ZR36060PQC datasheet(14/46 Pages) ETC

14 / 46 page

Integrated JPEG CODEC

3.4.4 Vertical up-scaling in decompression

As in compression, this is specified by

VScale:

VScale = 0b: No up-scaling

VScale = 1b:2:1 interpolation, by line replication

3.5 Active Area Size Restrictions

The maximum allowed size for the active area rectangle is 768

pixels x 64K lines.

The ZR36060 JPEG codec always processes an image with

dimensions of 2*8*x and 8*y pixels. This is because of the YUV

4:2:2 format, where the MCU is 2 blocks of Y, 1 block of U and 1

block of V. The active area of the video interface must be config-

ured to reflect the dimensions before down-scaling in

compression, and after up-scaling in decompression. show the

resulting restrictions imposed on the dimensions of the active

area.

In the internal sampling scheme, the first chrominance sample is

always assumed to be a U (Cb) sample. This is directly con-

trolled by the Hstart parameter. Hstart must be programmed to

an appropriate value (even or odd) in order for the ZR36060 to

sample first the U (Cb) pixel, otherwise U-V inversion occurs.

3.6 Spatial Mix of Video Streams

The ZR36060 is capable of spatially mixing (multiplexing) two

video sources for compression, and also of multiplexing the

ZR36060 output video with another video source during decom-

pression. The latter is a useful feature for video editing, e.g. to

superimpose titles or subtitles onto the images.

The SUBIMG output signal creates a sub-image rectangle

defined by the SHstart, SHend, SVstart, SVend parameters,

where one image is outside and the other one is inside the rect-

angle (see Figure 10). In compression, this signal can be

connected, for example, to two synchronized sources of live

video to multiplex their outputs. Some digital video sources have

a video bus which can be placed in a floating state (for example,

the Philips SAA7110 video digitizer/decoder); SUBIMG can be

used to float this bus while enabling a second video source.

Some possible options are to multiplex two video decoders, one

decoder and one field memory, one video decoder and one

MPEG decoder, etc.

There are several inherent problems in mixing video that the

system designer must consider:

• The two video sources must be synchronized. This means

that pixel clocks, horizontal and vertical timing must come

from only one source which is the sync master.

• Both video sources must work in the same mode (16-bit or 8-

bit).

• The SHstart and SHend parameters must be such that the

boundaries of the subimage rectangle (where SUBIMG

changes state) are exactly at the boundary between inde-

pendent YUV 4:2:2 units (units of two VCLKs, containing

related U and V samples) for both sources.

To permit video mixing during decompression (playback), the

SUBIMG output can be externally connected to the POE input.

This way, the ZR36060 places its video data only within (or

outside) the rectangle defined by SUBIMG, floating the output

video bus outside (or inside) the boundaries (see Figure 11). The

polarity of the SUBIMG signal is defined by the SImgPol param-

eter, and the polarity of the POE signal (to place ZR36060 data

inside or outside the rectangle during playback) is defined by

PoePol parameter. In Figure 11, the polarity of SUBIMG has

been chosen so as to float the video bus outside the subimage

rectangle.

Note that SUBIMG and POE operate independently of each

other, so they can also be used separately.

Table 2: Active Area, Horizontal Dimension (

HEnd -

HStart)

Horizontal scaling

Restriction

No scaling (1:1)

Multiple of 16

2:1

Multiple of 32

4:1

Multiple of 64

Table 3: Active Area, Vertical Dimension (

VEnd -

VStart)

Vertical Scaling

Restriction

No scaling (1:1)

Multiple of 8

2:1

Multiple of 16

Figure 10. Subimage Parameters In Compression

HSYNC

Source 1

SHstart

SHend

Source 2

Active Area

Rectangle

Subimage

Rectangle

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