"Nemosoft Unv." wrote: > > Hi, > > On 13-Jun-01 Christopher Ross wrote: > > > > The 4:2:0 is a standard format, derived from CCIR-601 (1982). > > To quote Benoit (ch2 Digitization of Video Signals): > > > > For applications that are less demanding in terms of resolution, > > and in view of the bit-rate reduction, a certain number of > by-products > > of the 4:2:2 standard have been defined as follows: > > > > The 4:2:0 format > > This format is obtained from the 4:2:2 format by using the same > > chroma samples for two successive lines, in order to reduce the > > amount of memory required in processing circuitry while at the > > same time giving a vertical resolution of the same order as the > > horizontal resolution. Luminance and horizontal chrominance > > resolutions are the same as for the 4:2:2 format > > [...snip...] > > [snip] > > Okay, interesting stuff, but it still fails to address the most basic > question: in what order are the bytes (supposed to be) arranged? It seems > nobody dared to propose a specific format. 4:2:0 is a chroma subsampling specification, not a component sample layout format. AFAIK the most common (only?) 4:2:0 layout formats in widespread use are the *planar* AVI "YV12" (Y, V, U) and "I420" (Y, U, V) formats. V4L VIDEO_PALETTE_YUV420P is the same as the AVI I420 format. Ben
