I'm having a problem with 4-channel audio capture over Firewire, and I wonder if someone can help please?

I bought a shotgun mic (Azden SGM-2X) for my XL-1S, and am feeding it into Audio-2 Left on my MA-200. Putting the camera into 4-channel 12-bit mode has the desired effect, with my onboard stereo mic recording onto the first two audio channels, the SGM-2X onto the third, and nothing on the fourth, with the gain turned all the way down. The audio sounds perfect on playback through headphones plugged into the XL-1S analog output.

When I capture, using Scenalyzer, on my desktop PC, I get clicks about every 1/4 sec, getting louder as the audio gets louder. When I capture on my laptop, the problem is the same. The problem is only with channel 3 and channel 4 capture. Everything works fine on channels 1 and 2, regardless of whether they're 12-bit or 16-bit.

My PC is a generic home-built P4 1.8GHz, Intel 850MV motherboard, 512MB RDRAM, Sound Blaster Live and the generic TI OHCI Firewire card that comes with Pinnacle Studio. OS is WinXP Pro. My laptop is a ThinkPad A30P, also WinXP Pro.

I swapped the connections between the MA-200 and the XL-1S, so that the MA-200's channels 1 and 2 fed into the XL-1S's channels 3 and 4. The problem persisted, so it's not just faulty channels on the MA-200.

Any ideas? Given that I'm using two different capture platforms, it seems unlikely that it's related directly to my hardware. I'm using Scenalyzer Live on both platforms, so that's a common factor. I'm wondering if there's something wrong with my XL-1S, although audio played off the tape sounds perfect through headphones. I know that the mic is working fine, because it doesn't exhibit this problem when fed into channels 1 or 2. Thanks!

I'm not a PC guy, sorry. But not all software supports 4 channel capture of audio. Is there a preference or setting in the software to change for 4 channel or 12 bit audio? I've read posts here of people using Scenalyzer so hopefully one of them will chime in.

Jeff

Does the sound play OK via analog out?

Can you get clean 4-channel capture wiht other systems?

My guess is a problem in the capture process where in for some reason your capture softwasre is having a problme with the channel 3/4 digital audio stream.

A good place to explore may be the support forums for your capture system.

Discreet's newsgroups discussed a similar problem with Cinestream. The speculation was that 4 track is recorded at 12 bit resolution (32kHz) and if you mix 48 and 32 in the same track you can get annoying clicks from resampling by the NLE.

The consensus was to keep 32 KHz stuff separate from 48KHz. The rendered track, can be either 32 or 48KHz without any problems.

Nathan Gifford

Thanks for the replies.

To answer Don's questions: yes, the sound is perfect via analog out and no, I don't have any other way of getting 4-channel capture other than using Scenalyzer's "second channel" capture option. Sound Forge reports the audio as 16-bit 32KHz, so Scenalyzer or something else along the way is upsampling from 12 to 16 bits. But, that shouldn't cause annoying clicks. They certainly sound like resampling errors. The clicks appear even during audio preview during capture, so this isn't something that an NLE is introducing.

Maybe this is because I'm using a generic (Pinnacle) OHCI card? However, I get the same problem on my laptop, although that, too, contains a TI OHCI chipset. I'm thinking of getting a DVStorm, which may solve the problem....

Mabe take a look at the wave file to see what the clicks are. Probably a gap/break in the waveform. Have you tried to capture from a different playback machine?

An alternative worka round is to capture the first two tracks via the firewire, and to capture the other analog via your sound card, and then sync them in post.

Unusual perhaps that it takes it to 32k/16-bit.

Duh. You're right, Don. I stupidly forgot that I have a Sony camcorder to try capturing from. I'll give that a try. I emailed the author of Scenalyzer, and he's looking into it, too. He said that he'd let me know tomorrow if it's a bug; great service, no?

I tried my Sony TRV-10, and here are the results:

The tape recorded on the XL-1S has the same problem playing back on the TRV-10: the second stereo pair captures with the same loud clicks.

Recording a 4-channel tape on the TRV-10 has the same problem, except to a much lesser degree. The clicks are there, and very noticeable, but not as loud.

So, this kinda sorta eliminates the XL-1S as having a problem, although not completely, because it's much worse on the XL-1S.

The only common denominators between all the various combos I've tried are the tape (Sony Excellence, so I don't suspect it of foul play), TI OHCI capture chipsets, and Scenalyzer Live.

If anyone's interested, I have a 160kb .wav file with the offending clicks, which I can email to you for your comments. Thanks, as always!

I just came across the same problem. Recording with both the onboard mike plus house sound running into audio 2, I get clicks and pops when I capture using Scenalyzer. Playing out the analog ports audio on all channels is fine. Please keep us posted with what you find.
-Brad

Ah, the sweet, and totally irrational, relief that one gets when you discover that "they all do that" :-)

I'll certainly keep y'all informed.

OK. Email the file to me at:
dpalomaki@cox.net.

Would be interesting to try the tape with a different capture system.

Standard PCI sound cards for the PC, like the Soundblaster series, all have PCI bus latency issues. The Soundblaster is notoriously problematic around this latency issue. There is a patch for the latency issue available from www.viahardware.com, as well as an explanation of just what the latency issue is. Most noteably, it causes pops and clicks during playback and recording. If you're serious about your video and audio, I would highly recommend replacing these run of the mill sound cards with a professional sound card from Midiman, Tascam, or EchoAudio. You'll find the low latency and residual system noise is an order of magnitude better with any of these professional, digital sound cards.

I use an Azden wireless mic connected to an MA-100 which is connected to the left side of stereo 2. I am using a manual gain setting on that channel. I am also using Scenalyzer Live to capture the second channel and have not noticed any clicks. Is it possible that the signal was recorded to hot and it just isn't as noticable until the signal reaches the computer?

I agree with Bill's coments about the SoundBlaster, and a sound card upgrade is on my list. However, in the the case of DV capture and editing, the SoundBlaster is merely a preview device and never plays a role in the encoding, manipulation or decoding of the sound. Of course, it'd be nice to know that the preview is as close as possible to the original, and the SoundBlaster is at best a "draft preview" solution only.

It's possible that the captured sound is perfectly ok and that the SoundBlaster is messing it up. However, as the problem only occurs on channel 3/4 capture, and almost identical sound on channel 1/2 sounds ok, I don't think that it's the SoundBlaster.

To Edward's point, I thought that this might be the case, but the problem exists in captures that are recorded with significantly lower audio gain, too. I'm interested in what your capture solution is, though. Is it generic TI/OHCI, or something meatier?

See the sound card reviews at: pcavtech.com. Some good information there as regards sound quality of many common sound cards in the low to moderate price range.

I use a SIIG OHCI firewire card connected to a Panasonic AG-DV2000 deck.

An update: I sent Don an audio clip on which I can hear clicks, and he can't. Interesting. It's possible that there's something in the waveform that causes the sound cards in my PC and laptop to generate clicks, or that something in the Windows XP sound system is freaking out. If so, it's strange that it does so only on channel 3/4 capture, and not channel 1/2 capture.

So, tonight, I'll do a capture from channels 3/4 of my XL-1S, send Don a clip, and then record back out to (fresh) tape. If there's no clicks on the re-recorded tape then, clearly, there's just something wrong with audio playback on my PC and laptop. This will encourage me to buy a better sound card. I'll report back.....

To add to the comment, FWIW, when I've seen clicks in captured digital audio files, they generally have been breaks or gaps in the wave form. sudden, total digital silence for a number of samples. Did not see any of those things or hear any either.

More info: I carefully recorded onto Stereo 2 left (i.e. channel 3 or 4, don't know how they're numbered), with the gain turned to zero on the other three channels. I used my Azden SGM-2X through the MA-200. Peak level was -12dB, so it shouldn't be too hot.

Analog playback is fine. During capture, and subsequent playback on my PC, the clicks are loud and obvious (much more so than from my TRV-10). I've sent Don a sample, just to confirm that he can see/hear them. I can see spikes (downward spikes, FWIW) in Sound Forge 6.0. Copying the captured file to Premiere's timeline and writing back out to tape over firewire, I can now hear the clicks through the XL-1S's analog audio outputs. So, the clicks seem to have been introduced via firewire capture and, of course, then persist when you write back out to tape.

At this point, my best guess is a Scenalyzer Live bug, possibly when it's upconverting 12 bit to 16 bit during capture. I'll contact the author again to see what he's found, and will report back.

Mine's fixed (knock on wood).
I forgot to ask myself the ever important question: "What did you do to it?"

Once I did, I disconnected the new external firewire drive enclosure and powered it off. Now my capture seems to work fine for both Stereo 1 and 2. My guess is that I was getting excessive PCI interrupts from the drive enclosure which was causing the capture to skip.

Note: I say skip because on mine, I eventually noticed that there seemed to be a frame missing everytime I heard a click. Scenalyzer did not report dropped frames however.

I heard from Andreas, the author of Scenalyzer. He's able to reproduce the problem on his computer, and is working on a fix. Note: this doesn't necessarily mean that it's a Scenalyzer problem....he didn't specify. It could just as easily be some weird PC architecture bug that he's developing a workaround for. As soon as I hear from him with the final results, I'll let y'all know.

Andreas sent me a test version of Scenalyzer, and the problem is fixed! How's that for great service? I've asked him if/when this will appear in future releases (I'm sure that it will).

Interestingly, I at first thought that he hadn't completely fixed the problem, because I could hear two tiny glitches. But, they're on the original recording when played in analog mode. I think that I've been wearing out the same piece of tape with too many experiments :-(

Thanks also to Don for listening to and looking at my audio samples.

What was the version number/date of Scenalyzer that he sent you?

Version 1.4, Jul 19 2002 02:40:04. Andreas sent me an email a few minutes ago describing the changes that he'd made. I quote:

"I have fixed one problem in the Dv-Audio-Resync-Module of sclive (this makes sure that the audio is perfectly synchronous to the video - this is a topic with some capture-cards) and one problem in the Audio-Channel-Swapper (swaps the two channel if you capture the second channel) of sclive."

He also said that, if all goes well with testing, he'll release a new version with these changes next week. Note: I haven't tested this build extensively. I'm in a rush to get my work done (I'm a venture capitalist in real life) before leaving for a joyful week of wildlife videography, so only quickly tested stereo 2 capture, which seemed to work. Doubtless, Andreas is doing full regression testing on this new release.

Holy god! thank goodness if you got this to work. I have a 45min mini-feature that needs to be recaptured and edited all because of those stupid annoying clicks.

If you can, e-mail me that version or tell me what version it is so i can get back to work and do some major re-editing.

I'd be oh so greatful!

Thanks,
Adam
adamjamalcraig@softhome.net

I don't want to violate Andreas' trust (he sent me the patched version as a "non-public" release), so would you mind emailing him at info@scenalyzer.com? He's been very responsive and I'm sure will send you that version. If he's not around, please email me at alex@trinityventuresnospam.com (removing nospam...I hate email address harvesting programs) and I'll try to help directly.

The version that Andreas sent me is 1.4, Jul 19 2002

Ok, i just e- mailed him. Thanks for the help of getting to the root of this problem.

Adam

I'm really trying to get a 4 channel capture to work with my DV Raptor card via the firewire. Scenalyzer loads up but doesn't seem to connect with it, then it crashes. I see that it's not compatible yet. I used to use raptor edit and capture the 2nd audio tracks via my sound card but their trial version (which used to work) doesn't work with Windows XP. It's becoming a long, tired job setting up wave files for perfect sync!
Any suggestions to get 4 audio tracks from my DV Raptor card?

Thanks...