Live streaming video latency

Question

Trying to determine what's "most" responsible for latency - the round trip my video makes from my encoder, to my server, and back down to the player in my browser.

I'm at about 12 seconds right now with a player I like. Is it buffering in my player? Buffering on the way out by FMLE?

The reason I ask is I feel I've eliminated other culprits with my little test scenario outlined below. And also, all else equal, swapping other players in produces the greatest variance in the latency. One takes it down to 4 seconds. Can't get any lower than that though.

Eliminating other culprits:

-Bad network? Nope, running it all locally. -The codec?, Nope, setting FMLE to VP6 or H.264 produces same latency. -Pushing too much data out of FMLE? Nope, 50kbs or 1000kbs produces 12 seconds -Framerate settings to intense? Nope, 5-29.97 fps changes effects motion quality but delay stays around 12 seconds.

I'm developing a small FMS based web presentation package so the latency will have to be down to a second at most. I've seen a similar package with almost no latency. Here's my test set up:

-Camera connected to Windows XP machine -Flash Media Live Encoder 3.0.1 -FLash Media Server 3.51 -Video Player - Sample dynamic streaming player in Adobe Flash Media Server productivity tools (kind of like a reference implementation for Adobe's ActionScript 3.0 Dynamic Streaming Class)

If I bounce my video off a server about 30 miles from me the result is nearly identical.

I ran a test with a CDN and a player they provided and the best I could do was 4 seconds.

Does anybody have a really fast player I can test?

Answer 1

Hi Robert,

I hope you'll pardon the product plug below. There are variable in JW Player which can be tuned to decrease latency (at the cost of increasing susceptibility to jerky video when the network hiccups). We have a post on our user forums which details the steps you can take when trying to decrease the latency experienced in streaming flash video. Check it out at: http://wowzamedia.com/forums/showthread.php?t=6136

One of our users has also kindly posted their own test results where they achieved some really low latencies (Stackoverflow won't let me post one more URL today- view post#6 in thread#15210 from user=bubbles01 ).

You can also grab a free copy of our product from our website (it is limited to 10 simultaneous video streams).

Hope this helps and good luck with your experiments.

Yours,

John [at] WowzaMedia {dotcom}

Answer 2

Take a look at NetStream.setBufferTime() and ns.bufferTime in the FMS documentation. Also like Robert mentioned the player has its buffer too.