Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: jlariv8957 on March 14, 2008, 10:11:22 PM
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Hi, how does ahi work to get 14 bit with paula ?
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It plays the same sample on two channels with different volumes.
Detailed documentation as well as the calibration program is in the Play16 archive on Aminet
Bye,
Thomas
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In an A1200? Good enough! But better if you have some Fast RAM or a proper accelerator.
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In short:
The higher 8bits are played with full volume as usual. The lower bits are played with volume 1. The amiga audio HW mixes the channels together.
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Hi, how does ahi work to get 14 bit with paula ?
AHI is not needed. AHI only slows down and reduces the quality of the sound.
Paula sound, so where does that 14bit audio come from?
http://lifeofliveforit.blogspot.com/2013/01/paula-sound-so-where-does-that-14-audio.html
without AHI, native 14bit Paula
Prayer2
SongPlayer 1.53 (deactivate AHI in prefs)
AMP2 (AmiDog's Movie Player 2) WOS
Symphonie Pro
and other.
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Paula sound, so where does that 14bit audio come from?
http://lifeofliveforit.blogspot.com/2013/01/paula-sound-so-where-does-that-14-audio.html
I believe the article is wrong
"So where does that 14bit stereo sound come from? You might have wondered, well after reading the hardware reference manual, it explains that 4 audio channels can be combined in to two.
In this mode, one of channels controls the volume (a value from 0 to 63) 6bits, and wave from is (127 to -127) 8bit, so if you add that up 6+8 = 14bit.
This not a hack, that's a urban myth, it was designed to be like this."
Instead I believe it uses two channels played at different fixed volumes. One channel has the top 8 bits played at full volume like normal, with 6 bits played quietly to smooth it out. What the article said would give you better resolution on quiet sounds but offer no improvement on loud sounds.
You can code it without AHI, but generally if you're writing software that outputs >8bit audio then you want it to work with other sound cards, because the sound cards are usually better for other reasons.
"I have also played whit Paula whit some help, few small errors, and this codes players a beep. I have not really found out about interrupts, the DMA is supposed to trigger a interrupt when sound was played, so you fill the buffer whit new sound, but I can't find any interrupt vector to configure in the hardware reference manual."
I think that sums up the article.
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http://amiga-news.de/en/news/AN-2014-03-00064-EN.html
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AHI only slows down and reduces the quality of the sound.
Indeed.
I believe the article is wrong
It is. That described method can't even be used, because volume modulation modulates two samples per 'modulation sample' if I'm not mistaken.
You can code it without AHI, but generally if you're writing software that outputs >8bit audio then you want it to work with other sound cards, because the sound cards are usually better for other reasons.
Depends. If you want maximum performance, bang the hardware and add an option for AHI if you want sound card support.
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Major problems of this mode is that a) you need to synchronize the channels (probably not too hard since Paula only updates the audio state machine every scanline) b) the D/A converter of Paula has only a limited precision, and hence every type of calibration has only limited success to recover all the imperfections and non-linearities built into the cheap D/A converter logic. c) you still have the issue of the limited frequency resolution, i.e. basically a 15Khz cut-off. So whatever you say, that's not "14 bit quality audio".
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So whatever you say, that's not "14 bit quality audio".
It's still a big improvement over normal eight bit audio.
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It's still a big improvement over normal eight bit audio.
(http://i657.photobucket.com/albums/uu293/mdmundt/haters-gonna-hate-2.jpg)
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It's still a big improvement over normal eight bit audio.
Likely. Or at least "it is some improvement, hopefully, if calibrated carefully". Whether the lower bits in this computation mean anything is really anybodies guess. The audio circuit hasn't been constructed with this in mind, thus... If you want high-quality audio, I would suggest a real audio card, or compute as 16-bit wav, burn on CD and play with your CD player. Turnaround-times are of course rather extreme if the last option is used. (-:
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Likely. Or at least "it is some improvement, hopefully, if calibrated carefully". Whether the lower bits in this computation mean anything is really anybodies guess. The audio circuit hasn't been constructed with this in mind, thus... If you want high-quality audio, I would suggest a real audio card, or compute as 16-bit wav, burn on CD and play with your CD player. Turnaround-times are of course rather extreme if the last option is used. (-:
It's actually very impressive when calibrated correctly. Have to use double scan screen modes though to get 44.1KHz or 48KHz playback, just as you would with normal Paula audio (for those who don't know).
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Likely. Or at least "it is some improvement, hopefully, if calibrated carefully". Whether the lower bits in this computation mean anything is really anybodies guess.
No, not likely, definitely. I use this myself, and it sounds quite good (depends on the source, of course). Quality ranges from 'an improvement' to almost CD quality (really). Depends on the music (and playback rate, and method of down sampling if any).
If you want high-quality audio, I would suggest a real audio card
If I want to use a sound card, I'll use my peecee.