30 HMX6801+B2/C2 and HMX6801+B4/C4 Installation and Operation Manual
Chapter 3: Operation
If any of the AES input channels are of a Non-PCM format, then a
channel summation (AES × Sum) of the channel for any OutxSrc is not
a valid selection. For example, if AES 1A or AES 1B (or both) are
Non-PCM, then AES 1 SUM is not a valid selection for any
OutxSrc parameter. See “Non-PCM Processing” on page 32 for the
handling of Non-PCM input channels.
Input Audio Rate
When embedding audio in PCM mode (OutxxFrmt = PCM or
OutxxFrmt = Auto and OutxxFrmFb = PCM), the input audio
sample rate may be from 32 kHz to 96 kHz. This input audio will be
sample rate converted to 48 kHz prior to embedding in the HD video
signal; as well, the embedder will indicate 48 kHz in the “Rate” word of
the audio control packet for each embedded audio group.
When embedding audio in Non-PCM mode (OutxxFrmt = Non-PCM
or OutxxFrmt = Auto and OutxxFrmFb = Non-PCM), the input
audio sample rate must be 48 kHz and frequency locked to the source
video. In this scenario, the sample rate conversion function is bypassed
and the embedder will indicate 48 kHz in the “Rate” word of the audio
control packet for each embedded audio group.
Channel Summing (PCM Processing only)
If you select AES 1 Sum, AES 2 Sum, AES 3 Sum, or AES 4 Sum as
the source, the result is the sum of the two parts of the channel divided
by two (the mean average).
For example, AES 1 Sum = (AES 1A + AES 1B) ÷ 2
Therefore, the stereo signal is averaged, creating a monaural signal. See
Figure 3-4 on page 31 for an illustration of this process.
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