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by sephamorr 2191 days ago
Why exactly do existing video streaming solutions use such small amounts of bandwidth and have terrible quality as a result? Does anyone have a deep dive into why this is the case? It seems that it would be a killer feature to make better utilization of bandwidth.

Even over wifi, speedtest shows 4ms/100mb/100mb on my internet connection, but Zoom, FaceTime, and others never use more than about 0.8Mbit/s for a video stream, and the resulting quality of audio and video is...understandably poor.

Latency too totally feels like a software problem, perhaps with too many layers of abstraction. (60fps->16ms for the camera, ~10ms for encoding with NVENC/equivalents, 35ms measured one-way latency from my laptop to my parents 4000km away, ~10ms decode, 16ms frame delay = 87ms one way). Maybe I'm asking for too much from non-realtime systems (I'm used to RTOS, extensive use of DMA, zero-copy network drivers, etc), but it seems that there is a lot of room to improve.

2 comments

It's worth mentioning that in our case, a significant chunk of the latency in our 130ms measurement is just the input lag of our display that we currently use. We were surprised by how slow they can be.
OnLive "solved" encoder latency 15 years ago. You dont wait 16ms for the next frame. Instead you progressively start encoding after receiving first tens of lines. This way your encoded video stream lags just couple of milliseconds behind, same for decoding. You could crudely emulate this by dividing screen into 4 rows and sending 4 concurrent video stream, instant 1/4 latency drop.
Sure, many of the operations in the list can be pipelined as you mention. Something like G-Sync would also allow you to sync the destination display to the arrival of the (start of) frame.