How to get back exact quality?

[kozikowski]

Modern compression is sneaky and they can get one by you if you're not paying attention.

You can tell where the limits of MP3 compression are by compressing a high quality mono show at 32 and a stereo show at 64. Those are the two quality limits. Most people can tell there's something wrong with the show, but few people can tell exactly what. It's only when somebody switches quickly between the compressed and the uncompressed show that the difference is perfectly obvious, but you can listen to the compressed one by itself all day long and not realize there's very much wrong.

Fraunhofer-Gesellschaft in their research to compress video found that they could, using the newer technologies at the time, separate the Stradivarius from the varnish. My joke is listening to two poor quality violins and one top quality one at the same time. As you compress the performance into tighter and tighter files, the differences between the instruments shrinks. If you compress to small enough sizes, there is no difference. You're just listening to three crappy violins. It doesn't just get muffled or have obvious sound problems. It's much too sneaky for that.

This gives you the artist's opinion of MP3 which isn't very high. It shrinks the difference between different quality singers.

It gets worse. MP3 is an end product. Make an MP3 for delivery to a music player or an internet posting and that's the end. You can't go back and edit an MP3 without causing more damage -- sometimes a lot more. People post all the time that they downloaded a ratty MP3 from the internet and did extensive production work on it in Audacity, but when they tried to go back to the same size MP3, it turned to honky garbage. You can export a new, edited file, but you'll never get that small file again. Export a very, very high quality (large) MP3 or Uncompressed (very large) WAV or AIFF, etc to avoid this effect.

Never do production in MP3. It waits until the very end to reveal its evil ways.

Koz

[spacely]

MP3 and MP4 are "lossy" formats. That means that each time it is encoded, a little bit more of the audio information is thrown away with some inevitable loss of sound quality. This is why it is highly recommended to work in a "lossless" format such as WAV, throughout the production process, and convert to MP3 (or whatever lossy format is required) right at the end of the process, so that sound quality loss due to encoding only occurs once. In practice it is not always possible to do this.

The losses due to encoding can be minimised by using a high bit-rate, at the cost of larger files, but MP3 encoding "always" loses some sound quality.

How did my 12mb MP4 become a 52MB WAV?? 11mb mp3 @ 328kbps.

By the way, I discovered Windows Media Player had it's "WOW" effects turned on, causing most of the playback distortion.

[kozikowski]

A WAV file at 44100, 16-bit, Stereo has a bitrate of about 1410.

How did my 12mb MP4 become a 52MB WAV??

I would expect it to be worse than that. I would expect up in the hundreds. 120MB or so. It depends on how aggressive the operator was when they made the compressed file.

It's a shock when people open a tightly compressed MP3 in Audacity and immediately run out of room on their computer. Audacity always works internally at 32-bit Floating, even better than straight 16-bit, in order that the sounds survive filters and effects.

Koz