NewContext occupies 5% of the CPU, even if no audio is played

[zwjjiaozhu]

os：macos 12.6

When the audio is not playing, I see that the idle wake-up thread is constantly increasing in the activity monitor software on the Mac
I don't know why it doesn't play audio and still takes up CPU to calculate
Is there any way to solve it? Thank you

[hajimehoshi]

Could you give me a minimized code to reproduce this issue?

[zwjjiaozhu]

Could you give me a minimized code to reproduce this issue?

thanks

package main

import (
	"github.com/ebitengine/oto/v3"
	"github.com/hajimehoshi/go-mp3"
	"os"
	"time"
)

func main() {
	file, _ := os.Open("test.mp3")
	defer file.Close()
	decoder, _ := mp3.NewDecoder(file)

	op := &oto.NewContextOptions{}

	// Usually 44100 or 48000. Other values might cause distortions in Oto
	op.SampleRate = 24100

	// Number of channels (aka locations) to play sounds from. Either 1 or 2.
	// 1 is mono sound, and 2 is stereo (most speakers are stereo).
	op.ChannelCount = 2

	// Format of the source. go-mp3's format is signed 16bit integers.
	op.Format = oto.FormatSignedInt16LE

	var otoContext *oto.Context
	var readyChan chan struct{}
	// 在newContext中会有5%的cpu
	otoContext, readyChan, _ = oto.NewContext(op)
	<-readyChan
	player := otoContext.NewPlayer(decoder)
	defer player.Close()
	player.Play()
	time.Sleep(2 * time.Second)
	player.Close()
	time.Sleep(200 * time.Second)
}

[hajimehoshi]

I'm not sure the issue. Your program plays an MP3 file.

[Asday]

You may need to share the MP3 file you're using.

[zwjjiaozhu]

test.mp3.zip

You may need to share the MP3 file you're using.

[zwjjiaozhu]

driver_darwin.go -> newContext -> loop()，

func (c *context) loop() {
	buf32 := make([]float32, c.oneBufferSizeInBytes/4)
	for {
		if !c.wait() {
			return
		}
		c.appendBuffer(buf32)
	}
}

I found that there was a constant loop here, and when I tried to print the variable buf32, I found that it kept printing [0,0,..., 0]. It should be using CPU calculation here.

[hajimehoshi]

I don't quite understand.

I don't know why it doesn't play audio and still takes up CPU to calculate

But your program plays an audio...

[zwjjiaozhu]

我不太明白。

不知道为什么不播放音频还占用CPU计算

但是你的程序播放音频......

After playing the audio, the CPU will still be used

[hajimehoshi]

Even though there is no player, Oto tries to fill 0s to the underlying audio buffer, so this is expected.

[hajimehoshi]

In order to optimize this, we might be able to pause the audio when there is no player, and resume when a new player comes. I am not sure I will do it.

[zwjjiaozhu]

Thank you. So, how should I close this context after I finish playing the audio

[hajimehoshi]

There is no way to close the context. You can call Suspend and Resume instead. https://pkg.go.dev/github.com/ebitengine/oto/v3#Context.Suspend

[zwjjiaozhu]

ok, Thank you.