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Mike_Simon5-Regular Member
5-Regular Member
February 12, 2020
Question

Vuforia Chalk video quality and network connectivity

  • February 12, 2020
  • 1 reply
  • 1744 views

Hi, I am looking for an answer on two questions that relate to Chalk video performance and network connectivity:

 

  1. When two users communicate with Chalk, is the video transmitted directly from user device to user device, or rather is an intermediate PTC Chalk server used between the users?
  2. The Vuforia Chalk Best Practices topic in the Help recommends "high bandwidth connections" for best performance which is neither specific nor objective.  Assuming iPhone 8 devices for each user, what is the maximum video size (e.g. 4k, 1080p) and frame rate (e.g. 24, 30, 60 fps) that Chalk will transmit video, and also what is the minimum?  What network bandwidth is recommended to obtain high quality video at the maximum video size and frame rate?

Thank you,

Mike

1 reply

R
rhawa12-Amethyst
12-Amethyst
March 19, 2020

Thanks, Mike, for those great questions.

 

Regarding the first topic:

Correct, though the initial connection is done via the server, all video, audio and images are delivered using a peer-to-peer delivery model (no intermediary server for transmission).

 

Regarding your second topic:

Our video streams are adaptive where we will adapt video resolution and frame rate to maintain a real-time view of the local user’s camera feed.

Examples: 

  • With an up-link bandwidth of 2.8 Mbps, the video resolution will be 1.280 x 720 p and the frame rate (target) will be 31 FPS
  • With an up-link bandwidth of 1.0 Mbps, the video resolution will be 640 x 360 p and the frame rate (target) will be 31 FPS
  • With an up-link bandwidth of 0.5 Mbps, the video resolution will be 320 x 180 p and the frame rate (target) will be 30 FPS (with an ~1 sec lag)

Below 500 Kbps (when the Remote Expert experiences choppy video where details cannot be made out) – we encourage the Remote Expert to enable our “low bandwidth mode”.

Then Vuforia Chalk will switch from video stream to an image stream delivered over HTTPS. There will be a trade-off between real-time and quality. So the low bandwidth mode ensures a usable and clear image and still allows annotations.

 

So the recommendation would be to have a bandwidth higher than 500 Kbps, but Vuforia Chalk is still able to support situation with low bandwidth connections. Exactly this is one of the unique strengths of Vuforia Chalk.

 

Best regards

 

Rayed

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