How Much Bandwidth Do I Need for a Live Streaming Video?

By Dan Eash

Live streaming video is the Internet equivalent of live TV broadcasting. It gives everyone the power to share breaking news with others around the world. Whether you're covering a meeting, trade show, seminar, concert, sporting event or social activism, streaming video is an effective way to get your message out. When you stream video, the amount of data you send through a connection during a specified time is your bandwidth and it has everything to do with your end result.

Video Dimensions

Streaming video is made up of still images, called frames, and the size of these frames affects your bandwidth. If these frames are 320 by 200 pixel 16bit JPEG images, each one is about 20K in size. A video with these dimensions takes two full seconds to display a single frame over a dial-up connection. The reason is that dial-up has a bandwidth of about 40 kilobits per second (kbps) so it can only receive about 10K of data per second. At this rate your video is more like a slide show. To give you a better idea of real world bandwidth requirements, it takes about 250 kbps to stream 320 by 200 video at 15 frames per second (fps) and 2000 kbps to stream 640 by 400 video at 30 fps.

Frame Rate

The more frames your video displays every second, the greater your bandwidth requirements but the actual amount varies according to what you're covering. If you're streaming a software demo and most of the change between frames is the position of your mouse pointer, little new data is streamed with new frames so your frame rate has little effect on bandwidth. This might also be true for static video of someone speaking behind a podium. On the other hand, streaming video of a sporting event can have many changes between frames so the bandwidth is greatly affected by the frame rate. If you're streaming sports at 15 fps and you bump it up to 30 fps, which is the frame rate of TV, your bandwidth consumption could go up by almost 100 percent.

Video Content

As discussed in the previous section, the subject of your video has a lot to do with its bandwidth requirements. Static video, where little changes from frame to frame, creates smaller files but when a camera and subject are moving, the file size increases dramatically. The audio component of your video also has a significant impact on bandwidth. More complex and better quality audio has higher bandwidth requirements, so if you're streaming video where the sound is important, such as a big band or community orchestra concert, you have to take this into account. 16bit uncompressed audio with a sampling rate of 22.050 kHz has a pleasing dynamic range but a mono recording with these settings requires 43 kbps of bandwidth and is impossible to stream over a 40 kbps dial-up connection. However, highly compressed audio with a sampling rate of 8kHz only consumes 5 kbps of bandwidth.

Number of Connections

When you're streaming a live video event, the size of your audience has the greatest effect on your bandwidth requirements. Every simultaneous connection to your video stream consumes the same bandwidth as the video stream itself, so if your stream is 250 kbps and 50 people are watching it, you'll need a 12,500 kbps connection to handle the bandwidth. If you're concerned about your ability to manage viewers, you can accommodate more of them with a streaming video server. It keeps your video from dropping frames by lowering the video bit rate when it detects network congestion.