Compressor and Expander in DSP

Discussion in 'Effects and the DSP' started by shineek, Jul 31, 2012.

  1. shineek

    shineek New Member

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    I want to add on start that im totally green when it come to all those DSP related stuff , ive read the tutorials and i still dont get how to do my own dsp setting so i thought if i ask maybe i someone will help me with this stuff .
    So im a radio dj and i have a lot of problems with different sound levels in songs , all those fancy and professional programs for doing radio auditions have compressor and expander for purpose of normalizing the sound on the fly , so i thought adding them will help , but here starts the problem , as im using a sound blaster live 5.1 i cant add anything more to the DSP . Can someone show me some screenshot of a modified default DPS setting with a compressor and expander added in .
    Or are there any plugins who can do it as well , i heard of a AGC plugin who was able to do it , but i cant seem to find any download of this plugin .
     
  2. jaromanda

    jaromanda Active Member

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    AGC plugin never worked for me, crashed my system constantly

    now ... on to your problem ... here's one possibility
     

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  3. jaromanda

    jaromanda Active Member

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    Though ... on a Live 5.1, I had a setup that was even simpler, including a plugin I wrote - I could have 3 sources, PFL source, two mics, two headphones for the DJ's with separate levels in each headphones for music and "self" (some people like to hear themselves, others do not) - and it uses very little resources of the DSP 178 instr, 81 GPR - room enough for 3 dynamic processors if you want - I don't use them, all my music is "pre-processed" anyway

    the screenshot below is on an Audigy2 - so the 2 mics can be stereo (using the UDA for second ADC) - but, if one mic comes in on line in (via suitable pre-amp) you can get two separate mono mic via profx ADC plugin ... I should point out, I use proFX plugins, hence the low resource usage
     

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  4. shineek

    shineek New Member

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    Is the dynamic processor working as a compressor and expander? Altough i only need to compensate for too silent songs , soo i just try those settings , but i need mix stereo , cause im using zara and edcast to stream auditions , so stereo mix is needed here .
     
  5. jaromanda

    jaromanda Active Member

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    stereo mix should still be available - I think the plugins I "removed" in the first example were extraneous fluff - core functionality should remain

    second example ... useful for edcastASIO (in fact, I WROTE edcastASIO to take advantage of kx drivers!! )
     
  6. Shaamaan

    Shaamaan New Member

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    Can I hijack the thread a little bit?

    I've also got a question related to the Compressor and Expander (or, their + counterparts), but as a gamer, rather than a radio DJ.

    I've once saw a screenshot someone posted of their Compressor+ settings for gaming: game sounds would be Wave 2/3 while communications (Skype, Ventrilo and TeamSpeak) would use Wave 4/5. He was able to have the Wave 2/3 become quiet(er) when someone was talking over a communications application.

    Now... I actually have those settings implemented (I just copied everything as I saw it). BUT, I can't really make heads or tails of what the actual sliders in the Compressor mean - especially since I'd like to tweak it some more! With my current settings when someone over, say, TeamSpeak has a poorly configured microphone I will still have trouble hearing them, despite all system sounds already having their volume reduced. Perhaps I would also need to add an expander? I tried to fiddle with the compressor sliders, but it was fiddling in the dark, so I either caused the compressor to stop working or didn't change a thing. >_<

    So, this is why I'm asking: is there some better documentation for the Expander+/Compressor+ DSP plugins? Or is there a wholly better way of doing what I'm trying to do?
     
  7. Russ

    Russ Well-Known Member

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    If you want to boost a quiet signal using a compressor, then you need to add output gain.

    i.e.
    The compressor basically attenuates the signal when it goes over the threshold value (thus making it quieter). The amount of attenuation depends on the ratio value. The ratio value basically sets the amount the level must go above the threshold level, in order to increase in gain by 1 dB.
    i.e. For every 'x' (ratio) amount over the threshold value, the output signal will only increase (over the threshold value) by 1 dB.

    e.g.
    With a ratio of 2: a signal level that is 10 dB over the threshold will only be allowed to raise (over the threshold value) by 5 dB (thus it is attenuated 5 dB). 20 dB over, it is held to 10 (attenuated 10 dB), etc.

    With a ratio of 10: a signal level that is 10 dB over the threshold will only be allowed to raise (over the threshold value) by 1 dB (thus it is attenuated 9 dB). 20 dB over, it is held to 2 (attenuated 18 dB), etc.

    i.e. Higher ratio results in more compression.

    The output gain is gain that is applied to the output of the compressor (e.g. it is basically the same as connecting a gain plugin to the output), and thus it boosts the signal level (after the attenuation is done). When combined with the (previous) attenuation it has the effect of amplifying quieter signals, while (depending on the ratio settings and amount of gain) still limiting the volume at the higher end (thus compressing the signal further).

    The threshold value determines the level at which the compressor starts compressing.

    Here is a picture showing a signal before and after compression as well as the effect of output gain, which will hopefully help to explain the above settings.

    The attack and release settings basically determine how fast the compressor turns on and off (i.e. how fast it responds to a change in the signal level that is above/below the threshold value).

    The "+" version (when used with the side chain input) is only going to reduce the the level of the input, and has no effect on the trigger signal. To also compress the trigger signal, you need to use another compressor on that signal.

    i.e.
    Use a compressor+ with no output gain to reduce other sounds when triggered by audio from your VOIP application, and use another compressor with output gain to boost the lower volume signals from your VOIP application.

    BTW: For the threshold setting to be accurate, the "APS Compressor+" (when used with side chain input) should have a "x4" plugin on the side chain input, and the "APS Compressor" should have a "x4" plugin on the input, and a "div4" plugin on the output. Otherwise it will be off by 12 dB.

    An expander basically does the opposite of a compressor, and probably would not help much here. i.e. It will attenuate signals below the threshold.
     
    Last edited: Nov 9, 2012
  8. Shaamaan

    Shaamaan New Member

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    :w00t:

    Awesome post! Thanks for clearing up how those DSP plugins work. :)
     

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