To those who have implemented tuning on the PC - Page 2

wirelessdreamer · 12-15-2007, 03:59 PM

I've been looking at how this can be done under linux for the past few weeks. So far this is what i've come up with, along with some linux audio basics so non-linux people can follow.

the linux equivalent to ASIO is called JACK, and requires that the rt (realtime) kernel patches are applied. With jack the output of one program can be internally "plugged" into the input of another, so i can run mplayer (a video player) with the jack audio driver, output it to preprocessing sw #1, send that to #2, then out to the speakers (technically processing differently for each speaker, at the cost of processing power).

So far i've been looking at this as 3 main categories, with some overlap.

1. Audio processing - eq, crossovers, delays.

Realtime eq and crossovers can be set, along with a number of other setting with a program called jammin. I've been doing some tests over the last week, and it seems stable and mature.

Delays would be set on a speaker individual basis, so they may need to be implemented a little differently.

2. Upsampling - take everything to play and upsample it to 5.1/7.1, along with any other effects that want to be used to enhance the sound.

This area i've found less information on, and am hoping this thread will be able to help get more information in this area out in the open. the closest program i've found that does "some" of this is ac3jack, but thats a batch program, not realtime, so it would need to be modified heavily.

3. Physical connections - How to get the upsampled dts sound to the right speakers, without loss of quality.

The threads on amps with s/pdif and optical inputs was a bit of a downer, as it sounds like most of these amps are hard to get working, or even ahold of. I'm planning on doing some tests when i have free time next year of output meathods. My experience with linux audio though has been mostly recording setups, so I know I'm a bit behind in the car audio world, i'll post test results if I come up with anything useful.

IMPORTANT INFORMATION:
if you are messing around with jack (the linux audio subsystem) for the first time, know it can be a little difficult to work all the bugs out of your kernel configuration to rt works with out xruns (dropping audio packets), so if you see xrun messages, know your audio won't work correctly untill they are taken care of (search google its your friend).

if anyone else is looking into this i'd enjoy hearing from you, either on this thread or in a pm.

pokki · 12-15-2007, 04:53 PM

Quote:

2. Upsampling - take everything to play and upsample it to 5.1/7.1, along with any other effects that want to be used to enhance the sound.

Technically that's not upsampling. More likely to find answers if you look for surround sound effects processing.

One of the main reasons why I'm implementing a CarPC is for the ability to run real time ambiphonics processing - note this utilises non standard speaker locations, and i've only found windows bassed "processors".

Felix509 · 12-15-2007, 07:06 PM

2. Upsampling - take everything to play and upsample it to 5.1/7.1, along with any other effects that want to be used to enhance the sound.

This area i've found less information on, and am hoping this thread will be able to help get more information in this area out in the open. the closest program i've found that does "some" of this is ac3jack, but thats a batch program, not realtime, so it would need to be modified heavily.

3. Physical connections - How to get the upsampled dts sound to the right speakers, without loss of quality.

We may need to move this to it's own thread...

Changing audio from Stereo to 5,1 or 7.1 would be called encoding.

There are a few sound cards out there that have real time encoding built in, called Dolby Live. They utilize the C-Media CMI8770 PCI chipset and it seems like quite a few other chipsets have the Dolby Live also.

A soundcard that had that feature would give you your outputs realtime from a stereo source.

wirelessdreamer · 12-16-2007, 08:09 AM

thanks for the initial info, is that the same chipset redgt is using?

So if i have a soundcard, or program running that re-encodes to 5.1 in realtime, i'm wondering if a Pioneer DEQ-P7000 would be a good solution between the computer and amps. then i can run an s/pdif signal to it from the computer, and output the channels correctly, and with little added noise (this is assuming i'm using software to reencode, and my soundcard doesn't have the high quality of redgt's setup), then use a 4 channel amp for the front speakers, and seperate amp for the sub off it.

I was looking online and found some cards that support Dolby Digital Live (DDL), but had trouble finding if they have linux support for DDL =(.

(seperate note)
for anyone not familiar with it Audacity (windows or linux) had a frequency generator built into it that could be used for tuning purposes.

RedGTiVR6 · 12-16-2007, 09:14 AM

Curious why the Pioneer over the Alpine, wirelessdreamer?

BTW - the chipset in the sound card I've modified (but have not put into the car...) is the C-Media CMI-8788.

Felix509 · 12-16-2007, 09:34 AM

Hey there wirelessdreamer, are you really sure you want to encode your audio, If you are setting up a Music only system There is not a lot of need to have 5.1 audio..

I suppose if you had video and watched all of your movies in your car, Surround processing would be okay.

Just that I do not see the benefit of it, although everyone has different likes..

pokki · 12-16-2007, 01:00 PM

Quote:

There are a few sound cards out there that have real time encoding built in, called Dolby Live.

And if your soundcard doesn't "support" Dolby Live, you can use the freeware application DolbyOutDS to add realtime DD encoding to any soundcard with digital out.

But per Felix post for a musical system i'd avoid such compression. And if you;re running a DVD playback then realtime decoding then encoding isn't necessary unless you want the PC to controll volume.

durwood · 12-16-2007, 01:11 PM

Quote: Originally Posted by Felix509

Hey there wirelessdreamer, are you really sure you want to encode your audio, If you are setting up a Music only system There is not a lot of need to have 5.1 audio..

I'd have to agree. There may be some other options depending on the reason "why" you want 5.1.

Options include but not limited to:
Stereo
Mono
Ambiophonics (2 channel - 6 channel)
Quadraphonics
Vector Based Amplitude Panning (VBAP)

pwntbypat · 12-24-2007, 12:12 PM

hey guys, I just wanted to pop in and say that the company who produced Frequency Allocator is running a $50 off special on the full program (that's 30%) I just picked it up for 89.99. use coupon code "allocator"!

RedGTiVR6 · 12-24-2007, 12:41 PM

hrmm - seems to be a normal XMas time discount for Jan.

Thanks for posting it!

wirelessdreamer · 03-27-2008, 09:22 AM

Sorry about the long absence, i forgot to tag this post and just saw the replies. I was looking at 5.1 mainly as an easy way to get 6 outputs at correct levels to send into amps / or have coming out of my amps. fr fl center rr rl subs. I assumed that running straight from speaker outs in the computer to the amp would induce noise to the audio signal, so by having no analog signal go from the computer to the amps that should eliminate most of the noise.

miztahsparklez · 04-08-2008, 09:54 AM

Are there any other programs like console but are freeware?

EDIT: Nevermind i found a program called VSTHost.

Ive also updated one of the links for free EQ alternatives as it was broken (i was able to locate its new location).

I currently have a 3 way active setup up front.. rear speakers (more for ambiance/depth/etc).. and sub stage.

Crossover work is done by 2 audio control units, a 6xs and a 3xs. It would be nice to cut down on hardware.

I found a neat 31 band eq that can do 6-12-24db of adjustment as well as EQ settings for high pass, low pass, and full range fine tune adjustment.

However, ASIO is supported, so it appears that I can use various VSTs to achieve various effects.

Currently, i use a dual mono eq plugin for winamp. The plugin is great.. however it only allows you to cut. a new eq that allows boosting would be nice. I think that having a fully functional eq will let me tweak my system a tad bit more, until im ready to mess with time alignment and all that. (By then ill probably run a mac mini and a firewire card.. M-audio 410 looks nice for the price)

im going to have to test to see how well it works with my audigy and car pc.. but im pretty satisfied with the quality of the output on my home pc. The only issue im having now is that winamp is outputting to a virtual audio cable (via the program) then from there VSThost picks it up and does my processing, and then outputs to channels on the sound card. Now to get ALL windows sounds to run through the VSThost, i have the virtual audio cable as my main sound device. Unfortunately, it takes over my control over the main volume buttons on my keyboard (which may affect my volume control using my griffin powermate). the volume buttons on my keyboard only controls the main line volume on the VAC, which does nothing for volume control. Do any of you know how to assign what device is controlled via keyboard buttons, but still keep all sounds run through the VAC?