Amiga.org
Amiga computer related discussion => Amiga Software Issues and Discussion => Topic started by: CU_AMiGA on March 27, 2004, 01:16:37 PM
-
Hello, would it be possible for MP3 playback on a stock Amiga 1200!!! At any quality? (Not including OctaMED!)
-
You need the MAS-Player Hardware for that
http://cgi.snafu.de/dcr/user-cgi-bin/Website?name=HTML_Welcome&l=en&tool=User
With this pice of Hardware you can Play MP3 even on a humble A500 with some extra fast-RAM.
Using only software there is no chance.
Minimum for Softwareplayback alone at 128kbps is a 68040 @ 25 MHz but don`t dare to touch the mouse during playback.
-
I've done it in software using an Amiga500 with an MTec Viper/030 clocked at 50MHz using 40ns simms rated for 133MHz. Running at full speed no less. The key, don't use any screenmode past 4 colors and avoid overscanning. I've also done software mp3 playing using a Derringer030 overclocked from 50MHz to 66MHz. The Derringer was a much nicer accel (features wise), but the MTec Viper was definately built better.
:pint:
-
My A1200 has a 40MHz 68030 card and I can get it to play mp3s just fine, but they suck in quality. I remember using mpega:
I hope I can remember this right
MPEGA mp3file.mp3 -d4 -q0 -m
d4 = divide frequency (44.1KHz) by 4 (11.025) KHz
q0 = accuracy level 0
m = mono
Those settings left me enough bandwidth to actually do a little multitasking :-) If you only have the stock 68EC020 CPU don't even bother because the lowest settings will still be too much for it. I have never used a 68060 so I couldn't tell you how well that works.
Oddly my 040/40 in my 3000T will lock up if I try and play MP3s.
Anyway it is possible but unless you have an mp3 hardware decoder or PPC card it kinda sucks.
-
an 060 clocked at 50mhz will play a 128kbps mp3 at full quality with about 50% load... :-)
my 160mhz PPC can play 192kbps (thats how all mine are encoded) with about 35% load.
-
I'm a little confused by the "not including OctaMED" bit... :-?
-
The only possibility to use MP3s with a stock A1200 would be to convert it to aiff and play that then.
-
I'm a little confused by the "not including OctaMED" bit..
Yeah, I don't think he is very familier with file types.
I would have thought that a 160mhz PPC would have been able to do better than 35% load on a 192Kb/s MP3 =/
-
For a low-end (ie stock) A1200, there is simply nothing to rival the parallel port MAS player doofer.
Your basic A1200 can send easily 16K/s (kilobytes, that is) through the parallel port (roughly what a 128kbps mp3 uses) to the litttle decoder chip inside. Better still, you get clean 16-bit stereo audio out, uncontaminated by blitter noise etc. that paula tends to suffer from.
If you have any kind of accelerator, CPU drain is zip ;-)
-
NightShade737 wrote:
I would have thought that a 160mhz PPC would have been able to do better than 35% load on a 192Kb/s MP3 =/
Well, the all infamous context switch comes into play. If your'e gonna do mp3 playback using PPC under WarpOS or PowerUP, you need a good length playback / load buffer to minimise the number of CPU switches between the 680x0 and PPC.
-
How come the 21 processors can't be used at the same time, i.e. like a CPU and FPU which doesn't screw up the performance of the machine?
Seems like an issue that should have been worked around...
-
In 2 words
Copyback Cache
First of all, the external FPU only accesses memory via the cpu itself (AFAIR), that is, when it wants to fetch some data from memory, it signals the CPU, which gets the data and then sends it to the FPU. It doesn't access memory by itself. This is part of the reason "on chip" FPUs are so much faster than external ones.
To the 680x0/PPC combo
Essentially, neither CPU was particularly designed for multiprocessing. Both the 68040/68060 and 603/604 implement copyback caches, so whenever they write to an area that is cacheable, it doesn't necessarily go to that area immediately. Instead it goes into an area of on-chip cache and will be pushed when it's most optimal to do so. Disabling this cache cripples both cpus (if you can turn off your copyback on an 040 or 060 card, you will see what I mean).
So, for peak performance, both CPUs have their copybacks enabled. Now, as long as they arent using the same memory area (like two totally different programs), things are fine. However, a ppc task and a mirror 680x0 task that are part of the same application obviously do need to share the same memory.
The context switch comes in when the PPC has to call the 680x0 (or vice versa). The PPC particularly needs the 680x0 to do OS calls on its behalf (eg reading files, putting things on screen etc). Anyway, when this happens, its quite possible the memory they are sharing and the caches of each chip are out of sync due to pending writebacks. So each CPU has to purge its cache, resyncing all the data.
It sounds bad, and indeed it is, but frankly there isn't much you can do about it. Disabling the copybacks cripples performance all of the time, cache flushing only cripples when it occurs. So the latter is generally better.
-
When I had my CSPPC a 128bit only took 9% of the load from the PPC where as a 192bit took only 7% using a custom GUI driven ConciertoMpega. I probably could have dropped the cpu usage even lower... I mean, it was a decked system.
:pint:
-
AmigaAMP/WOS, graphic equalizer enabled on my A1200 040+603 240, playing via AHI/paula from the motherboard IDE doesnt use more than 20% max.
It just comes down to finding the right balance of decode / playback length. Also, never use AHI5 on any 680x0 system! It murders the cpu...
-
Hello, Thanks for the replies. I am only asking in desperation really as i am waiting for the PPC card to arrive. I also said no OctaMED just incase someone mention it, i know its a player, not an extension! :-) Anyway, how would i convert mp3s to aiff, i thought aiff were larger?
Cheers,
-
"ConciertoMpega"???
There's an optimized mpega.library for the concierto? I have one, where can I download it?
-edit- ok, I found it :-)
-
You can convert mp3 into aiff with mpega.
Certainly the file will get over 10 times larger, a harddisk is needed.
mpega xyz.mp3 -s -A -o xyz.aiff
Then you can play it with Multiview, Play16 or so.
-
Don't forget the Delfina Flipper Clockport (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4598&item=4120628355) Edition.:-)
-
Cheers guys, iu will try that aiff thing on my Amiga tonight and laugh at the results! :-)
-
Ha! :-) Tried it yesterday and was pleasantly surprised at the outcome, the quality is pretty good. Took about just over an hour to decompress the mp3 to aiff! Worth it though. Thanks again.