ADAU146x SRC Latency
Hello,
I've got an ADAU1462 project that takes i2s in, sends through ASRC to internal sample rate of 96kHz.
When measuring the end-to-end latency of the system with fs_in = 48kHz, I get 1.521ms, and when I change sample rate of input to 96kHz, the latency drops to 583us. When I increase sample rate again to 192kHz, the latency drops to 333us. The internal ADAU1462 processing is still all happening at 96kHz, so I have to assume that the ASRC latency is dropping by a rather significant amount depend on input sample frequency.
Does this make sense? I can't find any sort of ASRC latency specifications in the datasheet.
Thanks,
Evan
Hello Evan,
Page 74 of the data sheet provides formulas for calculating the ASRC latency -- only they call it Group Delay:
For example, with a 48K input to a 96K system, the latency is:
16/48 + 32/96 = 0.667 mS
The rest of your delay is likely within the DACs, etc.
Best regards,
Bob
Bob,
Thanks for the reply. The first equation has fs_IN in denominator of both terms, but your example calculation has fs_out in the denominator of the 32/x term. Is this a mistake in the datasheet?
Thanks,
Evan
Oops, my goof. I didn't read the symbols closely enough. The data sheet should be correct. Thus my example should read: latency = 16/48 + 32/48 = 1.0 mS Only thing is, this equation simplifies to latency = 48 / fs in so I can't imagine why it shows as two terms in the data sheet.
Bob
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