[Haskell-cafe] Precise timing

[Alexander Scharinger]

I think it would be much easier to take a different approach. For 
example one of these:
* Use an audio library
* Write your own audio synthesis

John Lato already said something about the usual approach to audio software.

I will just sketch out how to write very simple audio synthesis:

* You need a sample rate!
* Think in terms of a modular audio synthesizer
* Write your own oscillator.
* Write an "amplifier", which scales the oscilators amplitude up and 
down. Whenever you want the oscilator to not make sound you have to mute 
the amplifier.
* Write an envelop generator, which generates an envelop for your amplifier.
* Write a sequencer, which controlls the envelop generator. The 
sequencer should take your prefered encoding (like 'cycle [1,1,2]')
* Write the output of the amplifier straight into the audio-out buffer 
of your OS. I don't know how you do that exactly. You have to find out. 
But I do know that on Linux you could also just write the output of your 
program to standard-out and pipe it into ALSA on the command line with 
the padsp command.

Advantages of this approach:
* IO-Monad is used only on the highest level of abstraction.
* If you write straight into the audio-out buffer of your OS, the OS 
will suspend and schedule your process as needed. Whenever the audio-out 
buffer is full, your process will be blocked by the OS on the write 
system call. You don't have to think much about scheduling.
* it's easy. Most of the components could be a single and simple function.

Just my 2 cents,
Alexander


On 10/22/2014 05:14 AM, Jeffrey Brown wrote:
> On a separate thread
> <http://haskell.1045720.n5.nabble.com/How-to-send-a-string-somewhere-via-UDP-td5758418.html>,
> Rohan Drape showed me how to send OSC. The following test, which
> simplifies the old one and replaces printf with OSC, demonstrates timing
> as perfect as my ears are able to distinguish.
>
>      import Control.Concurrent
>      import Control.Monad
>      import System.IO
>      import Sound.OSC
>      main = do
>          hSetBuffering stdout NoBuffering
>          mapM_ note (cycle [1,1,2])
>      withMax = withTransport (openUDP "127.0.0.1" 9000)
>      beat = 60000 -- 60 ms, measured in µs
>      note :: Int -> IO ()
>      note n = do
>          withMax (sendMessage (Message "sin0 frq 100" []))
>              -- set sine wave 0 to frequency 100
>          withMax (sendMessage (Message "sin0 amp 1" []))
>              -- set sine wave 0 to amplitude 1
>          threadDelay $ beat * n
>          withMax (sendMessage (Message "sin0 amp 0" []))
>              -- set sine wave 0 to amplitude 0
>          threadDelay $ beat * n
>
> This means I can use Haskell instead of Python or SuperCollider. I am
> beside myself with excitement.
>
> Thanks again, everyone!
>
> On Tue, Oct 21, 2014 at 2:24 AM, Brandon Allbery <allbery.b at gmail.com
> <mailto:allbery.b at gmail.com>> wrote:
>
>     On Tue, Oct 21, 2014 at 4:05 AM, Heinrich Apfelmus
>     <apfelmus at quantentunnel.de <mailto:apfelmus at quantentunnel.de>> wrote:
>
>         I would be hesitant to attribute your problem to the scheduler.
>         An alternative explanation could be the following: The sound
>         file played by the terminal when it encounters the \BEL
>         character is longer than 100ms. A new sound will be played only
>         when the previous sound has finished playing,
>
>
>     On most systems I've used, this isn't true; they're either
>     suppressed or they overlap, depending on system. (I've had to work
>     around this.)
>
>     --
>     brandon s allbery kf8nh                               sine nomine
>     associates
>     allbery.b at gmail.com <mailto:allbery.b at gmail.com>
>     ballbery at sinenomine.net <mailto:ballbery at sinenomine.net>
>     unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
>
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