On 20/03/2020 8:34 am, Tom Worthington wrote: > There is likely to be a high demand for Internet access over the next few > months due > to COVID19. So I suggest that video products be set to limit bandwidth use by > default. Video streaming and conference tools adjust to the bandwidth > available, but > try to use *all* that bandwidth. This makes them poor online citizens, like > someone > who fills their shopping trolley with toilet paper, if you let them. ;-)
With much respect, I'll take the contrarian view then. Actually, videoconferencing systems (unlike one-way streaming media like youtube) don't adjust to use all the bandwidth, and I'm not convinced its a problem these days except for people forced to use older, slow links. In a zoom call with ~10 endpoints, I see sustained downstream bandwidth use under 2 Mbps, only a few percent of the available link capacity. Auto-adjusting-quality video streams generally requires the video be pre-recorded and stored with several different different quality/bandwidth encoding versions of the whole video file stored in parallel, and the viewing client then selecting the appropriate file according to its measurement of congestion at the time. That isn't what is done with live video, as it isn't feasible to trans-code a stream after it has been transmitted due to the inherent delays and perception of lag that would introduce. Given the asymmetric nature of our broadband networks (and NBN incredibly wanting to make its products *more* asymmetric rather than less), its generally the upstream direction where congestion is apparent - and the user on the end of one of those links can turn off their own video to free up capacity for the audio quality to improve. I generally see this when a user is trying to use a cellular mobile connection - but even then, in many cases the quality is good. Rarely is there a constraint in the downstream direction, which is where making a blanket change for all VC endpoints might improve. > There were only a few brief dropouts in the audio (fewer than on ABC Radio > National > that morning). This was with Zoom, which is not my favorite product, as there > is no > way for participants to set the audio or video quality to reduce bandwidth. > But it > is possible to reduce data use to around 220 to 300 kbps by making the video > window > smaller. I find Zoom works very well, and supports better quality and more users for a given level of bandwidth than most, but horses-for-courses. 220, 300, or even 500 kbps on the network downstream, or even upstream, is not much these days, and not worth optimising further. Several Mbps perhaps, 500 kbps no. If links cannot support 500 kbps in either direction, then videoconferencing is not appropriate, and the user should dial-in instead. (controversial point for discussion ahead) concerns about a few hundred kilobits being meaningful represents 1990s thinking, not current network capabiities. If the access networks this decade cannot support, then the networks need to be improved, not pandering to last century expectations retained. It works fine on access links with only a couple of Mbps in each direction, which is not an unreasonable expectation for the 2020s. > It would be good if the video products, such as Zoom, used a low bandwidth > mode with > a small video window, by default. With live video such as videoconferencing, bandwidth reduction is done by reducing frame-rate rather than resolution or window size. Zoom does have controls to reduce bandwidth (high-def can be turned off), and to reduce frame-rate, at least for desktop-sharing presentations - again, to control for restricted upstream capacity of the person doing the presenting. In my experience, I often find the biggest constraint is not the network, but the limited processing power of older devices, with sluggish videoconference performance due to CPU is maxed out decoding and displaying the video without adequate GPU assistance. We may get better improvements by upgrading people's equipment, instead of their network connection. > > More at: > https://blog.tomw.net.au/2020/03/video-conference-on-covid-19-and.html > > Paul. _______________________________________________ Link mailing list [email protected] http://mailman.anu.edu.au/mailman/listinfo/link
