Xilinx HDMI 1.4 Product Manual page 87

In the case of more than 2 channels, every 2 channels are considered as a single AES3 audio
block. For example, using 8 audio channels, one audio block consists of 192*8 audio
samples. For the first 8 samples of an audio block, the preamble for audio ch0, ch2, ch4, ch6
are "Z". In remaining part of audio block, the preamble for audio ch0, ch2, ch4, ch6 are "X".
The preambles for audio ch1, ch3, ch5, ch7 are always "Y" through out of the whole audio
block. An illustration of 8 channel audio is shown below.
X-Ref Target - Figure B-3
If 8 channel audio is enabled in your design, only 6 out of 8 channels carry valid audio data.
For the unused channels, you must pack the audio data with zeros and the sub-frame data
allocation follows as per illustrated above.
HDMI 1.4/2.0 TX Subsystem
PG235 October 4, 2017 www.xilinx.com
Appendix B: Debugging
87
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