What is the minimum bandwidth requirement to use OpenTok?

Video quality dynamically adjusts based on the strength of a user's network connectivity. This is done by the Subscriber sending feedback packets to the publisher that say "My network quality is at 'x' level. Please adjust your published video bit-rate to accommodate my current bandwidth". The faster and more stable a Subscriber's broadband connection is, the better the video quality it will request.

This mechanism works well until a certain point. If a Subscriber's bandwidth drops below a certain threshold, or if a Publisher has very little bandwidth to upload video, behavior can be unpredictable. Video may be choppy, audio may have artifacts, and the connection could be dropped.

We recommend a minimum dedicated 350kb/s down per downloaded stream, as well as 350kb/s up per uploaded stream to maintain a stable video connection.

 

For various resolutions and quality combinations, the bandwidth requirements are outlined below.

  • Excellent - None or imperceptible impairments in media
  • Acceptable - Some impairments in media, leading to some momentary disruptions

Audio + Video Streams

For the given qualities and resolutions, all the following conditions must met.

Quality Video Resolution @ FPS Video kbps Packet Loss
Excellent 1280x720 @ 30 > 1000 < 0.5%
Excellent 640x480 @ 30 > 600 < 0.5%
Excellent 352x288 @ 30 > 300 < 0.5%
Excellent 320x240 @ 30 >300 < 0.5%
Acceptable 1280x720 @ 30 > 350 < 3%
Acceptable 640x480 @ 30 > 250 < 3%
Acceptable 352x288 @ 30 > 150 < 3%
Acceptable 320x240 @ 30 > 150 < 3% 


Note that the default publish settings for video are 640x480 pixels @ 30 fps in OpenTok.js and the OpenTok iOS SDK. The default is 352x288 @ 30 fps in the OpenTok Android SDK.

Audio-only Streams

For the given qualities, the following conditions must met.

Quality Audio kbps Packet Loss
Excellent > 30 < 0.5%
Acceptable > 25 < 5%
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