mj2

Overview ¶

Package mj2 implements Motion JPEG 2000 (MJ2/MJP2) per ISO/IEC 15444-3.

Overview ¶

Motion JPEG 2000 is a video format that uses JPEG 2000 for intra-frame compression within an ISO base media file format (ISOBMFF) container. Unlike most video codecs, MJ2 uses only intra-frame (I-frame) coding, meaning each frame is a complete, independently decodable JP2 codestream.

File Structure ¶

An MJ2 file consists of a sequence of boxes (atoms) following the ISOBMFF standard:

ftyp  - File Type Box (required, must be first)
moov  - Movie Box (required, contains metadata)
  mvhd  - Movie Header Box
  trak  - Track Box (one per track)
    tkhd  - Track Header Box
    mdia  - Media Box
      mdhd  - Media Header Box
      hdlr  - Handler Reference Box
      minf  - Media Information Box
        stbl  - Sample Table Box
          stsd  - Sample Description (mjp2 entries)
          stts  - Time-to-Sample
          stsc  - Sample-to-Chunk
          stsz  - Sample Size
          stco  - Chunk Offset (32-bit)
          stss  - Sync Sample (optional)
mdat  - Media Data Box (contains frame data)

Key Features ¶

• Each video frame is an independent JP2 codestream
• No inter-frame dependencies (all frames are sync samples)
• Random access to any frame without decoding other frames
• Supports multiple video and audio tracks
• Full timing and synchronization information

Usage ¶

Basic usage to extract and decode video frames:

// Create reader
reader := mj2.NewReader(data)

// Parse file structure
if err := reader.Parse(); err != nil {
    return err
}

// Get movie information
movie := reader.GetMovie()
fmt.Printf("Duration: %.2f seconds\n", movie.Duration())
fmt.Printf("Tracks: %d\n", len(movie.Tracks))

// Extract frames from first video track
for i := 0; i < movie.Tracks[0].FrameCount(); i++ {
    frame, err := reader.ExtractFrame(0, i)
    if err != nil {
        continue
    }
    // frame is a raw JP2 codestream that can be decoded
    // using the jpeg2000.Decoder
}

Security Considerations ¶

This package validates all input data and enforces security limits:

• Maximum box sizes are validated to prevent resource exhaustion
• Integer conversions use safe conversion utilities
• All array indices are bounds-checked
• Nested box depth is limited to prevent stack overflow

References ¶

• ISO/IEC 15444-3: Motion JPEG 2000
• ISO/IEC 14496-12: ISO base media file format

Package mj2 provides Motion JPEG 2000 (MJ2/MJP2) decoding support per ISO/IEC 15444-3.

Package mj2 provides Motion JPEG 2000 (MJ2/MJP2) decoding support per ISO/IEC 15444-3.

MJ2 is a video format that uses JPEG 2000 for frame compression within an ISO base media file format (ISOBMFF) container. Each video frame is an independent JP2 codestream that can be decoded without reference to other frames.

Key features:

• ISO base media file format container (similar to MP4)
• Each frame is a complete JP2 codestream
• All frames are intra-coded (no inter-frame prediction)
• Supports multiple video tracks
• Full timing and synchronization information