Continuing on from page 3, post 56 of the "DIY Digital Parametric EQ" thread....
Hi all,
(I wanted to start a thread here so as not to hijack the Parametric EQ thread with my ramblings)....
Hi,
@Kevin - I've been using PC based DRC for a few years now, and I've used ACXO Player etc. a few times. I'm currently using Denis Sbragion's DRC to generate the filters (as does ACXO), but the main goal is to try to get away from using a PC at all....
Firstly, I've got major problems with ASIO playback on my new Quad Core system - I have a nasty audio glitch which happens every 25 seconds or so (this can be 50 seconds, or 12 seconds etc. depending on the latency / buffer setting.)....
Although I have HD-DVD on the PC, and do use it to output to the projector, it would be great to have the amp perform the usual DD / DTS / THX processing and have DRC applied on the speakers at all times (with a choice of house curves / XO's etc.)
It seems that it would be much better to do everything in the digital realm rather than getting a sound card with 6 or 8 inputs, then having so many ADC / DAC conversions. Also, many integrated amps won't output audio from the internal decoder while allowing external inputs simultaneously.
Unless you encode back to AC3 or DTS again after DRC has been applied on the PC, you generally have to connect to the amp via analog cables. I my case, this would mean four or more 5-metre cables, probable noise problems, and ground loop issues etc. (I can't even get AC3 / DTS passthrough to work atm.)
All these issues mean that although DRC is still a HUGE improvement, there are often lots of unneccesary ADC / DAC conversions in the loop, and the practical hassles of using PC's takes some of the enjoyment out of things.
The other big reason I'm looking into a DSP project is simply for the learning experience and the fact that I can't find a commercial solution that's remotely affordable compared to a PC. I think it would be a hugely rewarding project, and I'd love to start programming a nice LCD UI and adding features.
Then again, as far as I've been told, it does take a large amount of processing power to compute the FIR filters.....
eg. if MACs = (filter length in samples) * (sample rate), then for a single 50ms filter at 48KHz, it would need 115,200,000 MACs !!!
Is this just the case for raw computation, or are there ways of partitioning the filter algorithms? As you can tell, I don't have much idea when it comes to DSPs, but I'm hungry to learn. I have a fair amount of experience with FPGA programming - would an FPGA be a better choice?
OzOnE.
Hi all,
(I wanted to start a thread here so as not to hijack the Parametric EQ thread with my ramblings)....
Kevin_Murray said:First of all hello everyone, this is my first post to this forum.I was very happy to find this thread because I'm planning a project of this type myself. I haven't even entered the design phase yet because I'm in the middle of a speaker project (TL, another great reason to be a member here) and well... the busy Christmas season will be here soon anyway.
OzOne: is this something you'd be interested in?
http://pcazeles.perso.cegetel.net/acxo.htm
It's for a PC but could help you get started. Near the bottom are links to digital filter generators and other useful stuff.
Mark, good progress! Hope you get the bugs worked out soon. Anyone else completed or currently working on a digital crossover/EQ project? I'm looking for collaborators. A year ago I took a job with a company specializing in embedded processing (which has taken me back to all the schooling in DSP that I've forgotten).This is primarily why I'm interested in pursuing a mostly digital signal path, I've now got the tools to do it effectively. When (and if) I finish I plan to post all my info, code, schematics and PCB artwork online for anyone interested to see. I'm a firm believer in sharing knowledge.
Kevin
Hi,
@Kevin - I've been using PC based DRC for a few years now, and I've used ACXO Player etc. a few times. I'm currently using Denis Sbragion's DRC to generate the filters (as does ACXO), but the main goal is to try to get away from using a PC at all....
Firstly, I've got major problems with ASIO playback on my new Quad Core system - I have a nasty audio glitch which happens every 25 seconds or so (this can be 50 seconds, or 12 seconds etc. depending on the latency / buffer setting.)....
Although I have HD-DVD on the PC, and do use it to output to the projector, it would be great to have the amp perform the usual DD / DTS / THX processing and have DRC applied on the speakers at all times (with a choice of house curves / XO's etc.)
It seems that it would be much better to do everything in the digital realm rather than getting a sound card with 6 or 8 inputs, then having so many ADC / DAC conversions. Also, many integrated amps won't output audio from the internal decoder while allowing external inputs simultaneously.
Unless you encode back to AC3 or DTS again after DRC has been applied on the PC, you generally have to connect to the amp via analog cables. I my case, this would mean four or more 5-metre cables, probable noise problems, and ground loop issues etc. (I can't even get AC3 / DTS passthrough to work atm.)
All these issues mean that although DRC is still a HUGE improvement, there are often lots of unneccesary ADC / DAC conversions in the loop, and the practical hassles of using PC's takes some of the enjoyment out of things.
The other big reason I'm looking into a DSP project is simply for the learning experience and the fact that I can't find a commercial solution that's remotely affordable compared to a PC. I think it would be a hugely rewarding project, and I'd love to start programming a nice LCD UI and adding features.
Then again, as far as I've been told, it does take a large amount of processing power to compute the FIR filters.....
eg. if MACs = (filter length in samples) * (sample rate), then for a single 50ms filter at 48KHz, it would need 115,200,000 MACs !!!
Is this just the case for raw computation, or are there ways of partitioning the filter algorithms? As you can tell, I don't have much idea when it comes to DSPs, but I'm hungry to learn. I have a fair amount of experience with FPGA programming - would an FPGA be a better choice?
OzOnE.