How to change bitrate (ref FLAC files)?

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Aitch
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Joined: Thu Aug 06, 2020 7:00 pm

How to change bitrate (ref FLAC files)?

Post by Aitch »

I have been making recordings and saving them to FLAC. The recordings are all similar content and length.
Previously, the resulting FLAC files were around 340mb.
The last one came out at 930mb.
Using media info I found that all the previous FLAC files had a bitrate of 538 kb/s (44.1 KHz, 24 bits).
The last file appears to have a bitrate of 1404 kb/s (44.1 KHz, 24 bits), which I assume accounts for the difference.
As far as I know I have made no changes to the recording set-up.
I can't find any way to change whatever setting has upped the bitrate.
Any clues how to sort this would be most welcome!

DougDbug
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Location: Silicon Valley

Re: How to change bitrate (ref FLAC files)?

Post by DougDbug »

It's unpredictable but FLAC level 8 will give you the maximum compression (smallest files = lowest bitrate). The actual bitrate also depends on the uncompressed format and the program material Some material is easer to compress and some is harder to compress. You can usually get a file that's about 60% of the uncompressed original. (A stereo file should compress better than a mono file, but it's still larger than the mono file.)

There are 8 bits in a byte so an uncompressed 24-bits/44.1kHz stereo file has a bitrate of 44.1kHz x (24/8) x 2 channels = 2117 kbps. A FLAC at half that bitrate would be "better than average" compression.
FLAC files had a bitrate of 538 kb/s (44.1 KHz, 24 bits).
I'd guess that's a mono file?
The last file appears to have a bitrate of 1404 kb/s (44.1 KHz, 24 bits),
Is that a stereo file?

Aitch
Posts: 2
Joined: Thu Aug 06, 2020 7:00 pm

Re: How to change bitrate (ref FLAC files)?

Post by Aitch »

Hi DougDbug

Thank you for the response!
In fact all the recordings are stereo.
All were saved to 'High compression, 24 bit, stereo' in the Gwave save attributes options.
As I wrote, I don't know of any setting that's changed between times that should result in these larger files.

I'm not aware of any way to choose any FLAC level within Gwave.

As is probably clear, I'm not a inner-workings tech whiz when it comes to Gwave: all fairly basic stuff.

Any further comment welcome!

Cheers.

DougDbug
Posts: 2066
Joined: Wed Feb 16, 2005 3:33 pm
Location: Silicon Valley

Re: How to change bitrate (ref FLAC files)?

Post by DougDbug »

I'm not aware of any way to choose any FLAC level within Gwave.
You're right, you can't select 0-8. I don't use FLAC that much so I'd forgotten that. I only see "Maximum" which is obviously level 8, and "High".

I just did a quick experiment and the "Maximum" file was only slightly smaller than "High. Less than 1% difference.
I don't know of any setting that's changed between times that should result in these larger files.
Besides compression level, the variables are sample rate, bit depth, number of channels, and program material (which you can't really control). I would expect a 1kHz test tone or a file with lot of silence to compress very well (low bitrate and small file).

GoldWave Inc.
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Re: How to change bitrate (ref FLAC files)?

Post by GoldWave Inc. »

A bitrate of 538kb/s seems too low for a stereo FLAC file, unless it contained very simple audio. If you applied certain effects or mixed other audio (with a noisy background), that would increase the bitrate required for lossless compression. Using Noise Reduction (or Noise Gate, if the audio contains a lot of silences) may help.

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