Cirrus Logic CS4970x4 - Manual (Page 93)

Introduction
CS4953x4/CS4970x4 System Designer’s Guide
DS810UM6 Copyright 2013 Cirrus Logic, Inc 6-2
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.
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