Streaming media is a unidirectional transmission of audio or video material by means of a data network. It can be used to stream media from websites to site visitors’ computers without the data being stored on the computer from a computer or dedicated drive in a home network to a media hub for viewing on a home theater setup. An encoder is a device or software that is used to convert data from a particular format or signal to another. A streaming media encoder is a hardware device or a software application that prepares a file for streaming, often by taking a large, high-quality digital file and compressing it in ways that make it compact and efficient for streaming.
Streaming media encoders vary widely in their scope and cost. The Windows® Media Encoder software is free, while a professional streaming media encoder can run into five digits. As is to be expected with such a wide range of cost, the functionality varies quite a bit as well.
One area of difference is in the output file choices. The Windows® Media Encoder will output audio files with a .wma (Windows Media Audio) extension and video files with a .wmv (Windows Media Video extension. With a professional streaming media encoder, the choices will be much wider, including output types such as Windows® Media, RealVideo®, AVI (Audio Video Interleave), and Adobe® Flash®; video format choices such as H.263 or H.264 or MPEG-4 (Moving Pictures Experts Group); and audio format choices such as AAC and MP3.
Another difference is subtler. Although Windows® Media Encoder and professional models all offer the option of pushing the file to a media server for broadcast or providing an arrangement to allow the file to be pulled from the streaming media encoder itself, experts advise that using Windows® Media Encoder in this way would yield poor results, given the bandwidth that this would require. Streaming media can be live or on-demand, and they can also be unicast or multicast. As far as the streaming media encoder goes, the live webcast is the case in which an encoder that can also stream is desirable.
The professional streaming media encoder hardware may have some additional capabilities. These may include a wider array of preprocessing capabilities, including deinterlacing, cropping, scaling, sampling, and HW gain and attenuation. Closed caption capability and extraction may also be provided.