UNZPP - ZIMO ZPP File Extractor

A CLI program in Go for extracting WAV audio files from ZIMO ZPP format files (unencrypted).

UNZPP is a command-line tool that parses ZIMO Sound project files (.zpp format) and extracts all contained audio files as WAV files with proper headers.

The program supports:

• 8-bit and 16-bit PCM files
• Sample rates: 11025 Hz, 22050 Hz, 44100 Hz
• Automatic detection of audio parameters from flags in the ZPP file
• Preservation of original sound file names
• Sound file type information (if defined)

./unzpp -i <input_file.zpp> [-o <output_directory>]

• -i - Required. Path to the input ZPP file
• -o - Optional. Output directory for extracted WAV files (default: output)

# Extract files from BR_194_ZIMO_16-Bit_S02_mfx.zpp to extracted_wav directory
./unzpp -i BR_194_ZIMO_16-Bit_S02_mfx.zpp -o extracted_wav

The program will create WAV files in the output directory with names in the format:

[number]-[name]_[type].wav

Examples:

• 002-Stand_BR194_typeFF.wav
• 015-Schaltwer_mix_01-1_type88.wav
• 037-Schaffnerpfiff_Echo_type08.wav

Each file contains:

• Valid WAV header (RIFF)
• Audio data in PCM format
• Correct sample rate and bit depth

The program supports unencrypted ZIMO ZPP files. File format:

1. Header (0x00-0x7F): Magic bytes "SP" + configuration data
2. File table (0x80-0x47F): 256 entries × 4 bytes:
   • Byte 0: Sound file type
   • Bytes 1-3: 24-bit offset (big-endian)
3. File data: Each file contains:
   • Flags byte (specifies bit depth and sample rate)
   • 3 × 3-byte offsets (little-endian): data_end, loop_start, loop_end
   • PCM audio data
   • File name (with length)

• Bit 7 (0x80): 16-bit PCM (if set), otherwise 8-bit
• Bit 5 (0x20): 44100 Hz sample rate
• Bit 2 (0x04): 22050 Hz sample rate
• Default: 11025 Hz, 8-bit

• 0x01 - Short whistle
• 0x02 - Long whistle
• 0x06 - Air pump
• 0x08 - Conductor's whistle
• 0x09 - Station announcement
• 0x0A - Coupling
• 0x80 - Idle
• 0x82 - Braking
• 0x83 - Thyristor
• 0x86 - Electric motor
• 0x88 - Switchgear
• 0x8E - Electric brake
• 0xFF - Engine

This project is for educational purposes and analysis of ZIMO ZPP file format.