Today, I had an idea which might be able to decrease the size of any lossless file by 50%.

My idea:

Using foobar+soundTouch, encode the wav file at 2x the speed using any lossless codec. I chose flac for this test.

I played the speed increased flac file back with the soundtouch switched off and it obviously played back a lot faster

Now, when I switched soundtouch back on and set it up to play the file back and 50% slower (which should have returned the file back to its original speed), it played back much slower ???

Why does this happen. I am guessing that SoundTouch is not very accurate, so I was unable to do any bitrate comparisons, or any further testing if the increased speed flac file lost bits or quality when speeded up, and then slowed down again, then re-encoded to compare. I was unable to get the original speed again.

Can anyone help, has this been tried before ???

If not, this could be a way forward for all lossless codecs, which automatically speed up the audio before encoding, play back at half speed, and reduce the speed when decoding

Its a thought which might work

Tell me what you think

hm i think you lose a lot of quality when doing that. if it would work you could just play a song 10000 times faster and afterwords just play it 10000 times slower and you would have file sizes of 10kb for one complete song.

this can't be working

You're going to lose the high frequencies.

If you still keep the sampling rate at 44.1 kHz when performing this, all the frequencies between 10 - 20 kHz are shifted above 20 kHz and thus will get lowpassed. Or even worse, they could get aliased into the lower part of the spectrum.

If you switch the sampling rate to 88.2 or 96 kHz, you probably won't gain any compression rate.

Yeah, I had a feeling that quality would be lost somewhere, but wasn't sure where.

Just did an ABX and all I can say is OMG, it has for sure lost high frequencies !!!

Is it not possible to increase the speed without losing quality ???

Well, since the speed change happens at a constant sampling rate and reduces your wav file size, you can be pretty sure to have lost data

Only way to speed up a WAV without destroying data, is to change its sampling rate to 96k and play it on a 24/96 soundcard ;-)

You won't gain space, but you'll gain time when listening to it - if you can keep up

Regards

If you double the speed and double the sampling-rate, everything stays the same.

But than's not what you want, I guess.

SoundTouch is not lossless at all. You would be better off to resample to half the sample rate (22050 usualy).

I expect a lossy codec with normal sample rates to give better results than this however.
Or try one of Wavpack hybrid or Otimfrog dualstream. They have a much more clever way to get at the bitrate you're aiming at.

I get the feeling that you guys are trying to tell me that its not gonna work

PLEASE STOP TYPING TOPIC TITLES IN ALL CAPS BECAUSE IT IS ANNOYING FOR OTHER PEOPLE, K THX
[edit: replaygained topic title and this post]

Absolutely it works!!! For sure !!!

You rise the speed and get smaller files - OK!

BUT : Now you have just changed a lossless format to a lossy one....

Quite a funny way to make a "lossy flac standard" - maybe just bit more studying for that further!

After all - if you want good and small audio files "near lossless", then just choose AAC variable high bitrates (Transcoding::Ultra with High Quality and Low Complexity at Nero's codec). The only bad [(:-(|] thing is : that it's not freeware...)

I bet that this will sound better and still have smaller size than "halfed flac"..

Sorry