What Is a Live Webcast and How to Stream?

A live webcast means taking the media and broadcasting it in real time over the Internet. Live media streams are generally provided by a means called true streaming. Live streaming sends the information straight to the computer or device without saving the file to a hard disk.

Basically, audio or video content from an audio/visual system (such as a video camera) is transferred to streaming software running on the host's computer. The content is encoded (compressed and digitized), and then sent to a specialized server known as a content delivery network (CDN). The CDN distributes and delivers the media onto the Internet - either as a live broadcast, or as "on demand" for later access. Potential end-users are able to view or listen to a webcast because a media publishing program on their computers (such as RealPlayer or Windows Media Player).This program decodes or converts the data stream from the CDN.

Live Webcast Flow
[A camera's video and audio feed is connected to a computer with capture cards (encoder) and proprietary software, which converts the signal into an internet-friendly format and sends it to a host server (or Content Delivery Network). From there, the signal is available to potential viewers on the Internet in formats such as Windows Media Player, Flash, or Microsoft Silverlight.]

A media stream can also be broadcasted on demand. On demand webcasting is provided by a means called progressive streaming or progressive download. On Demand streams are often saved to hard disks and servers for extended amounts of time; while in live webcasts, the streams are only available at one time only (e.g. during the Football game).

Streaming technologies like Adobe Flash, Apple QuickTime, and Microsoft Windows Media and Silverlight all include certain common components in their solutions. These include a player to play the media on the viewer's computer or mobile device, a defined file format or formats that the player will play, and often a server component that offers features like digital rights management and streaming.

All streaming technologies use compression to shrink the size of the audio and video files so they can be retrieved and played by remote viewers in real time. Common video compression technologies, also called codecs, include H.264, MPEG-4, VP6 and VP8, Windows Media Video (WMV), and MPEG-1/2, while common audio codecs include AAC (Advanced Audio Coding), Vorbis, Windows Media Audio (WMA), and MP3.

How to stream live webcasts?

Below are technical steps of streaming webcasts in real time:

  1. The audio stream is compressed using an audio codec such as MP3, Vorbis or AAC.
  2. The video stream is compressed using a video codec such as H.264 or V8.
  3. Encoded audio and video streams are assembled in a container bitstream such as FLV, WebM, ASF or ISMA.
  4. The bitstream is delivered from a streaming server to a streaming client using a transport protocol, such as MMS or RTP.
  5. The streaming client may interact with the server using a control protocol, such as MMS or RTSP.