I’m using Audacity to trim the opening and closing minutes of an audio file every week.
We’re exporting the UNEDITED version of this file from an MP4 recording from our sound system – to MP3 at 24 kbps, the audio is very clear and the file size is minimized-- love the sound I’m getting. We keep the full recording for our archives in this 24bit MP3 format.
Then when I go to trim the several minutes of lead-in and the several minutes at the end of the recording which I don’t want, I don’t seem to be able to export with the exact same quality – all I want to do is trim the audio, no further loss of audio quality-- even if I jack this 2nd generation’s export settings up to 96 or 128kbps, there’s hissing and modulation going on during the moments of quiet speaking or silence between speaking portions (the entire audio is a recording of a speech with multiple presenters) – how can I simply trim the few minutes off of either end without modifying the quality at all?
Yep. Just wondered if by now, Audacity had this capability (I don’t say that in an entitled way-- I’m happy for whatever Audacity has to offer… just was curious if I neophyte-missed something in Aud 2.x) .
Audacity converts incoming audio to its own high quality internal format in order to do effects, filters and production with no damage. That also means it has to make a new MP3 at the end which means it has to recompress and add to the original MP3 sound damage. No option.
I’m sure you noticed that the pure MP3 editors are very simple. No effects, or filtering, just straight cuts and maybe volume change. MP3 works by creating sound damage as it throws away carefully selected bits of sound, and then goes to great effort to hide the damage. The first time you apply a filter or effect, all that work goes straight into the bin and the show turns to trash.
The only way out is to stop using MP3 in production. It naturally limits what you can do with the work and there isn’t a lot to do about it. You may note that the first time somebody tries to recompress the work for their Portable Music Player, the exact same thing is going to happen.
You can help a little by using screaming high compression. In Audacity Export that would be 250 or 320. Of course, that makes the files much bigger, but you should be able to get away with one more step of compression before the show gets audibly damaged.
There was a posting from someone using downloaded MP3s for their broadcast radio show. He made it all the way through broadcast and bit the dirt when the station tried to create the download podcast.
“How do I clean that up?”
You don’t. You have to drop at least one stage of compression in your pipeline and the best place is to stop using download MP3s. MP3 is an end product delivery medium. Not a step in the middle.
I put download radio shows on my Music Player, but I do it either in the original format or high quality WAV and then delete them when I’m done.
Somebody always asks about exporting the work as WAV and then go for MP3. The trip through WAV doesn’t clean up the sound damage. There are pieces of the MP3 show actually missing and you can’t get software to put it back.
WAV will prevent the show from getting any worse. My silly joke is the WAV up-conversion will give you really high quality, excellent sound damage.
We’re exporting the UNEDITED version of this file from an MP4 recording from our sound system – to MP3 at 24 kbps, the audio is very clear and the file size is minimized-- love the sound I’m getting. We keep the full recording for our archives in this 24bit MP3 format.
If you convert from MP4 to MP3, that’s ALWAYS a lossy process. You may not always hear quality loss but these are both lossy formats. Any time you encode to a lossy format (MP3, MP4, AAC, AC3, etc.) there is theoretical quality loss.
Trimming some audio shouldn’t make any difference! If you open a file in Audacity (or any “normal” audio editor) it has to be decompressed. When you re-save (export) to MP3 again, it goes through a 2nd lossy compression step.
MP3DirectCut (and similar programs) can do trimming and other limited editing without decompressing. But they cannot convert from MP4 to MP3.
24kbps is low quality. It might be OK for speech, but if you compress a music CD to 24kbps you’ll definitely hear the quality loss! Most commercial MP3s (purchased from Amazon, etc.) are 256kbps.
Note that 24-bits would be bit depth, and that means something completely different. 24kbps is bit rate and it means 24,100 bits for each second of audio. MP3 doesn’t have a bit depth… it uses floating-point.
CDs have a fixed bit-depth of 16-bits. Each sample is represented by a 16-bit number. There are 44,100 samples per second and 2 channels. That gives CDs a bit rate of 1411kbps.