Understanding encoding

Encoding is the process of preparing the content for distribution. In some cases, how you encode the content can make a big difference in how the user experiences it. The following subjects cover the most common content encoding issues:

Using codecs

Streaming audio and video content can consume a lot of bandwidth on a network. By compressing the content, it can be broadcast using less bandwidth, which makes the content available to a larger audience. You can compress content by applying compression algorithms to the data, taking into account the desired output quality and available bandwidth. Before the content is played on a player, it is decompressed using decompression algorithms. These compression and decompression algorithms are called codecs. Codecs are designed to reduce a stream to a certain bit rate. The target bit rate determines how much the content must be reduced and therefore which codec is best suited to your needs. Files that are encoded at a higher bit rate produce content that usually sounds and looks richer and more dynamic, but it requires more bandwidth to stream.

There is an additional encoding method that can provide high-quality content to unicast clients with high-bandwidth network connections, while also ensuring that dial-up clients do not have to suffer long periods of latency. Windows Media Encoder can encode your content using multiple bit rates, allowing a single content file to be streamed to a variety of client connections. Before the encoding process begins, you can specify the target bit rates for your content encoded with. Then, when the client connects to the Windows Media server, information about the client's network connection is assessed. The server streams the bit rate that provides the best quality content with the least amount of latency.

Sources of digital media content

Digital media content can come from many different sources. Content from video cameras, microphones, television tuner cards, and video playback devices can be captured using a card or capture device that is installed on the encoding computer. Once the digital media content has been captured, it can be encoded into the Windows Media Format and streamed or saved to a file.

Defining encoding parameters

You should tailor your encoding process to the type of content being encoded, the audience, and the intended distribution method (file or broadcast). You need to define the following parameters:

• Audio quality. Audio content can be either stereo or mono. It can also be sampled at varying audio frequencies to provide greater range of sound differentiation. To determine the best encoding settings you should know whether the audio files contain voices only, music only, or both.
• Video quality. Video content can be played back in different windows sizes. Small video displays make it much harder to see errors in the video and are normally used with low bit rate content. Large video displays provide greater visibility and are most often used with higher bit rate content. Frame rate is also a major consideration. A high number of video frames displayed per second provides smoother video motion. If your video has high motion content, increasing the frame rate may be useful. If there is not much motion in your video, you may be able to decrease the frame rate and devote some of the bandwidth resources to other portions of the content.
• Target audience. To determine ideal encoding settings, you should think about whether the content needs to support clients that connect at different bandwidths or whether the audience has the same bandwidth capability. Increasing the audio and video quality causes an increase in required bandwidth. You will need to balance quality consideration against bandwidth limitations.
• Codecs. The audio and video codecs define the method of compression performed on the content. Some codecs are optimized for low bandwidth scenarios, others for high bandwidth scenarios, while other codecs are optimized for audio content, and some for video content.

You can simplify the encoding process by considering these parameters before setting up an encoding session.

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