What’s the difference in latency and why? Live streaming compared to a live TV broadcast

No matter how long I have been delivering live streams for or how familiar end clients are to live streaming events, I always get asked the same question quite frequently – what is the latency time and why?

Keeping that question in mind, all the live streams I have delivered over the years, the online audience does not have a reference point to the live event at the broadcast site so they have no idea how much latency they are experiencing so it’s never been an issue.

Live TV Broadcast Latency

Live TV content is captured and broadcast from the main station via the massive TV tower to thousands of viewers who watch that content at the same time.

Regardless of the type of antenna, a viewer has which may be a massive aerial or a wire coat hanger, every viewer will get the 6 o’clock news at, 6 o’clock.

That is the beauty of an analogue signal over RF (radio frequency), it’s easy to broadcast sound and vision covering vast areas. Live TV broadcasts do have a safety 7-second delay for technical issues and inappropriate content but every viewer receives the broadcast at the same time, regardless of reception quality.

TV Broadcast delay

Live Streaming Latency

With live streaming, it’s quite different with many factors contributing to the unintentional delay of the entire broadcast.

First, there is the upload at the broadcast venue, this is where the event is actually taking place. The quicker the upload, the quicker the transmission gets to the streaming servers.
I always test my upload connections with https://testmy.net/upload and https://fast.com/.

Next, the streaming servers will ingest the video stream and distribute the content to the stream page and hopefully, the servers are in the same country as the broadcast venue.

The final stage is the palms of the viewers and there are many factors on their side that affect the broadcast latency such as connection speed, congested networks, are they travelling on public transportation while watching on a mobile device skipping from tower to tower, browser version (very important as Internet Explorer is still being used), throttled corporate networks and VPN’s.

Live streaming latency

So when a live stream is due to kick off at 6 PM, all users will experience some level of latency compared to the live event at the broadcast site and for the reasons I’ve listed above, the latency time differences will be different for each viewer. All viewers will start to see the live stream between 6:00:05 to 6:00:45PM, generally.

None of this latency with live streaming has the “7-second” safety delay as there is in live TV.

Benefits of Live Streaming Latency

There is an upside with the latency associated with live streaming.

The longer the time the streaming servers take to ingest the live feed and capture all the data packets before releasing the content to the stream page, the lower the chance of the viewer experiencing buffering issues. Going live on YouTube now allows a broadcaster to choose a latency time to keep the buffering issue to a minimum for the viewer.

Live audience Q&A has to be text-based so by providing the means for the audience to submit a question to the presenters via text in real-time removes the “perceived latency” and makes the live event and online audience responses run in sync.