Hi, Kate,
Slow motion is a function of frames per second. In other words, you play
back at a slower frame rate than recorded. So, if you shoot a 60fps video and
play it back at 30fps, you get slow motion. With audio, sample rate would be
the equivalent of frame rate. Audio that is embedded in a video will play
slower or faster as you decrease or increase the frame rate of the video. The
audio will adjust to match it. An independent audio track can be adjusted
separately from the frame rate of the video. In the latter case, you could slo
mo the video without the audio playback rate being affected. Conversely, you
could slo mo the audio without affecting the speed of the video.
Bitrate is the amount of data per unit of time, kilobytes per second, I
think. Bitrate refers to factors like resolution and compression, and the codec
and settings that you use. Decreasing resolution and compression will not
create slow motion. Increasing the frame rate increases bitrate because of the
additional data required to store additional frames. However, it is not related
to the level of compression.
In iMovie you can edit an audio-only project. You can use the speed
adjustment feature to adjust the speed of the audio. When you select the audio
clip, you will see a speed adjustment handle in the upper right of the clip.
Slide that back and forth to adjust the speed.
-- Rich
