refactor(ffmpeg): generalize device and hardware support for multiple OS

- Rename `device_freebsd.go` to `device_bsd.go` and `hardware_freebsd.go` to `hardware_bsd.go` to reflect broader BSD support (FreeBSD, NetBSD, OpenBSD, Dragonfly).
- Update build tags in `device_bsd.go` and `hardware_bsd.go` to include FreeBSD, NetBSD, OpenBSD, and Dragonfly.
- Rename `device_linux.go` to `device_unix.go` and `hardware_linux.go` to `hardware_unix.go` to generalize Unix support excluding Darwin-based systems and BSDs.
- Add specific build tags to `device_darwin.go`, `device_unix.go`, `hardware_darwin.go`, and `hardware_unix.go` to correctly target their respective operating systems.
- Ensure Windows-specific files (`device_windows.go` and `hardware_windows.go`) are correctly tagged for building on Windows.

internal/ffmpeg/device/device_unix.go

@@ -0,0 +1,101 @@
+//go:build unix && !darwin && !freebsd && !netbsd && !openbsd && !dragonfly
+
+package device
+
+import (
+	"net/url"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+
+	"github.com/AlexxIT/go2rtc/internal/api"
+	"github.com/AlexxIT/go2rtc/pkg/core"
+)
+
+func queryToInput(query url.Values) string {
+	if video := query.Get("video"); video != "" {
+		// https://ffmpeg.org/ffmpeg-devices.html#video4linux2_002c-v4l2
+		input := "-f v4l2"
+
+		for key, value := range query {
+			switch key {
+			case "resolution":
+				input += " -video_size " + value[0]
+			case "video_size", "pixel_format", "input_format", "framerate", "use_libv4l2":
+				input += " -" + key + " " + value[0]
+			}
+		}
+
+		return input + " -i " + indexToItem(videos, video)
+	}
+
+	if audio := query.Get("audio"); audio != "" {
+		// https://trac.ffmpeg.org/wiki/Capture/ALSA
+		input := "-f alsa"
+
+		for key, value := range query {
+			switch key {
+			case "channels", "sample_rate":
+				input += " -" + key + " " + value[0]
+			}
+		}
+
+		return input + " -i " + indexToItem(audios, audio)
+	}
+
+	return ""
+}
+
+func initDevices() {
+	files, err := os.ReadDir("/dev")
+	if err != nil {
+		return
+	}
+
+	for _, file := range files {
+		if !strings.HasPrefix(file.Name(), core.KindVideo) {
+			continue
+		}
+
+		name := "/dev/" + file.Name()
+
+		cmd := exec.Command(
+			Bin, "-hide_banner", "-f", "v4l2", "-list_formats", "all", "-i", name,
+		)
+		b, _ := cmd.CombinedOutput()
+
+		// [video4linux2,v4l2 @ 0x204e1c0] Compressed:       mjpeg :          Motion-JPEG : 640x360 1280x720 1920x1080
+		// [video4linux2,v4l2 @ 0x204e1c0] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x360 1280x720 1920x1080
+		// [video4linux2,v4l2 @ 0x204e1c0] Compressed:        h264 :                H.264 : 640x360 1280x720 1920x1080
+		re := regexp.MustCompile("(Raw *|Compressed): +(.+?) : +(.+?) : (.+)")
+		m := re.FindAllStringSubmatch(string(b), -1)
+		for _, i := range m {
+			size, _, _ := strings.Cut(i[4], " ")
+			stream := &api.Source{
+				Name: i[3],
+				Info: i[4],
+				URL:  "ffmpeg:device?video=" + name + "&input_format=" + i[2] + "&video_size=" + size,
+			}
+
+			if i[1] != "Compressed" {
+				stream.URL += "#video=h264#hardware"
+			}
+
+			videos = append(videos, name)
+			streams = append(streams, stream)
+		}
+	}
+
+	err = exec.Command(Bin, "-f", "alsa", "-i", "default", "-t", "1", "-f", "null", "-").Run()
+	if err == nil {
+		stream := &api.Source{
+			Name: "ALSA default",
+			Info: " ",
+			URL:  "ffmpeg:device?audio=default&channels=1&sample_rate=16000&#audio=opus",
+		}
+
+		audios = append(audios, "default")
+		streams = append(streams, stream)
+	}
+}