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fix: report zero bit depth for non-ALAC M4A containers

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GetM4AQuality previously defaulted to 16-bit whenever the audio sample entry was not ALAC, which silently labeled lossy AAC downloads as CD quality in the library and in extension APIs. Only fill BitDepth when the atom is ALAC (including the ALACSpecificConfig refinement), and leave it as zero for AAC/mp4a, matching how the MP3 and Opus probes already report lossy sources. Tests cover both the ALAC and AAC branches.
This commit is contained in:
zarzet
2026-05-10 18:31:19 +07:00
parent 939407675b
commit 4b7146afe4
2 changed files with 18 additions and 8 deletions
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go_backend/audio_metadata_supplement_test.go
+16 -3
View File
@@ -308,16 +308,20 @@ func TestM4AMetadataAtomHelpers(t *testing.T) {
t.Fatalf("ReplayGain fields = %#v", fields)
}
qualityPath := filepath.Join(dir, "quality.m4a")
qualityPath := filepath.Join(dir, "quality-alac.m4a")
mvhd := make([]byte, 20)
binary.BigEndian.PutUint32(mvhd[12:16], 1000)
binary.BigEndian.PutUint32(mvhd[16:20], 180000)
sampleEntry := make([]byte, 32)
copy(sampleEntry[0:4], "mp4a")
copy(sampleEntry[0:4], "alac")
binary.BigEndian.PutUint16(sampleEntry[22:24], 24)
sampleEntry[28] = 0xAC
sampleEntry[29] = 0x44
qualityFile := append(buildM4AAtom("ftyp", []byte("M4A \x00\x00\x00\x00")), buildM4AAtom("moov", append(buildM4AAtom("mvhd", mvhd), sampleEntry...))...)
alacConfig := make([]byte, 24)
alacConfig[5] = 24
binary.BigEndian.PutUint32(alacConfig[20:24], 44100)
alacEntryPayload := append(append([]byte{}, sampleEntry[4:]...), buildM4AAtom("alac", alacConfig)...)
qualityFile := append(buildM4AAtom("ftyp", []byte("M4A \x00\x00\x00\x00")), buildM4AAtom("moov", append(buildM4AAtom("mvhd", mvhd), buildM4AAtom("alac", alacEntryPayload)...))...)
if err := os.WriteFile(qualityPath, qualityFile, 0600); err != nil {
t.Fatal(err)
}
@@ -327,6 +331,15 @@ func TestM4AMetadataAtomHelpers(t *testing.T) {
if quality, err := GetAudioQuality(qualityPath); err != nil || quality.SampleRate != 44100 {
t.Fatalf("GetAudioQuality M4A = %#v/%v", quality, err)
}
aacQualityPath := filepath.Join(dir, "quality-aac.m4a")
copy(sampleEntry[0:4], "mp4a")
aacQualityFile := append(buildM4AAtom("ftyp", []byte("M4A \x00\x00\x00\x00")), buildM4AAtom("moov", append(buildM4AAtom("mvhd", mvhd), sampleEntry...))...)
if err := os.WriteFile(aacQualityPath, aacQualityFile, 0600); err != nil {
t.Fatal(err)
}
if quality, err := GetM4AQuality(aacQualityPath); err != nil || quality.BitDepth != 0 || quality.SampleRate != 44100 || quality.Duration != 180 {
t.Fatalf("GetM4AQuality AAC = %#v/%v", quality, err)
}
if _, _, ok := parseALACSpecificConfig(make([]byte, 4)); ok {
t.Fatal("short ALAC config should not parse")
}
go_backend/metadata.go
+2 -5
View File
@@ -1695,9 +1695,10 @@ func GetM4AQuality(filePath string) (AudioQuality, error) {
// [26:28] reserved
// [28:32] samplerate (16.16 fixed-point)
sampleRate := int(buf[28])<<8 | int(buf[29])
bitDepth := int(buf[22])<<8 | int(buf[23])
bitDepth := 0
if atomType == "alac" {
bitDepth = int(buf[22])<<8 | int(buf[23])
if alacBitDepth, alacSampleRate, ok := readALACSpecificConfig(f, sampleOffset, fileSize); ok {
if alacBitDepth > 0 {
bitDepth = alacBitDepth
@@ -1708,10 +1709,6 @@ func GetM4AQuality(filePath string) (AudioQuality, error) {
}
}
if bitDepth <= 0 {
bitDepth = 16
}
return AudioQuality{BitDepth: bitDepth, SampleRate: sampleRate, Duration: duration}, nil
}