Add host-side gRPC audio injector for E2E tests

Generates a sine wave and streams it to the Android emulator's
virtual microphone via the injectAudio gRPC API.

Author: xaionaro@dx.center

tests/e2e/audio-inject/main.go

@@ -0,0 +1,93 @@
+// Audio injector: streams a sine wave to the Android emulator's virtual
+// microphone via the gRPC injectAudio API.
+//
+// Usage: audio-inject -port 8554 -freq 440 -duration 3s
+package main
+
+import (
+	"context"
+	"encoding/binary"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"math"
+	"time"
+
+	emupb "github.com/xaionaro-go/ndk/tests/e2e/audio-inject/proto/emupb"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+)
+
+func main() {
+	port := flag.Int("port", 8554, "emulator gRPC port")
+	freq := flag.Float64("freq", 440, "sine wave frequency in Hz")
+	dur := flag.Duration("duration", 3*time.Second, "injection duration")
+	sampleRate := flag.Uint64("rate", 48000, "sample rate in Hz")
+	flag.Parse()
+
+	addr := fmt.Sprintf("localhost:%d", *port)
+	log.Printf("connecting to emulator gRPC at %s", addr)
+
+	conn, err := grpc.NewClient(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		log.Fatalf("grpc dial: %v", err)
+	}
+	defer conn.Close()
+
+	client := emupb.NewEmulatorControllerClient(conn)
+	stream, err := client.InjectAudio(context.Background())
+	if err != nil {
+		log.Fatalf("InjectAudio: %v", err)
+	}
+
+	// Send audio in 10ms chunks.
+	samplesPerChunk := int(*sampleRate / 100)
+	totalSamples := int(float64(*sampleRate) * dur.Seconds())
+	sent := 0
+	phase := 0.0
+	phaseInc := 2.0 * math.Pi * *freq / float64(*sampleRate)
+
+	format := &emupb.AudioFormat{
+		SamplingRate: *sampleRate,
+		Channels:     emupb.AudioFormat_Mono,
+		Format:       emupb.AudioFormat_AUD_FMT_S16,
+	}
+
+	for sent < totalSamples {
+		n := samplesPerChunk
+		if sent+n > totalSamples {
+			n = totalSamples - sent
+		}
+
+		buf := make([]byte, n*2) // 2 bytes per S16LE sample
+		for i := 0; i < n; i++ {
+			sample := int16(math.Sin(phase) * 0.8 * 32767)
+			binary.LittleEndian.PutUint16(buf[i*2:], uint16(sample))
+			phase += phaseInc
+		}
+
+		pkt := &emupb.AudioPacket{
+			Audio: buf,
+		}
+		if sent == 0 {
+			pkt.Format = format
+		}
+
+		if err := stream.Send(pkt); err != nil {
+			if err == io.EOF {
+				break
+			}
+			log.Fatalf("send: %v", err)
+		}
+		sent += n
+
+		// Pace at roughly real-time to avoid overflowing the 300ms buffer.
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	if _, err := stream.CloseAndRecv(); err != nil && err != io.EOF {
+		log.Printf("close stream: %v", err)
+	}
+	log.Printf("injected %d samples (%.2fs) at %d Hz", sent, float64(sent)/float64(*sampleRate), *sampleRate)
+}