MP3 files and sound quality

Perhaps only peripherally DIY but there's such a lot of computer expertise
here.
I was surprised today to see a reference to "a poor quality fifth-generation
mp3 file" - I thought that digital files (of whatever format) reproduced
exactly from generation to generation with no deterioration at all. Am I
mistaken? If mp3s do indeed get progressively worse when repeatedly dubbed
I'm going to have to rethink the audio project I'm currently working on.
Thanks.
Reply to
Bert Coules
MP3 is lossy, the compression removes detail you can never recover.
For editing you need a lossless format, WAV or FLAC or ??
Reply to
DJC
If you copy the file over and over, it'll retain the same quality, but if you keep-re-encoding it, e.g. to mix in other channels each time, you'll get gradually worse, if you can arrange it so you mix in all the extra channels just once, so there's effectively only one extra generation you'll get away without problems.
Reply to
Andy Burns
Thanks for that. I'm using a multichannel mixer (MixPad) so I can keep all the components separate and just export the mix down to a single file when I'm finished. But since many of the separate tracks are mp3 files the subsequent final mixdown does represent a first-generation dub of many of them. But you confirm my suspicion that no deterioration is involved.
Reply to
Bert Coules
Oh sure, I appreciate that. But I was concerned about subsequent copies mp3 - mp3. Does the quality (compressed though it be) remain constant?
Some of the files I'm working with are m4a which isn't a format I was familiar with. Where do they stand in the quality hierarchy? Better than mp3?
Reply to
Bert Coules
It depends. Obviously if you copy the file, it will be the same, but if you encode to MP3, then re-encode that again for some reason, you get even more loss and it will start to sound (even more?) horrible. If you take a WAV, encode to MP3, then convert back to WAV, you don't get the same file back.
Quite *why* you'd re-encode an MP3 is another matter.
If you take a lossless format (FLAC or WAV), then encode that to MP3 there's only one lot of loss.
Reply to
Chris Bartram
No no no. Every decode and encode of a lossy compression adds more losses. If you want to edit mp3s then turn them into wav or flac files then you will only have two generations of loss. Brian
Reply to
Brian Gaff (Sofa)
Well its still not clear to me that you are not re encoding. For example if you import all the sounds you need all will have been decoded. When you do a mix it will be still not re encoded. Save a non compressed master of this intermediate mix, then save your new mp3. If changes are then required go back to the uncompressed version and add to that, not the mp3. Or use Reaper and simply save the project and do the editing afresh, but that software is really hard to grasp and not good for simple stuff. Brian
Reply to
Brian Gaff (Sofa)
That's essentially what I'm doing.
I'm not familiar with Reaper and while I wouldn't exactly categorise what I'm doing as simple, I'd prefer to stick to software that I'm familiar with. But Reaper sounds interesting and I shall give it a look, thanks.
Reply to
Bert Coules
Does saving my MixPad mixes (which include quite a few mp3 tracks) to single mp3 files mean that I'm re-encoding those particular elements?
Reply to
Bert Coules
If you simply copy the file, then you will have an identical file in the same way as copying any other digital file.
The only way you would introduce further quality loss is to in some way re-encode it, transcode it, or reconvert an analogue capture etc.
Its a successor to MP3, generally better results for the same bit rate, but still a "lossy" format.
Reply to
John Rumm
Or import all your MP3s to a lossless format, that won't degrade anything, then produce your project, and do a single export to MP3/M4A at the end (keep a lossless copy around too).
Reply to
Andy Burns
Yes. MP3 is a compressed audio stream uncompressed when you listen to it. You can crop and do certain other things to it losslessly but in general if you change things like amplitude slightly then it will be recompressed with additional quantisation losses every time you do it.
Standard approach for audio as with JPEG images is to keep all the intermediate working files in some lossless format like FLAC.
formatting link

There are transcoders that can do the available MP3 lossless operations directly on an MP3 stream to splice things together for example.
Yes. Although depending on your final quality requirements you might get away with it if you keep the bitrate high enough.
Sound files are generally small enough that using FLAC isn't too bad. Then you have a single generation lossy recoding right at the end.
There is a very slight advantage to using about the same compression quality parameters as your original source material.
Reply to
Martin Brown

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