initial Go port of streamrip

internal/audio/convert/convert.go

@@ -0,0 +1,123 @@
+package convert
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+
+	"streamrip-go/internal/config"
+)
+
+type profile struct {
+	codecLib string
+	ext      string
+	lossless bool
+}
+
+var profiles = map[string]profile{
+	"FLAC":   {codecLib: "flac", ext: "flac", lossless: true},
+	"ALAC":   {codecLib: "alac", ext: "m4a", lossless: true},
+	"OPUS":   {codecLib: "libopus", ext: "opus", lossless: false},
+	"MP3":    {codecLib: "libmp3lame", ext: "mp3", lossless: false},
+	"VORBIS": {codecLib: "libvorbis", ext: "ogg", lossless: false},
+	"AAC":    {codecLib: "aac", ext: "m4a", lossless: false},
+}
+
+func Convert(path string, cfg config.ConversionConfig) (string, error) {
+	if !cfg.Enabled {
+		return path, nil
+	}
+	if _, err := exec.LookPath("ffmpeg"); err != nil {
+		return path, fmt.Errorf("ffmpeg not found: %w", err)
+	}
+
+	p, ok := profiles[strings.ToUpper(strings.TrimSpace(cfg.Codec))]
+	if !ok {
+		return path, fmt.Errorf("unsupported conversion codec: %s", cfg.Codec)
+	}
+
+	base := strings.TrimSuffix(path, filepath.Ext(path))
+	finalPath := base + "." + p.ext
+	tmpPath := finalPath + ".tmp." + p.ext
+
+	args := buildFFmpegArgs(path, tmpPath, p, cfg)
+	cmd := exec.Command("ffmpeg", args...)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		_ = os.Remove(tmpPath)
+		return path, fmt.Errorf("conversion failed: %w: %s", err, string(output))
+	}
+
+	if path != finalPath {
+		_ = os.Remove(path)
+	}
+	if err = os.Rename(tmpPath, finalPath); err != nil {
+		_ = os.Remove(tmpPath)
+		return path, err
+	}
+
+	return finalPath, nil
+}
+
+func buildFFmpegArgs(inputPath, outputPath string, p profile, cfg config.ConversionConfig) []string {
+	args := []string{
+		"-y",
+		"-i", inputPath,
+		"-map", "0:a:0",
+		"-map_metadata", "0",
+		"-c:a", p.codecLib,
+	}
+
+	if p.lossless {
+		filter := buildLosslessFilter(cfg)
+		if filter != "" {
+			args = append(args, "-af", filter)
+		}
+	} else {
+		if cfg.LossyBitrate > 0 {
+			args = append(args, "-b:a", strconv.Itoa(cfg.LossyBitrate)+"k")
+		}
+	}
+
+	args = append(args, outputPath)
+	return args
+}
+
+func buildLosslessFilter(cfg config.ConversionConfig) string {
+	parts := make([]string, 0, 2)
+	if cfg.SamplingRate > 0 {
+		rates := allowedSampleRates(cfg.SamplingRate)
+		if len(rates) > 0 {
+			parts = append(parts, "sample_rates="+strings.Join(rates, "|"))
+		}
+	}
+	if cfg.BitDepth == 16 {
+		parts = append(parts, "sample_fmts=s16p|s16")
+	} else if cfg.BitDepth == 24 || cfg.BitDepth == 32 {
+		parts = append(parts, "sample_fmts=s16p|s16|s32p|s32")
+	}
+	if len(parts) == 0 {
+		return ""
+	}
+	return "aformat=" + strings.Join(parts, ":")
+}
+
+func allowedSampleRates(max int) []string {
+	all := []int{44100, 48000, 88200, 96000, 176400, 192000}
+	out := make([]int, 0, len(all))
+	for _, r := range all {
+		if r <= max {
+			out = append(out, r)
+		}
+	}
+	sort.Ints(out)
+	str := make([]string, 0, len(out))
+	for _, r := range out {
+		str = append(str, strconv.Itoa(r))
+	}
+	return str
+}