Forums > Jitter

scaling problem with YUV

December 18, 2009 | 3:54 pm

I am trying to program a kind of video scrub. I use the third channel of an audio file (float32) to control the frame number of a 3d matrix.

This is tha patch used to store the matrix in jit binary format and to store the number of the frames in the third channel of the audio file (which the sound is stereo).

– Pasted Max Patch, click to expand. –

I need to work in uyvy to save half the size in RAM.

But, when I try to read the video, the resolution looks half the resolution is should be (horizontal little lines everywhere…) This is the second patch.

– Pasted Max Patch, click to expand. –

Did I miss something to get the video back to its original dimension?


December 18, 2009 | 3:58 pm

I did a lot of tests. I defined the problem. The problem comes from writing the 3d matrix on the disk in binary format and reading it in another patch. The quality is good when I put the 2 patches together in the same patch avoiding saving the 3d matrix on the disk. Like in this patch:

– Pasted Max Patch, click to expand. –

But I need to write the matrix on the disk to be able to load quickly all the videos at the same time…


December 18, 2009 | 4:02 pm

These are samples of the image to compare the quality.

source: http://julienrobert.net/upload/source.png

the result coming from the first patch (2 different patches) with lost of quality: http://julienrobert.net/upload/imagejitter.png


December 18, 2009 | 5:06 pm

ok. This was the problem. The jit.qt.movie size fitted for the destination matrix which was in half vertical resolution, so it gave us 320×240 instead of 320×480. We have to use the parameter @adapt 1 to get a matrix of 320×480.

Thanks anyway!


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