Contents | < Browse | Browse >
From: Dirk Tust <Dirk.Tust@mni.fh-giessen.de>
It's good to read a new issue of Amiga Report after many weeks of waiting.
Although I have left the Amiga community some years ago I still have a look
at the development of the Amiga from time to time, and your AR is an
excellent way to do so.
However, in issue 5.04 you reported about one MPEG audio compression scheme
and, after listing some names for it, you decided to call it "MPEG3".
Unfortunately, this is defintely the wrongest one (greetings to Murphy 8-)
). To enlighten you, here is a short description of the MPEG family.
Video: non-interlaced video with frames up to 4095*4095 pixels
theoretically, real implementations mostly use 352*240 at 30 frames/s and
352*288 at 25 frames/s
Audio: 16 bit PCM audio mono or stereo at 32/44.1/48 kHz sampling rate
There are three encoding schemes for audio which are called Layer 1, Layer
2, and Layer 3. The different layers are optimized for different intended
target bitrates of 192, 128, and 64 kb/s per audio channel respectively
with maximum total rates of 448, 384, and 320 kb/s respectively.
System: How to mix video and audio data streams into one data stream
Video: interlaced and non-interlaced video with frames up to 16383*16383
pixels theoretically, real implementations with 720*480 at 30 frames/s,
720*576 at 25 frames/s (both used in DVD Video), 1920*1080 at 30 frames/s
(US digital television, maximum values)
Audio: same as MPEG-1 Audio, extended with specs for:
- sampling rates 16/22.05/24 kHz
- surround sound channels compatible with MPEG-1 Audio
- surround sound channels _not_ compatible with MPEG-1 Audio
System: as above, with compatible extensions
intended for High Definition TV (e.g. 1920*1080 pixels), but dropped
because MPEG-2 was sufficent for this, too
video and audio encoding for very low bitrates (ca. 64 kb/s), still under
More information is available via http://www.mpeg.org.
Summary and conclusion: The right name is "MPEG-1 Audio Layer 3".
- Thanks for the summary, Dirk. I understand the confusion the term
"MPEG3" doubtless causes among those who really understand MPEG but
the fact is that most of the resources our readers will be looking
through will indeed refer to MPEG-1 Audio Layer 3 as "MPEG3" or simply
"MP3". In a way that seems appropriate if the real "MPEG-3" is a
defunct standard. -Jason
From: email@example.com (Robert Atkins)
Subject: Why people wanted the Gateway AR issue...
There are two sources of information I believe for Amiga buyout related
news. Official press releases in comp.sys.amiga.announce, and the news and
editorial of AR. It's just not worth the trouble of believing anything
else these anymore.
Up until a couple of days after "the announcement", nothing had turned up
in c.s.a.a on my news server, and that's why *I* was hanging on for the
buyout issue of AR.
I think that's why people still wanted the GW buyout issue -- so we had the
real story from the source we trust. Thanks.