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A Pentium II could barely process DVD-resolution MPEG-2 in realtime.

According to http://www.vogons.org/viewtopic.php?p=423016#p423016 a 350MHz PII would've been enough for DVD, and that's 720x480@30fps; videoconferencing would more commonly use 320x240 or 352x288 which has 1/4 the pixels, and H261 or H263 instead as the codec.

Being able to Zoom call and see up to 16 live video feeds simultaneously is an amazing advance in technology.

I'm not familiar with Zoom as I don't use it, but it's very likely you're not actually receiving and decoding 16 separate video streams; instead a MCU or "mux box" is used to combine the streams from all the other participants into one stream, and they do it with dedicated hardware.

That said, video is one of the cases where increased computing power has actually yielded proportional returns.

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> videoconferencing would more commonly use 320x240 or 352x288 which has 1/4 the pixels, and H261 or H263 instead as the codec.

Modern videoconferencing solutions (WebRTC) usually use 1280x720 and either H264 or VP8. Some apparently use HEVC. Also most modern processors and SoCs come with hardware-accelerated codecs built in, so most of the work related to compression isn't even done by the CPU itself.

> I'm not familiar with Zoom as I don't use it, but it's very likely you're not actually receiving and decoding 16 separate video streams

Yes you are receiving separate streams.

Don’t think it can be an MCU box. You can select an individual stream from the grid to make it larger almost instantly. The individual feeds can display both as grid and a horizontal row. I’m assuming they send individual feeds and the client can ask for feeds at different predefined resolutions.

Without having used Zoom much I can't definitively say how it works, but I've used BlueJeans quite a bit and noticed compression artifacts in various parts of the UI (e.g. text underneath each video source). That means BlueJeans is definitely muxing video sources and it really does not have a noticeable delay when changing the view. Since each video is already so compressed I think they can get away with sending you really low bitrate streams during the transition and you'll barely notice.

Mixed plus whichever feed you request to enlarge sounds more reasonable.

With Skype you're definitely able to receive separate streams from each participant, as I can access them individually via NDI and pipe them into OBS to do live multi-party interviews. You can see the resolution of individual feeds change when their bandwidth drops, and you can choose high/low bandwidth and latency modes for each feed. I would guess Zoom does the same but doesn't provide an NDI feed (yet).

I have an iMac G4 from 2003 (the sunflower things) on which I installed Debian PPC and it is able to stream 720p content from my local network and play it back smoothly on VLC

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