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5.5 Recording and playback

Tapes: fast or real time

Tape files (.tap, .tzx) load two ways. Either way LOAD "" is typed in for you when the tape is attached.

Fast load is the default and is what you want almost always: JNEXT short-circuits the ROM's loading routine and the program appears in seconds.

Real time replays the tape as audio, at the speed of an actual cassette — several minutes, loading stripes, screeching and all. Use it for authenticity, or for the occasional program with a custom loader that fast-load cannot follow. Turn it on with Tape > Fast Load (uncheck it) or --tape-realtime.

.wav files are always real time; there is no ROM routine to short-circuit.

Tape > Open Tape File… (Alt+T) loads a tape, and Eject and Rewind do what they say. The status bar shows the tape name and, while loading, the block position.

Video

File > Record MPEG4 Video… (Ctrl+F5) starts recording video with audio to an MP4; Stop (Ctrl+F6) ends it. From the command line, --record FILE.

This needs ffmpeg installed and on your PATH — JNEXT feeds it the frames. If it is missing, --record fails immediately: JNEXT says so and exits non-zero without emulating anything, rather than running a session you would find out afterwards had never been recorded.

To capture only the audio, --wav-record FILE writes a standard WAV. It needs neither ffmpeg nor a sound card, so it works in automated runs.

Leaving JNEXT with a recording still running finishes the file rather than abandoning it — File > Quit, Alt+Q and closing the window all stop and finalise it.

RZX: recording what you did

An RZX file records your input rather than the screen, alongside a snapshot of the machine. Replaying it reproduces the session exactly, keystroke for keystroke — a walkthrough, a bug report, or a speedrun that stays honest.

  • File > Record RZX…, or --rzx-record FILE; Stop RZX to finish.
  • File > Play RZX Recording…, or --rzx-play FILE. Loading a .rzx with --load plays it too.

Because it stores input rather than pixels, an RZX is tiny compared with a video — but it only replays correctly in an emulator that models the machine the same way.

Every option mentioned in this chapter, and the ones that are not, are listed in full in the manual page — man jnext, or USAGE.md.