bb83426816
"Opus at 128 KB/s (VBR) is pretty much transparent" https://wiki.xiph.org/Opus_Recommended_Settings related #241
115 lines
6.1 KiB
Go
115 lines
6.1 KiB
Go
// author: spijet (https://github.com/spijet/)
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// author: sentriz (https://github.com/sentriz/)
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//nolint:gochecknoglobals
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package transcode
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import (
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"context"
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"fmt"
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"io"
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"os/exec"
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"time"
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"github.com/google/shlex"
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)
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type Transcoder interface {
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Transcode(ctx context.Context, profile Profile, in string, out io.Writer) error
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}
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var UserProfiles = map[string]Profile{
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"mp3": MP3,
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"mp3_rg": MP3RG,
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"opus_car": OpusCar,
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"opus": Opus,
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"opus_rg": OpusRG,
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"opus_128_car": Opus128Car,
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"opus_128": Opus128,
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"opus_128_rg": Opus128RG,
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}
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// Store as simple strings, since we may let the user provide their own profiles soon
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var (
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MP3 = NewProfile("audio/mpeg", 128, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libmp3lame -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f mp3 -`)
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MP3RG = NewProfile("audio/mpeg", 128, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libmp3lame -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f mp3 -`)
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// this sets a baseline gain which results in the final track being +3~5dB louder than
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// Foobar2000's default ReplayGain target volume.
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// this makes it easier to listen to music in a car, where all other
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// sources are usually ten thousand times louder than RG-adjusted music.
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//
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// opus always forces output to 48kHz sampling rate, but we can still use upsampling
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// to increase RG and alimiter's peak limiting precision, which is desirable in some
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// cases. ffmpeg's `soxr` resampler is quite fast on x86-64: it takes around 5 seconds
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// on my Ryzen 3600 to transcode an 8-minute FLAC with 2x upsample and RG applied.
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//
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// -- @spijet
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OpusCar = NewProfile("audio/ogg", 96, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "aresample=96000:resampler=soxr, volume=replaygain=track:replaygain_preamp=15dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -f opus -`)
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Opus = NewProfile("audio/ogg", 96, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f opus -`)
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OpusRG = NewProfile("audio/ogg", 96, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f opus -`)
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Opus128Car = NewProfile("audio/ogg", 128, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "aresample=96000:resampler=soxr, volume=replaygain=track:replaygain_preamp=15dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -f opus -`)
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Opus128 = NewProfile("audio/ogg", 128, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f opus -`)
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Opus128RG = NewProfile("audio/ogg", 128, `ffmpeg -v 0 -i <file> -ss <seek> -map 0:a:0 -vn -b:a <bitrate> -c:a libopus -vbr on -af "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled, asidedata=mode=delete:type=REPLAYGAIN" -metadata replaygain_album_gain= -metadata replaygain_album_peak= -metadata replaygain_track_gain= -metadata replaygain_track_peak= -metadata r128_album_gain= -metadata r128_track_gain= -f opus -`)
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PCM16le = NewProfile("audio/wav", 0, `ffmpeg -v 0 -i <file> -ss <seek> -c:a pcm_s16le -ac 2 -f s16le -`)
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)
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type BitRate int // kb/s
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type Profile struct {
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bitrate BitRate // the default bitrate, but the user can request a different one
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seek time.Duration
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mime string
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exec string
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}
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func (p *Profile) BitRate() BitRate { return p.bitrate }
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func (p *Profile) Seek() time.Duration { return p.seek }
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func (p *Profile) MIME() string { return p.mime }
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func NewProfile(mime string, bitrate BitRate, exec string) Profile {
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return Profile{mime: mime, bitrate: bitrate, exec: exec}
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}
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func WithBitrate(p Profile, bitRate BitRate) Profile {
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p.bitrate = bitRate
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return p
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}
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func WithSeek(p Profile, seek time.Duration) Profile {
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p.seek = seek
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return p
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}
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var ErrNoProfileParts = fmt.Errorf("not enough profile parts")
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func parseProfile(profile Profile, in string) (string, []string, error) {
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parts, err := shlex.Split(profile.exec)
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if err != nil {
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return "", nil, fmt.Errorf("split command: %w", err)
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}
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if len(parts) == 0 {
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return "", nil, ErrNoProfileParts
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}
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name, err := exec.LookPath(parts[0])
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if err != nil {
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return "", nil, fmt.Errorf("find name: %w", err)
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}
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var args []string
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for _, p := range parts[1:] {
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switch p {
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case "<file>":
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args = append(args, in)
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case "<seek>":
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args = append(args, fmt.Sprintf("%dus", profile.Seek().Microseconds()))
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case "<bitrate>":
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args = append(args, fmt.Sprintf("%dk", profile.BitRate()))
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default:
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args = append(args, p)
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}
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}
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return name, args, nil
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}
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