What Are the Bandwidth Requirements for Streaming Live Video?

What Are the Bandwidth Requirements for Streaming Live Video?

As live streaming becomes increasingly popular, one of the most common question asked by new broadcasters regards bandwidth. Specifically, how fast does your Internet upload speed have to be in order to live stream? Truthfully, there’s no hard or fast rule that answers this question. The answer depends on a wide variety of variables. Don’t worry, that’s why we’re here! Let’s take a look at these variables at play so that you can make a final decision about the bandwidth you need for your live streaming purposes.

Understanding Internet Speed: Upload and Download

When it comes to measuring the speed of an Internet connection, two things matter: download speed and upload speed.

Download speed is a measure of how fast data from the Internet can enter your network. You can think of it like a tube – the bigger the tube, the faster information can flow through it into your network. Upload speed, on the other hand, is a measure of how quickly you can send data from inside your network out to other computers or servers. Both download and upload speed are usually measured using Kbps (kilobits per second) or Mbps (megabits per second).

For live streaming, both download and upload speed are important. Upload speed is what determines how much data a broadcaster can send out as a live video feed. The faster the upload speed, the higher the video quality can be while broadcasting. Download speeds are important for viewers, rather than broadcasters. A slow download speed means that live streams may buffer or lag.

Warning: Uploads are Slower than Download!

It’s important to know that most Internet connections have upload speeds that are only a fraction of their download speed. It won’t matter if you have a lighting-fast download speed if your upload speed is too slow for your live stream.

You should also be aware that most Internet connections advertise speeds “up to” a certain number. This is a peak measure and often means that sustained speeds are 25% slower, frequently even 50% slower. Despite enabling you to watch live streams, these lower than advertised speeds may mean your connection is inadequate for actually live streaming.

What Are the Bandwidth Requirements for Streaming Live Video?

bandwidth requirements for live streaming video

The biggest single factor impacting your bandwidth requirements is broadcast quality. Streaming video at a resolution of 320 x 240 pixels doesn’t require much data. On the other hand, sending a video file with full high-definition resolution takes a great deal more.

High definition video files have up to 10 times the resolution of SD video, and can incorporate higher quality audio files as well. As the world begins to move towards 4K video, bandwidth requirements for streaming will face greater increases.

Another element that increases the size of video files is the frame rate. Frame rate refers to how many still images make up one second of video. Online, almost all video is encoded at 30 frames per second (fps). However, sports and video game streams are often encoded at 60 fps so viewers can catch the split-second action that occurs. Video at 60 fps is approximately twice the size of 30 fps video, requiring more bandwidth to stream.

Codecs and Bit-Rates

To understand the specific bandwidth requirements of a stream, you need to understand the basics of video encoding. Encoding is mostly about compression. It’s a way of taking video files and making them smaller so they can be transmitted more easily over the Internet.

For live streaming, the H.264 codec is by far the most common standard. H.264 produces small file sizes, and the resulting video can be played on just about any device. No matter the codec used, quality primarily depends on the bit rate the file is encoded at. This is essentially the amount of data that’s contained within one second of video, measured using Kbps or Mbps.

Comparing Video Bit Rate and Internet Upload Speed

The bit rate of your video stream will inform the upload bandwidth you need. For example, if your outbound video stream is being streamed at a bit rate of 500 Kbps, then your Internet upload speed will need to be at least 500 Kbps.

In reality though, Internet upload speeds fluctuate second-to-second. Connections drop, reconnect, and experience other speed bumps. Generally this means that to stream a video, you want your Internet upload speed to be at least double the bit rate of the video you plan to broadcast.

Single vs. Multiple Bit Rate

Most live streams require multiple bit rates for video to be streamed at the same time. This enables viewers to watch on both mobiles on the coffee shop WiFi network and Roku boxes connected to high speed cable internet. In essence, viewers with slow Internet speeds will automatically switch to low bit rate streams, and viewers with fast Internet will receive the higher quality streams.

This method provides a much better experience for viewers, and should be considered a standard practice. However, it does complicate things for broadcasters. Instead of broadcasting a single live stream, broadcasters now have to stream multiple different feeds simultaneously to accommodate different Internet speeds.

Modern live broadcasting formats like MPEG-DASH, HLS, HDS, and Microsoft Smooth Streaming use a process called “adaptive bit rate streaming” to automatically shift viewers to the best available stream.

Multi Bit Rate Streaming

Streaming a variety of different bit rates at the same time can be somewhat tricky. It requires more processing power and more upload speed. In terms of upload speed, all the bit rates you’re uploading add together to determine how much bandwidth you need overall. If you want quality 4K video, that tends to use at least 15 Mbps. So in order to get a stable 4K stream going, you’ll need to double that for an upload speed of 30 Mbps. Needless to say, that’s a great deal of upload speed.

In terms of processing power, more streams require more power. However, any powerful laptop computer should be able to handle encoding multiple streams. In a production environment or a situation where failure isn’t an option, you may want to consider a hardware encoder such as those produced by Teradek, Matrox or Niagara. These powerful, portable devices are capable of crunching plenty of data at once to ensure that these streams continue as smoothly as possible.

A Note on Codecs and Bit Rate

Codecs and bit rates operate independently, but only between different codecs. For example, an H.264 video encoded at 2 Mbps is going to have better quality than one encoded at 1 Mbps. However, an H.265 video encoded at 1 Mbps may actually be better than the 2 Mbps H.264 video.

Similarly, other video factors can change independently of bit rate. For example, frame size is unrelated to codec and only partially related to bit rate. Videos with different frame sizes can be encoded using H.264 at the same bit rate.

However, videos with larger frame sizes will “spread out” the data across a larger frame. This can lead to a perceived lower quality. Meanwhile, a low resolution video with a high bit rate can appear visually excellent, even though it is small.

Single Format or Multiple?

bandwidth requirements for live streaming video

In the past, the standard for streaming video over the Internet used the Macromedia – now Adobe – flash standard. However, times have changed. While flash video is still widely used on desktop computers, it’s not supported on many mobile devices. With the popularity of smartphones and tablets, broadcasters should be making mobile users a priority.

Most notably, iOS (iPhones and iPads) doesn’t support flash video. Some old versions of the Android mobile operating system do support flash, but it’s being phased out rapidly. This means you will either want to stream only in a modern format like HLS which can be played by most flash video players, or use multiple formats.

Flash will reach older computers and be fully backwards compatible. HLS is the standard streaming protocol for iOS devices that can be played on almost any device. HDS is Adobe’s latest offering that can also be played on most devices, although not iOS. Additionally, modern broadcasting is starting to rely on MPEG-DASH. If you need to broadcast in these multiple formats can potentially double or triple the amount of bandwidth required.

Making the Calculations

Now that you know all the required elements to calculate bandwidth requirements for live streaming, you can combine them into a simple formula to calculate your total bandwidth requirements:

(Bit rate per second of all combined video streams and the audio stream) x (Number of formats you are broadcasting in) x 2 = Required Upload Speed

This number should be taken with a grain of salt. For example, you may not need all of the 100% overhead bandwidth for a live stream. Sometimes you can get away with only 1.5 times more bandwidth if your connection is truly stable. But be wary here. Having a single weak link, like a slow upload connection, is one of the main reasons that live streams sometimes fail.

Account for Data Caps

Increasingly, more Internet service providers are putting a cap on the total amount of data that customers can use each month. These caps can quickly become a problem when it comes to streaming live.

A typical 8.5 Mbps stream chews through about 60 megabytes of data per minute, which works out to 3.6 GB per hour. If your ISP limits your data usage to 50 or 200 GB per month, you could quickly run up against your limit when live streaming. This is especially true if you’re streaming continuously or streaming a regular series of lengthy events.

Information for Viewers

bandwidth requirements for live streaming video

For those who simply want to watch a live streaming video, their Internet download speed must be faster than the bit rate of their chosen stream. Usually, stream selection will automatically default to the best quality that your Internet can comfortably handle.

The amount of bandwidth required will depend on the quality of the stream. For a ballpark estimate of the speed required for streaming live video, here are the estimates that Netflix provides to its users (which are roughly transferable to live streaming):

  • 500 Kbps – lowest required speed for streaming
  • 1.5 Mbps – recommended speed for quality viewing
  • 3 Mbps – Standard Definition video
  • 5-8 Mbps – 720p and 1080p High Definition
  • 25 Mbps – 4K Ultra High Definition

Final Verdict

As you can see, the amount of bandwidth required for live streaming depends on a wide number of factors. However, simple live streams can be achieved on most standard broadband Internet connections.

Higher quality live streaming operations will require greater levels of bandwidth. Luckily, faster Internet is becoming more common. Government initiatives now define broadband at Internet speeds of at least 25 Mbps and are pushing for every person in the U.S. to have access to this speed.

It’s likely that in the near future, fiber optic Internet will start to take hold. Major ISPs like Comcast and Time Warner are increasingly offering these super-fast connections at relatively affordable prices, and competitors like Google Fiber are driving down costs and strengthening the market.

These moves, combined with an upswing in 4K video content, will combine to change the situation around broadcast live streaming in the next couple years. New codecs will also make HD and 4K live streaming more feasible. However, even with all these technological changes, the basic formula for live streaming hammered out above remains the same. Fast upload speeds will always be needed.