File format specs for hi quality audio stream recording

Special Interest Groups Recording Techniques
1

Hi - I want to record an AAC-LC 320kbps 48kHz(?) stream of classical music using Audacity via Windows loopback.

I want to preserve the quality of the stream so what are the rules of thumb for selecting file format specs to record to, in this case?

What file type and specs would you recommend? (codec, bit rate, sample rate, bit depth)

thanks for your help

2

Save as lossless format, WAV, or lossless compressed format FLAC, (files will be big).
Lossy compression formats (AAC, Mp3, WMA, etc), trade-off quality for smaller file-size.

3

If you are going to record more than 3 hours and 22 minutes, extract to FLAC format. If the audio duration is less than that, WAV format will also work.

4

thanks, I’ll go off and experiment with those file types.

5

thanks - there’s a file size limit of 4GB to WAV I think? I’ll try to avoid creating files anywhere near that size!

1 Like
6

Correct. There is a 32-bit data-size field in the WAV header and it can’t “count” higher than 4GB.

AAC is actually immune to accumulated “damage” with multiple generations of re-compression (unlike MP3).

100 pass recompression test

So you should be able to use the same 320kbps settings without any degradation.

…I’m not sure you can create 320kbps AAC with Audacity. You might need to make a WAV or FLAC first, and then use a 3rd-party converter (like Kabuu Audio Converter) to make the AAC file.

7

Since AAC is a compressed format, recording it directly into another lossy format like MP3 or AAC can lead to quality loss. Recording in WAV or FLAC instead. This ensures you capture the stream’s full quality. You can convert the recording to AAC later if needed.

8

Not with AAC. Did you check the link to the 100-pass test shown no accumulated degradation after 100 generations of re-compression?

9

I’m just intending to record the AAC stream to archive for future listening, rather than create a new stream.
Sounds like FLAC is the way to go as with my brief tests files are about 50% of the WAV file size.
I will have a look and a listen to the 100 pass recompression link.
cheers

10

yep it sounds like FLAC is a good way to go :slight_smile:

1 Like
11

If you are recording in the box ( digital to digital ) Then the same format is the minimum
If you are leaving your PC thru an analog circuit and back in then the highest format should be used
Example 32bit 384 K
Note the larger the file the slower the response time when loading and making adjustments
to such files
You can always reduce the file to what ever your needs are after this
Do not record loud… after recording a loudness and a limiter can be used to bring it up to max level or preferred… like -3Db .

Cool Stuff… enjoy
MIKE

12

Thanks for the tips, much appreciated. Yes it’s all digital to digital happily.