Video bandwidths and resolutions used by StarLeaf

1. Preferred StarLeaf bit rate

StarLeaf uses the following preferred bit rates:

• 2.5 Mbps for room systems
• 1.5 Mbps for software clients, WebRTC, and H.323 registered devices
• Variable for mobile clients depending on the CPU of the device (iPhone 7, for example, uses 570 kbps)

On a StarLeaf-to-StarLeaf call (either 1.5 Mbps or 2.5 Mbps) this allows:

• Audio: 64 kbps AAC-LD
• Video: 1280×720 pixels at 30 frames per second (720p)
• Content: 1920×1080 pixels at 12 frames per second

This is the highest quality media that StarLeaf endpoints use.

For single-screen systems, the content and video bandwidths are in the ratio 3:1 (75% content). For dual-screen systems, the content and video bandwidths are in the ratio 1:3 (25% content).

StarLeaf can respond dynamically to changes in bandwidth availability or requirement. For example, StarLeaf can temporarily reduce bandwidth and resolution of the video channel while content share is in progress.

For admins: From the StarLeaf Portal, you can set maximum send and receive rates at a site level. By default these are set to Automatic, meaning the maximum rate possible, but you can choose to specify a fixed value between 64 kbps and 2496 kbps instead if you need to. To adjust these rates, go to Portal > Sites > Edit sites.

2. Speed testing on boot-up

To ensure that you experience the best call quality possible, all StarLeaf endpoints perform an upload/download speed test when they boot up. This is to assess the quality of their network connection to the StarLeaf service. The results of this test are used to set the transmit and receive bit rates that the endpoint uses for all the calls it subsequently makes, until the next time it is rebooted. If you need to manually select a bit rate to be used for a call, contact your administrator.

• If the speed test (for a room system) shows that more than 2.5 Mbps of bandwidth is available on the network, the StarLeaf endpoint uses a bit rate of 2.5 Mbps on all its calls, subject to the highest speed that remote endpoint is capable of.
• If the speed test shows that less than 2.5 Mbps of bandwidth is available on the network, the StarLeaf endpoint reduces the bit rate and quality of the video it transmits or receives as follows:
  • if less than 128 kbps is available, calls are audio only
  • if greater than or equal to 128 kbps is available, calls use low bit-rate audio, and there is video unless content is shared, in which case the call is audio and content
  • if greater than or equal to 192 kbps is available, calls use high-definition audio and there is video unless content is shared, in which case the call is high-definition audio and content
  • if greater than or equal to 256kbps is available, calls use high-definition audio and there is video and screen sharing allowed
• Upstream and downstream bandwidths are tested and set independently of each other, meaning that a low upload speed, on an ADSL connection for example, does not have a negative impact on the quality of a video that an endpoint can receive.

3. In-call media statistics

To see the media statistics of an in-progress call, press the Home button twice on a StarLeaf endpoint:

If the quality of the video you are experiencing on a StarLeaf call does not meet your expectations, look at the media statistics to see if the call bit rate is low, or if packet loss is present.

• If the bit rate is significantly lower than that which you know your Internet connection to be capable of, it could be that a lot of network bandwidth was in use by other applications when your StarLeaf endpoint performed its speed test. In this case, restart your StarLeaf endpoint to make it repeat the speed test with a result that is not impacted by other users. If restarting the endpoint has no effect, and you are not using StarLeaf app, contact your StarLeaf reseller for assistance. If you are using StarLeaf app, refer to section 4 below.
• If a lot of packet loss is present, refer to Identifying causes of packet loss in StarLeaf calls or contact your network administrator or StarLeaf reseller for assistance

4. StarLeaf app: Platforms with limited processor power

Unlike the hardware-based range of StarLeaf endpoints, the StarLeaf app is designed to install and run on platforms with a widely varying range of capabilities. It is able to reduce the bit rate and resolution of its video channel in line with the capabilities of the host CPU. On a modern full-spec PC or laptop, StarLeaf’s capabilities match those described in section 1 of this article. On lower-powered systems, for example mobile devices, lower bit rates and resolutions are selected in order not to over-power the processor.