I am a beginning C programmer (though not a beginning programmer) looking to dive into a project to teach myself C. My project is music-based, and because of this I am curious whether there are any ‘best practices’ per-se, when it comes to timing functions.
Just to clarify, my project is pretty much an attempt to build some barebones music notation/composition software (remember, emphasis on barebones). I was originally thinking about using OSX as my platform, but I want to do it in C, not Obj-C (though I know it would probably be easier…CoreAudio looked like a pretty powerful tool for this kind of stuff). So even though I don’t have to build OSX apps in Obj-C, I will probably end up building this on a linux system (probably debian…).
Thanks everyone, for your great answers.
There are two accurate methods for timing functions:
Single Process Execution
Most modern computers execute more than one program simultaneously. Actually, they execute pieces of many programs, swapping them out based on priorities and other metrics to look like more than one program is executing at the same time. This overhead effects timing in programs. Either the program gets delayed in reading the time or the OS gets delayed in setting its own time variables.
The solution in this case is to eliminate as many tasks from running. The ideal environment is for best accuracy is to have your program as the sole program running. Some OSes provide API for superuser applications to block all other programs or kill them.
Timer event handling / callback
Since the OS can’t be trusted to execute your program with high precision, most OS’s will provide Timer APIs. Many of these APIs include the ability to call one of your functions when the timer expires. This is known as a callback function. Other OS’s may send a message or generate an event when the timer expires. These fall under the class of timer handlers. The callback process has less overhead than the handlers and thus is more accurate.
Music Hardware
Although you may have your program send music to the speakers, many computers now have separate processors that play music. This frees up the main processor and provides more continuous notes, rather than sounds separated by silent gaps due to platform overhead of your program send the next sounds to the speaker.
A quality music processor has at least these to functions:
Start Playing
This is the function where you tell the music processor where your data is and the size of the data. The processor will start playing the music.
End Music Notification
You provide the processor with a pointer to a function that it will call when the music data has been processed. Nice processors will call the function early so there will be no gaps in the sounds while reloading.
All of this is platform dependent and may not be standard across platforms.
Hope this helps.