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View Full Version : Update on s/pdif issues



seanadams
2004-02-16, 13:13
B&K:

Just doesn't work with any format. Got a reference 50 receiver here and
confirmed this. One thing that's interesting though is that if you
connect a s/pdif cable from a CD player, and then quickly switch it
over to squeezebox, the squeezebox does play for about 1 to 5 seconds
before the input switches off again. I believe the problem is that it
doesn't like something in the control bits that we're outputting in the
s/pdif stream. I've ordered some equipment which will analyze our
s/pdif output and that of other products, so we can find out exactly
what it is that this receiver does not like. I called B&K and they
confirmed that the receiver does not use an off-the-shelf s/pdif
receiver chip (eg Crystal, Burr-brown), but custom logic that they've
done in a xilinx chip. This means I can't look up the specs for the
s/pdif receiver and will have to treat it like a "black box" and just
figure out what works. Will have more info on this later in the week
when I get the testing equipment.

Track startup delay:

This issue is only for MP3 format, only with some receivers. The
symptom is that the start of tracks will be cut off by about 0.5 sec.
We will have a fix for this soon. For PCM formats, squeezebox should
already be outputting 44.1KHz silence correctly between tracks - if you
are hearing otherwise, please let me know. (Please note there was an
unrelated streaming issue which could cause similar symptoms when the
server is running on Windows - it has been fixed already in 5.1.)

Wrong sample rate for WAV/AIFF:

Using a frequency counter on the internal frame clock signal, confirmed
wrong sample rate of 44.19 KHz. For MP3 the sample clock is correct at
44.10 KHz. This is easy to fix in software - it's an error in our
calculation of the PLL offset for the clock. Will have a firmware
update to address this ASAP.

Meridian speakers:

Need more information. Could somebody please confirm whether these work
for mp3s but not WAV/AIFF? If that's the case, then it's probably just
the error in the sample clock. Otherwise it's probably something more
like the B&K issue.

Inverted signal (*-1; not swapped channels) for WAV format

Confirmed - easy fix server-side.

Sample clock off-by-one (right channel shifted by one sample WRT the
left channel)

Fixed in 5.1

Channels swapped in some formats:

Fixed in 5.1