mp3 files are very large

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Martin Hairer
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mp3 files are very large

Post by Martin Hairer »

Hi,
I've got some field recordings that I'm editing minimally in their native .wav format and then exporting as .mp3s. The resulting mp3 files are very large--as big as commercial .flac files (over 20 MB). This seems to be especially true after I add metadata (song title, track number, artist name and art) even though the art is only about half a MB. My 13 minute song is 23 MB, and the 9-minute song is over 20. I've had this issue in the past but haven't followed up on why or how to make them smaller. I'd like them to be around 5-7 MB max, like the standard commercial recordings in my iTunes library.
If you click on "Settings" when exporting your recording you can adjust
all the parameters for the Mp3 encoder. If you are aiming for a specific size,
I would recommend to set the encoding type to ABR and then adjust the bitrate
as desired. The standard bitrate for iTunes recordings is 256kbps, so a 13-minute
recording would end up being even slightly above 23MB in size:

13min * 60sec/min *256kb/sec / (8000 MB/kb) = 24.9MB

(One megabyte (MB) equals 8000 kilobit (kb) since one byte has 8 bits.)

In my iTunes library for example, "Honesty" by Billy Joel which I purchased from
Apple's music store is almost exactly 4minutes in length and weighs in at 8.2MB which
is consistent with this.

If you want your 13 minutes recording to get down to 6MB you'll have to encode
it at 64kbps at which stage you'll probably have audible quality degradation, depending
on the quality of your recordings. In any case, I would then recommend using either
AAC or Ogg Vorbis which perform much better than Mp3 at lower bitrates. Best,

Martin

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CDJonah_alt
Posts: 379
Joined: Thu Mar 15, 2007 3:57 pm

mp3 files are very large

Post by CDJonah_alt »

Another thought -- can you convert to mono? If so, the quality will be
higher for a given bit rate.

Chuck

On 9/13/18 3:42 PM, Martin Hairer wrote:
Hi,
I've got some field recordings that I'm editing minimally in their native .wav format and then exporting as .mp3s. The resulting mp3 files are very large--as big as commercial .flac files (over 20 MB). This seems to be especially true after I add metadata (song title, track number, artist name and art) even though the art is only about half a MB. My 13 minute song is 23 MB, and the 9-minute song is over 20. I've had this issue in the past but haven't followed up on why or how to make them smaller. I'd like them to be around 5-7 MB max, like the standard commercial recordings in my iTunes library.
If you click on "Settings" when exporting your recording you can adjust
all the parameters for the Mp3 encoder. If you are aiming for a specific size,
I would recommend to set the encoding type to ABR and then adjust the bitrate
as desired. The standard bitrate for iTunes recordings is 256kbps, so a 13-minute
recording would end up being even slightly above 23MB in size:

13min * 60sec/min *256kb/sec / (8000 MB/kb) = 24.9MB

(One megabyte (MB) equals 8000 kilobit (kb) since one byte has 8 bits.)

In my iTunes library for example, "Honesty" by Billy Joel which I purchased from
Apple's music store is almost exactly 4minutes in length and weighs in at 8.2MB which
is consistent with this.

If you want your 13 minutes recording to get down to 6MB you'll have to encode
it at 64kbps at which stage you'll probably have audible quality degradation, depending
on the quality of your recordings. In any case, I would then recommend using either
AAC or Ogg Vorbis which perform much better than Mp3 at lower bitrates. Best,

Martin

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http://www.hairersoft.com/


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630-252-3471 CDJonah@anl.gov

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Martin Hairer
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mp3 files are very large

Post by Martin Hairer »

Thanks for this info and your input. I re-saved as you suggested--ABR set at 256--just to see what would happen. The resulting file was 36.2 MB. So then I went back, reset the bitrate to VBR, and removed the art (jpg, 588 KB). The resulting file was 14.5 MB--almost 11MB smaller than the same sound file with jpg attached.

Why would such a small change in the metadata create such a large difference in resulting file size?
The reason wasn't that you removed the image art, but that you changed from ABR to VBR.
VBR does *not* attempt to reach a certain bitrate (it ignores that field which is why it is then greyed out) but rather a certain quality. Regards,

Martin

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