Time lapse on Sky

[Prudie]

Anyone like to suggest why watching the GP on Skygo on a laptop is 30 seconds behind watching it on TV (BBC today) and BBCiplayer about 6 seconds behind?

[ChuckFickens]

Because it takes time for them to encode the video into a format suitable for streaming over the internet.

[Prudie]

OK thanks chuck, 30 seconds still seems quite long.

[ChuckFickens]

Seems about right to me.

I used to be responsible for live internet streaming of some motor sport events and the stream ran about 20-30 seconds behind the live action using adobes flash media server (which is one of the industry standards), although that did include the delay from a satellite up/down link too (but that is only a couple of seconds max)

[Prudie]

So, without getting too complicated, the method used to transmit to a satellite is different (and quicker) to that used to send via internet?

[ChuckFickens]

It's not the transmission of the signal that's causing the delay, it's the system used to take that signal and turn it into a suitable format for transmission across the internet that takes the time.

The signal would, in theory, only take about 0.3seconds to get to the satellite and back to earth (in practice it takes a little longer) which is a trip of 477800 miles. the time for it to get to you across the internet would be in milliseconds, for both parts of the journey the signal is going at the speed of light.

[chakka35]

These delays are often a nuisance. I used to watch the last night of the proms on TV while listening to the music on Radio 3 on my hi-fi. Then suddenly one year the two were out of sync, due to the fact (the BBC told me) that the sound went to BH by landline with no delay whereas the picture went via satellite with the unavoidable delay involved.
The same happens when I try to watch a footballl match on TV while listening to the Radio Five Live commentary on radio. I always hear about an incident seconds before I see it on the screen.

[heathfield]

The BBC has always had this sort of problem with the time pips broadcast on radio, more especially on DAB.