Hi,
Having posted this before at the TechTalk-dept I figured this would be a better place.
What would be an easy way to determine if
an S/PDIF (or AES/EBU) signal is 16, 20
or 24 bits ?
Any kind of solution would be welcome,
for instance in the form of a few CMOS
chips and a few LEDs, or as a check
in a .wav-editor of the recorded signal
or who knows there's even a dedicated
VST- plugin out there.
There's an article here:
http://www.digido.com/index/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=34
but it uses a scope. No problem, but something
more compact would be nice.
Thanks,
Peter
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That's a good question Peter. I don't know of any dedicated t
That's a good question Peter.
I don't know of any dedicated tools to do the function. I assume you already tried to find tech specs on the SPDIF device?
mitz
Thanks for the reaction.
Yep, the info on the S/PDIF format is available on various places. It's just that it could be convenient to know what a certain device is sending - so how many relevant (active) bits are there. The standard allows for up to 24, but if a wrong assumption is made (receiving/recording it as a 16-bit word for instance while it's in fact 20 wide), the wordlength would end up being truncated.
Bye,
Peter
True indeed. Try this: Play a file at full volume through
True indeed.
Try this:
Play a file at full volume through the spdif device in question. Something limited to hell so the signal level is pretty high and relatively constant (or maybe a sine wave at full volume). Record into a SPDIF device at 24 bits.
The result, if I'm not totally off-base here, should be a lower signal level for lower bit depths. Does this make sense, or am I totally in left field?
or you could listen for the truncation artfacts.
Both methods are extremely inexact, but its the best I could devise.
What is the device you are uncertain about?
Mitz
This all might (1) be all too much 'academic' or (2) really impo
This all might (1) be all too much 'academic' or (2) really important and easily overlooked. I guess it's often clearly one of the two, but not always the same one ! :-)
Could say that
The result, if I'm not totally off-base here, should be a lower signal level for lower bit depths. Does this make sense, or am I totally in left field?
I think it's the other way around. So the MSBs (most signif. bits) always reach 0 dB FullScale, but deep down there you have that sixteenth bit (LSB) working OK there - or you have a lonely soul that just saw his little brothers & sisters getting lost & trown away (the 17th-24th bit) !
So it'll probably matter only for reverb tails etc, but still - could imagine some detail gets lost, even during louder passages.
No device in particular I'm 'worried' about. it's just that I have stuff around that likely gives
16, 18, 20 or 24-bit - so it be great to have a simple indication ! It won't always be obvious to hear (except in extreme cases) so better to see it easily than to find out afterwards.
Bye,
Peter
Duh, you're right Peter, when going from a lower bitrate to a hi
Duh, you're right Peter, when going from a lower bitrate to a higher one, the msb bits would contain the signal. What was I thinking.
Maybe try opening the recordings in a hex editor to look at the contents of the file?
Sorry i can't help you any more than that
mitz
Maybe try opening the recordings in a hex editor to look at the
Maybe try opening the recordings in a hex editor to look at the contents of the file?
Sorry i can't help you any more than that
It's OK, there's always he possibility to amplify the signal by 16 times ~6.02 dB and see what's still unclipped. If so, then there were more bits than 16.
Maybe I'll build me something based on the link above.
Thanks for following this,
Peter
That's a good question Peter. I don't know of any dedicated t
That's a good question Peter.
I don't know of any dedicated tools to do the function. I assume you already tried to find tech specs on the SPDIF device?
mitz