1-12
Introduction
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
1.3.1
MPEG-1
The MPEG-1 International Standard (ISO/IEC IS 11172-2, -3) denes
both audio and video services and is targeted at compressing audio and
video services for storage on CD-ROM. Typically MPEG-1 video streams
will be Standard Image Format (SIF) resolution, which is 240 x 352 pixels
at 30 frames per second (NTSC). The total data stream is compressed
to 1.864 Mbits/s. The video and audio portions (11172-2 and 11172-3)
of MPEG-1 have been adopted as ISO International Standards, whereas
the conformance portion (11172-4) is still an ISO Draft International
Standard.
1.3.2
MPEG-2
The MPEG-2 International Standard (ISO/IEC IS 13818) more effectively
addresses the needs of the TV industry. The most signicant need is to
decompress a video stream of up to 720 x 480 resolution at 30 frames
per second (NTSC), with a compressed data rate above 10 Mbits/s. A
signicant limitation of MPEG-1 is that the video is encoded in a progres-
sive (non-interlaced) format, whereas TV source material is in an inter-
laced format in which each frame is comprised of two interlaced elds.
MPEG-2 allows the encoder to switch between eld or frame prediction
and coding at the macroblock level, depending on which produces the
best overall coding gain.
The MPEG algorithm is asymmetric, meaning in this case that the encod-
ing is more complex than the decoding. More expensive encoders than
decoders ts the scale of economy for these applications that require
many decoders to a few encoders.
The L64005 is fully complaint with the MPEG-2 standard main prole,
main level.1 As such it can also decode an MPEG-1 video sequence.
1. The MPEG-2 standard denes “proles” and “l(fā)evels” as a means of specifying subsets of
the syntax and semantics of the standard. Refer to the ISO/IEC 13818 standard for details.
1.4
Terms and
Concepts
The following section lists and denes terms and concepts that are help-
ful throughout this document.
3:2 Pulldown. 3:2 pulldown is used for conversion from lm to video.
Film material digitized at 24 pictures per second forms an excellent
source for the MPEG video bitstream. Sometimes source material avail-
able for compression consists of lm material that has been converted to
video at some other rate. The encoder can detect the rate difference and