' buffer
ByteBuffer result = 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(new MP4Packet(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();
}
您可以从项目网站或通过 Maven 下载 JCodec 库,为此将以下代码段添加到您的 pom.xml:
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>
安卓:Android 用户可以使用以下方法将 Android Bitmap 对象转换为 JCodec 原生格式:
Android: Android users can use something like below to convert Android Bitmap object to JCodec native format:
public static Picture fromBitmap(Bitmap src) {
Picture dst = Picture.create((int)src.getWidth(), (int)src.getHeight(), RGB);
fromBitmap(src, dst);
return dst;
}
public static void fromBitmap(Bitmap src, Picture dst) {
int[] dstData = dst.getPlaneData(0);
int[] packed = new int[src.getWidth() * src.getHeight()];
src.getPixels(packed, 0, src.getWidth(), 0, 0, src.getWidth(), src.getHeight());
for (int i = 0, srcOff = 0, dstOff = 0; i < src.getHeight(); i++) {
for (int j = 0; j < src.getWidth(); j++, srcOff++, dstOff += 3) {
int rgb = packed[srcOff];
dstData[dstOff] = (rgb >> 16) & 0xff;
dstData[dstOff + 1] = (rgb >> 8) & 0xff;
dstData[dstOff + 2] = rgb & 0xff;
}
}
}
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