One of the earlier video codecs developed was MPEG-1 in which compression is based on a Group of Pictures (GOPs) and I,B,P frames. This is the codec used in Video CD or VCD. Then MPEG-2 was released, becoming the transport stream for the Digital Video Broadcast (DVB) standard for satellite, cable and terrestrial transmission. This was also later adopted in the American ATSC and Japanese ISDB-T terrestrial transmission standards. MPEG-2 is also the codec used for DVD.
The need to put more content to the existing and developing media like IPTV also saw the development of H.264 r AVC (a flavor of MPEG-4) which can offer up to 50% savings in bandwidth compared to MPEG-2. This is now widely used by telco operators worldwide in deploying their IPTV systems and slowly gaining ground in professional broadcast applications. There are now H.264 encoding and decoding equipment from leading manufacturers like Tandberg and Scientific Atlanta.
The following lists show other popular video codecs developed for computer and internet applications :
• H.261 – developed for earlier videoconferencing equipment.
• H.263 – developed for later videoconferencing equipment and internet video.
• Sorenson 3 – used in Apple’s QuickTime Player.
• WMV – used in Microsoft’s Windows Media Player
• VC-1 – based on WMV 9 standardized by SMPTE. This is used both in HD DVD and Blu-Ray products.
• Real Video – mostly used for computer video.
• DivX – for computer and consumer products.
• Theora – for computer video.
Codecs for video camera acquisition:
• DVCAM- camera codec developed by Sony. Compression rate is 25Mbps and color sampling is 4:1:1.
• DVCPRO - camera codec developed by Panasonic. Compression rate is 25Mbps and color sampling is 4:1:1.
• DVCPRO 50 – variant of DVCPRO with compression rate of 50 Mbps.
• DVCPRO HD – variant of DVCPRO with compression rate of 100 Mbps and used for HD acquisition.
• HDV – based on MPEG-2 and used for both consumer and entry-level HD professional cameras.
• AVCHD - based on H.264 and used for both consumer and entry-level HD professional cameras.
• XDCAM HD422 – compression rate is 50 Mbps and color sampling is 4:2:2.
For video editing:
• MJPEG - mostly used for video post editing.
• JPEG2000 - mostly used for video post editing.
• ProRes 422 – developed by Apple mostly used for video post editing.
With the development of different codecs came the development of different types of encoding and decoding software. The more popular ones are the following:
• Windows Media Player – developed by Microsoft to support the WMV format.
• QuickTime – developed by Apple as player for its line of computers.
• VLC – an open source player developed by contributors worldwide (VideoLAN Project). Supports the widest variety of codecs and OS.
• RealPlayer – developed by RealNetworks and used mostly for PC playback.
• Winamp – developed by Nullsoft and used mostly for PC playback.
So, with the wide array of video codecs available, the question is which one is suited for a particular application? In doing the selection process, we should consider the following parameters:
• Image quality
• Storage media capacity
• Available bandwidth
• Type of application
If image quality is the primary concern like in the case of broadcast transmission, the best choice is MPEG-2 being a proven standard for many numbers of years now. If transmission bandwidth is an issue, we can select H.264, which can also offer the same quality video as MPEG-2 at a lesser bandwidth. These two formats along with VC-1 and DivX can also be considered for quality viewing using optical discs and other storage media. For lower quality PC playback or streaming applications, we can check on the other formats like WMV, RealVideo and Theora.
I suggest you to try for yourselves how to use the codecs discussed by using different media players available. The best I tried is VLC (www.videolan.org) which is an open source application developed by contributors worldwide. Aside from being capable of simple encoding and decoding of video content, it can also be used for transcoding (conversion from one format to another) and streaming (both unicast and multicast). We were actually able to set up a small IPTV system using this free application – from satellite capture to encoding, to multicast distribution and playback at individual workstation PCs.