Subject:Soundforge resampling

Posted by: kbouchard

Date:2/10/2005 9:09:32 AM

Here's the situation:

A tape (reel to reel analog) is recorded at 3.75 ips. NOW, the only available deck plays at only 7.5 and 15, so, the tape is played at 7 ips and burned to a cd.
Can I simply rip that file (sounds like the chipmunks :-), pull it into SoundForge (SF6) and resample it at 22.050 to make it sound normal? Now, assuming it sounds ok, how would I burn it back to a cd? (the sound file has to be 44.1 to go onto a cd)
No, I'm not worried about losing any high frequencies since the sound file is an old radio show taken off a transcription disk and I don't think there's much above 10KC anyway.

thanks, ken

Subject:RE: Soundforge resampling

Reply by: Chienworks

Date:2/10/2005 9:26:23 AM

This is extremely easy. Record at 44.1KHz (or any handy sampling rate really). After recording, there is a small box near the middle of the screen just below the wave form that shows the sampling rate. Double-click this box and type in a new value exactly half of the original value (use 22050 if you recorded at 44100). Save the file. Burn it to CD. Done. Whatever CD authoring program you use will automatically resample to 44100.

If you want to use Sound Forge's superior resampling rather than having the burning software do it, you can use Process / Resample and resample it back to 44100 before saving it. Set the Interpolation accuracy slider to High (4) for best results.

Subject:RE: Soundforge resampling

Reply by: Sonic

Date:2/10/2005 11:25:34 AM

That is, you essentially 'stomp' the existing sample rate to play it at the right speed, then actually resample (either in forge or your burn app of choice) to get it back to 44.1 kHz at the same speed.

I don't think it is a given that 3rd party burning apps will always resample for you. They may just reject the file or they may just ignore it, which would leave you with the same speed problem on a different piece of media.

But it's probably typical of the bigger burning products, Nero, Roxio, et al.

J.

Subject:RE: Soundforge resampling

Reply by: thx99

Date:2/24/2005 1:28:05 PM

My experiences with Roxio's CD-burning software (and with the former Adaptec equivalent) have not been favorable when it comes to burning audio CDs from files at sampling rates other than 44.1 kHz.

IIRC, Roxio will accept a file at any sampling rate (or possibly only those at factors of 44.1 kHz, like 11.025 and 22.05 kHz) and will perform its own resampling process to end up at 44.1 kHz. However, the program does not apply anti-aliasing filters during this process, which results in an audio CD which sounds worse than the original files. WIthout the anti-aliasing filters, audible artifacts are introduced that were not in the original file.

I can't comment on Nero or other CD-burning programs.

I highly recommend that you always use Sound Forge to resample files to 44.1 kHz (making sure that the anti-aliasing filter box is checked) and then import these files into your CD-burning software.

Subject:RE: Soundforge resampling

Reply by: edt

Date:2/25/2005 9:25:28 PM

what about timestreching?
woulnd this be an easy way with less quality lost than by resamling?
edt

Subject:RE: Soundforge resampling

Reply by: Chienworks

Date:2/26/2005 6:26:08 AM

Timestretching causes much more degradation than resampling does. However, timestretching allows the pitch to be preserved; changing the sample rate will affect pitch.

Subject:RE: Soundforge resampling

Reply by: thx99

Date:2/28/2005 8:49:36 AM

Another way to perform the speed adjustment would be to use the "Pitch Shift" feature.

Record the original at 44.1 kHz and then run "Pitch Shift", setting the # of semitones to -12 (if the original was played back at 2X nominal speed) or -24 (for 4x playback). This will result in the correct speed and will keep the file at 44.1 kHz, eliminating the need to resample it before burning it to a CD.

Subject:RE: Soundforge resampling

Reply by: Chienworks

Date:2/28/2005 10:32:49 AM

You will eliminate the manual resampling step, but SoundForge actually performs a resample as part of the pitch shift process. So while this method works very well, it doesn't avoid having the file resampled.

Subject:RE: Soundforge resampling

Reply by: thx99

Date:2/28/2005 11:42:46 AM

True. I guess I should have stated that it saves having to manually perform a separate resampling process. :)