使用视频写入器更改存储视频的大小

Question

我想在处理后以减小尺寸存储视频。目前，我正在使用与输入视频相同的大小。我正在用c++编写开放式简历。

Answer 1

如果你的目标是改变视频分辨率，然后使用resize()函数到一个矩阵，存储您的图像:

Mat source, destination;
IplImage new_img;
int fps = 30;
// Apply resize
resize(source, destination, Size(640, 360), 1, 1, 1);
// Create writer
CvVideoWriter *new_writer = cvCreateVideoWriter("video.mp4",CV_FOURCC('M', 'P', '4', '2'), fps, destination.size(), 3);
new_img = destination.operator IplImage();  
// 1-if image written or 0 if failed
int ret = cvWriteFrame(new_writer, (const IplImage*)&new_img);
printf("Written?: %dn", ret);
// And finally release writer
cvReleaseVideoWriter(&new_writer);

如果您的目标是减少磁盘上的视频大小，那么尝试创建具有各种编解码器的VideoWriter，例如:

CV_FOURCC('P','I','M','1')    = MPEG-1 codec
CV_FOURCC('M','J','P','G')    = motion-jpeg codec (does not work well)
CV_FOURCC('M', 'P', '4', '2') = MPEG-4.2 codec
CV_FOURCC('D', 'I', 'V', '3') = MPEG-4.3 codec
CV_FOURCC('D', 'I', 'V', 'X') = MPEG-4 codec
CV_FOURCC('U', '2', '6', '3') = H263 codec
CV_FOURCC('I', '2', '6', '3') = H263I codec
CV_FOURCC('F', 'L', 'V', '1') = FLV1 codec