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In Reply to: software upsampling add dynamics? posted by rick57 on October 30, 2006 at 04:42:21:
I've been "hella-busy" the last few days.No, I am not talking about clicks, pops and droputs. I keep a close eye on CPU utilization with each iteration and never let my PC get to the point where it is even close to doing that. There are some who have reported sonic degradation when they start reaching the *threshold* of CPU resources (especially when upsampling) and don't get dropouts per se, but they experience a different kind of sonic degradation. I guess I am more referring to added veils, or loss or detail and transparency and PRAT and involvement if too many DSP algorithms are used in sequence. My main concern is not really CPU usage. I have a 2.9 GHz PIV Hyperthreading CPU with 1 GB RAM and this thing EATS UP processor intensive tasks. I can run a convolver plugin (for room correction), a DSP Equalizer (for final tweaks) and a three way digital active crossover plugin ALL in Foobar ALL at once with less than 25% CPU usage. I can even add upsampling using SRC up to 24/96 but CPU usage starts to get higher than I would like - but I never get clicks or pops. (I have disabled quite a few XP services and run a pretty stripped down OS with no "XP Bling".)
There are three main ways (that I know of right now) to do active crossovers ONBOARD with a PC AND do realtime room correction.
1) Use Foobar with Convolver plugin (1st) and crossover plugin of your choice (2nd). Of course, use ASIO if possible.
2) Use Winamp with RealReverb Convolver plugin and Thuneau's VST plugin crossovers complete with the "phase arbitrator". Again, ASIO is availble and should be used if possible.
3) Use Brute FIR for implementing both crossover and room correction filters. Not for the faint of heart and quite a bit of PC and programming knowlege is probably in order. There is a software suite available to make the filters called the "Acourate Audio Toolbox" which is specifically designed to generate filters for Brute FIR. This also is not for the faint of heart and requires the user to have a measurement suite and the ability to use FRD files along with a crossover design tool to generate the filters.
Now, of course, you can do what AlJordan said and do some of these processes (like EQ or crossover functions) outboard and use the software player alone (or just for room correction). As AlJordan said "The DAC in the DEQ is not bad, but not outstanding either." this applies to the DCX2496 as well. But I think the ransparency and detail rendering ability of units like these has more to do with getting a low jitter spdif (or AES/EBU) input into the thing in the first place. Mark my words - if Behringer came out with a new DCX2496 that had a USB input that used I2S internallyt with NO conversion to SPDIF on the other end... put me down for two.
Behringer... did you hear that? :D
The trouble with Behringers is the digital inputs are only as good as the digital being supplied to them. Sure, they use the common phase-locked-loop for asynchronous connections and then upsample to 24/96... but I find that the Behringer will tell you very quickly when it does not like the digital stream you feed into it. Some folks have reported that the Monarchy Audio DIP Upsampler between their source and the Behringers open things up a bit, and I have had success with products like a Gensis digital lense as well.
But at the end of the day, and as it stands right now, the most transparency I am getting is doing the crossover work passively and only using the player for convolution. I am not upsampling now at all and since I've gotten the room correction thing working I've honestly put upsampling on the back burner.
Basically, what you do depends on how much you want to spend, how much PC horsepower you can afford, and what you personal "beliefs" are when it comes to "where to do" each individual process.
Right now I have my eye on a new system using shallow crossover slopes in a transient perfect filler driver design (using passive crossovers). This way I can use Winamp and Thuneau crossovers. Once the crossover "Phase Arbitration" is done for the 1st and 2nd order filters, THEN room correction can be done. I just need to ensure the Thuneau crossovers will work with Winamp before i get them - I think I need some sort of VST Plugin to make it go.
Anyways. The bottom line is that there are 1,000 different ways to go about doing this PC stuff. Add outboard options and then there are a 1,000,000 ways. Right now I am still experimenting with relatively cheap iterations to try and nail down what processes (and combination of processes) do the LEAST sonic "damage" to the music.
And I don't mean clicks and pops.
I mean interfere with the LIFE... the EMOTION of the music!!
Follow Ups:
PrestoThanks for the * very informative posts
Not suggesting that Behringers are the best at all, but what DACs have you used for reasonable money that are better?
Cheers
Presto wrote:
"Right now I have my eye on a new system using shallow crossover slopes in a transient perfect filler driver design (using passive crossovers). This way I can use Winamp and Thuneau crossovers. Once the crossover "Phase Arbitration" is done for the 1st and 2nd order filters, THEN room correction can be done. I just need to ensure the Thuneau crossovers will work with Winamp before i get them - I think I need some sort of VST Plugin to make it go."Hi Presto,
I would be interested in hearing more details about the shallow TP crossover system you are thinking about. Who designed the speakers and crossover?
I recently purchased the Thuneau Allocator so I can try some experiments with Winamp for you if it helps. I have been using the kernel streaming output of Foobar mainly for playback, but I have successfully configured my PC so that every sound made by any application will go through the Thuneau crossover/arbitrator. I particularly like the Thuneau crossover because it has parametric eq capabilities on each crossover leg. I can use the crossover to reduce the amplitude of standing waves and eliminate the DEQ 2496. The main problem is that my Lynx ASIO drivers will only let one application at a time access the ASIO drivers, which is why I have to use the kernel streaming driver in Foobar. I may consider looking into Console to see if it will allow me to stack multiple apps into the ASIO driver. I am also going to try to see if the M-Audio 410 ASIO drivers will allow multiple apps to access ASIO, although I am not sure the M-Audio mixer is flexible enough to accomplish the routing I need.
What sound card are you using?
Also, Jan at Thuneau mentioned that he is coming out with a new software package called Frequency Affirmer that will do "very good room correction and crossover at the same time". I am hoping that it will mimic DRC/BruteFIR in a package that allows for an easier visual configuration, but I have no details. I was able to get an impulse response under Linux and use BruteFIR, but the process was difficult even though I have a lot of linux experience. I would pay for a package that is easier to configure.
Alan:AP "I would be interested in hearing more details about the shallow TP crossover system you are thinking about. Who designed the speakers and crossover?"
Nobody... yet. I would be designing it myself. The design would consist of a high efficiency wide range driver used as a midrange (filler driver in this case) to join a woofer and tweeter in a TP configuration.
You can examine what different filter Q values you need for a given filter "Gamma" (overlap) using this cool little program created by an authority on transient perfect and transient perfect subtractive delay crossover designs: The (great) John Kreskovsky. He's one of the 'greats' not just because he's so darned smart, but because he shares so much of his work with the DIY community. (This goes for all of the contributors over at the frd consortium... THANKS guys!)
You can get the (filler driver) transient perfect designer here:
http://www.pvconsultants.com/audio/tp/tpdfil.htm
AP:"I have been using the kernel streaming output of Foobar mainly for playback, but I have successfully configured my PC so that every sound made by any application will go through the Thuneau crossover/arbitrator."
You said you need to use kernel streaming - I am guessing this is because the VST plugin for Thuneau Allocator is using ASIO to map the (8) output channels to the multi-channel ASIO card, meaning you can't use ASIO to map the (2) INPUT channels simultaneously. Honestly? I think ASIO is over-rated for playback applications. There are a number of ways to "bypass" windows k-mixer, and latency is not a major concern for non-live playback systems. Thanks for the info on you trials and tribulations (and methodology). It's nice when people share this information!
Here is another trick you can try. You can use a product called "Virtual Audio Cable" with an ASIO4ALL wrapper to map the sound from your app (Foobar) to the Allocator. I spent $50 on Virtual Audio Cable a while back - and I have not yet really NEEDED it for anything but it's just so darned cool I decided to get it "just in case" and support the very creative guy who wrote that software. Basically you can "interconnect" any two software programs via their I/O as if you were selecting soundcards - but you are not - you are simply tying (directly) the output of one app to the input of another and the sample rate / bit depth is controlled by your software. The "cable" does not interfere so long as the "requested" samplerate and bitdepth is within the range of settings that YOU can select (up to 24/192 I believe!)
Right now, I am using a (cheap but decent) M-Audio Revolution 7.1 which has ASIO capability to it's onboard DACs but no ASIO capability to it's SPDIF output. The analog outputs of this card are amazingly clean and sound really good - it's good enough (for now) for experimentation purposes. I really want a USB solution with I2S (not SPDIF) on the other end that is MULTICHANNEL so I can tri-amp, but the only folks doing more than 2 Channels with USB are the prosound/prosumer guys and with them it's hard to know how the thing will truly "sound" despite amazing specifications. I also do not want USB BUS power running my DACs. (I think if you're using USB bus power to drive your DACs in an external box you may as well use a good PCI card!!)
AP:"Also, Jan at Thuneau mentioned that he is coming out with a new software package called Frequency Affirmer that will do "very good room correction and crossover at the same time".
Like we're not going to try THAT software!! lol
I love this PC audio stuff!
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