Streaming Media: The Introduction

Video and audio streaming are everywhere, and they have radically changed the way people spend their free time. Not only is streaming used for pure entertainment, but it also plays a fundamental role in making knowledge accessible to everyone through online courses and virtual classrooms.

Streaming technology has also witnessed tremendous growth in the last few years with the emergence of enhanced processing power, better compression algorithms and increased bandwidth in network systems.

Streaming follows on a client /server model, where a client requests a video from the server, the server sends the video to the client (in a compressed form as small packets). Playback begins when some of the video data have been buffered at the receiver, without receiving the entire file at once from the server (Künkel, 2003).

Additionally, live streaming refers to a case where the video data does not exist in stored form but is being captured by a camera as it happens, compressed and transmitted to the receiver.

Real Networks was the first organisation to broadcast an audio event over the internet in 1995 and the first video streaming in 1997 (Ozer, 2011).

Basic streaming media concepts

Codec

Codec, a two-word process “compressor-decompressor” that uses specialised mathematical algorithms to tightly compress large video files discarding unnecessary data to create smaller files for storage and streaming, which is later decompressed for viewing (Ozer, 2011).

There are a number of video codecs available today including newer one with improved encoding efficiency and quality. H.264 is the most common video codec used in live streaming today, it has wider compatibility support among various devices, see Figure 1, although VP9 developed by Google is gaining popularity especially among Android and Google platforms.

Figure 1 - H.264 compatibility results (Source: Caniuse.com)

Bitrates

Bitrate refers to the number of bits processed within a given time period, measured in bits per second. The higher the bitrate, the better the quality. When streaming a live event, the bitrate for both the video and audio is defined in the encoder. Figure 2 and 3 shows examples of different bitrates.

Figure 2 - This media files was encoded and streamed at 2500 bits/sec

Figure 3 - The same media files as figure 2 but encoded and streamed at 5000 kbit/sec

Frame rate

Frame rate refers to the speed at which each video frame is shown. A video stream at 25fps, means each second of video contains 25 distinct images. The frame rate has a direct impact on the bitrate, for example dropping the frame rate of a video stream by 50% will reduce the bitrate by 50% with no loss in quality (Ozer, 2009).

Resolution
Resolution is the height and width of the video in pixels. The video resolution has a role to play when determining the bitrate of the video, this is because as the number of pixels in the file increase, so will the bitrate in other to maintain the same quality.

Streaming zone / stages

The process of streaming can be divided into 8 zone, some devices and software can handle more that one zone. These 8 zones include:

Media Content
This is the actual event or contnet intended for streaming. It can be anything from a personal vlog, sporting event, a music concert, a sermon or church service.

Media Transfer
This is the medium used to transfer the media content for capture on a streaming device

Media Capture
This is the device used to capture the incoming video or audio feed from the media transfer component.

Encoding
Encoding is a key aspect of live streaming, it refers to the process of converting raw video and audio data into a digital format suitable for transport across a network (e.g. the internet) and compatible with various platforms and devices using an encoder (Ruether, 2019).

An encoder is a piece of hardware or software that compresses raw video and audio data captured in real-time using special algorithms known as codec, packaged in a specific format and sent to a streaming server using specific streaming protocols for distribution (Ruether, 2019). Example OBS Studio, Wirecast and Matrox Monarch HDX.

Uplink
This refers to the network upload infrastructure used to transport the encoded media stream to the streaming server.

Streaming server or service provider
A streaming server is software hosted on a web server that is optimised for serving and delivering media contents to end users through a video player. The streaming server receives the compressed video sent from the encoder and delivers it to end users via a video player.

Broadcast
This refers to a content delivery network used to broadcast the live stream to the end users (viewer)

Playback / Client machine
This can be anything from a html5 video player or an application that is used to display the live stream to viewers.

References

Follansbee, J. (2004). Get streaming!. Amsterdam: Elsevier.

Künkel, T. (2003). Streaming media. Chichester, West Sussex, England: Wiley.

Miller, K. (2009). Adobe Flash Media Live Encoder. [online] En.wikipedia.org. Available at: https://en.wikipedia.org/wiki/Adobe_Flash_Media_Live_Encoder [Accessed 18 May 2019].

Ozer, J. (2009). Streaming 101: The Basics – Codecs, Bandwidth, Data Rate and Resolution. [online] Streaming Learning Center. Available at: https://streaminglearningcenter.com/articles/streaming-101-the-basics-codecs-bandwidth-data-rate-and-resolution.html [Accessed 21 May 2019].

Ozer, J. (2011). Video compression for Flash, Apple devices and HTML5. Galax, Va.: Doceo Publishing.

Ozer, J. (2011). What Is Streaming (2011 Version). [online] Streaming Media Magazine. Available at: https://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=129930 [Accessed 21 May 2019].

Ruether, T. (2019). The Complete Guide to Live Streaming | Wowza Media Systems. [online] Wowza Product Resources Center. Available at: https://www.wowza.com/blog/complete-guide-to-live-streaming [Accessed 16 May 2019].