Difference between revisions of "AGI/Specifications/Sound"

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Syntax highlighing
(Fixed Apple IIGS instrument header. There were duplicates for "Priority increment" and "Bend range" (I tested this with data, there shouldn't be).)
(Syntax highlighing)
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The actual frequency produced is the 10-bit frequency divisor given by F0 to F9 divided into 1/32 of the system clock frequency (3.579 MHz) which turns out to be 111,860 Hz. Keeping all this in mind, the following is the formula for calculating the frequency:
The actual frequency produced is the 10-bit frequency divisor given by F0 to F9 divided into 1/32 of the system clock frequency (3.579 MHz) which turns out to be 111,860 Hz. Keeping all this in mind, the following is the formula for calculating the frequency:


<syntax type="C++">
     f = 111860 / (((Byte2 & 0x3F) << 4) + (Byte1 & 0x0F))
     f = 111860 / (((Byte2 & 0x3F) << 4) + (Byte1 & 0x0F))
 
</syntax>


Note: The order of the bytes are reversed for AGI sound data.
Note: The order of the bytes are reversed for AGI sound data.
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My program reads in the duration as a 16 bit word. It then loads the two following bytes and calculates the frequency as follows:
My program reads in the duration as a 16 bit word. It then loads the two following bytes and calculates the frequency as follows:


<syntax type="C++">
     f = 111860 / (((Byte2 & 0x3F) << 4) + (Byte3 & 0x0F))
     f = 111860 / (((Byte2 & 0x3F) << 4) + (Byte3 & 0x0F))
</syntax>


The 111860 comes from the PCjr discussion above. Note that the bytes are in the opposite order from that mentioned in the PCjr information.
The 111860 comes from the PCjr discussion above. Note that the bytes are in the opposite order from that mentioned in the PCjr information.

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