MPEG, simply, is an acronym short for the Moving Picture Experts
Group which belongs to the family of ISO/IEC standards (International
Organization for Standardization and International Electrotechnical
Commission). It is a compression technology for digital video and
audio signals intended for consumer distribution. Included in the
MPEG family are:
MPEG-1 (Audio/Video)
MP3 or MPEG-1 Audio Layer 3 (Audio)
MPEG-2 (Audio/Video)
MPEG-4 (Interactive Multimedia System)
MPEG-7 (Multimedia Database & Retrieval)
MPEG technology is defined as a bit-stream representation for
synchronized digital audio and digital non-interlaced or interlaced
(MPEG-2 includes both) video compressed to fit into a certain bandwidth:
MPEG-1 -- 1.5-4-0 Mbps (megabits per second)
MPEG-2 -- 4.0-10.0 Mbps
MPEG is responsible for multiplexing and synchronizing one video
stream with a single or multiple audio streams. MPEG-1 was designed
to reproduce VHS/VCR quality in a digital format, while the MPEG-2
concept, similar to MPEG-1, is intended to cover a wider range of
applications including DVD quality and its primary goal of an
all-digital transmission of broadcast TV at coded bitrates between 4
and 9 Mbps.
What is Pan&Scan, Letterbox and Widescreen?
Ever since the conception of DVDs, you have heard of this terminology
repeatedly but never had a clue as to what they are. You're in luck,
because this section is exactly intended for explaining these
prevalent DVD terms.
Starting off, everyone should consider the transference and hardship
of all those involved when a movie has had its run at the box office
(or your local theater) and is about to be shipped onto DVD, VCD, LD
(laserdisc), or even VHS. The majority of movies are filmed using
width to height ratios of 2:35:1 to 1:66:1. Why you may ask? Simple.
Our eyes are suited for viewing "wider" screens, for it
basically is in line with our vision. You may even proclaim that the
standard televisions nowadays are ill-suited for our dear eyes but
movie theaters' screen sizes are perfect for viewing video content.
Transferring is tremendously tricky, so that's where Pan&Scan,
letterbox, and widescreen displays come into play:
The Pan&Scan feature is available for some DVD software or
hardware players that allow users to watch the movie in its original
aspect ratio (i.e. a lot wider than 4:3) without those black bars!
Since most users have standard television sets (4:3), they won't be
able to view the entire area at the same time but are allowed to
control which portion they want to view.
Letterbox simply means a 4:3 or 1:33:1 ratio, which describes TV set
ratios found in the majority of everyone's home. When watching movies
with wider screen ratios on your letterboxed TV, the sides are cut
off. If you see black bars, that means the screen ratio is not 4:3
and therefore more closely resemble its original screen aspect ratio,
but you are sacrificing screen area when this occurs.
Widescreen's ratio is 16:9 or 1:66:1 where widescreen TVs will soon
replace all those 4:3 letterbox TVs once everyone saves up! New TVs,
such as HDTVs (High Definition Television), will utilize this ratio.
What is NTSC and PAL?
The NTSC (National Television Systems Committee) and PAL (Phase
Alteration Line) are television standards used for commercial
television broadcasting around the world. Both NTSC and PAL use interlaced
content at thirty frames per second (approx. 60 fields) and 25 frames
per second (approx. 50 fields) respectively.
Because fields in interlaced signals are independent of other fields
within a given frame, problems arise when two fields--containing
different imagery data--are interleaved for display on non-interlaced
computer monitors. When video imagery with superfluous movement is
displayed, it usually causes motion artifacts (visual imperfections).
DVD titles whose content originates directly from films produced from
Hollywood studios (24 frames/second) won't possess motion artifacts.
What is DirectShow?
Formerly known as ActiveMovie back in the prehistoric days, Microsoft's DirectShow
is a multimedia architecture and a dramatic improvement over the previous one
known as the Media Control Interface (MCI). Because of the inherent limitations
of the 16-bit MCI such as the requirement of bloated single-function drivers,
DirectShow was designed to accommodate the vast array of new and emerging multimedia
hardware and technologies that the aforementioned could not. Based on Microsoft's
Component Object Model (COM), MCI's major headache of inconsistent interfaces
is now a thing of the past when using the multithreading and multitasking DirectShow.
DirectShow is one of the DirectX technology components which also includes
DirectDraw, DirectSound, DirectInput, Direct3D, DirectAnimation, DirectMusic,
etc. DirectX, a set of low-level application programming interfaces (APIs) for
creating high-performance multimedia applications with its overriding design
goal being speed, was originally designed to enhance Windows 95's gaming platform.
But with the advent of the DVD, DBS and a host of other technologies, today
it serves as the gateway in accessing different hardware peripherals and acting
as an integral part of Windows OS (98 and ME editions) and Windows NT 5.0
PowerDVD is fully compliant with DirectX technology. One of the essential components
of PowerDVD is DirectDraw, which accesses hardware directly and thereby increases
graphics speed. It gives developers a common user interface and works in conjunction
with HAL (Hardware Abstraction Layer) and HEL (Hardware Emulation Layer). HAL
allows developers to access hardware devices without explicit knowledge of the
brand's model or its details. HEL is where DirectX features can be emulated
if the device itself does not support those features.
