CS4953xx Data Sheet
32-bit Audio Decoder DSP Family
3. Code Overlays
The suite of software available for the CS4953xx family consists of an operating system (OS) and a library of
overlays. The overlays have been divided into three main groups called Decoders, Mid-processors, and Post-
processors. All software components are defined below:
1. OS/Kernel - Encompasses all non-audio processing tasks, including loading data from external memory,
processing host messages, calling audio-processing subroutines, error concealment, etc.
2. Decoders - Any Module that initially writes data into the audio I/O buffers, e.g. AC-3®, DTS, PCM, etc. All the
decoding/processing algorithms listed below require delivery of PCM or IEC61937-packed, compressed data
via I2S- or LJ-formatted digital audio to the CS4953xx.
3. Mid-processors - Any module that processes audio I/O buffer PCM data in-place before the Post-
processors. Generally speaking, these modules alter the number of valid channels in the audio I/O buffer
through processes like Virtualization (nÖ2 channels) or Matrix Decoding (2Ön channels). Examples are Dolby
ProLogic IIx and DTS Neo:6.
4. Post-processors - Any module that processes audio I/O buffer PCM data in-place after the Mid-Processors.
Examples are Bass Management, Audio Manager, Tone Control, EQ, Delay, Customer-specific Effects, Dolby
Headphone/Virtual Speaker, etc.
The overlay structure reduces the time required to reconfigure the DSP when a processing change is
Y requested. Each overlay can be reloaded independently without disturbing the other overlays. For example,
when a new decoder is selected, the OS, mid-, and post-processors do not need to be reloaded — only the
new decoder (the same is true for the other overlays).
R Table 2 below lists the firmware available based on device selection. Please refer AN288 CS4953xx Firmware
PRELIMINA User’s Manual for the latest listing of application codes and Cirrus Framework™ modules available.
DS705PP3
Copyright 2008 Cirrus Logic
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