MD/MJPEG

Microfirmware for the SidecarTridge Multi-device by Neil Rackett

Introduction

MD/MJPEG turns your SidecarTridge Multi-device into a video player for your Atari ST: drop an .AVI file onto the SD card and it plays full-screen, full-motion video with sound on a stock ST — no hard drive, no accelerator, no extra hardware.

Why? Because why watch videos at 4K resolution in 16.7 million colours when you can watch them at 0.3K in 16!

Every frame is decoded from MJPEG on the SidecarT's RP2040, quantized to a fresh 16-colour palette (median cut, blue-noise dither and a saturation boost, so each frame gets the best colours the ST can show), and blitted to the screen over the cartridge port at up to 25 fps. Sound is 8-bit 25 kHz DMA audio on an STE, or the YM2149 (~5.6 kHz) on a plain ST — the firmware detects which machine it's on and picks the best it can do. Video and audio stay in sync by design: the audio clock paces the video, and busy scenes drop frames rather than drift.

When it starts, the app lists the .AVI files in the /mjpeg folder of the SD card. Use Up/Down to choose one and Return to play it. During playback, Left/Right skip back/forward 10 seconds, Space pauses and resumes, and ESC returns to the list (a time readout pops up briefly when you seek or pause). When a video reaches the end it returns to the list too. From the list, ESC quits back to GEM.

Click here for more information about this project and video conversion.

Installation

1. Download the files below.
2. Copy the .uf2 and .json files to the /apps folder of your SidecarT's microSD card and the AVI files to /mjpeg.
3. On the Booster screen, press ESC for the app list and select the MD/MJPEG app.
4. Use video_to_avi.sh to convert videos into ST-friendly MJPEG AVI format.
5. To return to Booster, power on while holding SELECT.