Bitrate is how many bits per second a compressed audio stream consumes, quoted in kbps, and it is the master dial trading quality against size and bandwidth. Rough landmarks: 128 kbps AAC stereo is good for video, 256 kbps is near-transparent, Opus voice runs 16-32 kbps, and 5.1 E-AC-3 sits around 384-768 kbps. The relationship to quality is codec-dependent and non-linear — a better codec sounds the same at a lower rate — and it interacts with sample rate and channel count. Choosing a bitrate is really choosing a point on each codec's quality curve for your audience's networks and devices, which is what adaptive streaming automates with a ladder of rates.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
Audio bitrate is a small share of a video stream, so teams either overspend on it or starve it until voices sound metallic. Volume 4 covers audio bitrate in detail within codecs: AAC, Opus and speech codec bitrates, channels and layouts, CBR versus VBR and quality targets for voice and music. Written by Nikolay Sapunov, CEO at Fora Soft.
Setting the right audio bitrate for your streams or calls?
Tell us your content and bandwidth limits, and we will set audio bitrates per codec and layout and check them on your material. 250+ video products shipped since 2005.
