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Old 10th April 2008, 05:43 PM   #1
squib is offline squib  United States
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Default intentional dynamic compression for MP3's

At risk of asking a heretical question...has anyone else experimented with dynamic compression for ripped (AAC, MP3, etc.) tracks? I've been trying recently to produce separate versions of my small collection of symphonic music for more casual listening in the kitchen. The problem with the originals is the large dynamic range for much of this music makes it difficult to use as background music. Quiet passages are lost when the volume is adjusted to keep the loudest passages from overwhelming conversation (or scaring the wee kiddies). I've grown accustomed to listening to public radio broadcasts of classical music, but lately have found the selections rather off-putting (ie. lots of John Williams and other hollywood soundtracks). The music is being played through a Tivoli PAL radio, so high fidelity in the source is large wasted.

I've tried importing tracks to Audacity and compressing at -12bd and -18db using a 2:1 or 2.5:1 ratio. I'm exporting the processed file as a VBR MP3 (200-250 kbps). Depending on the content of the track, the results have been promising, but I'm curious if anyone else has done this and might offer some tips.

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Squib
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Old 10th April 2008, 06:01 PM   #2
squib is offline squib  United States
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Default graphical example

Here's an example of a track that is rather difficult to manage...

Shostakovich Symphony No. 8 in C minor OP 64 - Largo
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Old 11th April 2008, 01:57 AM   #3
dangus is offline dangus  Canada
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I expect there's plug-ins for Winamp that emulate a compressor, but I presume you'd want something that works for a portable player. Maybe the "Rockbox" firmware includes that feature; Rockbox can be installed on a number of brands of MP3 player, including some Ipods.
Rockbox

(edit) No it doesn't, but someone might be working on it, or not.
dynamic range compression?
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Old 11th April 2008, 02:07 AM   #4
squib is offline squib  United States
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Thanks for the suggestion, dangus.

It would be handy to have the ipod handle the compression. Creating multiple copies of even a small music library is daunting, and I'd just as soon skip it.

RE: Rockbox. I've been tempted in the past, mostly for Ogg support and because the Apple firmware continues to choke on their own hardware. I have to reset the Ipod at least once a month because it refuses to power down. One hiccup for 3rd party firmware is my DLO HomeDock. I don't think it will get along with RockBox, but I confess I've never looked into it. Looks like I have another date with google!

Thanks again,
Squib
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Old 11th April 2008, 08:45 AM   #5
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Quote:
Originally posted by squib
One hiccup for 3rd party firmware is my DLO HomeDock. I don't think it will get along with RockBox, but I confess I've never looked into it. Looks like I have another date with google!

Thanks again,
Squib
Audio out should work, but the remote will not. Proprietary Apple Accessory Protocol is completely unimplemented in RockBox, and I don't think they really want it there, since it has been at least partially documented.
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Old 11th April 2008, 01:48 PM   #6
squib is offline squib  United States
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Default Audio out, but no remote

Alas, for me that's a deal breaker. I don't see much advantage to using the HomeDock if the remote is non-functional.

As a side note: While googling for info on RockBox/DLO compatibility, I bumped into numerous posts from DLO owners complaining that the HomeDock is hosing their Ipods. Perhaps I was too quick to blame apple for my power down problems with my Nano.

I've downloaded a firmware update for the HomeDock and will see if that helps.

Thanks for the info!
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Old 12th April 2008, 12:16 AM   #7
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Audacity will do compression, etc.

http://audacity.sourceforge.net/about/features

Take your ripped .wav, run it through audacity with compression, and than convert to mp3. There may even be a way to set up a script to do it as a one-click operation.

I_F
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Old 12th April 2008, 09:23 PM   #8
squib is offline squib  United States
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That's what I've been doing so far (see 1st post). I was curious what settings other people have tried, assuming I'm not the only one attempting this...

Audacity does some pretty impressive processing. I've used it in the past to clean up digital rips of obscure music from 20-year old cassettes.

Thanks again for the input!
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Old 13th April 2008, 01:07 AM   #9
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Doh! (slapping forehead)

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Old 13th April 2008, 04:27 AM   #10
dangus is offline dangus  Canada
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Another thought: use a very small analog compressor between the Ipod and the headphones. The SSM2120 did pretty much everything in one chip, and was used by Rane and PAIA. Unfortunately it has been discontinued.

It might be worth looking at Rane's current product docs and seeing what chip they're using now.
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