What would be the cheap and/or ready-made options for playing four (4) recorded audio signals simultaneously? The required provision is that they must begin at exactly the same time to maintain an engineered mark space ratio between them.
This facility is not provided by a standard sound card or stereo gear.
Any ideas?
Ken Gillmore
On a sunny day (Wed, 30 May 2012 15:21:31 +1000) it happened snipped-for-privacy@interlux.com wrote in :
It is very easy, if mono signals. Multiplex the 4 audio signals into one 4 channel wave file, and play via 5.1 soundcard, front left, front right, rear left, rear right, or something.
If you have a Linux PC use my program 'multimux'.
That's a definite solution. I have a program called "MultiPlayer" that does this in Windows.
But, for this application, a stand-alone approach is required. Or a cost-effective, four channel recorder/storage unit that will play back channels separately without mixing.
This capability seems hard to find, without purchasing specialized lab gear.
Ken Gillmore
Alesis Adat HD recorder or similar by other companies.
Steve
I see clues which say "this is on a PC", so.... assuming that.
A Frontier Designs ADAT Lightpipe card and a behringer ADA8000 can do this. This requires a PCI slot.
I've measured this. Play the same, one-bit pulse back on a DAW four times, record the output. All four recorded pulses will be in synch ( I've only tested it at 44.1kHz ).
I don't use a Frontier ( I bought a Terratec when they were still in production ) but I'd give the Frontier a try - I bet it does better than the terratec. The terratec at least has completely deterministic latency, with ASIO or WDM ( and I forget about the other driver models ) drivers.
If you use USB for this, you can (IMO) never guarantee the timing. SFAIK, you can still buy motherboards with real PCI cards - I did last year ( a ZT Systems ). There may be some way to adapt ePCI to real PCI - I never had to actually do that, but it looked like there was.
( I care about this because I have a Fostex VF16 that chases SMPTE/MTC sync, so I measure these things.... )
-- Les Cargill
*Sigh*. Requirements creep in one post :)
There are standalone digital recorders. I know a Fostex VF16 will do this, but you have to use the AUX outs. They're getting old.
-- Les Cargill
+1
-- Les Cargill
Quite a lot of laptops and PCs these days have sound cards / interfaces which are actually multi-channel capable. The codec chips have multiple channels, and the connections between the codec I/O pins and the external I/O jacks are "soft" and can be reprogrammed by software. Many cards have both "front" and "rear" line-level outputs, and on some of those which do not you can reprogram the "line in" jack to act as a second set of outputs.
If you configure a multi-channel interface in this way and then write "four-channel" output to it, you should get excellent synchronization from the channels - I believe many will synchronize within +/- 1 sample time.
Whether your operating system and application actually expose this level of control flexibility is another matter. I'm pretty sure it can be done (on competent hardware) with the ALSA sound driver on Linux... there's a fairly steep learning curve to ALSA configuration but it's very flexible indeed.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
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Older blackface XTs can even be modified for DC coupling in and out. Most of the really good, nearly pro sound cards such as the older Echo Layla are time coherent and have DC coupling with either a mod or stock. There is some really good audio stuff out there, if you dig.
I use DC coupled ADATS for recording the signals for my laser show hobby. The galvo scanners for the vector graphics only need a 3-4 kilohertz response, so adat is just fine.
Steve
Sorry if I did not make it clear. I am looking for a non-PC approach.
A circuit and/or series of storage-type devices to store and playback four audio channels in sync.
I thought this was an engineers' newsgroup ;-)
Ken
you've been given an embarassment of options. And no, you weren't clear.
-- Les Cargill
Poor Old Ken does not realize we have no trains around here!
Jamie
Mostly along the same lines. The OP implied I did not want to go via a soundcard. I don't know how you deduced this, "I see clues which say "this is on a PC", so.... assuming that." You probably skewed the whole discussion.
This is online fantasy. Everyone should have the opportunity to clarify. So you are unable to help and feel better maling it look like my own fault. Hope that works for everyone here.
Ken
Not so much. there've been a few approaches that are not a PC posted in the thread. The general class of standalone harddisk recorders look a lot like test equipment.
Probably so. I latched onto the word "standard".
Sure. I'd agree.
Nah, I was simply trying to show that there was some ambiguity in what was asked for. Unless there are additional constraints, the OP should be good to go.
-- Les Cargill
Well, we could tell you to just get a PIC, four DACs and an SD card, and you can make one your self. Plenty of us would be glad to build you such a system for a couple of grand... ;-)
Charlie
NO PC, we can play that game.
OK, Arduino with SD card shield, a Ti or Max DAC quad chip with double buffering, a MP3 freeware source code for the Arduino, and lots of time recoding.
Seriously, unless you need lots of them or a very portable unit, a standalone HD recorder or a similar instrumentation recorder is the way to go.
If there was a quad channel, standalone, cheap AD_DA solution with a DC to high audio bandwidth, I'd probably have found it by now, and so would about 600 of my professional friends in the laser industry who have similar needs and share those needs on a forum. The biomedical folks have a similar need for waveform recording and they also use ADAT.
Nearly everything I have found is Stereo and MP3 based, and that looses sync somewhat in the compression.
Steve
Very astute answer. Thanks. Sounds like money to be made in selling something like this.
And ... I found this interesting little item. Perhaps by using four wired to a single "play" button. No programming required.
I wonder how closely the stop-start times would match from device to device. The manufuacturer doesn't know. Would anyone take a guess?
Ken
Well, its not a product designed for general mass consumption, but because your really reaching, this is for lasershows, but has a WAV mode for a specific wave. If the 8 x 12 bit limitations and the fact that you will need to add your own level shifters on 6 of the outputs, this WILL read a WAV off a SD card. I own one.
For a laser show, we need +/- 10V for the X and Y position of the laser beam, and 0-5V for the color control channels per international (ILDA) standard. With some work, you can can level shift 6 of the 0-5 outputs and go from there.
It will stand alone, and play a script on startup. You'll have to create your WAV files off board.
Sync is very, very tight, we can see a 1/30,000 of a second error in the X-Y signals when we project.
With some work, you can treat it as a 8 channel WAV playback device at ONE sample rate.
Steve
You mentioned a sound card in your very first post. Would that not tend to drive the discussion toward PC platform class answers.?
^^^^^^^^^^
BTW 4 and more channel systems are readily available on decent sound cards, external USB Audio equipment, etc.
?-)
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