Audio 2 (Back to the Basics series)
Just as a computer thinks of video as a set of images, it thinks as
audio as a whole lot of "snapshots" of this sound wave - tens of
thousands of snapshots every second. Each of those tiny little
snapshots reflects the energy of the sound wave at that point. Now,
the human ear is capable of hearing frequencies that repeat up to about
20,000 times per second (20,000 Hertz). Because of some fancy math, we have a rule of thumb: if the computer taps in to the sound wave twice as many times
as the highest frequency we want to represent, it will describe the
sound fully for us. That's where the most common full-quality sample
rates - 44,100Hz and 48,000Hz - come from.
Like I said, each sample makes a note of how intense the
sound is at that point (its amplitude). It measures that intensity as
a number. Recall that computers store numbers using bits: do 8-bit, 12-bit, 16-bit, and 24-bit audio sound familiar? An 8-bit number can have values from 0 to 255 - while a 16-bit number can have values from 0 to 16535, and a 24-bit number can go up to millions of values. The difference between different bit levels of audio
is simply that a sound that records each snapshot with more bits is able
to capture much, much more precise nuances in individual sound
samples. That means that it's much better at describing both changes in loudness and the frequencies involved with the sound waves.
To elaborate the differences, here is A Chart:
To elaborate the differences, here is A Chart:| Bits | Meaning | |
|---|---|---|
| 8-bit | Sounds like an ancient Nintendo | |
| 12-bit | Some poorer consumer-grade cameras like to capture 12-bit audio. It sounds worse than 16-bit, Final Cut really hates it, and there's no good reason to use it. Don't. | |
| 16-bit | The normal standard for our kind of video editing. Sounds great, well-supported. | |
| 24-bit | Industrial-strength sampling for audiophiles and folks doing serious audio compositing. Although your ear probably can't hear the improvement over 16-bit audio, it allows audio editors much more flexibility as they edit. Think of it being like when you drag a giant 10-megapixel picture into Final Cut, and you can zoom/twist/whatever without the picture getting pixelated. |
Whew - next time, normalizing your audio
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