User guide

Chapter 3: Interfaces 3–5
Avalon-ST Video Protocol
January 2013 Altera Corporation Video and Image Processing Suite
User Guide
A color pattern can represent more than one pixel. This is the case when consecutive
pixels contain samples from different color planes—There must always be at least one
common color plane between all pixels in the same color pattern. Color patterns
representing more than one pixel are identifiable by a repeated color plane name. The
number of times a color plane name is repeated is the number of pixels represented.
Figure 3–4 shows two pixels of horizontally subsampled Y' CbCr (4:2:2) where Cb and
Cr alternate between consecutive pixels.
In the common case, each element of the matrix contains the name of a color plane
from which a sample must be taken. The exception is for vertically sub sampled color
planes. These are indicated by writing the names of two color planes in a single
element, one above the other. Samples from the upper color plane are transmitted on
even rows and samples from the lower plane transmitted on odd rows as shown in
Figure 3–5.
Table 3–2 lists the static parameters and gives some examples of how you can use
them.
The Avalon-ST Video protocol does not force the use of specific color patterns,
however a few MegaCore functions of the Video and Image Processing Suite only
process video data packets correctly if they use a certain set of color patterns.
Chapter 4, Functional Descriptions describes the set of color patterns that the
MegaCore functions use.
Figure 3–4. Horizontally Subsampled Y'CbCr
Figure 3–5. Vertically Subsampled Y'CbCr
Cb Cr
YY
Cb
Cr
Y Y
Plane for even rows
Plane for odd rows
Table 3–2. Examples of Static Avalon-ST Video Data Packet Parameters
Parameters
Description
Bits per Color Sample Color Pattern
8
Three color planes, B’, G’, and R’ are transmitted in alternating sequence and each
B’, G’, or R’ sample is represented using 8 bits of data.
10
Three color planes are transmitted in parallel, leading to higher throughput than
when transmitted in sequence, usually at higher cost. Each R’, G’, or B’ sample is
represented using 10 bits of data, so that, in total, 30 bits of data are transmitted
in parallel.
10
4:2:2 video in the Y’CbCr color space, where there are twice as many Y’ samples
as Cb or Cr samples. One Y’ sample and one of either a Cb or a Cr sample is
transmitted in parallel. Each sample is represented using 10 bits of data.
RGB
B
G
R
Cb Cr
YY