Bandwidth consumption and usage with Twilio Programmable Video

Twilio Programmable Video is based on participants who communicate tracks, where each track represents a video source (e.g. webcam, screen capture) or an audio source (e.g. microphone).

Tracks are encoded using variable bit rate codecs for all communication. This means that the quality of a track will be dynamically adjusted to adapt to changing network conditions, and therefore the bandwidth usage will vary throughout the duration of the call.

Use the following table as a guide for estimating the approximate data rates that each track requires for common use cases. Actual bandwidth consumed will vary based on network conditions.

Media Data transfer rate in Kilobits per second (Kbps)
HD Audio only (no video) 40 Kbps
Lo-res Video (240x180) + HD Audio 150 Kbps VP8/H.264 (240 Kbps Simulcast)
SD Video (640x480) + HD Audio 540 Kbps VP8/H.264 (865 Kbps Simulcast)
HD Video (1280x720) + HD Audio 1,500 Kbps VP8/H.264 (2,500 Kbps Simulcast)

Group Room Bandwidth Caps

Additionally, Twilio Programmable Video enforces the following caps on bandwidth:

  • When Small Group Rooms are used, the maximum subscriber video bandwidth (i.e. downlink bandwidth) of a participant is 4,000 Kbps.
  • When Group Rooms are used, the maximum subscribe video bandwidth (i.e. downlink bandwidth) of a participant is 8,000 Kbps.

Bandwidth Evaluation Tips

The following rules of thumb may be useful for evaluating participants' required network capabilities.

When P2P Rooms are used:

  • The upstream (publish) bandwidth will grow proportionally to the number of subscribers, as tracks are sent once per subscribed participants.
  • The downstream (subscribe) bandwidth will grow proportionally to the number of subscribed tracks.

When Small Group Rooms are used:

  • The upstream (publish) bandwidth will be independent of the number of participants, and will depend only on the number of published tracks.
  • The downstream (subscribe) bandwidth will grow proportionally to the number of subscribed tracks, up to 4,000 Kbps - the upper limit for Small Group Rooms.

When Group Rooms are used:

  • The upstream (publish) bandwidth will be independent on the number of participants, and will depend only on the number of published tracks.
  • The downstream (subscribe) bandwidth will grow proportionally to the number of subscribed tracks, up to 8,000 Kbps - the upper limit for Group Rooms.
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