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I have some ripped tracks from an audio CD which originally had the music in 44100Hz bitrate, but it's encoded as 48000Hz. The pitch is definitely higher and so is the speed. How do I properly reduce the bitrate without losing audio quality?

I have Sound Forge 10 application I could use to do that if it's possible.

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There are no tags for bit-rate, sample-rate, resampling, play-speed or whatever, but I'm sure the site would benefit from some variation of them. –  user1306322 Jun 29 '13 at 19:43
    
What you're referring to is called sample rate and I'm not sure if that is causing the change in pitch and speed. Could you maybe post an information log (filesize, bit rate, sample rate, lenght, etc.) of the 44.1 kHz and 48 kHz file? –  Bart Arondson Jun 29 '13 at 22:57
    
@BartArondson I only have the "wrong" 48kHz files. I just know the tune should be played at 44.1kHz. –  user1306322 Jun 30 '13 at 7:34
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1 Answer

up vote 5 down vote accepted

You simply re-sample them from 48 kHz to 44.1 kHz.

I believe in Sound Forge you go to the Process menu and select re-sample.

Or you can do it by using one of the many free audio editing software such as these:
http://www.hongkiat.com/blog/25-free-digital-audio-editors/

Don't apply pitch-shifting or time warp, only plain and simple re-sampling.

You won't normally loose any data re-sampling as it is merely about setting playback speed in the file header. You are only telling the player to play the exact same data, but at a lower rate. The opposite is what you're experiencing, the data played at a higher frequency resulting in higher pitch and faster playback.

However, be aware of that some program look at the system's playback rate and can actually interpolate the data and so forth. Therefor I would advice you to check other programs as well if you run into lowered quality.

If none should allow you there is a more low-level approach you can use by altering the audio file header directly (and header only) to set new playback rate. For this you can use for example sox:
http://sox.sourceforge.net/sox.html

(Audacity apparently has a bug related to re-sampling - dunno if that is fixed by now.)

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