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
89 lines
2.1 KiB
Go
89 lines
2.1 KiB
Go
package sdlplay
|
|
|
|
import (
|
|
"gopher2600/hardware/tia/audio"
|
|
|
|
"github.com/veandco/go-sdl2/sdl"
|
|
)
|
|
|
|
// the buffer length is important to get right. unfortunately, there's no
|
|
// special way (that I know of) that can tells us what the ideal value is. we
|
|
// don't want it to be long because we can introduce unnecessary lag between
|
|
// the audio and video signal; by the same token we don't want git too short because
|
|
// we will end up calling FlushAudio() too often - FlushAudio() is a
|
|
// computationally expensive function.
|
|
//
|
|
// the following value has been discovered through trial and error. the precise
|
|
// value is not critical.
|
|
const bufferLength = 1540
|
|
|
|
type sound struct {
|
|
id sdl.AudioDeviceID
|
|
spec sdl.AudioSpec
|
|
buffer []uint8
|
|
bufferCt int
|
|
}
|
|
|
|
func newSound(scr *SdlPlay) (*sound, error) {
|
|
snd := &sound{}
|
|
|
|
snd.buffer = make([]uint8, bufferLength)
|
|
|
|
spec := &sdl.AudioSpec{
|
|
Freq: audio.SampleFreq,
|
|
Format: sdl.AUDIO_U8,
|
|
Channels: 1,
|
|
Silence: 127,
|
|
Samples: uint16(bufferLength),
|
|
}
|
|
|
|
var err error
|
|
var actualSpec sdl.AudioSpec
|
|
|
|
snd.id, err = sdl.OpenAudioDevice("", false, spec, &actualSpec, 0)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
snd.spec = actualSpec
|
|
|
|
// make sure audio device is unpaused on startup
|
|
sdl.PauseAudioDevice(snd.id, false)
|
|
|
|
return snd, nil
|
|
}
|
|
|
|
// SetAudio implements the television.AudioMixer interface
|
|
func (scr *SdlPlay) SetAudio(audioData uint8) error {
|
|
scr.snd.buffer[scr.snd.bufferCt] = audioData + scr.snd.spec.Silence
|
|
|
|
scr.snd.bufferCt++
|
|
if scr.snd.bufferCt >= len(scr.snd.buffer) {
|
|
return scr.FlushAudio()
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// FlushAudio implements the television.AudioMixer interface
|
|
func (scr *SdlPlay) FlushAudio() error {
|
|
err := sdl.QueueAudio(scr.snd.id, scr.snd.buffer)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
scr.snd.bufferCt = 0
|
|
|
|
return nil
|
|
}
|
|
|
|
// PauseAudio implements the television.AudioMixer interface
|
|
func (scr *SdlPlay) PauseAudio(pause bool) error {
|
|
sdl.PauseAudioDevice(scr.snd.id, pause)
|
|
return nil
|
|
}
|
|
|
|
// EndMixing implements the television.AudioMixer interface
|
|
func (scr *SdlPlay) EndMixing() error {
|
|
defer sdl.CloseAudioDevice(scr.snd.id)
|
|
return scr.FlushAudio()
|
|
}
|