Metadata Extraction

MediaMatic provides metadata extraction using three specialized libraries:

Library	Purpose	Formats
MimeDetective	MIME type detection	All files
MetadataExtractor	EXIF/image metadata	JPEG, PNG, GIF, BMP, TIFF, WebP
TagLibSharp	Audio/video tags	MP3, MP4, MKV, AVI, etc.

MIME Type Detection

Content-Based Detection

MimeDetective analyzes file content (magic bytes), not just extensions:

using MJCZone.MediaMatic.Metadata;

var detector = new MimeTypeDetector();

// Detect from stream
using var stream = File.OpenRead("file.dat");
var mimeType = detector.Detect(stream);

Console.WriteLine($"MIME Type: {mimeType}"); // e.g., "image/jpeg"

Why Content-Based?

Approach	Detects	Misses
Extension-only	file.jpg → image/jpeg	renamed_virus.jpg.exe
Content-based	Actual file content	Nothing (14K+ signatures)

Common MIME Types

// Images
var jpeg = detector.Detect(jpegStream);  // "image/jpeg"
var png = detector.Detect(pngStream);    // "image/png"
var webp = detector.Detect(webpStream);  // "image/webp"

// Videos
var mp4 = detector.Detect(mp4Stream);    // "video/mp4"
var webm = detector.Detect(webmStream);  // "video/webm"

// Audio
var mp3 = detector.Detect(mp3Stream);    // "audio/mpeg"
var flac = detector.Detect(flacStream);  // "audio/flac"

Image Metadata (EXIF)

Extracting EXIF Data

using MJCZone.MediaMatic.Metadata;

var extractor = new ImageMetadataExtractor();

using var stream = File.OpenRead("photo.jpg");
var metadata = extractor.Extract(stream);

// Basic properties
Console.WriteLine($"Width: {metadata.Width}");
Console.WriteLine($"Height: {metadata.Height}");
Console.WriteLine($"Format: {metadata.Format}");

// EXIF data
if (metadata.ExifData != null)
{
    Console.WriteLine($"Camera: {metadata.ExifData.CameraMake} {metadata.ExifData.CameraModel}");
    Console.WriteLine($"Date Taken: {metadata.ExifData.DateTaken}");
    Console.WriteLine($"ISO: {metadata.ExifData.IsoSpeed}");
    Console.WriteLine($"Aperture: f/{metadata.ExifData.Aperture}");
    Console.WriteLine($"Shutter: {metadata.ExifData.ShutterSpeed}");
    Console.WriteLine($"Focal Length: {metadata.ExifData.FocalLength}mm");
}

// GPS location
if (metadata.GpsData != null)
{
    Console.WriteLine($"Location: {metadata.GpsData.Latitude}, {metadata.GpsData.Longitude}");
    Console.WriteLine($"Altitude: {metadata.GpsData.Altitude}m");
}

Available EXIF Properties

Category	Properties
Camera	Make, Model, Lens, Serial
Settings	ISO, Aperture, Shutter Speed, Focal Length
Date/Time	Date Taken, Date Digitized, Date Modified
Image	Width, Height, Orientation, Color Space
GPS	Latitude, Longitude, Altitude, Direction
Software	Software, Copyright, Artist

Handling Orientation

EXIF orientation tag indicates how to rotate the image:

var orientation = metadata.ExifData?.Orientation;

switch (orientation)
{
    case 1: // Normal
        break;
    case 3: // Rotated 180°
        break;
    case 6: // Rotated 90° CW
        break;
    case 8: // Rotated 90° CCW
        break;
}

Video Metadata

Extracting Video Info

using MJCZone.MediaMatic.Metadata;

var extractor = new VideoMetadataExtractor();

var metadata = await extractor.ExtractAsync("video.mp4");

// Video properties
Console.WriteLine($"Duration: {metadata.Duration}");
Console.WriteLine($"Width: {metadata.Width}");
Console.WriteLine($"Height: {metadata.Height}");
Console.WriteLine($"Frame Rate: {metadata.FrameRate} fps");
Console.WriteLine($"Bitrate: {metadata.Bitrate} kbps");
Console.WriteLine($"Codec: {metadata.VideoCodec}");

// Audio properties
Console.WriteLine($"Audio Codec: {metadata.AudioCodec}");
Console.WriteLine($"Audio Channels: {metadata.AudioChannels}");
Console.WriteLine($"Sample Rate: {metadata.SampleRate} Hz");

// File info
Console.WriteLine($"Format: {metadata.Format}");
Console.WriteLine($"Size: {metadata.FileSize} bytes");

Video Metadata Properties

Property	Description
Duration	Total duration (TimeSpan)
Width	Video width in pixels
Height	Video height in pixels
FrameRate	Frames per second
Bitrate	Total bitrate in kbps
VideoCodec	Video codec (H.264, H.265, etc.)
AudioCodec	Audio codec (AAC, MP3, etc.)
AudioChannels	Number of audio channels
SampleRate	Audio sample rate in Hz
Format	Container format (MP4, WebM, etc.)

Audio Metadata

Extracting Audio Tags

using MJCZone.MediaMatic.Metadata;

var extractor = new AudioMetadataExtractor();

var metadata = extractor.Extract("song.mp3");

// Basic tags
Console.WriteLine($"Title: {metadata.Title}");
Console.WriteLine($"Artist: {metadata.Artist}");
Console.WriteLine($"Album: {metadata.Album}");
Console.WriteLine($"Year: {metadata.Year}");
Console.WriteLine($"Genre: {metadata.Genre}");
Console.WriteLine($"Track: {metadata.TrackNumber}");

// Audio properties
Console.WriteLine($"Duration: {metadata.Duration}");
Console.WriteLine($"Bitrate: {metadata.Bitrate} kbps");
Console.WriteLine($"Sample Rate: {metadata.SampleRate} Hz");
Console.WriteLine($"Channels: {metadata.Channels}");

// Album art
if (metadata.AlbumArt != null)
{
    File.WriteAllBytes("cover.jpg", metadata.AlbumArt);
}

Audio Tag Properties

Property	Description
Title	Song title
Artist	Artist name
Album	Album name
Year	Release year
Genre	Genre
TrackNumber	Track number
AlbumArt	Embedded cover image
Duration	Song length
Bitrate	Audio bitrate
SampleRate	Sample rate in Hz

Privacy Considerations

Stripping Metadata

Remove sensitive metadata before sharing:

var options = new ImageProcessingOptions
{
    StripMetadata = true, // Remove all EXIF data
};

var result = await processor.ResizeAsync(stream, 800, null, options);

Sensitive EXIF Data

Be aware of these privacy-sensitive fields:

Field	Risk
GPS coordinates	Location tracking
Date/time	Schedule tracking
Camera serial	Device identification
Software	System fingerprinting

Selective Stripping

Preserve some metadata while removing sensitive data:

var options = new ImageProcessingOptions
{
    PreserveMetadata = new[]
    {
        MetadataType.ColorProfile,
        MetadataType.Orientation,
    },
    StripMetadata = new[]
    {
        MetadataType.Gps,
        MetadataType.Software,
        MetadataType.DateTime,
    },
};

Common Use Cases

File Validation

Validate uploaded files by content:

var detector = new MimeTypeDetector();
var mimeType = detector.Detect(uploadStream);

var allowedTypes = new[] { "image/jpeg", "image/png", "image/webp" };

if (!allowedTypes.Contains(mimeType))
{
    throw new InvalidOperationException($"File type {mimeType} not allowed");
}

Photo Gallery

Extract and display photo information:

var metadata = extractor.Extract(photoStream);

var photoInfo = new
{
    Dimensions = $"{metadata.Width}x{metadata.Height}",
    Camera = metadata.ExifData?.CameraModel,
    DateTaken = metadata.ExifData?.DateTaken,
    Location = metadata.GpsData != null
        ? $"{metadata.GpsData.Latitude}, {metadata.GpsData.Longitude}"
        : null,
};

Video Streaming Platform

Generate video info cards:

var metadata = await extractor.ExtractAsync(videoPath);

var videoCard = new
{
    Duration = FormatDuration(metadata.Duration),
    Quality = GetQualityLabel(metadata.Height), // "1080p", "720p", etc.
    FileSize = FormatFileSize(metadata.FileSize),
};

Music Library

Build music database:

var metadata = extractor.Extract(songPath);

var song = new Song
{
    Title = metadata.Title ?? Path.GetFileNameWithoutExtension(songPath),
    Artist = metadata.Artist ?? "Unknown Artist",
    Album = metadata.Album ?? "Unknown Album",
    Duration = metadata.Duration,
    Year = metadata.Year,
};

Error Handling

try
{
    var metadata = extractor.Extract(stream);
}
catch (UnknownFileTypeException)
{
    // File format not recognized
}
catch (CorruptedFileException)
{
    // File is damaged
}
catch (Exception ex)
{
    logger.LogError(ex, "Failed to extract metadata");
}

Next Steps

• Image Processing - Process images with metadata
• Video Processing - Process videos
• Browser Detection - Format negotiation