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Comparison between MPEG 1 & 2

MPEG-1 and MPEG-2 are both popular formats, but what is the difference and where might you use each? Almost without exception, MPEG-2 is a superset of the MPEG-1 standard; building on the earlier format to expand its capabilities and improve the quality. We look at some of the advantages that MPEG-2 gives you in order to create higher quality movies, although MPEG-1 widespread acceptance still makes it a viable format.

Resolution
MPEG-1 is limited to 352x288 as its maximum resolution if you wish to stay within the standard profile (a profile is a sub-set of the possible parameters). Most MPEG-1 decoders support the standard profile, so you should encode within these parameters if you wish your video to be widely accepted. MPEG-2 supports higher resolutions as part of its standard profile, including resolutions like 480x480 and 720x480 which are used for TV playback.

Interlacing
MPEG-1 compresses each frame as a single picture. This is fine for computer use, however television builds frames from two fields in an effect called interlacing and MPEG-1 does not have support for this. MPEG-2 fully understands interlacing and can take advantage of this knowledge by creating better compression by compressing across fields, rather than frames.

Bitrates
MPEG-1 is optimised for use with Video CD applications and works with bitrates around 1.5 Mbps. Higher bitrates are supported, but the quality advantages tend to be relatively small if you keep within the resolutions that are part of the standard profile. MPEG-2 is typically used between 4 Mbps and 9 Mbps, which is necessary to store the extra information that is typically present in the higher resolution video.

Scalability
MPEG-2 supports extra features which allow video to be scaled in terms of resolution and frame rate. Although this is not important for the majority of users, for digital broadcast uses where the video may be decoded on a wide range of systems then this feature can be valuable.

Compatibility
MPEG-1 is not covered by any license restrictions that involve payment, so there are many MPEG-1 encoders and decoders available. MPEG-2 is covered by patent license agreements which require royalty payments to be made. As a result, all MPEG-2 encoders and decoders are subject to charges controlled by the MPEG Licensing Administrator. As a result of these charges, MPEG-2 is not as widely available and is best used where compatibility is ensured (eg. DVD).

Summary
MPEG-1 is best suited to computer applications and can produce quality similar to VHS when played through a TV. MPEG-2 is very much more powerful and supports higher quality encoding and is used for DVD and digital broadcast applications. MPEG-1's relative simplicity and lack of licensing costs will ensure that this remains a popular format for many years to come.