Chris Capel's Dynamic Compressor

Sadly, Chris passed away on 15th March 2011.

In his legacy he left the latest beta version of his famous dynamic compressor (commonly known as “Chris’s Dynamic Compressor”).
We are able to post it here as it was licensed under the MIT license.

;;Permission is hereby granted, free of charge, to any person obtaining a copy
;;of this software and associated documentation files (the “Software”), to deal
;;in the Software without restriction, including without limitation the rights
;;to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
;;copies of the Software, and to permit persons to whom the Software is
;;furnished to do so, subject to the following conditions:

;;The above copyright notice and this permission notice shall be included in
;;all copies or substantial portions of the Software.

;;THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;;IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;;FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
;;AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
;;LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
;;OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
;;THE SOFTWARE.

Note that this is beta software and has not yet been tested by anyone in the Audacity Team.
More information to follow.
compress-b1.ny (18.9 KB)

The algorithm used in the 1.2.7 beta version is slightly changed from previous version, with the addition of the following parameters:
“Compress bright sounds” [0/1]
“Boost bass sounds” [0/1]

To get the same results with 1.2.7 as the default 1.2.6 version settings, set “Hardness” to 0.25861 and “Compress bright sounds” to “No”.

The default values in 1.2.7 beta are:
Compression level: 0.5
Hardness: 0.611
Floor: -32
Noise gate falloff: 0
Renormalize: 0.99
Compress bright sounds: 1
Boost bass sounds: 0

Personally I don’t think that the perceptual modelling (the “Compress bright/bass sounds”) is quite right yet. The idea is that it makes the compressor follow the way in which hearing responds to volume at different frequencies, but in my tests I find that a more natural sound is produced without this feature (ie with the 1.2.6 version).
Anyone else?

Here’s the beta version with the advanced options enabled.
This can be installed at the same time as the regular 1.2.7 beta version and will appear in the Effect menu as “Compress dynamics (advanced)…”
compress-b1a.ny (18.9 KB)

The shape of equal loudness curves does depend on the loudness …
400px-Lindos1.svg.png

So any corrections Chris has applied can only be correct when played at a particular volume.

[Chris included this link slightly different version of equal loudness curves in the plugin]


The inverse of ISO 226 (below red) may be worth a try …
400px-Lindos3.svg.png

Chris's corrections.png
Chris’s corrections don’t agree with inverse of ISO 226

I host a “how-to” podcast about podcasting and using Audacity and would highly recommend Chris’s Dynamic Compressor for podcasters and other Audacity users.

In Chris’s memory, and with his dad’s help, I am hosting Chris’s Dynamic Compressor on my own site. I found a bug in the 1.2.7 beta, so I’m currently offering just 1.2.6, but I keep a copy of 1.2.7 also on my server.

http://theaudacitytopodcast.com/chriss-dynamic-compressor-plugin-for-audacity/

If you’d like to contribute some documentation (especially illustrated), or work on improving the project, please contact me.

If you could give details we can probably fix it.

I’ll have to play with it again to get better details. But from my memory, 1.2.7 wouldn’t normalize the audio after compression, if something was set a certain way. I’ll test and get back with you. Thanks for offering to help! I’ll host any updates on my site, too.

http://theaudacitytopodcast.com/chriss-dynamic-compressor-plugin-for-audacity/

By the way, Chris’s dad has given me the complete archive of Chris’s website, and we’re working to transfer the domain to me so people can still easily find it. I’ll be updating the above URL (if it posts this time) with Chris’s original documentation and will be happy to include any revisions or additions.

That may just be an effect of the new “perceptual loudness model” feature (“Compress bright sounds” is enabled by default in 1.2.7). As with “ReplayGain” and other “perceptual loudness” models, this will override the peak amplitude setting. If that feature is not selected, then peak normalizing should work as previously.

Now that Audacity 2.0 is out (yay!), can we assume that Chris’ 1.2.6 version will run with 2.0? How about the beta, 1.2.7? I’d be interested to test the beta. Yes, I did try to answer this question in the FAQ and the wiki and I don’t see it.

Yes, it works fine with 2.0. I’ve been using and recommending 1.2.6 with Audacity 1.3.x beta for a while. Audacity 2.0 is just Audacity 1.3 final (with new bugs, which I’m working to document).

2.0.0 did actually fix some bugs in 1.3, but if you have found steps to reproduce for new bugs in 2.0.0 (that are not mentioned in the Release Notes), please report them to our feedback address.


Gale

I used to work with Chris at his Dad’s company. And I feel compelled to voice that even beyond his technical genius, Chris was one of the kindest, entertaining and complex people I have ever had the privilege of meeting. He was a very gifted individual.

Just started to use this marvelous compressor. I just have one problem, the final word always seems to be louder that the rest of the announcement after I have used the compressor. Has anyone got any ideas? (sends a silent prayer that it is not a blindingly obvious solution).

Using Audacity 2.0.3

Which version of Chris’s compressor are you using?
(if you open the “compress.ny” file in a text editor it should have the version number at around line 30)

Got my attention. I collected the versions before the site when dark, and I’m using 1.2.6 as current. If you have it loaded, it will also announce the version in the Effects list.

I’m using it for the exact reason it was designed, to listen in the car. Or in the truck in my case (Lori, my lorry).

I host a “how-to” podcast about podcasting

Just go back to the head of the web site?

Koz

A workaround : Copy a couple of seconds of sound from your track, (a bit with average volume values), then add (paste) it to the start and end of your track, apply Chris’s compressor, then delete the bits you added on.

http://manual.audacityteam.org/index.php?title=Tutorial_-_[b]Copy_and_paste_a_section_of_audio[/b]

Thanks, Trebor. Hmm, that page seems to be completely orphaned so is not in the released Manual that we should normally link to in replies. And I see from Bill’s comments that there are issues with the images and explanations. And no explanation of what crossfading is.

Should we tweak that and add it to this Tutorial Audacity Manual ?

Or expand it as a standalone Tutorial to include other methods of repairing takes such as Steve’s EZ-Patch ?

Or a brief FAQ pointing to a Wiki page on repairing takes without re-recording?

Or just add a little to Audacity Manual ? I think that is probably already as long as it can take, actually.



Gale

I was just trying to include a link to a page on copying and pasting in Audacity, just in case the OP was a novice.
If there is a more appropriate page on copying and pasting in the Audacity manual feel free to change my link.

Sure. :slight_smile:

As I explained, there isn’t :frowning:

We need to decide what if anything to do about that.


Gale

I don’t use Chris’s Compressor, but would adjusting the “Release speed” help?


Gale