A: This article specifically covers the video formats
used up to Amiga Forever 6.0 (released in 2004). Amiga Forever
2005 and higher use industry standard glass-mastered dual layer
video DVDs.
The CD Edition of Amiga Forever contains several
hours of video footage which has to be "encoded" (compressed) to
save disk space while trying to preserve as much visual quality as
possible.
The first versions of Amiga Forever used MPEG-1 to encode
videos. This technology, released by the Moving Pictures Experts
Group (MPEG) of the International Standards Organization (ISO), is
also used on Video CDs (VCDs). Some of the advantages of MPEG-1
include:
- Well-defined specification with little or no unsupported
variations and few incompatibilities between encoders and
decoders (i.e. player software)
- Availability of players on all platforms (Amiga, Windows,
Mac, GNU/Linux, Unix, etc.)
- Ideal for playback using average CPUs of 1997, including the
Amiga's Motorola 68000 series
- Royalty-free distribution of encoded video files
Since 1997, new encoding specifications and software were
released and more powerful CPUs became popular, making it possible
to add more video footage to Amiga Forever while at the same time
significantly improving the video quality with respect to the
previously released MPEG-1 files. Not only did MPEG-2, the
successor of MPEG-1, become popular on digital cable and satellite
TV, and as the format used on DVDs, but MPEG-4, the successor of
MPEG-2, started moving from the labs to real world applications.
Unfortunately, MPEG-4 took much longer than expected both to be
finalized and to gain acceptance, while competing technologies
were gaining ground. For example, Apple released different
versions of its QuickTime video encoding specification and
software, and Microsoft did the same with its own Windows Media
codecs.
Between 1998 and 1999:
- Microsoft released a new "version 3" Windows Media Player
codec based on preliminary MPEG-4 specifications. This codec,
like previous MPEG-4 codecs released by Microsoft, only
supported MPEG-4 data wrapped in Microsoft's proprietary ASF
file and streaming formats.
- The ISO adopted Apple's QuickTime file format (not video
compression technology) as a container for MPEG-4 data.
- J�r�me Rota modified Microsoft's preliminary codec, allowing
it to play back MPEG-4 videos stored in "normal" files (e.g.
AVI) and releasing it as "DivX;-)". This modified codec, which
did not have the blessing of either Microsoft or the ISO MPEG-4
committee became unexpectedly popular and also known as "the MP3
for video."
To further clarify some common misunderstandings, when
Microsoft states that it was one of the first companies to adopt
MPEG-4, this doesn't mean that Windows Media Player as shipped
until 2003 can play back, or ever was able to play back, .mp4
video files (because Microsoft only supported MPEG-4 in .asf files
or streams). Similarly, when Apple says that the ISO adopted the
QuickTime file format, that only refers to the file format (which,
like the Amiga's IFF, is a generic "wrapper" or "container"), and
not to the video or audio encoding technology used by QuickTime
before Apple itself adopted MPEG-4.
During 2002 and 2003, while the MPEG-4 video compression
methods such as Simple Profile (SP) and Advanced Simple Profile
(ASP) were being embraced by companies like Apple and Real
Networks, the ISO was busy working on new MPEG-4 extensions such
as H.264 (also known as AVC, or MPEG-4 Part 10). In the meantime,
Microsoft released version 9 of the Windows Media encoding
technology (WM9), formerly code-named "Corona". The WM9
video decoding technology also goes under the more
platform-neutral reference title of VC-1.
The Windows Media 9 video codec, released as a standard by the
Society of Motion Picture and
Television Engineers under the name of "VC-1" is, according to independent
reviews and experts, not only superior in terms of both quality
and compression to both ASP and AVC, but it also offers a few
other advantages over MPEG-4:
- No major incompatibilities between Microsoft's encoder
(Windows Media Encoder) and decoder (Windows Media Player and
codecs) software
- Free encoder and decoder software
- No royalties to distribute WM9/VC-1-encoded video files
Until the end of 2003, while there were MPEG-4 players for different
computing platforms (e.g. Windows, Mac, GNU/Linux, Amiga),
Microsoft had made available its WM9/VC-1-capable codecs for Windows only
(the appropriate codec is automatically downloaded when Windows
Media Player 7.1 or higher are used). On November 8, 2003, less
than a month after Apple released its iTunes music software for
Windows, Microsoft released Windows Media Player 9 for Mac OS. In
March 2004 the Steering Committee of the
DVD Forum, which oversees
official DVD formats, gave preliminary approval to VC-1 (in
addition to MPEG-4 AVC and MPEG-2) as a codec for use in the HD
DVD Video specification, to be implemented on its new 20 GB blue
laser DVD media. In September 2004 the
Blu-ray Disc Association,
which is proposing its BD-ROM specification as an additional
possible evolution to the DVD, also endorsed DV-1 as part of its
standard.
Unlike Apple,
Microsoft decided not to support MPEG-4 video files in its Media Player
for Windows, which therefore only supports MPEG-4-encoded movies
if a third-party codec is installed. As
of early 2004, neither Microsoft nor Apple supported the MPEG-4
AVC profile in their respective players.
In spite of technical, usability and economical advantages of
Windows Media 9 (superior quality, shorter files, ease of playback
under Windows, free encoding software and free redistribution of
encoded files), Cloanto originally selected MPEG-4 as the new video format of
choice for the Amiga Forever CD-ROM, because of the anticipated superior
cross-platform support of MPEG-4 over Windows Media 9 technology. MPEG-2 was
bypassed because it offered inferior quality and compression
results compared to even the simplest MPEG-4 profiles.
The videos stored on the Amiga Forever 6.0 CD-ROM were to be encoded
using the MPEG-4 Advanced Simple Profile (ASP). The ASP
codec was chosen instead of AVC (H.264) because of the following
reasons:
- Limited support for AVC in encoding software
- Limited support for AVC in decoding software (players)
- AVC playback requires more powerful CPUs than ASP
- The original videos themselves are mostly not better than
VHS quality
In practice, once the contracts for the distribution of the
videos under an MPEG-4 patent portfolio license had already been
signed, it turned out that, even with the latest encoding software
versions, in order to create MPEG-4 video files which were
compatible with major player applications
on different platforms (e.g. Windows Media with DivX or 3ivx
codex, QuickTime Player, DivX Player) unexpected quality
compromises had to be accepted in order to retain compatibility.
This significantly diminished the value of the (theoretical)
technological advantage of MPEG-4 over, for example, MPEG-2. The
original goal of uncompromising quality with maximum
cross-platform compatibility had become a victim of the complexity
of MPEG-4 and its partial implementation in different players on
various platforms.
Considering the overall situation, it was at that point decided
to use the highest quality Windows Media 9 codec options to
prepare the Amiga Forever videos for distribution, and to further
add a HighMAT data layer which would make the media not only
compatible with Windows and Mac versions of Windows Media Player,
but also with hardware players. Amiga Forever 6.0 was therefore
released with WM9/VC-1 video content, resulting in a picture quality
which is even superior to that of MPEG-4 AVC, as tested for
possible future use in Amiga Forever.
It is expected that during 2004 and 2005 not only will AVC be
better supported, but Microsoft itself may perhaps include MPEG-4
support in its Windows Media Player series. Also, the choice of new codecs for the next-generation DVD
standard will in turn influence the acceptance of such codecs.
At Cloanto we hired some of the best professionals and
equipment in the video field to digitally preserve the original
Amiga video tapes. We are excited that WM9 makes it possible to
now release these historical videos in a quality which is almost
always better than that which can be achieved with a home VCR
playing back 15-year old VHS tapes. We will closely monitor the
evolution of video codecs, which keeps surprising even the experts
in this field for some of its unexpected innovations, and decide
accordingly for the future use of new codecs.
If you would like to share your thoughts on this
topic please do not hesitate to let us know.
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