User guide

Introduction

CS4953x4/CS4970x4 System Designer’s Guide

6.1.2.2 Decoding Stream Types Over HDMI

When decoding audio streams over HDMI, follow these practices:

• In case of Multichannel PCM input over HDMI, specific AC3 decoder modes are used, that is, those

modes specifically dedicated to Multichannel PCM inputs over HDMI. Refer to the sample

flash_image.xml file, which is automatically installed when dspcondenser.exe is installed. Do not

change the decoder mode when PCM over HDMI is detected.

• Before determining whether the audio output from the CS4953x4/CS4970x4 DSP has stopped,

verify the status of audio output of the HDMI Rx fed into the CS4953x4/CS4970x4 DSP. HDMI Rx is

known to behave differently for different input stream types, especially the HD streams.

For example:

In case of SI9135 chips, ensure that the audio FIFO and control registers are reset correctly.

• Ensure that the Extended Display Identification Data (EDID) configurations are available for all the

stream types to be supported on the system.

• In case of PCM over HDMI, Cirrus Logic recommends that the Host Controller obtain the information

to distinguish streams between stereo PCM and Multi-channel PCM from the HDMI Rx. The

following stream information can be provided by the CS4953x4/CS4970x4 DSP:

- Fs detection

- Even though the DSP can obtain the number of channels when decoding multi-channel PCM,

Cirrus Logic recommends that number of channels be derived from the Audio Information frame

registers of the HDMI receiver.

6.1.3 Other System Design Considerations

• SPDIF output from the CS4953x4/CS4970x4 DSP is not available for 192 kHz streams.

• Ensure that the power rail (1.8V and 3.3V) ramp-up process is clean and glitch-free.

• Cirrus Logic recommends that only supported Flash devices listed in Section 1.1.1.be used in the

design.

§§