Video Streaming Problems - Computerphile

Why does my neighbour hear the score in the big game before I do? Dr Steve Bagley looks at why video streams suffer delays.

This video was filmed and edited by Sean Riley.

[DavidChipman]

Please do a video on how multicast works in more detail!

[antivanti]

Back in the analog days because of the relationship between the speed of light versus the speed of sound and the fact that you sit closer to the TV than the audience does to the tennis court you probably heard McEnroe's yelling at home before the people that were actually there did.

[jmalmsten]

"I felt a great disturbance among lovers of celluloid film, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened."

04:08

[Nadia]

During this World Cup it happened a lot. Aerial SD was first, then aerial HD, then cable and last HD satellite. The delay could be from one second to five, so your low budget neighbor would spoil all the goals to the entire neighborhood.

[keineangabeyt]

I just had to explain someone, that Google is not the internet, this video just saved me from insanity
!!!!

[Pan.Puszek]

I love Dr Bagley and Dr Pond videos. I could watch them all the time.

[DirtyPoul]

I was wondering about this a few weeks ago when I watched the World Cup on my TV and computer simultaneously and saw the almost 2 minute delay. I had previously noticed that there was a delay, but never 2 min! Thanks for the video.

[gregf]

First rate! Next, do multiplexing and start from how stereo FM works then expand on that to explain how multiplexing in digital transmission lines work.

[kamil]

There is only single stream that needs live broadcasting: sports matches. Because your neighbour will yell GOAL before you will see goal on the screen - and this is big deal for sport fans. For everything else latency does not matter. That being said it is still interesting problem to solve.

[DarthMeeka]

FYI @Wimbledon for your example, the pictures (once recieved in the Broadcast trucks/media centre) are converted to an IP format (ST2110) before getting to the vision mixers. The whole video plant at Wimbledon is using 2110 so 1080i video (all except Centre Court which is 4k) is at about 1.1Gbps as 2110 leaves just the video and other meets days is carried in a separate flow

[RobertDelGreco]

I work on the service side of publishing a video site. Most common chunk sizes I've seen are 5 to 10 seconds, and our advice to people writing clients is to start three chunked video files off live. That would also add into a significant amount into that backset.

[notpublic]

I really love all your videos, Thanks for all the excellent knowledge, cheers.

[zubmit]

That ending need it's own video.
Thanks for making these videos!

[Lysergesaure]

Multicast is a can of worms, I doubt it'll ever be used any time soon. Just look at how IPv6 is still barely deployed.

[usbpc]

I have to say the explanation of streaming and what introduces delay was very good, but I dislike that the example with the BBC iPlayer you used indicated that every stream on the Internet has a massive delay of around 90 seconds.
That is very clearly not the case when looking at livestreams on sites like youtube, twitch or mixer. All those have a massivly lower delay on a decent internet connection unless they are set up to have more delay. Mixer even has a protocol they call FTL that allows for delay of less than a second if you have a good internet connection.

Hope I could clear things up for some people, as that was really the only part in this Video that was not great, but a bit misleading.

[AdamWelchUK]

Years ago my ISP did a trial with the BBC to multicast their transmissions. Funny that we’re looking at that again.

[ZachariasEinstand]

Live broadcast is a serious topic on its own, that seems to be obsolete if not hardly ever holdable and not much notecable any more. Deligthful video about a for me personelly completely underestimated topic.

[Jegorex]

Twitch can get below 2 seconds delay between the streamer and the viewer. I guess they have really small blocks and no buffering?

[VRJosh]

Hey Computerphile, great video! Could you do a follow up on streaming via platforms such as Twitch? They allow individuals to stream from their home computer with a delay to the viewer of only a couple seconds. It would be interesting to hear discussion on why there's so little delay on a user-generated platform vs big broadcasters. I would assume its partially because the user isn't starting with a broadcast camera outputting 1Gbit/sec of data.

[stuartmcconnachie]

Multicast doesn’t allow rewind, you’d need a separate stream for that.. But presumably DASH is better for that so long as your ISP has buffered the http file locally?