MPEG: A Brief Overview

Motion Picture Experts Group, better known as MPEG (pronoounced "M. Peg"), is the group responsible for developing and standardising three of the world's most popular media encoding formats. The MPEG encoding is using in almost all digital broadcasting services, and also in a variety of digital video discs (DVD, HD DVD, Blu-Ray).

MPEG-1
This is the first MPEG standard, whose first version was finalised in 1993. It was developed with the idea of fitting audio and video into a Compact Disc (CD). The format was made the base of the Video CD, a compact disc containing MPEG-1 encoded video which became most popular in Asia.

MPEG-1 allowed for acceptable quality with a resolution only upto 352x288 pixels, and with a maximum bitrate of around 1.5 Mbps. The video quality was similar to that of a VHS tape, except for the pixelation. The audio consisted of only one channel (mono). The standard is almost obsolete today, but is important as it gave way for the more advanced MPEG standards we use today.

MPEG-2
This is the most widely used multimedia encoding standard in the world today, mainly because of its usage on DVDs. MPEG-2 is used worldwide for digital broadcasting as well.

MPEG-2 supports upto 720 × 576 resolution with max. 8 Mbps bitrate for usual DVD-quality video. It also supports High Definition video upto 1080p with a high bitrate. MPEG-2 Audio allows 2 (stereo) or more channels to be included, using MP2 or AC3 encoding.

MPEG-2 has less quality and a much higher bitrate requirement for HD video. Nevertheless, it is popular for broadcasting in High Definition.

MPEG-4
This is the newest MPEG standard available today, and hopes replace its predecessor MPEG-2 very soon. It was finalised in 1998, and first became popular for use in encoding media to share on the internet. Later it was adopted as the standard encoding format for the Blu-ray and HD DVD media discs.

There are substandards which work under MPEG-4, including MPEG-4 AVC, x264, DivX and Xvid. The actual quality and bitrate-efficiency depends on the substandard used. H.264 is arguably the best, with bitrates as low as 3.75 Mbps for HD video.

MPEG-4 is most advantageous over MPEG-2 because it can encode very high quality video with much lower bitrates than before. It also supports High Definition video. Bitrates vary according to the substandard used. A regular DVD-quality video using 8 Mbits in MPEG-2, can use as little as 2 Mbps on MPEG-4 to with hardly any quality loss.

Many DTH services now use MPEG-4 because of its low bandwidth usage. On satellite DTH services, even more channels can be squeezed into a transponder using MPEG-4. This can reduce costs greatly for service providers, as less transponders are required. DirecTV, Dish Network (both in USA), Reliance Big TV and Sun Direct (in India) all use MPEG-4 for broadcasting, and many existing services will upgrade to the new technology within the next few years.

The MPEG-2 standard would become obsolete very soon if DVDs did not exist and/or HD DVDs and Blu-ray discs did not cost so much.

In Sri Lanka - Dialog TV hopes to add new channels using MPEG-4 very soon. I will be covering that subject in another post, coming soon.