Audio is bad after capture

Question

I am capturing footage from my sony camera, thru my mac and onto my external harddrive. I am using a firewire cable to connect my computer to the camera and a USB calbe to connect my computer to my external hard drive. I have captured hours of footage this way, but have only recently been having this audio problem:
The audio on the tape is good, I can play it back on the camera and it sounds just fine. But when I capture in Final Cut Pro, there are weird audio glitches that keep happening. Also, I can't hear the audio coming from my computer unless I check the "preview" box under clip settings for audio. I don't remember having to do that before.
My Device Control setting is: FireWire NTSC Basic
My Capture/Input setting is: DV NTSC 48kHz
Any ideas? Maybe just a bad cord, but I'm hoping not as I don't want to have to buy a new cord to figure this out. If anyone has any suggestions, let me know!! Thanks guys.
-Chelsea

Answer 1

Theoretically you should have enough bandwidth in a FW card to daisy chain a FW hd to the computer. What this means is plugging the FW cable from the HD into the computer's one port and then plugging the camera's fw output into the drive's second port. This is the cheap way to do it, but I would very strongly advise you to follow Jim's excellent advice and get a card.
The computer has circuits for different types of data streams. These circuits are called busses as they bus info from one place to another. Your machine has but one FW bus, as do most machines. By getting a card you're creating a second independent bus route, one for the flow of data from the camera to the computer, the other for the computer to the hard drive. The card just plugs into the card slot, piece of cake.
Adam Wilt summarizes it far better than I could at http://www.adamwilt.com/Tidbits.html.
Cut and paste from the site:
"FireWire Frustrations: FireWire 400 (FW400) has more than enough bandwidth even for dual-stream DV, yet plenty of problems can occur when running FireWire disks and FireWire cameras on the same bus. There are a few possible reasons for this:
* The FW bus can only run as fast as the slowest device on it. Although Macs, PCs, and most drives should be talking S400 (400 Mbit/sec), many cameras and decks, both consumer and pro, only support S100 or S200 speeds. If you hang an S100 deck on your bus, you've just cut max throughput by a factor of four.
* A DV stream runs about 29Mbit/sec (including audio, aux data, etc.). That's nearly 1/3 of the usable bandwidth on an S100 FW bus, leaving only two raw streams' worth of bandwidth for disk I/O. However, due to the bursty nature of disk I/O, one needs about twice DV's data rate to ensure timely delivery of data--and that's with internal ATA drives. Given the "thin pipe" of the remaining 71 Mbit/sec bandwidth, playing/recording a single stream of DV while supporting DV I/O on the same bus is getting uncomfortably close to the limit.
* Some devices do not like to co-reside on a FW bus. Some Canon single-chip camcorders, Apple iSight webcams, and even some disk drives have been cited as "not playing well with others".
Many cameras / decks / converter boxes have used a very minimalist implementation of the 1394a spec, barely sufficient to find a compatible A/VC host on the bus and talk to it. Hence the oft-observed "baby duckling syndrome": hook up two FireWire decks to a Mac or PC, turn 'em on, and the first thing each one sees is mommy. Sometimes the decks talk to each other, ignoring the computer, sometimes one talks to the computer and the other is ignored, etc.
FireWire bridge chips in disk housings have comparable pathologies. Folks report that some drives work well on the end of a daisy chain but not in the middle of a daisy-chain, for example.
All these same caveats also apply when using a FW800 bus, of course.
I routinely play/record using a 7200rpm IBM DeskStar in a three-year-old ADS Pyro case using the Oxford 900 chipset with a Sony DSR-11, DHR-1000, or PD150 daisy-chained off it on an 800 MHz TiBook. I'm just lucky in that all this stuff happens to play nicely together. Your mileage may vary, depending on what equipment you're using.
Also note that using a common, low-cost FireWire hub will not help solve these sorts of problems. The best workaround I know of is to segregate disks on one bus, and your DV device on another. If you have a desktop or tower computer, you can add a PCI FireWire card; if you have a laptop with a CardBus slot, adding a CardBus FireWire adapter is the way to go."