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Thread: How to implement DSP (Digital Signal Processing) through software.

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  1. #1 How to implement DSP (Digital Signal Processing) through software. 
    Member Demitryk's Avatar
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    I know people have done this before, but I thought I would do a write up on
    how I did it considering I could not find one and it took about a week of
    research, trial, and error to get it to work the way I wanted. I had to go
    to many different sources to figure this out so I thought I would try and
    consolidate it for anyone who is interested. The reason I even started down
    this path is because some of my lower end amps do not have high pass filters
    so I wanted a way to filter out the low frequencies before it even left the
    sound card. Also, I will be purchasing an omni-mic to measure my systems
    response using True RTA software and i wanted a highband EQ (30 or more) to
    equalize it.

    What is DSP? It allows you to filter, equalize, crossover, time correct,
    etc. your audio digitally.

    In conventional DPS systems operate like shown below.

    From Sound card or head unit > DSP device > to amp

    With a CarPC your audio is already in the digital domain so that initial ADC
    is not needed. This gives you less of a chance of induced noise. The changes
    are made before they are affected by fans, HDDs, and other I/O devices.

    External quality sound processors such as the ones from Audio Control are
    expensive and are nowhere near as versatile as some of the available
    software for the PC.

    What you need.-Virtual audio device software. This gives you
    an output, other than your sound card, for all the software with an audio
    output and allows it to be the input for and other piece of software. Think
    of it as a digital patch cable.

    -DSP software. This is a combination of two things, Virtual Studio
    Technology (VST) host - the software that that allows you to implement your
    plugins, and VST plugins - the actual affect (filters, EQs). There are a lot
    of options out there for both paid and freeware. Audiomulch (VST host) had
    the most appealing GUI of the ones I looked at. Voxengo plugins are nice. If
    you type VST host/plugins in to Google you can see all your options.

    -Volume2. Freeware, this allows volume control within Centrafuse.
    (explained below)

    -ASIO4ALL. (Depends on your Output mode explained below)Freeware


    The way it works


    For My virtual audio device I went with Virtual Audio Cable (VAC). It cost
    $35 and was probably the most popular software of this kind.

    Now for the DSP software I went with JRiver which is actually a media
    player. JRiver has a live loopback function that allows any audio in the
    computer to be fed through it. I went with JRiver for a number of reasons.
    First it uses 64bit floating point internal processing, second it comes with
    all the DSP effects built in to its DSP studio. JRiver also supports VST
    plugins if you would prefer to use those instead. Any filter you need is
    available in the JRiver DSP studio. You can set these filters to any
    frequency at a variety of roll off slopes. You also have the capability to
    increase or decrease the amplitude of any frequency at any Q (bandwidth). So
    essentially 22K band EQ. It also has a conventional 10 band EQ (with the
    sliders). JRiver has built in Time correction and allows you to mix or
    replace any channel with any signal you want. All effects can be applied to
    all or one channel of your choosing. This software is very versatile and I
    am still discovering features.


    Installation instructions

    Virtual Audio Cable
    Just do a normal install, it's pretty straight forward. Once installed you
    will notice a new device in your playback devices called "Line 1 - Virtual
    Audio Cable". Set this as your default device. Now when you play audio you
    will not hear any output at the speakers but you will see activity in the
    audio meter (green bars on right).


    Centrafuse
    Set Audio device either to default or Line 1 - Virtual Audio Cable

    Jriver
    Run installation

    Once installed add it to your startup programs so it starts with Centrafuse
    when the computer is turned on.

    Open JRiver go to File > Open URL, and enter "live://loopback" (without the
    quotes). Hit "OK", now you should see Loopback in your playlist. Now all
    audio playing in your system is being played through JRiver


    Next, go to Tools > Options > Startup (left column), under "Startup
    Actions" make sure "Start Playing Current Playlist" is checked. This will
    automatically start playing loopback when the program is started.

    After, go to Tools > Options > Audio (left column) Set your "Output Mode"

    This is where the trial and error comes in. This depends on your hardware.
    The best quality output modes are the hardware direct. These communicate
    directly with the hardware without Windows or any other layer doing
    resampling or other processing of the signal. These are listed from best to
    worse. A lot of this info was pulled from the Jriver Wiki Site.

    ASIO is said to be the best but can only be used if you sound card
    has native, well behaved ASIO drivers.

    WASAPI and WASAPI Event Style, This is Vistas and above version of
    ASIO. It's Microsoft's most modern method for talking with sound devices. If
    Event style is supported use that one. Some devices (most commonly USB
    DAC's) will start stuttering during playback when using WASAPI. This is due
    to a bug in Microsoft's WASAPI system itself, or in the stock Microsoft
    driver, where the circling buffers get out of order. Stopping and restarting
    playback is required to reset the stuttering. Using Event style should fix
    this.

    Kernel Streaming is a hardware direct way to speak directly to a WDM
    audio driver. It works on XP, so is useful when the above two options are
    not possible

    Direct Sound is Windows default and the most compatible output
    method. It plays through the system mixer. This means all formats will be
    converted by Windows to the native format of the card. It is highly
    compatible, but it is not the highest quality method.
    There are more options but you shouldn't have to resort to any lower quality
    settings

    I have a cheap 7.1 USB sound card I purchased from Newegg. With this sound
    card I had a lot of stuttering issues. I experimented with buffers and
    setting but I could not get it to work. It's probably user error since all
    this software is new to me. I ended up finding a universal ASIO driver
    called ASIO4ALL that fixed my problems. I installed this and selected my
    sound card and set Jriver to AISO and it worked!

    Once your output mode is selected, open the DSP studio and make your
    changes.

    I have one final problem; since you have two output sound devices, you have
    two windows volume mixers, one for you sound card and one for VAC. When you
    change the centrafuse volume it does not change the systems volume output
    because it is set to VAC. Whenever you adjust the volume of Centrafuse it
    adjusts the master volume of VAC but actually has no effect on volume. All
    the application sliders move with the VAC slider as well, but no difference
    is made. Only when you move the application sliders individually it affects
    the volume of that application. To overcome this, I leave the VAC and all
    the application sliders on max and installed a freeware program called
    Volume2. This program allows you to adjust the volume of an output device by
    dragging your finger along the edges of the screen. You can set it to any or
    all edges and make it invisible. So I can adjust the volume without
    minimizing Centrafuse.
    Attached Thumbnails Attached Thumbnails 410px-DSP_block_diagram_svg.png  
    Last edited by Demitryk; 04-04-2013 at 12:02 AM.
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  2. The Following 3 Users Say Thank You to Demitryk For This Useful Post:

    BoyScout (04-07-2013),Louk (04-05-2013),Mark (04-04-2013)

  3. #2  
    Member Demitryk's Avatar
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    Why does it keep cutting my post off?
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  4. #3  
    Member Demitryk's Avatar
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    post fixed
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  5. #4  
    Member Demitryk's Avatar
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    Update for my install - i use a USB soundcard that had a bunch of studdering issues. I did some futher reasearch and found ASIO4ALL is just Kernel streaming in an ASIO wrapper, and that you might as well use kernel streaming. Tried experimenting with that, no luck. i went back to trying to use WASAPI Event Style and got it to work better than using ASIO4ALL. I selected WASAPI Event Style as my output mode and left everything on defualt except for one setting. The thing i was missing is "Open Device For Exclusive Access" in the Output Mode Settings. One i checked that and restarted the program ... no studdering!!! What this does is it gives only JRiver access to this device.
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    Now that you have JRiver working it's magic, keep in mind that it will only process VSTs in 2 channels...UNLESS...you use a VST host that can be installed as a VST. The only one I'm familiar with in Plogue Bidule. You can install the VST Host has a VST and it opens up the world of multichannel VST goodness.
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    Member Demitryk's Avatar
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    I haven’t even tried implementing VST plugins yet but I’ll keep that in mind. So far JRiver's DSP Studio is fulfilling all my DSP needs. ashman5, thanks for the JRiver recommendation in the first place would have never thought to use it.
    Last edited by Demitryk; 04-09-2013 at 02:34 PM.
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    Hi Demitryk,
    Firstly, thanks for taking the time to write this awesome guide, i followed it word for word and have you to thank for an awesome system!

    In regards to the volume I didn't want to go through the route you suggested, so instead i made a program that fixes it for me, basically whenever the default audio device is changed (which Centrafuse is set to use) it also adjusts the volume of the Audio output that JRiver is using. It only requires 30 seconds of setup and runs perfectly for me through restarts and hibernations and is only 200KB, so not really that big a resource drain either.

    Since you took the time to write this awesome guide I thought the least I can do is offer you the same program. If you'd like it feel free to PM me and I can send it to you and explain in more detail how it works.

    Cheers,
    Dark
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    I just started to have issues with volume control and VAC... Older CF (say the version from last year) didn't have this issue.

    I'm running CF -> VAC - > AudioMulch(Karma_FX) -> Creative 5.1 sound card.

    What is everyone else using? I have been doing this for over a year and had to re-evaluate it after I just formatted.
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    Centrafuse Operations Mark's Avatar
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    Quote Originally Posted by YellowSnow View Post
    I just started to have issues with volume control and VAC... Older CF (say the version from last year) didn't have this issue.

    I'm running CF -> VAC - > AudioMulch(Karma_FX) -> Creative 5.1 sound card.

    What is everyone else using? I have been doing this for over a year and had to re-evaluate it after I just formatted.
    There has been a major re-write of CF core audio in the recent update. I'll let Louk discuss the specifics, but it's possible that might be the issue.
    Mark

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  11. #10  
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    This is a sort of double post; I already responded on the other thread.
    Drive on...
    Louk.
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