hctape - 8-Bit Homecomputer Datatape Extractor

The repository contains:

• hctape - a program to extract 8-Bit computer datatapes
• libtr - a library for reading raw audio files (WAV)

Contact

Author: David Schalig aka mrhill/Icebird

WWW: http://kc85.datahammer.de Email: kc85 () datahammer.de.spam (replace () and remove .spam)

Introduction

This tool allows to extract data from 8-bit homecomputer datatape recordings. It takes a WAV sample of the cassette tape as input and batch-extracts all data.

To extract your tapes, first digitally record them to WAV samples. You can use programs like Audacity, GoldWave, or Soundforge for this. For good results choose a high quality sampling format, like 44.1 kHz, 16 bit, stereo. Then feed the WAV sample into hctape to batch-extract all files.

Currently only the modulation format for KC85/HC900/KC87/Z9001 series computers is supported. Eventually I will add support for Z1013 and KC turboloader formats.

Usage

hctape is a command line tool. See command line help (run without parameters) for syntax.

How hctape works

hctape uses some special techniques to reconstruct even bad recordings. To detect waveforms it uses correlation, this allows to extract data from recordings with background noise. It is also jitter-resistant to some extend.

Todos

I am planning to do the following improvements if I find the time:

• recording speed detection (some tapes cannot be extracted, because the basespeed differs from the internal reference speed)
• advanced jitter correction using automatic resync
• automatic fall back to other stereo channel on biterrors
• biterror correction using the packet CRC
• add Z1013 support
• add turboloader support

Data Modulation, Packet and File Formats

KC85/HC900/KC87/Z9001 CAOS (Cassette Aided Operating System)

Modulation format

130 byte packets:

• Synctone, N waves, 1200 Hz
• Stopbit, 1 wave, 600 Hz
• Byte, 8 waves, 0 = 2400 Hz, 1 = 1200 Hz
• Stopbit, 1 wave, 600 Hz

Packet format

Files are stored in packets (chunks) of 130 bytes each:

< Long Synctone >< Packet 1 > < Synctone >< Packet 2 > ... < Synctone >< Packet N >

• 1 byte : Packet ID
• 128 bytes : Data
• 1 byte : CRC, all 128 data bytes added up

The first packet of a file has ID 0x01. Each subsequent packet will increase the ID by 1, wrapping at 0xFE. The last packet always has ID 0xFF. If a file's size is not multiple of 128, the last packet will be padded with 0 bytes.

File formats

Packet 0x01 contains a file header, which is specific to the type of the file.

CAOS Machine Code program or memory dump BASIC program

See CAOS system handbook for packet formats.

Z1013

tbd

KC Turboloader

tbd

Version History

1.0 Initial release from 2008 2.0 recovered lost source code, made it compile on Linux with CMake