Re: Recording Audio for a DVD

Hi Andrew

There's a great article on this which I saw on
http://www.videouniversity.com/audio1.htm.
I've included an excerpt here:

During the course of setting up a video shoot, sound is usually one of
the last things considered. This is unfortunate because regardless how
much you spend on the set or the talent, audio has the power to make or
break your video. I can't tell you how many "professional" product
videos I've seen that sound like they were recorded with a consumer
camcorder. The point is, even though the packaging is dazzling and the
video is gorgeous, if the audio stinks, it cheapens the value of the
entire project.

In this section, we will deal with audio-for-video as it applies to
different tape formats and how to get that audio on your tape.

Related Articles
· Audio For Video Part 2
· Audio For Video Part 3

VHS and S-VHS use the same methods for sound recording and
reproduction, so we'll start with them. There are two separate types of
audio on a VHS tape - HiFi and Linear. The HiFi track is stereo, has a
broad dynamic range and very low noise. In fact, when properly
recorded, you would have a hard time distinguishing it from CD sound.
HiFi audio is recorded (with a separate head) along with the video
signal as the tape passes by the rotating video drum. Linear audio is
recorded along the edge of the tape with a stationary head - just like
a cassette deck.

8mm and Hi8 use a method similar to the VHS HiFi approach, except Sony
has dubbed this "AFM" audio (Audio Frequency Modulation). AFM is
usually mono on 8mm cameras and stereo on Hi8 decks. Although the specs
are not quite as good as VHS HiFi, the sound is very clean. There is no
provision for linear track audio on the 8mm format. Some Hi8 decks (but
not all) include a stereo digital soundtrack recorded separately from
the AFM sound. The quality of this digital soundtrack is similar to FM
radio and has the added ability to be recorded after the video has been
shot.

Although most people don't shoot on 3/4" tape today, you may edit to it
from time to time, so we'll go over that too. 3/4" tape - or U-Matic -
uses two independent linear audio tracks, recorded along the edge of
the tape similar to VHS. The difference here is that each track can be
recorded independent of the other, at any time in the production
process. There are several ways to take advantage of this capability.
The most obvious is you can record a stereo soundtrack if you are
shooting a music program. Most news crews use one channel for location
background noise and the other channel for the on-camera talent. This
allows a lot of flexibility later while editing. You can also use one
channel for your narrator/on-screen talent and the other for a music
bed.

The new DV formats have a couple of options (although not available on
every camera). You can choose a high-quality two-channel mode that
records CD quality digital stereo sound. You can also choose a slightly
lower quality four-channel mode that records two independent stereo
pairs of digital tracks - one pair for the shoot and another pair for
voice-overs or post-production tricks. One more interesting DV audio
goodie: Many DV cameras allow a "Still" or "Photo" mode where the video
camera becomes high capacity still camera. While shooting the still
shot, you are allowed a few seconds to record verbal notes. The audio
quality is mediocre but handy for sorting things out later.

ADVANTAGES AND DISADVANTAGES:

Each tape format has it's own little audio quirks and idiosyncrasies,
but none so much as the VHS/S-VHS camp. Since the HiFi soundtrack and
the linear audio track are located in different physical locations on
the tape, most industrial and professional decks (and some camcorders)
allow for audio and/or video insert editing. This means you can replace
various segments of your master tape at will as you edit - this is very
handy. Unfortunately, it also imposes certain limitations and causes
some problems.

As we mentioned, the linear track is recorded separately from the HiFi
track so you can replace some or all of the linear track audio on your
edited master. This is all well and good, but you must settle for sound
quality on par with cassette tape (with no noise reduction). So why
can't you use the HiFi track instead? Well, you can if your program
consists only of direct cuts from your source tapes - with no
additional narration or music. Those of us producing training,
marketing and special interest videos can't usually do that. Since the
HiFi track is recorded (combined, really) with the video signal,
whenever you edit the video portion of your master, you are editing the
HiFi audio track as well. This can make for some pretty choppy audio.
It also makes silence when you insert a still shot or title in your
video.

OK, the linear track sounds bad and the HiFi track is impossible to
manage - so now what do you do? Here is a trick I learned over the
course of 3 years producing training and marketing videos exclusively
on S-VHS equipment. It's not perfect, but it works. Let's use a
marketing video as an example. All good marketing videos contain
testimonials and/or the CEO on camera, right? But you also need to
manage a narrator (or two) and some fill music. First, assemble your
video as per the script (or storyboard) - titles and all. The only
difference is to record silence during the clips that will ultimately
have the narrator or music over them (just unplug the audio cables or
turn down the audio at your mixer. Don't just turn down the record
volume on the record deck - it usually doesn't affect the linear
track). All testimonials are recorded with sound, fading in at the
beginning and fading out at the end. Next, time the entire video, top
to bottom - making notes about specific audio cues (narration for a
clip, graphic or sound effects). The next step is to produce the
soundtrack, complete with music and timed narration - leaving silent
gaps for the testimonials. Then, starting at the beginning, audio dub
(or insert) the soundtrack on the linear audio track of your master,
making sure to dub silence during the testimonials. It may take a few
tries to get the timing right, just be patient.

Now, the playback. Virtually all S-VHS decks (and a few camcorders)
have a switch or button that allows you to choose to listen to the HiFi
audio, linear track audio or a mix of the two. You need to find the
"mix" option. When you play the finished video, you will magically hear
the soundtrack, narration and testimonials in perfect alignment (or as
close as your gear allows). You may need to fudge on the narration
start and end times, allowing some extra slop at each end. You will
probably find the HiFi track plays louder than the linear track. Just
record the testimonials at a slightly lower volume. Experiment till you
find the right blend.

This will work in many situations with a few tweaks but here are some
important tips. You MUST record silence or the soundtrack on the linear
track throughout the ENTIRE video. If you don't, you will likely hear a
strange echo or reverb during the testimonials. This is because the
HiFi and linear tracks are seldom in perfect alignment - you are
hearing both at slightly different times. Remember, you cannot play the
master tape in a deck that does not have an audio mix switch. Along the
same lines, if you are sending the master out for duplication, make
sure your duplicator knows about your audio trickery and can
compensate. You might also make a note on the label or box indicating
the "multi-track" audio so you don't forget to flip the switch six
months from now.

This trick (or a modified version) will work on some of the other
formats as well. Specifically, Hi8 and DV with the additional digital
soundtrack, and 3/4" tape with it's two independent audio tracks. If
you have the privilege of editing your videos in a computer, you
probably don't understand why this is such a big deal.

HARDWARE:

Now that you know how the different formats record and play back audio,
how do you get the sound onto the video in the first place?
Unfortunately, there is a different answer for just about every camera
on the planet so I'll try to simplify things.

If you are shooting with a consumer or pro-sumer camcorder, your only
input option is probably the 1/8" mini microphone jack (if your
camcorder even has one!). On some cameras this is a mono (single
channel) mic jack - on other cameras it is stereo (dual channel). The
hardest part is just getting plugged in. These mic jacks are typically
near the built-in mic, opposite the viewfinder - not the most
convenient location. A trip to your local Radio Shack can remedy this
if you are willing to spend $20-$25 and use a string of adapters almost
8" long! Several companies have addressed this shortcoming lately with
adapters designed for professional "XLR" microphones and other audio
devices. This seems like a much better solution. You can also build an
adapter for a single professional mic if you are handy with a soldering
iron and have some patience (more on this later). Just remember that
whatever you plug into this microphone jack, the cable should not be
any longer than 20-25 feet. Otherwise, you will experience noisy sound
and possibly interference from a local radio station (or two). You
should also know that you cannot attach a cassette deck or CD player to
this input - your sound will be distorted and garbled at best. These
devices output "line level" signals that are many times louder than
that of a microphone.

There are a few industrial-grade camcorders that include microphone and
line level inputs (the Panasonic AG-460 and Sony V1000 leap to mind)
along with input level meters. This makes hookup a breeze and is very
convenient for one-man operations because all the connections and
adjustments are centralized. Unfortunately, most manufacturers aren't
this forward thinking or are too miniaturization-minded. At the other
end of the scale are some of the new DV cameras that require special
adapters (not included!) to attach an external microphone. Sony is
famous for this in their audio products and continues the tradition in
some DV products.

Some industrial-grade and virtually all professional-grade equipment
allows you to plug a professional microphone directly into the camera.
Professional microphones have an industry-standard 3-pin "XLR" type
plug that snaps in place. This is called a "balanced" connection and
allows cable runs of several hundred feet without any significant loss
or interference.

If you are shooting for a living or serious hobby, bite the bullet and
buy a real microphone mixer. No, not one of those toys they sell in the
backs of the video magazines - you need a real honest-to-goodness
professional microphone mixer. They are not as expensive as you might
think and can serve several functions including line-to-mic level
matching (for your camcorder). Several companies make excellent mixers
these days, but the one you want is the Mackie MS-1202VLZ. This is a
truly professional piece of equipment that will last through many years
of abuse. Not only is it a high-quality microphone mixer, but you can
use it back in the edit suite to adjust audio levels, sweeten narration
tracks and blend music. Not bad for a list price of $429 (even cheaper
on the street).

If your camcorder contains a headphone jack, you should also invest in
a pair of headphones. These can be a simple lightweight model or a
professional model, just remember - you get what you pay for. It should
also have the same size headphone plug as your camera. There is nothing
worse than a missing adapter just before a shoot. The function of
headphones is simply to ensure your microphones are working properly
and the record level is set correctly (if you can adjust it). Some
camcorders feature a small speaker on the left side so you can listen
as you use the viewfinder. This is handy for making sure the mic works,
but it can't do much else. Headphones allow you to check for hum and
buzz in the microphone(s) and stop potential problems in their tracks.
You can also use them with your new microphone mixer!

MICROPHONE ADAPTER FOR SHOESTRING BUDGETS:

Here is how to build a simple, inexpensive adapter cable you can use to
plug one professional microphone into your 1/8" microphone jack.
Disclaimer: This is not the "right" way to attach a mic to your camera,
but it will work fine in most cases. You'll need three items: one (1)
three-conductor female "XLR" type connector (RS #274-011), 20' of
two-conductor shielded microphone cable, and one (1) 1/8" shielded
stereo mini-plug (RS #274-858).

Plug in your pencil soldering iron (not gun - too hot and clumsy) and
carefully strip back about 1" of cable jacketing for the XLR
connection. Pull the guts out of the female XLR and slide the shell
over the stripped end of the cable. Fold back the shield conductor(s)
and strip 1/4" of insulation from the two center conductors then solder
the light-colored wire to pin #2 of the XLR and the dark-colored wire
to pin #3. Twist the shield wires together to make one conductor and
solder it to pin #1 (make sure there are no loose wire "hairs" touching
any other connections). Now you can slide the shell back up onto the
connector and snug up the screws. Alternatively, you could buy a
pre-made XLR microphone cable and cut off the male plug (RS# 33-4002).

Now for the fun part. Disassemble the 1/8" plug and remove the spring
in the end (there won't be room for it and the cable too). Slide the
shell down the cable, carefully strip away 1/2" of the cable jacket and
fold back the shield wires. On the 1/8" plug, squeeze the tip and ring
solder tabs together and spread the cable clamp apart. Strip 1/8" of
insulation from the light colored conductor and all the insulation from
the dark colored conductor. Solder the light-colored conductor to the
tip and ring tabs, making sure solder flows across both connections and
the wire. Twist the stripped dark-colored wire together with the shield
wires and neatly solder them to the ground connector/cable clamp. This
can be tricky for two reasons: If you solder to the inside of the cable
clamp, there must be plenty of clearance between the shield wires and
the tip/ring connection. If you solder on the outside of the cable
clamp, you should flatten the wires as much as possible to allow
clearance for the connector sleeve. Trim any excess then gently squeeze
the cable clamp on the jacket, slide the sleeve up to the connector and
carefully thread the sleeve on the connector.

If all went well, you have an inexpensive solution to a widespread
problem. You can use your new adapter to connect any professional
microphone - handheld or wireless. Just remember that we have cheated
with this adapter. There is no provision for impedance matching or an
isolation transformer - all of which are included in the commercially
available adapters. You should also treat the adapter with care -
especially at the camera end. Don't leave the wire dangling where you
can trip on it. You don't want to repair the mic jack in your camera! I
have used this type of adapter for several years on a number of
different cameras - all with great success. Enjoy!


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Gary Hendricks
http://www.desktop-video-guide.com/index
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