Subject:recording length

Posted by: timbergreg

Date:1/26/2004 3:01:45 AM

I have SF6 and want to record a long radio show. I've recorded the show before in stereo, 44.1 16bit and the recording always stops around the 3:22:00 mark, roughly an hour short of the show time. If I record at 32.0 16 bit, how long of a recording will I get? Anyone know? Any chance it would record for 5 hours at this setting? I have roughly 30 gigs of drive space on my pc so space isn't really an issue.

Subject:RE: recording length

Reply by: wigworld

Date:1/26/2004 3:33:57 AM

Isn't there a limit to file size in Sound Forge (might be 2GB, I'm not sure, but I think it's a limit inherent to the .wav format). Also, FAT32 can't handle files larger than 2GB - which OS and file system are you using?.

Subject:RE: recording length

Reply by: Chienworks

Date:1/26/2004 5:23:33 AM

You're hitting the 2GB limitation of .WAV files. This isn't a FAT32 thing since FAT32 is limited to 4GB files, not 2GB.

The size of the file is proportional to the sampling rate x the bit rate. So, if you decrease the sampling rate from 44.1 to 32 then the length of time you can record will be 44.1/32 longer. Well, not exactly. 44.1K is 44100 but 32K is really 32768. So that means instead of 202 minutes you can record 271.86 minutes. Sorry, still not quite 5 hours, but closer anyway. What are you recording? Is it possible to get away with 22050 instead of 44100? I record all our church services at 22050 and for that material it's pretty much impossible to hear the difference even during the music. At that rate you'd be able to record 404 minutes which is well over 6 hours.

An alternative you might want to try, and this is at your own risk! I won't guarantee it because i really don't have time to test it right now ... Under the Internal Preferences tab is an option to "Render large Wave files as Wave 64". This option is set to FALSE. It's conceivable that setting this to TRUE would allow Sound Forge to record past 2GB and save the result as a .w64 file instead of a .wav file. It probably wouldn't hurt to try, but i'd experiment sometime before you are doing the necessary recording.

As always, the standard disclaimer in these situations ... Making changes to the internal preferences is done at your own risk. Neither i nor SONY media software nor any other forum participant will guarantee results nor support you with any problems you may have by making these changes. If you find you've messed things up, quit Sound Forge, then hold down the Ctrl & Shift keys while starting it again. This will reset ALL preferences, including all the ones you really wanted changed, back to their default settings.

Subject:RE: recording length

Reply by: metrazol

Date:1/26/2004 12:58:44 PM

Hehe, ah the joy of .w64.

I agree with Chienworks that playing around can lead to some nasty side effects for your system. Nothing serious is all that likely to happen, but working with large files in Windows is slow and having to delete 2gb of junk is a lot of time wasted watching that little "deleting files" bar fill up.

Much, much, much simpler is to just drop to 22.050 mono, or stereo if you're recording FM and the signal is in stereo (your tuner should have a little "FM St." light if it is). See, it's radio, right? 44.1 is, well, major overkill. There's nothing being broadcast in between 22khz and 44.1khz. The higher sampling rate is entirely wasted. It's the same thing with phones. They only have an 8khz dynamic range, so anything above 8khz is overhead. For AM it's some ridiculously low range and FM is much better, but still what most audiophiles would call junk. Try it, you'll probably see no difference between the two rates and you'll save some time and disk space.

Subject:RE: recording length

Reply by: R0cky

Date:1/28/2004 11:33:27 AM

Nyquist criterion. If you want to record a given bandwidth of material, you must sample at greater than or equal to 2x the maximum frequency contained in your material. Otherwise you will get errors known as "aliasing".

Example: 20 KHz max requires minimum 40 Khz sample rate. This is how the CD standard of 44.1 KHz was arrived at. You really need some margin for practical apps.

8 KHz phone bw needs 16 KHz to capture all.
If you sampled at say, 10 KHz then 8 Khz frequencies would be aliased to 10-8 = 2 KHz in your sampled data.

To prevent aliasing you must filter the material before sampling. Continuing the phone example, if you wanted to sample at 10 KHz you'd need to filter out everything above 5 KHz to prevent aliasing errors.

Practically, for lo-fi material like phone data, you might never notice.