I am curious too, how upstream and down stream data bandwidth changes depending on which factors.
This is my understanding based on tests when you have:
Jitsi upload and download varies based on your video quality setting and the size of the window/tile that you are viewing which itself is dependent on your screen resolution and/or the number of participants.
For each video quality being viewed by a meeting participant, the person they are viewing is sending a data stream of that resolution. For example, if your video quality is set to HD, and one person is watching in HD then you send one HD video stream, if someone is watching in SD, then you send in SD, and if someone is watching in LD then you send an LD video stream. If three people are watching you in each of these resolutions (HD, SD, & LD), then you would be sending three video streams, one of each of these resolutions.
However for the viewer, they will only receive data streams that can be displayed in their window/tile.
- That is if they are viewing in Presentation mode (one large window and the other in small tiles, then they would could be receiving one HD stream and the rest in LD.
- For Tile view, it will depend on their screen resolution how many HD tiles they can display on their screen at one time. If they don’t have enough screen space for the tiles to be in HD, then SD could be used, and as the number of meeting participants increase, all tiles become smaller in size, they will be displayed as LD video streams as the viewer’s Jitsi web browser only needs to receive LD streams.
But does this mean that if you are viewing 20 people in Tile view, your download bandwidth is 20 times a single LD bandwidth?. If a single LD video is 230Kbps, then 20x230Kbps is 4.4Mbps. I do not have more than 20 instances to test with, so I don’t know what happens to the Tile view when, say 50 people are in the meeting.
In Tile view, 4K screens should be able display more HD video streams (720p) than a 1K HD screen could, or that of a 1366x768 resolution screen.
I hope someone with more experience/understanding of Jitsi, might comment further.