How much Internet bandwidth do I need for live broadcasting? At our company we go around and around on this subject. There is no absolute right answer, other than the more the merrier. So let me give you the tools you need to determine if a venue has “enough” Internet bandwidth for you to send a single live video stream out to a CDN. We will not discuss the CDN to end user network issues in this post.
There are two things that you need to keep in mind with live video. First is that unlike many Internet services, video uses different kinds of packets to transmit its data. Most internet traffic uses the TCP protocol which guarantees delivery of each packet of data. Video on the other hand uses the UDP protocol which is a streamlined packet type with one important distinction. Unlike TCP packets, UDP packets do not come with a delivery guarantee. They are not resent if they are lost or dropped in transmission. Therefore network congestion is one key to determining how much bandwidth you need upstream.Even a 1-2% packet loss will visibly affect a streaming video signal if that congestion is in the network between your broadcast venue and the CDN servers. A video signal that is contaminated with packet loss on the way up to the CDN will never get better when the CDN resends it to viewers.
The second issue is absolute capacity of the upstream Internet connection from the venue. Here is an example: We typically deliver live broadcasts encoded for 500Kbps (that’s kilobits per second) for the video and 128kbps for the audio channel for a total of 628kbps for our signal. That looks pretty good online. 50% of headroom upstream would mean almost a full megabit of upstream capacity. Our producers like even more than that since these numbers do not take into consideration the effects of packet loss as mentioned above or the effects of shared network bandwidth at a venue (like WiFi on the same network). Arguably if you have double the network capacity upstream from a live broadcast venue then you are likely pretty safe. In this case that would be roughly equal to a T1.
And oh, by the way, don’t take the venue tech’s word for it if this is your first time broadcasting from this venue. Test the Internet connection at the venue yourself well in advance of the live broadcast so you can inform your client.
MAY
About the Author:
George Hall Founder/President of VideoSSC. He has over 30 years’ experience as a high technology engineering executive. With significant experience in high performance computing, Military electronics, IP networks and Video Broadcasting. Board member Public Television. An author and frequent guest on technology programs and panels. He holds a BA in mathematics from Hillsdale College.