Introduction to XL1 Audio
an article by Jon Burkhart and Don Palomaki

Some basic questions about XL1 audio involve the practical applications of four audio channels, which currently available NLE systems allow capture of all the channels in a single pass, whether you have to capture the extra channels in a second operation how do you maintain proper sync. Other concerns are: can you record all four channels on the XL1 at the same time, and can all four channels use external mics... or are you limited to two external and the internal stereo mic? Let's take a closer look at these issues.

The XL1 allows audio recording in several modes including the two-channel modes found on most DV camcorders, and a four-channel mode generally not provided by other prosumer DV camcorders. The sampling rate for the XL1's four channel audio is 32kHz, 12-bit sampling. It sounds just fine to me, but maybe I've worn too many headsets for too long! It's plenty good for what I do.

Here's the way it works. The on board mic is usually plugged into the Stereo 1 input on the camera. I use it for natural sound of the event or sometimes close in interviews with a directional mic replacing the Stereo mic supplied with the camera. It is possible to unplug this mic, and with a simple splitter from Radio Shack, feed two mono mics, one into each of the two channels of Stereo 1.

The Stereo 2 inputs (channels 3 and 4) are fed by RCA connectors. I usually feed a couple of wireless mics into each of these channels. I don't mess with any XLR adapters, etc. The mics are fed directly into the RCA connectors, which work very well (much better than those crappy 1/8" plugs which make very poor contact).

By the way, I usually use two XL1's both outfitted this way so that I have two directional on-board mics and three or four wireless mics gathering sound for me. This arrangement provides great choices for sound in editing.

Canopus DVRaptor, DVRex and DVStorm non-linear editors can all simultaneously capture the video, Stereo 1 (Channels 1 & 2) and as a separate .WAV file Stereo 2 (Channels 3 & 4). I usually stick the two picture tracks from each of the cameras with their Stereo 1 audio on the timeline along with the second Stereo 2 (Channels 3 & 4) on an additional audio channel and hack away.

Sure, it may seem goofy, but I get some amazing sound on many of my productions. I don't think I'll be giving up my XL1s anytime soon.

One word of caution to the faint-of-heart: the XL1 records audio in a rather strange way. The 12-bit 32kHz mode can cause some strange sync drift from time to time, depending on the capture hardware and software you may be using.

For instance I recently edited a 30 minute program, shot with two cameras. Both cameras were shooting in the 12-bit, 32kHz mode with two wireless mikes feeding into channels 3 and 4. My NLE hardware and software is Canopus DVStorm. I also have had similar experiences with capturing on the Canopus DVRex M1.

I captured this material in five minute segments (wanted to stay under the two gigabyte capture limit if I needed to do work on the sound in Sound Forge). I did a simultaneous firewire capture of the video track along with the Stereo 1 (channels 1 & 2) and a separate .WAV file was captured at the same time to get Channels 3 and 4.

When I placed each of these five minute segments on the timeline, I could see that the .WAV file was two frames longer than the .AVI file (which contained the video and Stereo 1). By sticking two five-minute segments of both .AVI and .WAV files on the timeline for a total of ten minutes, I saw an error of four frames and indeed the sound was out of sync by four frames. I fixed the problem by going back along the five minute .WAV file and deleting a frame (during a silent spot) about one-third of the way down the line, and then at about two-thirds of the way down the line. The sound stayed in perfect sync with the picture.

The lesson learned here: look carefully on the timeline of your NLE at the .AVI and .WAV files you simultaneously capture. Make sure they are exactly the same length before you start editing.

I had noticed this error between the .AVI and .WAV files some time ago, but it seems to change depending on how long the capture is. I have done some one hour recordings and captured both the .AVI and .WAV files but have not been able to find constancy in the drift.

Of course if 16-bit 48kHz audio is a must for you, then you can record only Stereo 1 in 16-bit, 48kHz. In this mode, Stereo 2 is not available. This "drift in the audio sync" may be less of a problem also.

Don Palomaki adds: The XL1 allows four channels of audio in 12-bit mode. A typical configuration is ambient sound from the camcorder mic on the Stereo 1 pair (ch. 1 and 2), and external mics to the Stereo 2 pair (ch. 3 and 4). You can get all four audio channels at the same time from the XL1's four analog audio output jacks. Thus, you could capture channels 3 and 4 with a sound card if your video capture card will not do it from the firewire.

With your external VCR you probably have a selection where you could go back and play audio channels 3 and 4 and capture them from the analog outputs. Whether or not you can grab all four channels over firewire depends on your video capture system. Some allow only two channels, others allow you to grab all four. The issue here is usually with the capture card and its drivers. You have to read the specs of the system you have (or are considering to buy) in order to determine its capability.

For example, one can set Dazzle/FAST's DV Now (which shipped with Premiere 5.1c) to grab two or four channels. The sound is stored as separate .WAV files for each channel! Cool for editing and mixing.

And, you can obtain analog playback of the four audio track from the same four RCA jacks when the camcorder is in VCR playback mode.

The Stereo 1 channels give you a choice of the 3.5mm mini-phone jack for the Canon mic, or a pair of RCA jacks. You can use Automatic Gain Control (AGC) or manual gain for the Stereo 1 pair, with input levels MIC, MIC ATT, and line (line being consumer -10 dBV). The manual controls are level and balance. You can connect the MA-100 output to the Stereo 1 input.

The Stereo 2 channels are gold-plated RCA jacks, and offer a choice of MIC, MIC ATT, or line level. The level control is AGC or manual using individual level controls in this case. You can connect the MA-100 output to the Stereo 2 input if you like.

Mode selection is a combination of menu and switches. Some folks may be challenged by this the first few times out. Read the manual carefully, and remember, practice makes perfect!

You can monitor Stereo 1, Stereo 2, or a mix of both stereo pairs (all four channels together) from the head phone jack. You can also select which audio is displayed on the VU meters. And, you can obtain analog playback of the four audio track from the same four RCA jacks.

Although I've not tried it, I suspect one can do four XLR mics nicely by connecting a MA-100 and adding a Studio 1 XLR Pro or the similar Beachtek XLR adapter.

One last thing of which to be aware. Some wireless systems provide what looks like a stereo output cable that can connect to the 1/8" mic input jack. This may actually be a balanced monophonic signal. Connected to the mic jack, this will result in the left and right channels being recorded out of phase, and can resulted in cancellation (near silence) on a VHS VCR linear (mono) track if copied on a stereo VCR.

With some capture cards, one may need a to add Canon setting in the setup or .INI file to ensure proper sync of audio with video.


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