Originally Posted by arnyk
I have worked with literally 100s of audio components with SP/DIF and TOSLINK inputs, and have never had one that took any visible action when the link was receiving bad data.
For the most part, I would not think anything would be visible. Audible, sometimes. But more on that below.
I have worked with products that had lights that indicated the presence of an input signal, but they would remain on even when bit errors were being received.
Typically, those lights are an output from the S/PDIF receiver's PLL. It indicates that the PLL is locked to the incoming frequency, and not whether the data is any good.
I called my client to ask if I could use the results of the tests. I have not heard back. But here is what I can
My Audiotron supports the transmitting of the valid bit. If it is not actively playing music, it still sends an IEC958 stream, but the valid bit indicates "invalid".
My SH-AC500D indicates that no audio is present on the front panel when it receives the valid bit as "invalid".
The parity bit is supported by any device that uses a Freescale Symphony DSP with a built in S/PDIF module. I've been using the dual-core DSP56721, whose reference manual I can quote from:
"When an incoming S/PDIF data parity error or bit error is detected, and if the next S/PDIF word for that channel is error-free, the S/PDIF word in error is replaced with the average of the previous word and next word. When an incoming S/PDIF data parity error or bit error is detected, and the next S/PDIF word is in error, the previous S/PDIF word is repeated."
So the goal is to try to accommodate the error in such a way that you don't hear it. So there is
something you can do about a parity error.
I've seen devices with digital inputs mute, but they only muted when there was no data.
Would your ears be able to detect it if only one sample was muted? Also, do many of your devices put out noise
when the data is bad?
This was one of my quick & dirty tests:
Partly pull out one end of the optical cable, and find the point where the signal is marginal. If you hear a lot of noise, parity is not being supported. But if you hear it alternating between sound and silence, than parity is supported.