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Best way to save CV_16SC3 frames

asked 2017-02-15 04:42:30 -0500

victor.dmdb gravatar image

VideoWriter doesn't seem to have any 16bit codecs (or am I wrong about that?), so should these be saved with FileStorage instead? Assuming I need to save 16bit images at 25+ fps.

I'm actually trying to save an 8U, 16U and 16S at the same time, so I just merge all three into an CV_16SC3 Mat. Or is there a better solution to this?

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I'm actually trying to save an 8U, 16U and 16S at the same time, so I just merge all three into an CV_16SC3 Mat.

why on earth would you need that ? also, you cannot save different datatypes in the same image, you you'd have to convert them to a common type anyway.

berak gravatar imageberak ( 2017-02-15 05:09:47 -0500 )edit

Need to store different data types to hold multiple data sources for each frame. All the data have the same resolution. Yep I was converting them to 16S before merging anyway.

victor.dmdb gravatar imagevictor.dmdb ( 2017-02-15 07:00:40 -0500 )edit

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answered 2017-02-15 05:41:36 -0500

kbarni gravatar image

updated 2017-02-15 05:45:42 -0500

As Berak said, it's not a good idea to combine these images into a single 3 channel image. You make unnecessary memory operations and disk writing.

For vodeo files (avi or similar) there are no 16 bit codecs. You can save a series of 8 and 16 bit TIF files, but I think it's quite slow, so it won't work at 25+ fps.

The best way to do this (especially if the image size is known) would be to dump directly the data to the disk. Something like (c++ code, only with two frames to keep things simple):

ofstream myfile;
myfile.open ("video.dat",ios::binary);
uchar *frame1=new uchar[w*h];
ushort *frame2=new ushort[w*h];
Mat i1(w,h,frame1,CV_8UC1);
Mat i2(w,h,frame2,CV_16UC1);
....
myfile.write(frame1,w*h);
myfile.write(frame2,w*h*2);
...//repeat for every frame
myfile.close();

When reading the data, just do the opposite operations:

while(!myfile.eof()){
    myfile.read(frame1,w*h);
    myfile.read(frame2,w*h*2);
}

By knowing the size of a data chunk (sizeof(frame1)+sizeof(frame2)+...), you can jump directly to a given frame, too.

If the image size can vary, you can write these parameters as the first bytes of the file.

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Also sorry, the fps thing wasn't related to the speed, but most just stating i'm storing large 16bit matrices at a high rate. My concern would actually more be towards compression than speed.

victor.dmdb gravatar imagevictor.dmdb ( 2017-02-15 07:45:14 -0500 )edit
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Asked: 2017-02-15 04:42:30 -0500

Seen: 134 times

Last updated: Feb 15 '17