Bitrate
/ˈbɪtreɪt/ · noun · compression
How much data per second a media file uses. Higher bitrate, higher quality, bigger file.
In more detail
Bitrate measures how many bits are used to represent each second of audio or video. It’s the main dial behind the quality-versus-size trade-off.
For still images the equivalent idea is the quality setting: more data preserves more detail at the cost of a larger file.
How bitrate affects a file
Bitrate is normally written as kilobits per second (kbps) for audio and megabits per second (Mbps) for video. A five-minute audio file at 320 kbps contains roughly twice as much encoded data as the same recording at 160 kbps, so its file size is also roughly twice as large.
A constant bitrate spends the same amount of data every second. A variable bitrate gives simple passages less data and complex passages more, which usually produces better overall quality at a similar final size. The codec, resolution, frame rate, and source quality still influence what a particular bitrate looks or sounds like.
Choosing a bitrate
Choose bitrate for the final use rather than selecting the highest number automatically. Speech can remain clear at a much lower audio bitrate than dense music. A small phone video needs less video data than a 4K recording with fast movement and fine texture.
Increasing bitrate cannot restore detail that was already removed from a low-quality source. Start from the best original available, test a short representative section, and compare the result on the device or platform where it will actually be used.
Key points
- Higher bitrate usually means a larger file and potentially better quality.
- Variable bitrate allocates data according to the complexity of the media.
- Codec, resolution, frame rate, and source quality determine how much bitrate is enough.