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OS X : Looking for an efficient data-compression software & compression info Analog Processors (HW)
Old 23rd August 2017
  #31
Gear Maniac
 
Nico@SunnySide's Avatar
 

I can confirm something interesting : having had to send, again, many folders of data recently after a drum session and then a full band, ZIP or RAR compresses the data more depending on the loudness of the audio.

On one long track (15 minutes) with 10 drum microphone tracks, a drummer was asked to improvise quietly on existing music with only cymbal sounds with mallets or spaghetti sticks, and did multiple full takes.

These recorded drums were pretty quiet, with max RMS levels around -26/-22 dBFS and virtually no peaks, and some stretches of close-to-silence audio.

The folder containing the session is 3.06 GB

When zipping (with right-click compress on OS X) : 1.46 GB
With RAR : 1.02 GB

66% of compression : great!

On other tracks with much louder drums, the compression is systematically lesser and closer to earlier findings in this thread.

In the end, I wonder from a technical point of view regarding integrity of the audio, if you have louder recorded audio : is there any drawback in subtracting 20dB of gain (or more) on all the audio files post-recording, save the session and brief the artists/mixer to add 20dB of gain in the same DAW when they open the session pre-mixing/editing etc...?

If not, this would be a viable solution to share large audio sessions easily.

Best

Nico
Old 25th August 2017
  #32
Lives for gear
 
sardi's Avatar
 

Re: the integrity of the audio - did you unRAR the files and do a null test?

Would be pretty easy to test if anything changed.

I must admit, I'm pretty shocked at the 500Mb difference. This is not the experience I have had had.

I might do some tests over the weekend if u get the chance.
Old 25th August 2017
  #33
Gear Maniac
 
Nico@SunnySide's Avatar
 

Quote:
Originally Posted by sardi View Post
Re: the integrity of the audio - did you unRAR the files and do a null test?

Would be pretty easy to test if anything changed.

I must admit, I'm pretty shocked at the 500Mb difference. This is not the experience I have had had.

I might do some tests over the weekend if u get the chance.
Hey Sardi, (morning coffee fingers? see above, unless you really want me to test

Yes, I just did the null test by using 10 tracks of the original session and 10 tracks of the decompressed RAR : absolute null, no sound and no info at all on analyzer.

I decided to put my idea to the test and lower the gains by -30DB of all the session audiofiles in question to check : A = the size reduction with RAR and B = re-adding 30dB of gain and see if that nulls with the original unprocessed files.

The results are quite interesting :

A = It went from 3.06 GB to 627 MB = almost 80% data compression !! see first attached picture

B = When reopening a session (tested in Reaper)
- I added the -30dB files + the original ones
- I used Airwindows Purest Gain to add back the 30dB (tested with a few other utility/gain plugs and it seems not all gain plugins are accurate with just gain processing )
- It almost nulls : it nulls by ear, but with analyzer (see 2nd attachment) there is some noise at around -130dBFS - mind you for 20 audio tracks.

So technically speaking it is not 100% accurate.

But listening there is no audible difference.

I've been wondering for some time, in various scenarios if such a small difference of "seeable" ultra-low level noise - that you could never hear - affects sound further down the line with additional DSP or analog processing, and possible artefacts that might come into play and be detrimental to the sound?

Best

Nico
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OS X : Looking for an efficient data-compression software & compression info-screen-shot-2017-08-25-11.43.04.png   OS X : Looking for an efficient data-compression software & compression info-screen-shot-2017-08-25-14.27.22.png  
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