Use direct ReadStereo, then convert floats ourselves

audio/format/opus/opus.go

@@ -1,5 +1,10 @@
 package opus
 
+/*
+#cgo CFLAGS: -I"${SRCDIR}/../../../cgo" -march=native -Ofast -std=c99
+#include "audio.h"
+*/
+import "C"
 import (
 	"bytes"
 	"git.gammaspectra.live/S.O.N.G/Kirika/audio"
@@ -31,24 +36,20 @@ func (f Format) Open(r io.ReadSeekCloser) (audio.Source, error) {
 		defer stream.Close()
 		defer close(newChannel)
 
-		blockSize := BlockSize * 2
+		buf := make([]int16, 120*FixedSampleRate*2)
 
 		for {
 
-			buf := make([]float32, blockSize)
-
-			n, err := stream.ReadStereoFloat32(buf)
+			n, err := stream.ReadStereo(buf)
 			if err != nil {
 				return
 			}
 
-			blockSize = n
-			if blockSize < 1024 {
-				blockSize = 1024
-			}
+			buffer := make([]float32, n*2)
+			C.audio_int16_to_float32((*C.int16_t)(&buf[0]), C.size_t(n*2), (*C.float)(&buffer[0]), C.int(16))
 
 			if n > 0 {
-				newChannel <- buf[:n*2]
+				newChannel <- buffer
 			}
 		}
 	}()