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feat(encode): add hi-gain RG and upsampling support

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This commit is contained in:
Serge Tkatchouk
2021-06-21 12:14:49 +08:00
committed by sentriz
parent 93608d04b4
commit 616b152fed
1 changed files with 33 additions and 5 deletions
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38
server/encode/encode.go
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@@ -10,6 +10,7 @@ import (
"os"
"os/exec"
"path"
"strings"
"github.com/cespare/xxhash"
)
@@ -24,6 +25,8 @@ type Profile struct {
Bitrate int
ffmpegOptions []string
forceRG bool
hiGainRG bool
upsample bool
}
func fileExists(filename string) bool {
@@ -36,10 +39,11 @@ func fileExists(filename string) bool {
func Profiles() map[string]Profile {
return map[string]Profile{
"mp3": {"mp3", 128, []string{"-c:a", "libmp3lame"}, false},
"mp3_rg": {"mp3", 128, []string{"-c:a", "libmp3lame"}, true},
"opus": {"opus", 96, []string{"-c:a", "libopus", "-vbr", "constrained"}, false},
"opus_rg": {"opus", 96, []string{"-c:a", "libopus", "-vbr", "constrained"}, true},
"mp3": {"mp3", 128, []string{"-c:a", "libmp3lame"}, false, false, false},
"mp3_rg": {"mp3", 128, []string{"-c:a", "libmp3lame"}, true, false, false},
"opus": {"opus", 96, []string{"-c:a", "libopus", "-vbr", "constrained"}, false, false, false},
"opus_rg": {"opus", 96, []string{"-c:a", "libopus", "-vbr", "constrained"}, true, false, false},
"opus_car": {"opus", 96, []string{"-c:a", "libopus", "-vbr", "constrained"}, true, true, true},
}
}
@@ -94,9 +98,33 @@ func ffmpegCommand(filePath string, profile Profile) (*exec.Cmd, error) {
}
args = append(args, profile.ffmpegOptions...)
if profile.forceRG {
aBaselineGain := 6
if profile.hiGainRG {
// This baseline gain results in final track being +3~5dB louder
// than Foobar2000's default ReplayGain target volume.
// This makes it easier to listen to music in a car, where all other
// sources are usually ten thousand times louder than RG-adjusted music.
// -- @spijet
aBaselineGain = 15
}
aFilters := []string{
fmt.Sprintf("volume=replaygain=track:replaygain_preamp=%ddB:replaygain_noclip=0", aBaselineGain),
"alimiter=level=disabled",
"asidedata=mode=delete:type=REPLAYGAIN",
}
// opus always forces output to 48kHz sampling rate, but we can still use upsampling
// to increase RG and alimiter's peak limiting precision, which is desirable in some
// cases. ffmpeg's `soxr` resampler is quite fast on x86-64: it takes around 5 seconds
// on my Ryzen 3600 to transcode an 8-minute FLAC with 2x upsample and RG applied.
// -- @spijet
if profile.upsample {
aFilters = append([]string{"aresample=96000:resampler=soxr"}, aFilters...)
}
aFilterString := strings.Join(aFilters, ", ")
args = append(args,
// set up replaygain processing
"-af", "volume=replaygain=track:replaygain_preamp=6dB:replaygain_noclip=0, alimiter=level=disabled",
"-af", aFilterString,
// drop redundant replaygain tags
"-metadata", "replaygain_album_gain=",
"-metadata", "replaygain_album_peak=",