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Contant Peak, Constant RMS, How to get a fixed value for peak and RMS
terataz
post Dec 12 2012, 21:32
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Hi, we are trying to set a default standard for the volume of the audio files we are working on.
We are looking for a tool that, given a bunch of mp3 files, will be able to normalize them at a given db.

For example : 0db for Peak levels and -9db for RMS.

Ideally, we'd love to use sox as we can chain it with other effects we're using without the need to convert multiple time the file from mp3 to wav and back.

We tried sox gain -n , sox gain -ne, sox gain -nb, sox loudness but none of them keep a constant RMS without varying the Peak level as well.
Any help appreciated.
Thanks
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splice
post Dec 13 2012, 07:40
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It looks like Francesco is building playlists for use in "muzak" type situations - restaurants, bars etc. His media options appear to include MP3 players, audio-only DVDs that can be played on a standard DVD player without a visual display, and music servers that can be updated automatically over the Internet. He wants to:
- Automatically classify tracks using parameters such as "tempo, pitch, loudness, signature, beats, key and so on".
- Arrange the tracks into playlists by genre etc using the above classifications.
- Use MP3 or AAC format to make the track files as small as practical.
- Process the tracks to a consistent loudness for each genre.
- Store the playlists in a format that can be accessed with a minimal user interface (a few buttons).

This post has been edited by splice: Dec 13 2012, 07:43


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Regards,
Don Hills
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terataz
post Dec 13 2012, 18:18
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QUOTE (splice @ Dec 13 2012, 07:40) *
It looks like Francesco is building playlists for use in "muzak" type situations - restaurants, bars etc. His media options appear to include MP3 players, audio-only DVDs that can be played on a standard DVD player without a visual display, and music servers that can be updated automatically over the Internet. He wants to:
- Automatically classify tracks using parameters such as "tempo, pitch, loudness, signature, beats, key and so on".
- Arrange the tracks into playlists by genre etc using the above classifications.
- Use MP3 or AAC format to make the track files as small as practical.
- Process the tracks to a consistent loudness for each genre.
- Store the playlists in a format that can be accessed with a minimal user interface (a few buttons).


Splice,
not sure how you did it, but you're quite right on all you've said wink.gif

Thanks all for your replies.

We did have a good go with ReplayGain via mp3gain, but could not find a consistent way to normalize files with it.
Instead, it seems mp3gain does a batch analisys and make some sort of average.
When you change the audio batch, the average change, making the volume inconsistent between batches.
What we look for instead is a sort of standard that we and our clients can refer to.

For reference only, this is how we managed to achieve our goal.
It is not the most elegant solution, but it seems to work.

Per each single file:
1) Peak normalization to 0db using sox
2) normalize-audio -a -9dBFS for a standard RMS of around -9db
3) sox vol 0db 0.01 for a soft limiter to prevent clipping


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