Hey guys, I’m working with a user who records his lectures in GarageBand on a Mac, and he uses Audacity (for Mac) to edit them. We’ve been talking about him using lossless ALAC for his master files, though he’s more an academic and not very tech savvy.
I was able to export a file using the M4A file type:
Notice the difference in file sizes in the figure above: 655k CBR vs 1624k using External command line.
It says in the HELP file:
“Currently this slider has no effect with the version of FFmpeg recommended for Windows and Mac. The exported file is always a constant bit rate (CBR) 196 kbps (stereo) or 98 kbps (mono) file.”
That’s exactly what I got 98 kbps when tested it in VLC player:
Then used the EXTERNAL PROGRAM file type and Command Line string to do it right:
Here’s the stats on the EXT PROG file: So the question is: which file is compressed LOSSLESS and which one is LOSSY?
Also… he says he exports his audio in Mac GarageBand to an MP4 container? Is that correct?
If you want lossless, I’d recommend sticking with 16-bit WAV (compatible with everything), 24-bit WAV (all studios should be able to support this, but 50% bigger than 16-bit, and rather over the top for speech recording), or FLAC (half the size of WAV and much better metadata support).
If you really want ALAC, you could try Foobar2000 to convert from WAV.
Note that these days, a $10 memory stick can hold many hours of uncompressed mono WAV files.
The Mac user guy says the container is MP4, which sounded lossy to me.
BTW, the 1624k file I exported to M4A using `External Program´ command line is equivalent to the 1632k file exported in FLAC as follows:
So I assumed they were both lossless compressed, and don’t want to mis-advise the Mac user guy.
Maybe need to come up with a verification test of some kind?
A “regular” 16-bit 44.1kHz stereo FLAC or ALAC is usually in the ballpark of 700kbps. At 22kHz, you’ve got half the data, and I assume your file is mono. (22.050kHz, 16-bit mono uncompressed is 352kbps.)
Although it’s a good idea to record & produce in a lossless format it’s more practical to distribute in a more-compressed format. You are not likely to hear any difference, especially with a spoken word, which I assume is recorded under non-ideal conditions in a “noisy” lecture hall.
BTW - If you are going to use lossless, you might as well record at 44.1 or 48kHz. Your lossless files will be larger, but you don’t have to distribute those original files.
Isn’t ALAC supposed to be lossless? like FLAC? What am I missing? Is there no lossless Apple format?
Yes, ALAC is lossless. I don’t know if your AAC file is ALAC.
, which sounded lossy to me.
What does that mean? Sounded lossy compared to what?
With the original track still in Audacity, import the M4A file.
Apply the “Invert” effect to the M4A track.
Select both tracks and “Tracks menu > Mix > Mix and Render”.
The result should be absolute silence if both tracks were identical (the inverted copy is the exact equal and opposite of the original).
To test for “absolute” silence:
Select the track and open the Amplify effect. The Amplify effect should say the the “New peak amplitude” will be “-Infinity”.
Note that if the original track is greater than 16-bit precision, this test will not give “absolute” silence (due to rounding of the sample values). It will give extremely low level hiss at around -90 dB
Would like to post the final `cleaned up´ file lists, as there were errors and inconsistencies in the file names during experiments. MediaInfo
The file names are self explanatory.
Hope the programmers could improve the M4A Export dialog box and make in more straight forward.
