Film - A Practical Guide to Video and Audio Compression - page 58

an issue with this format, but slightly less so than for standard 8mm. This is somewhat
smaller than European TV picture sizes, though.
The camera gate is still larger than the projector gate, so there is some variability of
image size according to how you scan it in.

4.9 Audio Synchronization

Be aware that the audio track is running at the same speed as the film being transported
through the projector but is not placed adjacent to the frame to which it should be syn-
chronized. The 8mm home movie film format has a de-facto standard 56-frame offset. This
distance is different for all formats, and there is no guarantee that the films you are con-
verting have the same offset even though they are shot on the same size stock.
Digitizing the picture and sound separately is a good idea. Modern nonlinear edit-
ing systems allow the audio and video to be processed independently of each other and
then merged back together on the desktop. The timing of the audio may need to be
adjusted so it is the same as the video. The start and end of both media must coincide, and
any lip sync might need to be fixed. Resampling the audio within your editing system will
correct the sample rate, although you may want to perform that in an external audio-pro-
cessing application to achieve the best-possible quality.
If you are doing a lot of this work, investing in some good audio-processing tools
would be worthwhile. Final Cut Pro on the Macintosh is supplemented by adding a copy
of the Apple/E-Magic Logic application.
Apart from Logic, MacOS supports other tools such as Bias Deck, Peak or Cubase,
and Pro Tools. PC-based systems can deploy tools that work well with Avid editors or
Adobe Premier. Pro Tools is a good example. There are many other alternatives for
Windows users and far fewer for Linux.
Bear in mind that for some formats, the speed of the film through the projector will
seriously affect the available audio bandwidth. For 8mm movie film, the frequency range
is between 35 Hz and 9 KHz, which results in a lot of top-end loss, and audio resolution
is therefore somewhat limited. This plays into your hands, though, when compressing the
audio, as the reduced detail yields some slight bit-rate benefits.

Projector
gate

Sound
head

Figure 4-13 Audio track offset on film.