> >> For me a compressed image format is a format that have losses. e.g. > >> I take 5*5 pixels and calcul the mean of it. So the size is smaller > >> as further. In the normal status you dont see the quality losses > >> but if you zoom in. Do you understand, what I mean with compressed? > >> OK but after I had saved the images I want to analyse it with > >> Matlab. And I've been afraid that if I use compressed images which > >> had information losses, the results are wrong. That's all. > > > > > > An entirely valid reason to avoid any lossy image format. > > > Absolutely. But then the first thing to avoid is to go through YUV420P > (which uses only 1.5 bits of info per pixel) or even through any other > pixel format than the one that will be used for the image processing in > Matlab. > > So, the specs are: 25fps (BTW at what size and for how long a time), a > lossless codec, which has to be acceptable to MATLAB, and no lossy > colorspace conversions. Thus JPEG is out (lossy), and XPM too (uses a > colormap). That leaves BMP and maybe GIF (does a TrueColr GIF exist?), > and maybe PGM and PPM - I dont know much about them, are they really > lossless *and* free of colorspace conversions? > You lose color information using YUV420 (and it's 1.5 bytes/pixel.) (*) Only the brightness part of the image is unchanged. PPM is a raw format, basically same as (non-RLE) 24-bit BMP. But there's no point in converting YUV420 to RGB24; grab packed RGB24 frames and you got yourself a "rawbits" PPM minus the header. "man ppm" gives the details. I have never used Matlab, but my 3rd eye (not the one in the back ;) tells me that you can read raw binary data into it? In this case one could use those raw buffers as they are. Jonk (*) Provided a true RGB camera is used. With an ordinary PAL camera no information is lost.