Glossary
What is bitrate?
MarkdownWhat bitrate is
File size is roughly bitrate multiplied by duration. A 128 kbps audio file uses about 1 MB per minute. Video bitrates are far higher and depend on resolution, frame rate and the codec.
Why it matters on a Mac
It is the setting that decides how big an exported or compressed file ends up. Newer codecs such as HEVC reach the same quality at a lower bitrate than H.264.
How to check it on macOS
In QuickTime Player, choose Window > Show Movie Inspector to see the data rate. Media Info in Toolbox shows the overall bitrate and the bitrate of each track.
How Toolbox handles it
Extract Audio and Convert Audio let you pick 128 to 320 kbps for MP3 or M4A. Compress Video uses quality levels (High, Balanced, Small) rather than a bitrate number.
Frequently asked questions
Does a higher bitrate always look better?
Only up to a point. Past that point the file grows with little visible gain.
What bitrate should MP3 be?
128 kbps is fine for speech. 192 to 320 kbps is common for music.
What is constant versus variable bitrate?
Constant bitrate uses the same data every second. Variable bitrate spends more on complex moments and less on simple ones.
