AS0260CSSC28SUD20 datasheet(45/83 Pages) ONSEMI

45 / 83 page

AS0260 DS Rev. G Pub. 5/15 EN

©Semiconductor Components Industries, LLC, 2015.

AS0260: 1/6-Inch 1080P High-Definition (HD) System-On-A-Chip (SOC) Digi-

tal Image Sensor

MJPEG Format

The AS0260 supports an MJPEG formatted data output stream. The descriptions

following are based on what the SOC will deliver to a host USB bridge device with which

the SOC would be combined to form a camera for PC applications. The USB Bridge host

is responsible for assembling the individual frames from the SOC into a USB Video Class

(UVC) video data stream.

Stream Breakdown

An MJPEG video stream consists of the following sequence of data sections. Each JPEG

frame must have the following characteristics:

•Color Encoding is YCbCr

• 8 bits per color component, (24 bits/pixel before subsampling)

• 422 Subsampling

• Baseline sequential DCT (SOF0)

Video Stream Header

This section of the video stream is not implemented in the AS0260. The content of this

section is determined by the host.

MJPEG Frame Header

This section of the video stream is not implemented in the AS0260. The content of this

section is determined by the host. This section is just 8 bytes of information at the start

of each frame. The first 4 bytes are:

0x30 0x30 0x64 0x62 # 00db

The next 4 bytes are the length of the following JPEG frame including all the bytes

described in sections 3.3 - 3.5. The 4 byte count value is output LSB first. For example, if

the JPEG data was 0x0002_51dc bytes long, the last 4 bytes in the MJPEG frame header

would be:

0xdc, 0x51, 0x02, 0x00

Since this field contains the byte count of the compressed JPEG data, it cannot be added

by the AS0260, but must be added by the host after frame compression is complete and

the byte count known.

JPEG Header Without Huffman Tables

This is a normal JPEG header except for the fact that the DHT segment (Define Huffman

Table) is not included. The Huffman table is not included because the MJPEG spec

defines the Huffman table to be fixed for all frames. The header segments that will be

included are listed below including examples. Note that data values in the examples are

in hex. Comments are in decimal.

• SOI, Start of Image. 2 bytes.

ff d8

• APP0, Application Segment 0. N bytes. Example JFIF marker:

ff e0 00 10

4a 46 49 46 00 01 02 00 00 01 00 01 00 00

• DQT, Define Quantization Tables. 134 bytes. Example:

ff db 00 84

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