Simple idea on audio compression, must be a simple answer why not. quality loss?

[cypher_soundz]

I was just thinking, is there a reason why we couldnt speed up a track (like turning a vinyl record really fast) so that its just a few seconds long then compress it and to decompress just slow it back down etc? could we not store any other info in another file if there was quality loss?
am i talking crazy? it is late lol :confused:
Regards
cyph

[Moitah]

This would basically be the same as lowering the sampling rate.

[scharfis_brain]

am i talking crazy?

Yes. You do! ;)

Speeding up the audio equals to sampling it at lower sampling rate. -> lower cutoff frequency -> loosing high frequencies.

also it means, the timings of psycoacoustical compression schemes are out of their human boundaries. this means, you'll hear all those nasty audio-compression artifacts (flanging, metallic, noise etc.) even if a considered high bitrate was used in your speedup-compression->decompression-slowdown
filter chain.

[cypher_soundz]

Originally posted by scharfis_brain
am i talking crazy?

Yes. You do! ;)



k, just checking :p
Regards
cyph

[b0b0b0b]

It's been explained already, but I thought I'd add this analogy--

Imagine taking a wallpaper BMP, reducing the resolution, and applying JPEG to it, and then stretching that JPEG to be your new wallpaper.

[Mug Funky]

3 words: high speed dubbing :)

the reverse of this is (kinda) true. if i lower the speed on my turntable i can get higher frequency response out of my rather poor stylus. i lose a bit of the bass though (usually doesn't matter). and often it just reveals that there was never anything over 22050 because the original recording was done at that rate (i get a lot of crackle above 22050 though).