TCL plugin script for openMSX Emulator to record a video of MSX software that makes use of switching frame rate frequencies.

vblank.tcl

# TCL plugin script for openMSX Emulator 
#   by Albert "BiFiMSX" Beevendorp and Filip H.F. "FiXato" Slagter
# Used to record a video of MSX software that makes use of switching frame rate frequencies.
# Version 0.7
#
# `toggle_vblank` enables/disables auto-'splitting' of videos at the frame rate change.
# `record_with_vblank` is a wrapper that enables the vblank detection, and allows for 
#   passing along `record start` parameters such as -prefix and -doublesize. 
# It automatically starts the video recording and will stop and start recording a new video when
#   the frame rate change is detected.
#
# Usage examples:
# Manually:
#   record start
#   toggle_vblank
# Automatically:
#   record_with_vblank -doublesize -prefix "\[MSX\] N.O.P. - Unknown Reality"
#
# Changelog:
#   0.1 Initial `toggle_vblank` and `check` script by BiFiMSX
#   0.2 Removed extra ) in `check` proc
#   0.3 Added `record_with_vblank` proc and support for $record_args to toggle_vblank
#   0.4 Bugfix: called variable on cur_wp in `record_with_vblank`
#   0.5 Put the watchpoint creation in a helper proc and made it conditional to prevent 
#       duplicate watchpoints.
#   0.6 Refactored some more and removed the helper proc again.
#   0.7 Added some output to indicate the Frame rate changes, and the start of a new video.

namespace eval vblank {

variable cur_wp ""
variable old_r9 0
variable record_args ""

proc check {} {
  variable old_r9
  variable record_args

  # TODO: Implement check if video recording is already in progress.
  if {[expr [vdpreg 9] & 2] != $old_r9} {
    puts "Frame rate change detected from [expr ($old_r9 eq 0) ? 60 : 50] to [expr ([expr [vdpreg 9] & 2] eq 0) ? 60 : 50]. Starting recording of next video."
    set old_r9 [expr [vdpreg 9] & 2]
    record stop
    eval [linsert $record_args 0 record start]
  }
}

proc toggle_vblank {} {
  variable cur_wp

  if {$cur_wp == ""} {
    variable old_r9
    set old_r9 [expr [vdpreg 9] & 2]
    set cur_wp [debug set_watchpoint write_io 0x99 1 { vblank::check }]
  } else {
    debug remove_watchpoint $cur_wp
    set cur_wp ""
  }
  return ""
}

proc record_with_vblank { args } {
  variable record_args
  variable cur_wp

  set record_args $args
  if {$cur_wp == ""} {
    toggle_vblank
  }
  eval [linsert $record_args 0 record start]
}

namespace export toggle_vblank
namespace export record_with_vblank

}; #namespace

namespace import vblank::*