The .sca format is designed for storing frame-based animations on the ZX Spectrum. The base format (type 0) is a sequence of uncompressed full-screen frames, each 6912 bytes in size. Frame delays are specified in units of vertical interrupts (1/50 second). The file consists of a header, a delay table, and frame data.
Byte order: little-endian (least significant byte first).
| Offset | Size | Description |
|---|---|---|
| 00–02 | 3 bytes | Marker: ASCII string "SCA" |
| 03 | 1 byte | Version (format version) |
| 04–05 | 2 bytes | Frame width in pixels |
| 06–07 | 2 bytes | Frame height in pixels (max 192) |
| 08 | 1 byte | Recommended border color |
| 09–10 | 2 bytes | Frame count |
| 11 | 1 byte | Payload type |
| 12–13 | 2 bytes | Payload offset (from start of file) |
The structure of the payload depends on the specified type.
Contains N bytes, where N is the number of frames.
Each byte represents the delay for the corresponding frame in units of vertical interrupts (1/50 second).
Each frame is 6912 bytes of ZX Spectrum screen memory in SCREEN$ format (bitmap + attributes).
Frames are stored sequentially with no padding.