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Merged
kryptobi merged 1 commit into from
May 13, 2026
Merged

add WAV, M4A, and FLAC audio format detection #168

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119 changes: 119 additions & 0 deletions MagicBytesValidator.Tests/Models/AudioFormatMatches.cs
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namespace MagicBytesValidator.Tests.Models;

public class AudioFormatMatches
{
[Fact]
public void Should_match_wav()
{
var wav = new Wav();

// RIFF....WAVE header
var wavTestData = new byte[]
{
0x52, 0x49, 0x46, 0x46, // RIFF
0x24, 0x08, 0x00, 0x00, // file size (arbitrary)
0x57, 0x41, 0x56, 0x45 // WAVE
};

Assert.True(wav.Matches(wavTestData));
}

[Fact]
public void Should_not_match_wav_with_avi_riff()
{
var wav = new Wav();

// RIFF....AVI (not WAVE)
var aviTestData = new byte[]
{
0x52, 0x49, 0x46, 0x46, // RIFF
0x24, 0x08, 0x00, 0x00, // file size
0x41, 0x56, 0x49, 0x20 // AVI
};

Assert.False(wav.Matches(aviTestData));
}

[Fact]
public void Should_not_match_wav_with_invalid_data()
{
var wav = new Wav();

var invalidTestData = new byte[] { 0x00, 0x00, 0x00, 0x00 };

Assert.False(wav.Matches(invalidTestData));
}

[Fact]
public void Should_match_m4a_with_m4a_brand()
{
var m4a = new M4a();

// ftyp box with M4A brand
var m4aTestData = new byte[]
{
0x00, 0x00, 0x00, 0x20, // box size
0x66, 0x74, 0x79, 0x70, // ftyp
0x4D, 0x34, 0x41, 0x20 // M4A
};

Assert.True(m4a.Matches(m4aTestData));
}

[Fact]
public void Should_match_m4a_with_m4b_brand()
{
var m4a = new M4a();

// ftyp box with M4B brand (audiobook variant)
var m4bTestData = new byte[]
{
0x00, 0x00, 0x00, 0x20, // box size
0x66, 0x74, 0x79, 0x70, // ftyp
0x4D, 0x34, 0x42, 0x20 // M4B
};

Assert.True(m4a.Matches(m4bTestData));
}

[Fact]
public void Should_not_match_m4a_with_isom_brand()
{
var m4a = new M4a();

// ftyp box with isom brand (generic MP4 video)
var mp4TestData = new byte[]
{
0x00, 0x00, 0x00, 0x20, // box size
0x66, 0x74, 0x79, 0x70, // ftyp
0x69, 0x73, 0x6F, 0x6D // isom
};

Assert.False(m4a.Matches(mp4TestData));
}

[Fact]
public void Should_match_flac()
{
var flac = new Flac();

// fLaC magic marker followed by metadata block header
var flacTestData = new byte[]
{
0x66, 0x4C, 0x61, 0x43, // fLaC
0x00, 0x00, 0x00, 0x22 // STREAMINFO block header
};

Assert.True(flac.Matches(flacTestData));
}

[Fact]
public void Should_not_match_flac_with_invalid_data()
{
var flac = new Flac();

var invalidTestData = new byte[] { 0x66, 0x4C, 0x00, 0x00 };

Assert.False(flac.Matches(invalidTestData));
}
}
15 changes: 15 additions & 0 deletions MagicBytesValidator/Formats/Flac.cs
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namespace MagicBytesValidator.Formats;

/// <see href="https://en.wikipedia.org/wiki/FLAC"/>
/// <see href="https://en.wikipedia.org/wiki/List_of_file_signatures"/>
public class Flac : FileByteFilter
{
public Flac() : base(
["audio/flac"],
["flac"]
)
{
// fLaC magic marker
StartsWith([0x66, 0x4C, 0x61, 0x43]);
}
}
18 changes: 18 additions & 0 deletions MagicBytesValidator/Formats/M4a.cs
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namespace MagicBytesValidator.Formats;

/// <see href="https://en.wikipedia.org/wiki/MPEG-4_Part_14"/>
/// <see href="https://www.garykessler.net/library/file_sigs.html"/>
public class M4a : FileByteFilter
{
public M4a() : base(
["audio/mp4", "audio/x-m4a"],
["m4a"]
)
{
// ftyp box at offset 4, followed by M4A or M4B brand
StartsWithAnyOf([
[null, null, null, null, 0x66, 0x74, 0x79, 0x70, 0x4D, 0x34, 0x41, 0x20], // ftypM4A
[null, null, null, null, 0x66, 0x74, 0x79, 0x70, 0x4D, 0x34, 0x42, 0x20], // ftypM4B
]);
}
}
15 changes: 15 additions & 0 deletions MagicBytesValidator/Formats/Wav.cs
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namespace MagicBytesValidator.Formats;

/// <see href="https://en.wikipedia.org/wiki/WAV"/>
/// <see href="https://en.wikipedia.org/wiki/List_of_file_signatures"/>
public class Wav : FileByteFilter
{
public Wav() : base(
["audio/wav", "audio/x-wav"],
["wav"]
)
{
// RIFF header (52 49 46 46) followed by 4 bytes of file size, then WAVE (57 41 56 45)
StartsWith([0x52, 0x49, 0x46, 0x46, null, null, null, null, 0x57, 0x41, 0x56, 0x45]);
}
}
3 changes: 3 additions & 0 deletions README.md
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Expand Up @@ -255,11 +255,13 @@ This can be useful when debugging or validating newly added FileTypes.
| DOCX | docx | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| DXR | dxr, dcr, dir | application/x-director |
| EXE | exe, com, dll, drv, pif, qts, qtx , sys, acm, ax, cpl, fon, ocx, olb, scr, vbx, vxd, mui, iec, ime, rs, tsp, efi | application/x-dosexec, application/x-msdos-program |
| FLAC | flac | audio/flac |
| GIF | gif | image/gif |
| GZ | gz | application/gzip |
| HEIC | heic, heif | image/heic, image/heif |
| ICO | ico | image/x-icon |
| JPG | jpg, jpeg, jpe, jif, jfif, jfi | image/jpeg |
| M4A | m4a | audio/mp4, audio/x-m4a |
| MIDI | midi, mid | audio/x-midi |
| MP3 | mp3 | audio/mpeg |
| MP4 | mp4 | video/mp4 |
Expand All @@ -285,6 +287,7 @@ This can be useful when debugging or validating newly added FileTypes.
| TIF | tif, tiff | image/tiff |
| TSV | ts, tsv, tsa, mpg, mpeg | video/mp2t |
| TXT | txt | text/plain |
| WAV | wav | audio/wav, audio/x-wav |
| WEBM | mkv, mka, mks, mk3d, webm | video/webm |
| XLS | xls, xla | application/msexcel |
| XLSX | xlsx | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet |
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