XL1 Audio Step by Step, Part Two
an article provided by Canon USA
The Watchdog Notes: Before we can get into the exact procedures required for each audio recording mode, it's necessary to understand how 16-bit and 12-bit audio work in the XL1 and how they differ. Also, a few other important terms are explained along with the steps to select the audio output when the XL1 is in VCR playback mode. This second part of Canon USA's XL1 Audio Step-by-Step continues now, starting with a description of the three digital audio modes available in the XL1.
16-bit stereo (48kHz, 2 channel) for the highest sound quality. "16-bit" refers to the amount of data recorded and the range of the data (16-bit converted to decimal numbers means that there are 65,536 different numbers that can represent any sample). 16-bit represents the most data for the truest and fullest range of sound. DV specifications call for a sampling rate of 48kHz (48 thousand times per second), 44.1kHz or 32kHz. (DAT uses 48KHz sampling and CDs use 44.1kHz sampling).
12-bit stereo (32kHz, 2 channels) records on two of the four available channels (Stereo 1), leaving two other channels (Stereo 2) available for the addition of sound, music, narration, etc.
The 16-bit mode produces CD quality sound, two channel sound on one track. The 12-bit mode divides the audio track into two, recording two channels on one track while leaving the remaining track open for post production audio recording with separate editing gear. In other words, you can add new sound later using a DV VCR. You cannot add new sound to a tape using the XL1.
12-bit stereo (32kHz, 4 channels) for simultaneous recording on four channels (Stereo 1 and Stereo 2). Audio can then be output as four independent channels.
With 12-bit audio, the sound quality is just slightly lower, because the amount of data gathered through the sampling and quantization procedures is lower than with 16-bit (4,096 variations for 12-bit compared to 65,536 for 16-bit). The 12 bit sound is sampled at 32 KHz. Because there is less data, it does not take up all the space available to audio on the tape, resulting in 2 two-channel tracks.
Also with 12-bit audio, you can use the microphone mounted on the camcorder plus up to two remote microphones, all recording on separate channels, at the same time. At the editing stage, selections can be made for the desired mix for the finished video. Or, if only two channels are used, the original audio can be left on the tape while new audio (music and narration, for example) can be added without erasing the original sound during the editing process.
Unbalanced audio equipment is generally found on consumer camcorders, and indeed all previous Canon camcorder models have used a 3.5mm mini-jack as their input. An unbalanced microphone may work well attached to the camera, however if it’s range is extended, the microphone cable frequently picks up interference from extraneous electro-magnetic fields resulting in hum.
Attaching the MA-100 allows the use of two professional XLR microphones, or two wireless microphone receivers on the XL1. Balanced XLR microphones contain a noise-canceling cable that greatly reduces unwanted interference. The MA-100 converts balanced signals from the XLR microphones to unbalanced signals. The MA-100 includes RCA plugs which can be connected directly to the camcorders RCA audio terminals.
Locked and Unlocked Audio
The XL1 records sound in "unlocked" audio. Unlocked audio does not mean out of sync audio. Unlocked audio is always completely in sync with the video. The difference has to do with the number of audio samples per video frame. With locked audio the sample rate per frame of video is fixed, while unlocked audio allows for some slight variations in the number of samples per frame.
Terminals vs. Tracks
The XL1’s 3.5mm stereo mini jack is used for the supplied microphone. Audio 1 and Audio 2 refer to the physical location of the audio inputs. The Audio 1 terminals appear on the back of the camcorder, the Audio 2 terminals are on the right side of the handle. Stereo 1 and Stereo 2 refer to the stereo tracks available on the tape.
Using the Audio Monitor selector is only effective when using 12 bit (Stereo 1 and Stereo 2) mode, since this is the only mode which would have a selection. If you are recording using 16 bit mode or 12 bit (ST1), then the sound is fixed in Stereo 1 only.
Located just below the audio meter, on the left side of the camera, the audio monitor button allows you to select the sound source you want to record:
Stereo 1, Stereo 2 or a mix of both. Use headphones to monitor the audio while recording. Press the AUDIO MONITOR button to make a sound check. With each press you can cycle through…
- ST 1 (Stereo 1 only)
- ST 2 (Stereo 2 only)
- MIX (Mixture of ST 1 and ST 2 at a default ratio of 1:1)
Your choice is selected a few seconds after you press the button, and shown in both the viewfinder and audio LCD panel.
Selecting the Audio Output in VCR Playback Mode
During playback, the XL1 only plays the audio you have selected with Audio Monitor. When playing back a tape in which the audio was recorded in 12 bit (Stereo 1, Stereo 2) mode, you can select the output you would like to hear. Press the AUDIO MONITOR button to cycle through these four selections:
Stereo 1, Stereo 2, Default Mix (1:1), or Variable Mix (your ratio)
When you have chosen the output, then STEREO 1, STEREO 2 or MIX will be shown in the top left corner of the viewfinder and in the audio LCD panel. If you turn the power off, the output (and display) defaults to STEREO 1.
If the sound was recorded in 16 bit mode, it only contains Stereo 1 sound and you can not select an audio mix. You also can not select the audio mix if 12 bit Stereo 1 mode was used, unless new sound has been added with a DV VCR.
If you choose MIX Selection (1:1), then a mixing ratio of the Stereo 1 level to the Stereo 2 level is 1:1.
If you choose MIX Selection Variable, then a mixing ratio of Stereo 1 to Stereo 2 can be adjusted. For this adjustment, you can use the + (up) and - (down) cursor keys to choose the mix balance (or use the ST-1/ST-2 MIX BALANCE buttons on the remote control. There are ten steps displayed on the screen. The center position indicates a mixing ratio of 1:1.
Choosing the Output Channel
Make sure the camera is set to VCR mode. Open the menu and select the output channel you wish:
L/R (Stereo) is the default setting.
In the normal stereo mode, the left-side signal is output at the left channel terminal and the right-side signal is output at the right channel terminal.
- If the audio mode is 16 bit or 12 bit Stereo 1, the audio signal will be sent to the RCA jacks labeled L and R.
- If you chose Stereo 1 for the output at stage A, Stereo 1 (L&R) will be sent to the RCA jacks labeled Audio 1 (L&R). In addition, stereo 2 (L&R) will be sent to the RCA jacks labeled Audio 2 (L&R). This gives you four independent audio signals.
- If you mixed the balance at stage A, the combination of left channels from Stereo 1 and Stereo 2 will be sent to the left channel of Audio 1, and the combination of right channels will be sent to the right channel of Audio 1.
L/L -- only the left-side signal is output to the RCA left and right jacks. For reproducing only main voice of bilingual information recorded on other equipment.
R/R -- only the right-side signal is output to the RCA left and right jacks. For reproducing only sub voice of bilingual information recorded on other equipment.
L + R/R -- gives a mono output. Sound from the left and right channels are combined and sent to the left RCA jack.
See also Part One, Part Three and Part Four
of XL1 Audio Step-by-Step by Canon USA
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Thrown together by Chris Hurd