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Added a simple metric for measuring surprise. Which will hopefully allow me to reimplement PAL/NTSC auto-selection for the Atari 2600.

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Thomas Harte 2016-02-18 23:22:06 -05:00
parent c7f54d649e
commit 570d88a876
1 changed files with 15 additions and 0 deletions
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15
Outputs/CRT/Flywheel.hpp
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@ -69,6 +69,8 @@ struct Flywheel
} }
else else
{ {
_number_of_surprises++;
if(_counter < _retrace_time + (_expected_next_sync >> 1)) if(_counter < _retrace_time + (_expected_next_sync >> 1))
{ {
_expected_next_sync = (_expected_next_sync + _standard_period + _sync_error_window) >> 1; _expected_next_sync = (_expected_next_sync + _standard_period + _sync_error_window) >> 1;
@ -165,6 +167,17 @@ struct Flywheel
return _standard_period - _retrace_time; return _standard_period - _retrace_time;
} }
/*!
@returns the number of synchronisation events that have seemed surprising since the last time this method was called;
a low number indicates good synchronisation.
*/
inline unsigned int get_and_reset_number_of_surprises()
{
unsigned int result = _number_of_surprises;
_number_of_surprises = 0;
return result;
}
private: private:
unsigned int _standard_period; // the normal length of time between syncs unsigned int _standard_period; // the normal length of time between syncs
const unsigned int _retrace_time; // a constant indicating the amount of time it takes to perform a retrace const unsigned int _retrace_time; // a constant indicating the amount of time it takes to perform a retrace
@ -174,6 +187,8 @@ struct Flywheel
unsigned int _counter_before_retrace; // the value of _counter immediately before retrace began unsigned int _counter_before_retrace; // the value of _counter immediately before retrace began
unsigned int _expected_next_sync; // our current expection of when the next sync will be encountered (which implies velocity) unsigned int _expected_next_sync; // our current expection of when the next sync will be encountered (which implies velocity)
unsigned int _number_of_surprises; // a count of the surprising syncs
/* /*
Implementation notes: Implementation notes: