Internet video broadcasting is rapidly becoming the medium of choice for delivery of video entertainment and news. There are no geographic limitations or technical licensing requirements for broadcasting on the Internet, which allows any individual to produce and distribute multimedia to a global audience. Content producers have many technical options for creating video for broadcasting on the Internet, which includes the method of encoding the video, method of content delivery and end user requirements for viewing the video. It is important for content producers to understand these available options.
Multimedia encoding is the most important technical consideration for Internet broadcasting. It is necessary to compress the content into a manageable amount of data because video production creates a large quantity of digital data. Without reducing the size of the video content, the uncompressed multimedia would require very large amounts of network resources for content distribution and electronic storage. This would effectively limit the ability to transport or store the video data and prevent the content from being delivered in a cost effective manner.
The goal of video encoding is to achieve the greatest amount of data compression while retaining the best visual quality and clarity of the original content. Specialized software applications called codecs are used to encode / compress the video content. This technical term stands for coder / decoder or compressor / decompresser. Codecs use complex mathematical algorithms and specialized processes to compress the data, which allows the video content to retain its quality and clarity. Most codecs use algorithms that are based on lossy data compression, which enables multimedia compression by slightly altering the content to be encoded. This results in the encoded video being slightly different from the original content, but still providing quality visual representation.
There are many available codecs that can be used for encoding video content for broadcasting, with each one having unique properties. Some of these are proprietary and may require the purchase of a end users license, and some are open source that do not require the purchase of a end users license.
Technical limitations for the use of these codecs may include the following:
- specific operating system requirements
- encoder bandwidth limitations
- encoder system resource use or end user playback software requirements.
Here is a list of the current open source and proprietary codecs that are available for use with Internet video broadcasting:
Open Source Codecs
- Dirac uses Wavelet Compression instead of Discrete Cosine Transforms as the basis for its compression algorithm. It promises results comparable to or better than current proprietary codecs such as H.264.
- Theora is derivative of VP3. Theora aims at improving the original VP3 implementation through optimizing the encoder software and actual codec structure.
- VP3 uses a multi-step approach to video encoding. These steps include Discrete Cosine Transforms, Quantization, Run Length Encoding, Zigzag Ordering, Differential, Motion Compensation, Entropy Coding, Variable Length Run Length Booleans, YUV Colorpsace and Frame Type. This codec also uses a unusual feature that consists of encoding data from bottom to top, rather than from top to bottom.
- H.264 is is known as MPEG-4 Part 10 or MPEG-4 AVC. It uses block-orientation and motion-estimation to achieve superior compression performance when compared to other video codecs.
- VP6 – The current generation of the VP codec is called True Motion. Some of the key milestones of VP6 include the support of multi-pass encoding, improved error recovery and direct access to the data reconstruction buffer.
- Windows Media Video is based on MPEG-4 AVC. The current version of WMV has achieved several improvements that include native support for interlaced video, non-square pixels, and frame interpolation.
- Real Video uses very accurate motion modeling, proprietary spatial pixel prediction methods, context adaptive entropy coding, psycho-visually tuned segmentation, filtering schemes, rate-distortion optimized encoding algorithms and two-pass encoding.
Both proprietary and open source codecs offer many unique features, with the most important feature being the ability to provide quality video presentations at low bandwidth and the ease of use for end users. Excessive bandwidth consumption can severely limit the ability to deliver the video content to a wide audience and complicated software set up for audience participants will dissuade people from viewing the multimedia content.
Understanding the process of video encoding and multimedia compression is important. Choosing the appropriate codec for an Internet broadcast will ensure the production of quality video that will be available for the viewing audience. It is also important to have adequate network and computer resources to support the requirements for your broadcast.
Dave Childers is a freelance Internet broadcast consultant, writer and webmaster of http://www.scvi.net – The Winamp TV, NullSoft Video information website