Subject:L-R Channels Swapping on Long Recordings

Posted by: smithbo

Date:12/22/2001 9:49:36 AM

I am recording backups of book cassettes, using the left and right channels as separate voice tracks to create more compact cassettes.
Using SoundForge XP 4.5, about 2.5 hours into a recording, I find that the left and right channels have swapped themselves at some point. If I notice this, I can painstakingly find the point and perform a channel swap on the remainder of the recording to get back where I should be. Anyone ever notice this? It has happened to me several times, and I am not sure of the integrity of the many many backups I have written to CD.

Bob

Subject:RE: L-R Channels Swapping on Long Recordings

Reply by: Rednroll

Date:12/22/2001 11:22:32 AM

Hmmmm, definitely sounds strange. First off, where do you find a cassette that is 2 1/2 hours long, and then on that same note, where do you find a CD to transfer it too,which is also 2 1/2 hours long? The longest CD I've seen is 99Minutes and the longest cassette I've seen is 120minutes (60 per side). Maybe when you're doing the transfer, the cassette is flipping due to an autoreverse function and what is getting swapped is the cassette head outputs. That would seem more probable to me than the inputs of sound forge doing a swap.

I've heard of wife swapping in some swinger forums, but never heard of channel swapping in the sound forge forum. :-)

Regards

Subject:RE: L-R Channels Swapping on Long Recordings

Reply by: smithbo

Date:12/22/2001 12:09:04 PM

Interesting take on the question--I've browsed the forum and enjoyed your style and contributions.
I guess you don't have any experience with this problem, and admittedly--it's a strange thing.
To answer your inquiry, I have two auto reversing 2-deck Tascam tape decks. In order not to have to supervise the play-in for all those hours, I can leave a 90-minute tape on each transport playing into SF when I leave work. The first tape plays, auto-reverses, and sequences to the next tape which does the same. This adds to 3 hours of play time. The tapes continue to cycle back and forth until SF stops (usually at about 4 hrs, with 32 KBS sampling), and I discard the "replays". Using the two tape transports into two computers, I have 12 hours of reading backed up by the time I get home (adding R and L tracks).

The track swapping occurs in the middle of a tape when nothing particular is happening with the tape decks, and suddenly, the audio material swaps sides in the wave file for no apparent reason. (I actually do other more refined things with SF that actually involve on-site recording and music production and mixing--along with my VS-880 digital recorder--but SF is the best line input "wave recorder" that I have come across so far for the books thing.

Thanks for the response.

Bob

Subject:RE: L-R Channels Swapping on Long Recordings

Reply by: smithbo

Date:12/22/2001 12:20:33 PM

Also, you mention the size of CDs--I'm converting the wav's to 128 kbs MP3s, so that I can back up 7-8 90 minute tapes on 1 CD (depending on whether the tapes run a full 90 minutes or not). That adds up to 24 hours of reading on a single 700 MB CD.

The 128 Kbs Codec is the most compression that MP3 can provide where the left and right channels are truly isolated--all lesser sampling codecs that I have seen blend the channels to one extent or another.

Subject:RE: L-R Channels Swapping on Long Recordings

Reply by: Rednroll

Date:12/22/2001 6:35:07 PM

Ok, thanks for the more informative response. You're really not making a 2 hour CD then, you're making a CDrom, I know..same shape not the correct term though. Although I have never seen this problem before, I would suspect a hardware problem rather than sound forge. You will want to make sure that your sound card is not sharing an IRQ or DMA with any other hardware. I had a similar problem, where I was using dual sound cards sharing the same IRQ and the sound cards would occasionally swap inputs/output assignments with each other (in other words normally sound card 1 would be outputs 1-8 and sound card 2 would be outputs 9-16.) When the sound cards would swap my mixes would be messed up, since the output routings where wrong. I would suspect the same thing in your situation, where an IRQ is being shared, maybe with a network card. Your sound card should have it's own IRQ and DMA if available. I would also look at your sound cards driver that you're using in Sound Forge. Are you using the "Microsoft Mapper" or your actual sound card driver? It is always best to use your sound cards driver rather than the sound mapper. You might want to check to see if there is an updated driver for your sound card and also reinstall the current driver if there isn't one.

Subject:RE: L-R Channels Swapping on Long Recordings

Reply by: smithbo

Date:12/22/2001 7:39:17 PM

Thanks, Red. Good observations. I'm doing the same thing using two different installations of SF-XP, one on a Win 2K system with 256MB memory and a Turtle Beach Montego (along with a disabled sound card on the mother board), and the other a small 32 MB Pentium 233 with a Turtle Beach Pinnacle (Humongous 16-bit card, but great sound and noise ratio). My most recent "swap-jink" happened on the small machine.

When I read your message, I looked at the driver setups and noticed that I did have the mapper running on the larger system (ugh--must have defaulted that way), but the small system was using the card's driver, and has only the one sound card. Could be a programming bug not trapping a memory-related error since the machine is so tight on memory (haven't found any additional dims that won't lock it up). You'd think the other machine with 2 sound cards and the mapper running would be more likely to experience the problems you described.

Well, I've changed the device settings anyway, and now I need to monitor closely to see if it's just happening on the one machine or on both. (Caught me off guard the first time it happened, and I didn't even notice which machine made the wave file). Also, I just ordered Sound Forge 5.0 with the noise suppressor in that $199 bundle from safe harbor, so I'll be installing that soon. In fact, I may be doing more of my work on the Vegas Lite that comes with it--can't wait to test drive it all.

Thanks again. Bob