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Main Menu

rgb curves

This submenu has options for changing RGB curves. By changing these curves it is possible to change brightness, contrast, gamma etc.

  • brightness - change screen brightness from -100 to 100
  • contrast - change screen contrast from -100 to 100
  • blue/yellow - change white balance from -100 to 100
  • green/magenta - change white tint from -100 to 100
  • gamma - change gamma correction from 0.4 to 2.5
  • reset - reset all curves to standard flat 1:1 curves


This submenu has special picture filters such as green, amber mono monitor, negative, scanline, smoothing etc.

  • color - mono monitor emulation with many variants (green,amber,cyan,sepia,red)
  • special
    • threshold - all values below 128 set to 0 and all values above 127 set to 255 - this is good option for binary signal (ST mono)
    • negative - negates all R,G and B values
    • 512 colors - round all color values to 512 color palette
    • 4096 colors - round all color values to 4096 color palette
    • ZX/CPC colors - round all color values to 27 color palette
  • pixel
    • scanline - every second line made darker (emulates old CRT scanlines)
    • pixel mode - every second line and every second column made darker (emulates old LCD displays)
    • noise - add noise to picture (emulates connecting to old TV sets)
    • sl+noise - scanline + noise
  • smoothing - decreases noise. If difference between current pixel and previous is smaller than given value then pixel value is blended with previous pixel - makes picture more even and with less noise. Although you can set it from 0 to 255, using values higher than 10 is not recommended.
  • reset - reset all special filters to default values (smoothing to 0 and "no filter" for all other options)


This submenu has options for moving picture left/right, up/down and also for changing window size (you can think of it as an output resolution)

  • xshift - move picture left and right (during movement picture may disappear for a moment - it is a normal reaction of the displaying device when something is changing)
  • yshift - move picture up and down (same as above - during movement picture may disappear)
  • dvi width - set display window to specific width (be aware that some displays do not accept all widths, so during changing for example from 720 to 800 screen may be black when values are in between, also every width change usually means sync lost, so it is better to change these values using OLED, not OSD)
  • dvi height - set display window to specific height (same as above)
  • dvi presets - beacuse usually we want to use well defined screen sizes, there are presets for screen width and height. When selected preset's height or width is too big for current input resolution, it is lowered to maximum possible value. Current firmware displays only available modes (lower than current native resolution).
    • 1280x1024 (mainly for viking mode in MIST)
    • 1024x768 (standard old Mac/PC)
    • 800x600 (whole screen in PAL modes - with all borders)
    • 720x576 (standard PAL resolution - most compatible for PAL modes)
    • 720x480 (standard NTSC resolution - most compatible for NTSC modes)
    • 640x480 (standard VGA resolution - very compatible)
    • 640x400 (good for ST mono)

rgb only

This submenu has options that are used only when picture is processed by RGB A/D converter (front LED is red, on OLED info says that source of signal is RGB "RGB: xxxxxxx"). In current firmware this menu is only visible when RGB signal is processed.

sample phase
  • sample phase - sets sample phase of pixel. Pixels have to pe sampled in "the middle of the pixel". When pixels are sampled "in between" then the picture looks blurry and often noisy. This option should be adjusted individually for every device connected to Medusa - this is a very important option !!!.
  • pixels/line - for all recognised modes this option shouldn't be adjusted - for all known computers this parameter is predefined in Medusa, but when you connect something that is not recognised ("unknown PAL", "unknown NTSC", "unrecognised lo" or "unrecognised hi") you can set this option to improve picture quality.
  • double res - doubles X resolution (practically useful only for Amiga's "Super Hires" modes)
  • double lines - doubles Y resolution (standard for PAL/NTSC modes)
  • auto levels - runs a routine, that tries to find best offset and gain for R, G and B signals - use it, when the picture is too dark or too light - usually it is automatically performed whenever you connect a specific device for the first time, but if you have two cables for the same computer then after a cable change you may need to run this manually.
  • component mode - changes R,G,B to Y,Cr,Cb (Y on green, Cr on red and Cb on blue) - after changing this option "auto levels" is always re-run
    • when active source is VGA
      • RGB mode - standard RGB
      • YCrCb - Y on green, Cr on red and Cb on blue)
      • Mono on G - use green only as a mono signal, ignore red and blue
    • when active source is SCART
      • YCrCb [Y<-CV] - Y on CV SCART pin, Cr on red, Cb on blue)
      • YCrCb [Y<-G] - Y on green, Cr on red, Cb on blue)
      • Mono [Y<-CV] - use CV as a mono signal, ignore red, green and blue signals
      • Mono [Y<-G] - use green as a mono signal, CV as a synchro input, ignore red and blue
      • Hybrid mode - Special S-Video mode. Process luma signal by RGB A/D and chroma by SDTV A/D. Experimental mode that increases S-Video quality.
  • digital mode (only when digital signal is processed) - switching between MDA/Hercules, RGBI/C128/CGA and EGA
  • lowpass filter (switch on/off lowpass filter in RGB A/D and external SCART-only LP filter)
  • luma delay (only when hybrid mode is active) - adjust chroma/luma shift
  • fingerprint - Medusa recognises input devices using "fingerprint" mechanism. For each device there is a predefined fingerprint in the firmware. But sometimes it may happen that your device is not recognised correctly, or it is not in Medusa's database at all. This option displays fingerprint parameters for currently connected device. These values may be used by Medusa developers to improve devices detection and adding new ones.

global options

This submenu has global options (DVI, timeouts, audio freq itp.)

  • DVI mode
    • auto - automatically detect if the receiver is capable of audio processing.
    • extended DVI - always send audio packets on DVI (not compatible with DVI, but usually recognised correctly by HDMI devices connected to Medusa via appropriate cables)
    • pure DVI - pure DVI signal without audio (compatible with most old LCD 17" and 19" displays)
  • DVI extras (only in extended DVI mode)
    • audio only - send only audio packets
    • audio + info - send audio and info packets
  • SCART mode
    • auto - switch between RGB/SDTV automatically (using SWITCH pin on SCART)
    • sdtv only - always process signal using SDTV A/D (composite video / s-video)
    • rgb only - always process signal using RGB A/D
  • SDTV mode
    • auto - automatically recognise CVBS (composite video) and S-Video
    • force CVBS - process signal as composite video (luma and chroma together)
    • force S-Video - process signal as S-Video (luma / chroma separated)
  • Audio source
    • auto - use SCART as an audio source when it is used as a video source, and 3.5" jack otherwise
    • SCART only - always use SCART as an audio input
    • Jack only - always use 3.5" Jack as an audio input
    • SCART + Jack (rev B only) - mix signals from SCART and Jack.
  • Aud mix ratio (only when SCART + Jack is selected) - switch mix ratio 1:7,2:6,3:5,4:4,5:3,6:2,7:1
  • OLED rotation - optionally rotate OLED content
  • Audio freq (rev B only and only in extended DVI mode) - change audio sample frequency (192,176.4,96,88.2,48,44.1,32) kHz
  • Audio bits (only in extended DVI mode) - change audio sample bit depth (24,20,16) bits
  • No Signal FPS - change "no signal screen" mode (50Hz/60Hz)
  • Lost sync wait
  • Sleep timeout
  • OSD timeouts
    • main menu
    • sub menus
    • start info
    • change mode
    • no signal
    • return to top


Reset settings (all settings are also reset when you turn on Medusa with pressed both left keys - 'up' and 'down')

  • rst glob opts - resets only global options (DVI mode and OSD timeouts)
  • rst curr prof - resets current profile (all curves, filters, etc. only for currently connected device)
  • factory reset - same as running with 'up' and 'down' pressed - clears whole flash memory with all settings