3 ms·

> 64 packets transmitted, 64 received, 0% packet loss, time 156ms rtt min/avg/max/mdev = 2.293/6.699/63.116/7.364 ms So if a video frame consists of 64 packets

by NavinF 4y ago

> 64 packets transmitted, 64 received, 0% packet loss, time 156ms rtt min/avg/max/mdev = 2.293/6.699/63.116/7.364 ms So if a video frame consists of 64 packets, the whole frame will be delayed by 63.1ms. Yes there are ways around this (FEC), but getting 1ms 99%ile latency over wifi IRL is nontrivial. Btw fat-client PCs have much smaller latency spikes, but even those spikes are noticable and make games feel jittery. That's why we compare GPUs based on "1% lows" instead of average FPS. Also see frame pacing.

deleted 4y ago
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Dylan16807 4y ago
> Yes there are ways around this (FEC), but getting 1ms 99%ile latency over wifi IRL is nontrivial. Streaming video is extremely nontrivial to start with. Use FEC when necessary. Also I just threw a thousand 1400B packets over my wifi and 99% was something like 5ms, max 10ms. 5ms is close enough for me, and I could probably hit 2ms with light effort.
- NavinF 4y ago
  Naw, streaming video is trivial if you have a 1 second latency budget so you can use LL-DASH and CMAF. We hit that target with <100 hours of dev work on a co-watching/cloud-streaming project with only 2 PoPs in the US. WebRTC FEC is a relatively modern and wasn't on the table in 2020. Btw you almost certainly tested on an unloaded connection so you're not seeing any HOL blocking like a real video stream would. Try playing a 20mbps YouTube video in the background while you ping. Oh and turn on a microwave oven when you're 3 walls (a room and a hallway) away from the AP for extra hilarity on the order of 80ms
  - Dylan16807 4y ago
    I meant game control video. You don't get a second of buffer for the player. And you don't need to use webrtc, or you can add your own FEC on top for your client software. And yes a 4k YouTube video makes it worse but "don't do that" is a valid response and realtime video won't be so bursty. I can get a very nice ping while more stable bandwidth hogs are running. Microwave is also "don't do that".
  - vel0city 4y ago
    A ping result from my WiFi 6 laptop while watching YouTube on the laptop playing through Bluetooth headphones, messing around in an RDP session, a few SSH consoles actively refreshing, chatting on Teams, music streaming over WiFi on the audio receiver, while cooking lunch in my microwave: Ping statistics for router.home.lan: Packets: Sent = 793, Received = 793, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 5ms, Average = 1ms

by NavinF 4y ago

deleted 4y ago

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Dylan16807 4y ago

> Yes there are ways around this (FEC), but getting 1ms 99%ile latency over wifi IRL is nontrivial. Streaming video is extremely nontrivial to start with. Use FEC when necessary. Also I just threw a thousand 1400B packets over my wifi and 99% was something like 5ms, max 10ms. 5ms is close enough for me, and I could probably hit 2ms with light effort.

NavinF 4y ago
Naw, streaming video is trivial if you have a 1 second latency budget so you can use LL-DASH and CMAF. We hit that target with <100 hours of dev work on a co-watching/cloud-streaming project with only 2 PoPs in the US. WebRTC FEC is a relatively modern and wasn't on the table in 2020. Btw you almost certainly tested on an unloaded connection so you're not seeing any HOL blocking like a real video stream would. Try playing a 20mbps YouTube video in the background while you ping. Oh and turn on a microwave oven when you're 3 walls (a room and a hallway) away from the AP for extra hilarity on the order of 80ms
- Dylan16807 4y ago
  I meant game control video. You don't get a second of buffer for the player. And you don't need to use webrtc, or you can add your own FEC on top for your client software. And yes a 4k YouTube video makes it worse but "don't do that" is a valid response and realtime video won't be so bursty. I can get a very nice ping while more stable bandwidth hogs are running. Microwave is also "don't do that".
- vel0city 4y ago
  A ping result from my WiFi 6 laptop while watching YouTube on the laptop playing through Bluetooth headphones, messing around in an RDP session, a few SSH consoles actively refreshing, chatting on Teams, music streaming over WiFi on the audio receiver, while cooking lunch in my microwave: Ping statistics for router.home.lan: Packets: Sent = 793, Received = 793, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 5ms, Average = 1ms