video backend CLI flag

cmd/mxl-pattern/main.go

@@ -43,11 +43,12 @@ type appArgs struct {
 	overlayY    int
 	overlayPos  string
 
-	videoWidth  uint
-	videoHeight uint
-	videoFPS    string
-	videoUUID   string
-	noVideo     bool
+	videoWidth   uint
+	videoHeight  uint
+	videoFPS     string
+	videoUUID    string
+	noVideo      bool
+	videoBackend string
 
 	audioChannels     uint8
 	audioSamplingFreq string
@@ -136,6 +137,9 @@ func validateVideoArgs(args *appArgs) error {
 	if args.noVideo {
 		return nil
 	}
+	if _, err := parseVideoBackend(args.videoBackend); err != nil {
+		return err
+	}
 	if !video.HasPattern(args.pattern) {
 		return fmt.Errorf("unknown video pattern %q (use --list-patterns to see available patterns)", args.pattern)
 	}
@@ -284,6 +288,7 @@ func addFlags(fs *pflag.FlagSet, args *appArgs) {
 	fs.StringVar(&args.videoFPS, "fps", "25", "Video pattern FPS")
 	fs.StringVar(&args.videoUUID, "video-id", "", "Video UUID. Will be created, if not provided")
 	fs.BoolVar(&args.noVideo, "no-video", false, "Disable video generation; audio must be enabled")
+	fs.StringVar(&args.videoBackend, "backend", string(video.BackendAuto), "Video generator backend: auto, gpu or cpu")
 	// Audio pattern flags
 	fs.Uint8VarP(&args.audioChannels, "channel", "c", 0, "Amount of audio channels. Each channel: num * 1kHz")
 	fs.StringVarP(&args.audioSamplingFreq, "freq", "f", "48", "Sampling frequency of test audio feed in kHz")
@@ -319,6 +324,22 @@ func parseArgs(argv []string, stdout, stderr io.Writer) (parseResult, error) {
 	return parseResult{args: args, shouldRun: true}, nil
 }
 
+func parseVideoBackend(value string) (video.Backend, error) {
+	if value == "" {
+		return video.BackendAuto, nil
+	}
+	backend := video.Backend(value)
+	switch backend {
+	case video.BackendAuto, video.BackendGPU, video.BackendCPU:
+		return backend, nil
+	default:
+		return "", fmt.Errorf(
+			"unsupported video backend %q (supported: auto, gpu, cpu)",
+			value,
+		)
+	}
+}
+
 func buildVideoConfig(args appArgs) (*video.Config, error) {
 	if args.noVideo {
 		return nil, nil
@@ -370,6 +391,11 @@ func buildVideoConfig(args appArgs) (*video.Config, error) {
 		return nil, fmt.Errorf("unknown video pattern %q", args.pattern)
 	}
 
+	backend, err := parseVideoBackend(args.videoBackend)
+	if err != nil {
+		return nil, err
+	}
+
 	return &video.Config{
 		Definition: definition,
 		Pattern:    args.pattern,
@@ -379,6 +405,7 @@ func buildVideoConfig(args appArgs) (*video.Config, error) {
 			Y:        args.overlayY,
 			Position: args.overlayPos,
 		},
+		Backend: backend,
 	}, nil
 }
 

cmd/mxl-pattern/main_test.go

@@ -9,6 +9,7 @@ import (
 
 	"mxl-pattern-generator/internal/audio"
 	"mxl-pattern-generator/internal/flowdef"
+	"mxl-pattern-generator/internal/video"
 )
 
 func TestParseArgsHelpStopsBeforeValidation(t *testing.T) {
@@ -112,6 +113,46 @@ func TestValidateVideoArgsSkipsDisabledVideo(t *testing.T) {
 	}
 }
 
+func TestParseVideoBackend(t *testing.T) {
+	tests := []struct {
+		name    string
+		value   string
+		want    video.Backend
+		wantErr bool
+	}{
+		{name: "zero value defaults to auto", want: video.BackendAuto},
+		{name: "auto", value: "auto", want: video.BackendAuto},
+		{name: "gpu", value: "gpu", want: video.BackendGPU},
+		{name: "cpu", value: "cpu", want: video.BackendCPU},
+		{name: "unknown", value: "other", wantErr: true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := parseVideoBackend(tc.value)
+			if tc.wantErr {
+				if err == nil || !strings.Contains(err.Error(), "unsupported video backend") {
+					t.Fatalf("error = %v, want unsupported backend error", err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("parseVideoBackend: %v", err)
+			}
+			if got != tc.want {
+				t.Fatalf("backend = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestValidateVideoArgsRejectsUnknownBackend(t *testing.T) {
+	args := appArgs{videoBackend: "other"}
+	if err := validateVideoArgs(&args); err == nil || !strings.Contains(err.Error(), "unsupported video backend") {
+		t.Fatalf("error = %v, want unsupported backend error", err)
+	}
+}
+
 func TestValidateMediaSelection(t *testing.T) {
 	tests := []struct {
 		name       string
@@ -187,6 +228,30 @@ func TestBuildVideoConfigFromArgs(t *testing.T) {
 	if cfg.Rate().Num != 30000 || cfg.Rate().Den != 1001 {
 		t.Fatalf("rate = %d/%d, want 30000/1001", cfg.Rate().Num, cfg.Rate().Den)
 	}
+	if cfg.Backend != video.BackendAuto {
+		t.Fatalf("backend = %q, want %q", cfg.Backend, video.BackendAuto)
+	}
+}
+
+func TestBuildVideoConfigBackends(t *testing.T) {
+	for _, backend := range []video.Backend{video.BackendGPU, video.BackendCPU} {
+		t.Run(string(backend), func(t *testing.T) {
+			cfg, err := buildVideoConfig(appArgs{
+				videoUUID:    "5fbec3b1-1b0f-417d-9059-8b94a47197ed",
+				videoWidth:   1920,
+				videoHeight:  1080,
+				videoFPS:     "25",
+				pattern:      "ebu75",
+				videoBackend: string(backend),
+			})
+			if err != nil {
+				t.Fatalf("buildVideoConfig: %v", err)
+			}
+			if cfg.Backend != backend {
+				t.Fatalf("backend = %q, want %q", cfg.Backend, backend)
+			}
+		})
+	}
 }
 
 func TestBuildVideoConfigDisabled(t *testing.T) {