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audio: use int constants (C style enums) instead of string.

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Change-Id: Ifb6db04c4bbf6c66e5a63dcaeee704ab02e711b0
Reviewed-on: https://go-review.googlesource.com/6423
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Nigel Tao 2015-03-02 15:22:29 +11:00
parent 388f1b8302
commit fc5f7c74c8
1 changed files with 42 additions and 30 deletions
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72
audio/audio.go
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@ -18,33 +18,60 @@ import (
) )
// Format represents an PCM data format. // Format represents an PCM data format.
type Format string type Format int
const ( const (
Mono8 = Format("mono8") Mono8 Format = iota
Mono16 = Format("mono16") Mono16
Stereo8 = Format("stereo8") Stereo8
Stereo16 = Format("stereo16") Stereo16
) )
var formatToCode = map[Format]int32{ func (f Format) String() string { return formatStrings[f] }
// formatBytes is the product of bytes per sample and number of channels.
var formatBytes = [...]int64{
Mono8: 1,
Mono16: 2,
Stereo8: 2,
Stereo16: 4,
}
var formatCodes = [...]uint32{
Mono8: al.FormatMono8, Mono8: al.FormatMono8,
Mono16: al.FormatMono16, Mono16: al.FormatMono16,
Stereo8: al.FormatStereo8, Stereo8: al.FormatStereo8,
Stereo16: al.FormatStereo16, Stereo16: al.FormatStereo16,
} }
var formatStrings = [...]string{
Mono8: "mono8",
Mono16: "mono16",
Stereo8: "stereo8",
Stereo16: "stereo16",
}
// State indicates the current playing state of the player. // State indicates the current playing state of the player.
type State string type State int
const ( const (
Unknown = State("unknown") Unknown State = iota
Initial = State("initial") Initial
Playing = State("playing") Playing
Paused = State("paused") Paused
Stopped = State("stopped") Stopped
) )
func (s State) String() string { return stateStrings[s] }
var stateStrings = [...]string{
Unknown: "unknown",
Initial: "initial",
Playing: "playing",
Paused: "paused",
Stopped: "stopped",
}
var codeToState = map[int32]State{ var codeToState = map[int32]State{
0: Unknown, 0: Unknown,
al.Initial: Initial, al.Initial: Initial,
@ -121,7 +148,7 @@ func (p *Player) prepare(offset int64, force bool) error {
if n > 0 { if n > 0 {
size += int64(n) size += int64(n)
b := al.GenBuffers(1) b := al.GenBuffers(1)
b[0].BufferData(uint32(formatToCode[p.t.format]), buf[:n], int32(p.t.samplesPerSecond)) b[0].BufferData(formatCodes[p.t.format], buf[:n], int32(p.t.samplesPerSecond))
bufs = append(bufs, b[0]) bufs = append(bufs, b[0])
} }
if err == io.EOF { if err == io.EOF {
@ -259,26 +286,11 @@ func (p *Player) Destroy() {
} }
func byteOffsetToDur(t *track, offset int64) time.Duration { func byteOffsetToDur(t *track, offset int64) time.Duration {
samples := offset return time.Duration(offset * formatBytes[t.format] * int64(time.Second) / t.samplesPerSecond)
if t.format == Mono16 || t.format == Stereo16 {
samples /= 2
}
if t.format == Stereo8 || t.format == Stereo16 {
samples /= 2
}
return time.Duration(samples * int64(time.Second) / t.samplesPerSecond)
} }
func durToByteOffset(t *track, dur time.Duration) int64 { func durToByteOffset(t *track, dur time.Duration) int64 {
size := t.samplesPerSecond * int64(dur) / int64(time.Second) return int64(dur) * t.samplesPerSecond / (formatBytes[t.format] * int64(time.Second))
if t.format == Mono16 || t.format == Stereo16 {
// Each sample is represented by 16-bits. Move twice further.
size *= 2
}
if t.format == Stereo8 || t.format == Stereo16 {
size *= 2
}
return size
} }
// lastErr returns the last error or nil if the last operation // lastErr returns the last error or nil if the last operation