What is a video bitrate ?

About

A video bitrate is the number of bit per unit of time that a video sends to the display buffer (and sound).

It's given in:

  • bps - bits per second
  • kbps - kilobps
  • mbps - megabps

It may be parameter that you give to your video editing software as a target to determine the file size.

The lower the bitrate is:

  • the more the software has to compress the video
  • which leads to loss of information
  • which makes the video quality worse.

Formula

<MATH> Bitrate = \frac{fileSize}{Duration} </MATH>

Example: if the video file output of 200 MiB is desired for a movie of 10 minutes (600 seconds) long

The image bitrate is: <MATH> \frac{(200 * 8192 )}{600} =~ 2730 \text{ kBit/s total bitrate} </MATH> The video bitrate is (with a 128kb/s desired audio bitrate) <MATH> 2730 - 128 = 2602 \text{ kBit/s video bitrate } </MATH>

Streaming

The max bitrate you can set it to when streaming is limited by:

  • your internet connection upload speed (If your upload speed is 12 mbps (megabits per second) then your max bitrate limited by your internet is 12,000
  • the minimum and maximum of your streaming website
Facebook Live a max bitrate of 4,000 Kbps, plus a max audio bitrate of 128 Kbps
YouTube Live a range between 1,500 and 4,000 Kbps for video, plus 128 Kbps for audio.
Twitch a range between 2,500 and 4,000 Kbps for video, plus up to 160 Kbps for audio.

Recording video locally, no limited to the bitrate

Note that because youtube is going to compress it anyway, there's no point in waiting for the big video file to upload.


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