"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
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