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MPEGA 2.2

All of you should have heard about MPEG. Standing for the Motion Picture Expert Group, this standards body invented the video compression system used on Video CDs. Movies aren't all pictures though and the standards body endorses standards for compressing audio as well.

MPEG audio comes in three flavors, known as layers 1 to 3. Each increasing in complexity, compression rate and CPU power needed to encode and decode. The latest standard, MPEG audio layer 3 is truly a miraculous thing. Able to compress CD quality 44Khz 16-bit audio by about 12:1 with so little loss of quality as to be unnoticable to most.

The whole thing has taken off in a big way on the PC platform. The compressed files postfixed '.mp3' can contain an entire CD quality song and only be a couple of megabytes in size. For more information, it's worth popping into the mpeg3 faq.

Until recently the process required so much CPU horsepower that even the most powerful Amiga was incapable of playing back layer 3 audio in real time, though you could use some Unix hack/ports to decode it for play later. The less demanding and less compressed layer 2 had been done before by the French Stéphane Tavenard who wrote a raw assembly player for Delitracker.

MPEGA

Stéphane Tavenard has come to the rescue again by implementing layer 1 to 3 decoding in a stand alone CLI based player inspiringly called 'mpega'. The most stunning aspect of this is the highly optimised, hand coded assembly layer 3 playing routines. The first version miraculously played real time layer 3 audio on a 50Mhz 68060 and this was way ahead of the others at the time (still is). However when 2.2 was released, CPU time fell 20% futher so that 40Mhz 68040s can play layer 3 audio.

All is not lost for Amiga owners of lesser CPUs however. Mpega has the facility to decrease the output frequency by a factor of 2 or 4. At 2 the output is at 22Khz and 4, it is a measly 11. There's also a quality level setting which has a small effect on the sound quality but decreases CPU consumption yet further. Naturally there's versions of the main executable for all groups of the 680x0 family with and without FPU (not much point in this). I found that the program stops on accessing menus and such forth which is a bit annoying. A partial work around was to set the -t buffer to something silly like 10000. Play16 doesn't suffer from this so I think this feature may be fixable in a forthcoming release.

Here's a dump of Mpega's CLI options;

MPEGA V2.2 (C)1995-1997 Stéphane TavenardD
Release date: Apr  5 1997 (68040/60+FPU)
Email: Tavenardd@xiii.univ-angers.fr
Freeware MPEG Audio decoder for Layers I,II and III

Usage: mpega [<options>] <MPEG Audio file> [<out pcm file>]
Options:
-d <freq_div>   frequency division: 1, 2 or 4
-q <quality>    output quality: 0 (worst), 1 or 2 (best)
-h              display header only
-n              no frame counter
-m              mono output (left channel)
-p              play audio
-f 0|1          audio filter off/on (default = auto)
-x <freq>       audio mixing frequency (default = none)
-t <ms>         audio buffer time in ms (default = 1 sec)
-v <vol>        audio volume (0..64 or 65..256 for boost)

Enjoy fast MPEG :-)

There's absolutely no doubt in my mind that mpega is the most efficient software mpega layer 3 player in the world. The PC varieties use around 75% CPU time on a Pentium 150 and these claim to be optimised. It's people like Stéphane Tavenard that continue to enable the Amiga to sit up there at the cutting edge of computing technology with fast efficient coding rather than mountains of expensive hardware resources.

I'm extremely exited about this program, it's only a matter of time until it grows the ability to connect over the Internet like Winplay on the PC. Then you'll be able to tune into the MPEGA layer 3 radio stations and such forth. I've encoded a number of my favorite albums and put on a single gold CD which I play on the office 4000T at random, something I didn't think it was going to be possible to do on the Amiga. The sound quality is absolutely superb, having plugged in my Sennheiser headphones to the back of the 4000T, I might as well be listening to CD.

I can't recommend this program highly enough, if you've got a 68040 or above, it's essential but it will run in the lowest quality settings on a 50Mhz 68030 machine. When AHI V3.0 is released, mpega will play to virtually any 16-bit sound card via the audio: device so that's going to improve the quality yet further. However, the best part of all is that it's totally free so click below to get it now.

5 star Download mpega (220k lha archive).

Stop press! 2.3 released, even less CPU required!

Mat Bettinson

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