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#1
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
Greetings,
I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Some preliminary thoughts are to use a version of *IX as the o/s and layer ALSA and LADSPA with plugins on it, connected with the 'jack' framework, and for testing just control it through remote shell command scripts until a complete control program is written. Since I'm using low-end hardware, I had dismissed using 'Pulseaudio' as a framework (unless convinced otherwise). Should I be considering some other o/s or RTOS? Has this been done as an opensource or freeware project (I don't find much on the 'net)? Replies are much appreciated. Michael |
#2
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
msg wrote:
I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Why do you want to do this rather than use an existing device that does this? There are a bunch of devices like this out there, including a popular one from Roland that is well-documented. Some preliminary thoughts are to use a version of *IX as the o/s and layer ALSA and LADSPA with plugins on it, connected with the 'jack' framework, and for testing just control it through remote shell command scripts until a complete control program is written. Since I'm using low-end hardware, I had dismissed using 'Pulseaudio' as a framework (unless convinced otherwise). Should I be considering some other o/s or RTOS? If I were doing something like this and I were having to use generic PC hardware, I would consider RTLINUX. It would be different if the PC were just a front end to a dsp, though. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#3
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
msg wrote:
Greetings, I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Some preliminary thoughts are to use a version of *IX as the o/s and layer ALSA and LADSPA with plugins on it, connected with the 'jack' framework, and for testing just control it through remote shell command scripts until a complete control program is written. Since I'm using low-end hardware, I had dismissed using 'Pulseaudio' as a framework (unless convinced otherwise). Should I be considering some other o/s or RTOS? Has this been done as an opensource or freeware project (I don't find much on the 'net)? Replies are much appreciated. Michael PCDJ will let you controll multiple outputs, not sure if it had a remote function - but it can be controlled via keyboard short cuts and I have seen somewhere a keyboard rs232 interface so that a dumb terminal can be used as a keyboard on a remote machine bit like a remote KVM. There are also KVM's via ethernet about. thoughts about your hardware - can you get four PCI cards in a 1u rack, is there physically enough space ? |
#4
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
Scott Dorsey wrote:
msg wrote: I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Why do you want to do this rather than use an existing device that does this? There are a bunch of devices like this out there, including a popular one from Roland that is well-documented. Acquisition cost - I need to make several of these and can't afford commercial versions. snip Should I be considering some other o/s or RTOS? If I were doing something like this and I were having to use generic PC hardware, I would consider RTLINUX. It would be different if the PC were just a front end to a dsp, though. Thanks - I'll look at RTLINUX. |
#5
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
f825_677 wrote:
snip thoughts about your hardware - can you get four PCI cards in a 1u rack, is there physically enough space ? I have a few M/B choices that permit four PCI sound devices in 1u; the first is three PCI cards and one integrated audio chipset, the other is a low-profile riser PCI bus with dual opposing slots (four slots). Michael |
#6
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
On Thu, 20 Nov 2008 11:47:51 -0600, msg wrote:
Greetings, I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Some preliminary thoughts are to use a version of *IX as the o/s and layer ALSA and LADSPA with plugins on it, connected with the 'jack' framework, and for testing just control it through remote shell command scripts until a complete control program is written. Since I'm using low-end hardware, I had dismissed using 'Pulseaudio' as a framework (unless convinced otherwise). Are the four cards locked together via spdif or workclock? I don't think jack will work nicely (easily) with four separate sound cards. It definitely won't if they are not locked together. You could run a separate jackd server for each card, I suppose. I wouldn't use Pulseaudio either. Should I be considering some other o/s or RTOS? What kind of latency is acceptable? What standards of reliability? (Will you lose your job if it breaks? ). I'd use PureData with straight forward ALSA. It can interface with virtually anything and will run headless perfectly happily. It's great for rapid prototyping of audio ideas. Also, have a look at Faust. I think a Linux Music distro like 64Studio would be easier than a RTLinux or other *nix. Otherwise you will spend all your time compiling obscure libraries and messing about just to replicate the work others have already done. Has this been done as an opensource or freeware project (I don't find much on the 'net)? Linux-audio-users/dev mailing lists would be a good place to ask. Replies are much appreciated. Michael |
#7
Posted to rec.audio.pro
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remote controlled audio mixer/equalizer project
philicorda wrote:
On Thu, 20 Nov 2008 11:47:51 -0600, msg wrote: Greetings, I would appreciate some suggestions for implementing a stand-alone audio mixer/equalizer box using commodity components, in the shortest development time at the least possible cost. I am tending to want to to use four PCI sound cards in an older PIII 1u rackmount cpu to create a four audio bus/eight inputs mixer, with four independent equalizer channels. It should be controllable using an arbitrary protocol over RS232 or ethernet, not require a resident GUI, nor local mass storage except perhaps flash for program loading, and won't do any local capture, only audio I/O at 44.1 or 48kHz sampling rate to and from unbalanced line level connections. Some preliminary thoughts are to use a version of *IX as the o/s and layer ALSA and LADSPA with plugins on it, connected with the 'jack' framework, and for testing just control it through remote shell command scripts until a complete control program is written. Since I'm using low-end hardware, I had dismissed using 'Pulseaudio' as a framework (unless convinced otherwise). snip I don't think jack will work nicely (easily) with four separate sound cards. It definitely won't if they are not locked together. You could run a separate jackd server for each card, I suppose. Thanks for the heads-up; I had not considered creating a single virtual sound device but only a 'jackd' per card. I found considerable discussion of this topic on the web, for example a good overview: http://www.sound-man.co.uk/linuxaudio/ice1712multi.html If I combine the cards, I'll distribute one hardware clock to all of them. In your view, what advantages are there to combining them for my application? I wouldn't use Pulseaudio either. Should I be considering some other o/s or RTOS? What kind of latency is acceptable? On the order of 10ms as I currently see it. What standards of reliability? (Will you lose your job if it breaks? ). Should be stable for up to four hours I'd use PureData with straight forward ALSA. It can interface with virtually anything and will run headless perfectly happily. It's great for rapid prototyping of audio ideas. Interesting, sort of an audio LabView... You are suggesting controlling my remote audio processor in an X-window? Also, have a look at Faust. I think a Linux Music distro like 64Studio would be easier than a RTLinux or other *nix. Otherwise you will spend all your time compiling obscure libraries and messing about just to replicate the work others have already done. Indeed, I am guilty of tending to do the latter. For the use of old hardware as I intend, what kernel version would you recommend? I have preferred 2.4.27-xxx in the past. Thanks, Michael |
#8
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
On Thu, 20 Nov 2008 12:06:34 -0600, msg wrote:
f825_677 wrote: snip thoughts about your hardware - can you get four PCI cards in a 1u rack, is there physically enough space ? I have a few M/B choices that permit four PCI sound devices in 1u; the first is three PCI cards and one integrated audio chipset, the other is a low-profile riser PCI bus with dual opposing slots (four slots). Can you post a link to these options. I have had occasions in the past where I needed to fit a "standard" PC into odd enclosures, and having links to these type of products is always helpful. Regards Anton Erasmus |
#9
Posted to rec.audio.pro
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remote controlled audio mixer/equalizer project
On Fri, 21 Nov 2008 10:14:49 -0600, msg wrote:
snip snip I don't think jack will work nicely (easily) with four separate sound cards. It definitely won't if they are not locked together. You could run a separate jackd server for each card, I suppose. Thanks for the heads-up; I had not considered creating a single virtual sound device but only a 'jackd' per card. I found considerable discussion of this topic on the web, for example a good overview: http://www.sound-man.co.uk/linuxaudio/ice1712multi.html If I combine the cards, I'll distribute one hardware clock to all of them. In your view, what advantages are there to combining them for my application? If you want to mix the inputs from one card to the outputs of another, then they will have to be locked. If the cards are considered totally separate channels, there is no advantage. It would be much easier to keep the cards totally separate in many ways, especially as most cheap sound cards cannot be clocked together. Buying four of the cheapest that *can* will cost more than the cheapest 8 io card. Making single virtual devices from many different cards using ALSA or jack is still a bit raw IMHO. The article you link is about joining two cards of exactly the same kind which are clocked together. Still, I've never tried it so it might just work fine. I'm not quite sure what your application is, so I don't know what the advantages would be! I wouldn't use Pulseaudio either. Should I be considering some other o/s or RTOS? What kind of latency is acceptable? On the order of 10ms as I currently see it. This will be straightforward. If the machine is doing nothing else then you may not even require an RT kernel. One thing to note is that in Linux/Jack the latency is generally specified for the entire round trip (from input to output). Under Windows/ OSX it's normally specified for only the output. Therefore a 10ms latency under Linux is often counted as a 5ms latency under Windows. What standards of reliability? (Will you lose your job if it breaks? ). Should be stable for up to four hours I'd use PureData with straight forward ALSA. It can interface with virtually anything and will run headless perfectly happily. It's great for rapid prototyping of audio ideas. Interesting, sort of an audio LabView... You are suggesting controlling my remote audio processor in an X-window? You could do that. There are plenty of other ways to control PD. OSC over ethernet, midi, serial port, PD's own guiport. I don't think a simple X session would be good as you would want to be able to turn off or crash the controller computer and reconnect again without interrupting anything. Do look at Faust (http://faust.grame.fr/) too. It's neat as you can code in a 'DSP for dummies' way and it will output as stand alone alsa-gtk software or PD externals or a ladspa plugin etc. Also, have a look at Faust. I think a Linux Music distro like 64Studio would be easier than a RTLinux or other *nix. Otherwise you will spend all your time compiling obscure libraries and messing about just to replicate the work others have already done. Indeed, I am guilty of tending to do the latter. For the use of old hardware as I intend, what kernel version would you recommend? I have preferred 2.4.27-xxx in the past. If it works there is no reason not to use 2.4.27. I think the RT performance of the 2.6 kernel (with RT patches) from 2.6.25 onwards has got worse. The good news is that they are actually fixing the deep problems Linux has with low latency (removing Big Kernel Lock etc). The bad news is that earlier kernels are often better. Thanks, Michael |
#10
Posted to sci.electronics.repair,rec.audio.pro,rec.audio.tech,comp.arch.embedded
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remote controlled audio mixer/equalizer project
Anton Erasmus wrote:
On Thu, 20 Nov 2008 12:06:34 -0600, msg wrote: f825_677 wrote: snip thoughts about your hardware - can you get four PCI cards in a 1u rack, is there physically enough space ? I have a few M/B choices that permit four PCI sound devices in 1u; the first is three PCI cards and one integrated audio chipset, the other is a low-profile riser PCI bus with dual opposing slots (four slots). Can you post a link to these options. I have had occasions in the past where I needed to fit a "standard" PC into odd enclosures, and having links to these type of products is always helpful. As a rabid proponent of reuse most of my projects are based upon salvaged items; in this case I have a selection of custom mainboards and chassis from various old IP firewalls, compression protocol accelerators, industrial controllers, etc., which stand only a remote chance of appearing on auction or recycle sites. If you still want data, I can poke at them for model and ID information later on N.B. some time back I began a list of salvage items that contained reusable FPGAs and posted it with a few updates to the newsgroups but that effort produced mostly disinterest. Michael |
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