A bit of info which might be useful. I am not an expert here, but we used jpeg compression a lot.
1. Our internal tools allow you to specify compression, as well as sampling. For sampling we offer "4:2:0" (half res chroma), "4:2:2" (half res horizonally, full res vertically) and "4:4:4" (full resolution in each direction). (*) 2. The jpeg_component_info struct has "comp_info" for each channel, and these have h_samp_factor and v_samp_factor which are set based on the sub-sampling you want. 3. High quality work will want 4:4:4. Lots of high quality video sources use 4:2:2, Maybe this is legacy from analog video signals which were 4:2:2. The web says most jpegs are 4:2:0, which makes sense to me for a snapshot with square pixels. On Thu, Oct 16, 2014 at 2:59 PM, Justin Israel <[email protected]> wrote: > "4:4:4" - Calls jpeg_set_colorspace() with JCS_RGB > I don't know if it matters, but you might want to stay YUV, but with 4:4:4 sampling. I think that is what we do. --jono (*) when I double checked this, I noticed that what in the GUI of our tools since at least 1996 has been called "4:1:1" is actually "4:2:0". I realized this when I double checked what "4:1:1" means and realized it's not what I thought.
_______________________________________________ Oiio-dev mailing list [email protected] http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
