John Gonzalez

Basic Streaming Terminology Explained
By John Gonzalez

As the consumption of media over the Internet grows, so too does the demand for available online content. Communities, companies, and municipalities who have provided their content solely in the cable broadcast world are now being asked to live stream events and provide video-on-demand (VOD) over the Internet. Adding an Internet presence can be difficult, as for many it is taking a step into a world previously unexplored. One of the major hang-ups for those adding an Internet presence is understanding the new vocabulary.

Bandwidth

One of the first words you’ll hear when you start looking into streaming is bandwidth. A common misconception is people believe your bandwidth measures your speed. Your bandwidth actually refers to the maximum size of the “pipe” through which data can flow. So while bandwidth does not directly measure the speed at which data travels, it certainly affects the speed of your download. A helpful analogy to help understand bandwidth is the filling and draining of a pool.

In this analogy, the water represents the file being transmitted to (or from) your computer over the Internet. With streaming video you need to be aware of the fact that you have both inbound and outbound bandwidth. In this pool analogy the size of the drain will represent your outbound bandwidth and the size of the hose will represent your inbound bandwidth. When filling up your pool, assume the water is going to come out of the hose at a certain constant speed. The speed at which the water travels will not change regardless of what size hose you use; however, if you use a wider hose you will allow more room for the water to travel. Therefore you will not increase the speed at which the water travels but your pool will fill up faster because you have a larger hose or more inbound bandwidth. Below is an illustration to give you a graphic reference for this analogy.

Pool_Vector_fill

Outbound bandwidth works the same way and can be analogized to draining the pool. The water is going to travel through the drain at the same speed, but if you increase the size of the drain, the draining process will take less time. Again a graphic reference has been provided below.

Pool_Vector_drain

Again, it’s important to understand that you have both inbound and outbound bandwidths and they may not be the same. Since you are streaming video out of your server for others to access, you’ll need to know what your outbound bandwidth is. Sticking with the pool analogy, if you want to drain your pool (or send data out of your server), the size of the hose you used to fill up your pool really doesn’t matter. Most people know their inbound bandwidth but don’t know how much outbound bandwidth they have. For the LEIGHTRONIX live streaming encoder, the PEGstream-SD2™, and PEG Stream™ live streaming service, you need one sustained 768 kilobits per second (kbit/s) outbound stream. The video is then streamed to LEIGHTRONIX servers and we carry the bandwidth load from there. Be aware that if your Internet connection only has a 768 kbit/s outbound stream and that has to be shared with other outbound data transfers, you will most likely not meet the 768 kbit/s requirement. You need to be sure you have enough outbound bandwidth for the outbound stream plus any other traffic required at your organization.

Bit Rate

The other term you’ll need to be familiar with is bit rate. Bit rate can actually refer to two different things. The first is the rate at which data is transferred, which is measured in bits per second (bit/s). Your bit rate can change depending on your connection type; for example, a DSL connection may be able to download at 768 kilobits per second (kbit/s) while a Firewire 800 connection transfers data at a rate of up to 800 megabits per second (Mbit/s).

**Note: You may also see bits per second written as bps. This is also correct but may cause confusion with bytes per second which is denoted as Bps. By writing it as bit/s you can avoid any confusion.

In video, bit rates can also describe the quality of the file. A video with a higher bit rate is represented by more data than the same video with a lower bit rate. Much like an image with a higher resolution is clearer and higher quality, a video with a higher bit rate is also of higher quality.

You may notice both bandwidth and bit rate are measured using the same units; this is another hang-up for those new to streaming. When we talk about bit rate where video and audio are concerned, it’s usually in reference to how much video or audio data will transmit for each unit of time specified, typically in bits/s as mentioned earlier. When we talk about bandwidth it is usually referencing the maximum bit rate a network connection has available or the total bit rate being consumed at the time (again we would measure this in bit/s).

Live Streaming vs. Video-on-Demand Streaming

Now that you have a basic understanding of bandwidth and bit rate, it is important to understand that the bandwidth needed for live streaming and the bandwidth needed for video-on-demand (VOD) streaming differs. The main reason for this is because of how the file is being accessed. With the PEG Central® video-on-demand and web hosting service, you upload the VOD file to the server and once the file is uploaded, viewers can access it whenever they want through the PEG Central® website. Because viewers are accessing the file after it has been completely uploaded, the download speed is more dependent on their inbound bandwidth. Your outbound bandwidth will affect how long it takes the file to upload to the server but won’t affect the viewing experience.

With the PEG Stream live streaming service, the viewer is accessing the file in real time. If your outbound bandwidth is inadequate and struggles to send the file, the viewer’s experience will be directly affected. To insure your content is delivered without any hiccups, LEIGHTRONIX requires at least a single sustained 768 kbit/s outbound stream. As long as you have the required bandwidth, you can be confident your stream will be delivered to all the viewers who want to access your content.

I don’t expect a single blog post to make someone unfamiliar with video streaming an expert, but I hope this at least helps you understand a few of the concepts related to streaming. If you are interested in learning more about LEIGHTRONIX’s live or VOD streaming solutions, you can visit leightronix.com/streaming. If you have questions about bandwidth or bit rate in regards to LEIGHTRONIX streaming solutions, please call or email a solution specialist at (800) 243-5589 or sales@leightronix.com.

John manages the daily operations of the LEIGHTRONIX Technical Support team and coordinates software and firmware testing and releases. He also troubleshoots analog and digital video systems, provides software support, and handles TCP/IP networking.

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