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ADV601

GETTING THE MOST OUT OF ADV601

The unique sub-band block structure of luminance and color

components in the ADV601 offers many unique application

benefits. Analog Devices will offer a Feature Software Library as

well as separate feature application documentation to help users

exploit these features. The following section provides an over-

view of only some of the features and how they are achieved with

the ADV601. Please refer to Figures 2 and 3 as necessary.

Higher Compression With Interfield Techniques

The ADV601 normally operates as a field-independent codec.

However, through use of the sub-bands it is possible to use the

ADV601 with interfield techniques to achieve even higher levels

of compression. In such applications, each field is not com-

pressed separately, thus accessing the compressed bit stream

can only be done at specific points in time. There are two gen-

eral ways this can be accomplished:

• Subsampling high frequency blocks

The human visual system is more sensitive to interframe

motion of low frequency block than to motion in high fre-

quency blocks. The host software driver of the ADV601

allows exploitation of this option to achieve higher com-

pression. Note that the compressed bit stream can only be

accessed at points where the high frequency blocks have just

been updated.

• Updating the image with motion detection

In applications where the video is likely to have no motion for

extended periods of time (video surveillance in a vacant build-

ing, for instance), it is only necessary to update the image

either periodically or when motion occurs. By using the wave-

let sub-bands to detect motion (see later in this section), it is

possible to achieve very high levels of compression when

motion is infrequent.

Scalable Compression Technology

The ADV601 offers many different options for scaling the im-

age, the compressed bit stream bandwidth and the processing

horsepower for encode or decode. Because the ADV601 em-

ploys decimators, interpolators and filters in the filter bank,

the scaling function creates much higher quality images than

achieved through pixel dropping. Mixing and matching the

many scaling options is useful in network applications where

transmission pipes may vary in available bit rate, and decode/

encode capabilities may be a mix of software and hardware.

These are the key options:

• Extract scaled images by factors of 2 from the compressed bit stream

This is useful in video editing applications where thumbnail

sketches of fields need to be displayed. In this case, editing

software can quickly extract and decode the desired image.

This technique eliminates the burden of decoding an entire

image and then scaling to the desired size.

• Use software to decode bit stream

Decoding an entire CCIR-601 resolution image in real time at

50/60 fields per second does require the ADV601 hardware.

Analog Devices provides a bit-exact ADV601 simulator that

can decode a scaled image in real time or a full-size image off-

line. Image size and frame rates depend on the performance

of the host processor.

• Scale bit stream

The compressed video bit stream was created with simple

parsing in mind. This type of parsing means that a lower

resolution/lower bandwidth bit stream can be extracted with

little computational burden. Generally, this effect is accom-

plished by selecting a subset of lower frequency blocks. This

technique is useful in applications where the same video

source material must be sent over a range of different commu-

nication pipes {i.e., ISDN p(128 Kbps), T1 (1.5 Mpbs) or

T3 (45 Mbps)}.

• Use software to encode

In this case, a host CPU could encode a smaller image size

and fill in high frequency blocks with zeros. Again, image

quality would depend on the performance of the host. The

Bin Width may be set to zero, zeroing out the data in any

particular Mallat block.

Parametric Image Filtering

The ADV601 offers a unique set of image filtering capabilities

not found in other compression technologies. The ADV601

quantizer is capable of attenuating any or all of the luminance or

chrominance blocks during encode or decode. Here are some of

the possible applications:

• Parametric softening of color saturation and contrast during encode

or decode

Trade off image softness for higher compression. Attenuation

of the higher frequency blocks during encode leads to softer

images, but it can lead to much higher compression perfor-

mance.

• Color saturation control

This effect is achieved by controlling gain of low pass chromi-

nance blocks during encode or decode.

• Contrast control

This effect is achieved by controlling the gain of the low fre-

quency luminance blocks during encode or decode.

• Fade to black

This effect achieved by attenuation of luminance blocks.

Mixing of Two or More Images

Blocks from different images can be mixed into the bit stream

and then sent to the ADV601 during decode. The result is high

quality mixing of different images. This also provides the capa-

bility to fade from one image to the next.

Edge or Motion Detection

In certain remote video surveillance and machine vision applica-

tions, it is desirable to detect edges or motion. Edges can be

quickly found through evaluation of the high frequency blocks.

Motion searches can be achieved in two ways:

• Evaluation of the smallest luminance block. Because the size

of the smallest block is from 20

× 15 pixels (for square pixel

NTSC) to 24

× 18 pixels (square pixel PAL), the computa-

tional burden is significantly less than doing an evaluation

over the entire image.

• Polling the Sum of Squares registers. Because large changes in

the video data create patterns, it is possible to detect motion

in the video by polling the Sum of Squares registers, looking

for patterns and changes.

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