mirror of
https://github.com/JetSetIlly/Gopher2600.git
synced 2025-04-02 11:02:17 -04:00
9f50f3c77e
- implemented audio
- using Ron Fries' method as the basis
- removed sample playback - performance of Fries' method is good
enough that we'll never need it again
- sdl audio routines using QueueAudio() - maybe better if we use
callbacks?
- sketched wavwriter AudioMixer - not usable yet
91 lines
2.5 KiB
Go
91 lines
2.5 KiB
Go
package polycounter
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import "fmt"
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type table []string
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// Poly6Bit is the polycounter sequence over the space of 6 bits
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var Poly6Bit table
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// Poly5Bit is the polycounter sequence over the space of 5 bits
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// (used by audio generator)
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var Poly5Bit table
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// Poly4Bit is the polycounter sequence over the space of 4 bits
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// (used by audio generator)
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var Poly4Bit table
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// initialise the 6 bit table representing the polycounter sequence. we use to
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// match the current count with the correct polycounter pattern. this is
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// currently used only in the String()/ToString() functions for presentation
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// purposes and when specifying the reset pattern in the call to Reset()
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func init() {
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var p int
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// poly 6 bit generation
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Poly6Bit = make([]string, 64)
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Poly6Bit[0] = "000000"
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for i := 1; i < len(Poly6Bit); i++ {
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p = ((p & (0x3f - 1)) >> 1) | (((p&1)^((p>>1)&1))^0x3f)<<5
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p = p & 0x3f
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Poly6Bit[i] = fmt.Sprintf("%06b", p)
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}
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// sanity check that the table has looped correctly
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if Poly6Bit[63] != "000000" {
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panic("error during 6 bit polycounter generation")
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}
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// force the final value to be the invalid polycounter value. this is only
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// ever useful for specifying the reset pattern
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Poly6Bit[63] = "111111"
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// poly 5 bit generation
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Poly5Bit = make([]string, 22)
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Poly5Bit[0] = "00000"
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for i := 1; i < len(Poly5Bit); i++ {
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p = ((p & (0x1f - 1)) >> 1) | (((p&1)^((p>>1)&1))^0x1f)<<4
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p = p & 0x1f
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Poly5Bit[i] = fmt.Sprintf("%05b", p)
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}
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// sanity check that the table has looped correctly
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if Poly5Bit[21] != "00000" {
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panic("error during 5 bit polycounter generation")
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}
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// force the final value to be the invalid polycounter value. this is only
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// ever useful for specifying the reset pattern
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Poly5Bit[21] = "11111"
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// poly 4 bit generation
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Poly4Bit = make([]string, 16)
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Poly4Bit[0] = "0000"
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for i := 1; i < len(Poly4Bit); i++ {
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p = ((p & (0x0f - 1)) >> 1) | (((p&1)^((p>>1)&1))^0x0f)<<3
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p = p & 0x0f
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Poly4Bit[i] = fmt.Sprintf("%04b", p)
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}
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// sanity check that the table has looped correctly
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if Poly4Bit[15] != "0000" {
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panic("error during 5 bit polycounter generation")
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}
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// force the final value to be the invalid polycounter value. this is only
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// ever useful for specifying the reset pattern
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Poly4Bit[15] = "1111"
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}
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// LookupPattern returns the index of the specified pattern
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func (tab table) LookupPattern(pattern string) int {
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for i := 0; i < len(Poly6Bit); i++ {
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if Poly6Bit[i] == pattern {
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return i
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}
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}
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panic(fmt.Sprintf("could not find pattern (%s) in 6 bit lookup table", pattern))
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}
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