Quality of Service and You: Chasing the 1080p Unicorn
(Here at Twitch we’re all about trying to educate you beautiful people as much as we can. An educated viewership is an empowered viewership, and we could most certainly use your help when it comes to fighting key quality of service battles. A lot of times when viewers experience lag on Twitch, the problem doesn’t actually exist on our end, but somewhere in between. Here to explain some of the problems that can create lag, and what you can do about it, is our Manager of Customer Support, Jason Maestros. — Jared)
There are two major issues to consider when attempting to watch 1080p or any high bitrate video: your computer’s configuration and available processing resources and your Internet connection.
Inspecting your computer
Believe it or not, watching live, streaming HD video is actually quite straining on your PC, even modern ones at that. We assume you know your computer pretty well, but keep these factors in mind:
How many programs are active and fighting for resources?
Do you have trouble playing Flash videos?
Do you have enough [good] RAM?
The Internet: How does your ISP serve your Twitch requests?
Here’s a simple look at how a Twitch video request works for viewers. When you visit a Twitch channel, your player sends a request for the video through the Internet to one of Twitch’s servers. Upon successful connection, that Twitch server starts to send video back through your ISP to your player. So why can this lead to issues?
First, the path from your ISP to Twitch is mostly likely not direct (only ISPs who connect directly to Twitch have this luxury). When connecting to Twitch servers, ISPs commonly send data through many hops before hitting our server clusters. A 1080p video stream has a high bitrate, as may a 720p stream since not all broadcasters use the same bitrate. A high bitrate means more data, which means a greater chance the routes provided by your ISP between Twitch and your home are unable to sustain the necessary speed to carry all data in sequence without delay.
We know our users are top end Internet consumers who try to buy the best advertised connections available. Unfortunately, many ISPs are still working to deliver consistent, high-bitrate video streams. Netflix has monitored the average sustainable bandwidth they can sustain to users during video playback and has published an ISP Speed Index. When reviewing the NetFlix report, note that almost all ISPs are below 2.35 Mbps. Thus, if a broadcaster is pushing a 1080p stream with a bitrate above 2350 bits per second, most viewers may have trouble watching that stream quality.
TLDR; If the broadcaster you’re watching sends out a bitrate that is too high for the lowest point in your ISPs path to Twitch (1080p or not), you will see lag.
FYI: The main reason we offer lower resolutions in our Partner program is to make sure viewers can find a display resolution that works for them.
What you can do
Call your ISP. Call your ISP. Work with them to understand the route they are providing to our site. If they’ll do a traceroute, have them try live.twitch.tv and explain the results such as the number of hops and the response time — more than 100 ms is a big concern for live video. Explain to them why you purchased the high bandwidth package that you did: to play games and watch/stream videos over the Internet. Ask them to connect directly with Twitch.
One truth and one myth
Truth: Live video data is the most resource intensive data that is served across the Internet. Unlike on-demand videos (VODs), live video must have a VERY short buffer in order to provide the most real-time feel for both viewing and chatting.
Myth: “My speedtest results lead me to believe I should be able to do anything across the Internet.” A speedtest is a very basic test to prove that your ISP provides what they sold you. However, the results are not what you are guaranteed for all forms of data from all sites at all times of day. In many cases, the speedtest results are preconfigured. That is, your ISP provides an optimized, preset route to the speedtest endpoint to maximize results.