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Add a core option for automatic frame skip
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@vircon32
vircon32 committed Mar 4, 2024
1 parent 72f6025 commit 56c429a
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Showing 3 changed files with 161 additions and 35 deletions.
14 changes: 13 additions & 1 deletion ConsoleLogic/V32Console.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -134,12 +134,24 @@ namespace V32

// -----------------------------------------------------------------------------

void V32Console::RunNextFrame()
// if a device can't run at 60 fps, some frames may be
// skipped to prevent audio crackling; however, know
// that this may cause video stutter and other issues:
// input reading will be less reliable and in some
// games audio desynchronization might cause problems
void V32Console::RunNextFrame( bool FrameSkipped )
{
// do nothing when not applicable
if( !PowerIsOn )
return;

// for a skipped frame we will only generate audio
if( FrameSkipped )
{
SPU.UpdateOutputBuffer();
return;
}

// STEP 1: Begin a new frame by sending
// a frame change message to components
Timer.ChangeFrame();
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2 changes: 1 addition & 1 deletion ConsoleLogic/V32Console.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ namespace V32
// control signals
void SetPower( bool On );
void Reset();
void RunNextFrame();
void RunNextFrame( bool FrameSkipped );

// general status queries
bool IsPowerOn();
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180 changes: 147 additions & 33 deletions libretro.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,89 @@ const struct retro_controller_info controller_ports[] =
};


// =============================================================================
// HANDLING FRAMESKIPPING
// =============================================================================


// internal configuration variable
bool enable_frameskip = false;

// we will store audio buffer status and use
// it to decide when we should skip a frame
bool audio_buffer_active = false;
bool audio_buffer_underrun_likely = false;
unsigned audio_buffer_occupancy = 0;

// -----------------------------------------------------------------------------

// callback to receive audio buffer status
static void retro_audio_buff_status_cb( bool active, unsigned occupancy, bool underrun_likely )
{
audio_buffer_active = active;
audio_buffer_occupancy = occupancy;
audio_buffer_underrun_likely = underrun_likely;
}

// -----------------------------------------------------------------------------

// frameskip will need to be configured both initially
// and whenever its value is changed in the front-end
void configure_frameskip()
{
struct retro_audio_buffer_status_callback buf_status_cb;
buf_status_cb.callback = retro_audio_buff_status_cb;

// with frameskip enabled, tell front-end we want to receive audio buffer status
if( enable_frameskip )
{
// careful: automatic frameskipping needs audio buffer info;
// however, some front-ends might not support this
if( !environ_cb( RETRO_ENVIRONMENT_SET_AUDIO_BUFFER_STATUS_CALLBACK, &buf_status_cb ))
{
LOG( "Automatic frame skip has been disabled because frontend does not support audio buffer status monitoring." );
audio_buffer_underrun_likely = false;
return;
}
}

// otherwise no need for that
else environ_cb( RETRO_ENVIRONMENT_SET_AUDIO_BUFFER_STATUS_CALLBACK, nullptr );
}


// =============================================================================
// HANDLING CORE-SPECIFIC OPTIONS
// =============================================================================


// configuration variables for this core
struct retro_variable config_variables[] =
{
{ "enable_frameskip", "Automatic frame skip; Disabled|Enabled" },
{ nullptr, nullptr }
};

// -----------------------------------------------------------------------------

static void update_config_variables()
{
// use this to ask frontend for a variable value
struct retro_variable variable_state =
{
"enable_frameskip", nullptr
};

if( environ_cb( RETRO_ENVIRONMENT_GET_VARIABLE, &variable_state ) && variable_state.value )
{
enable_frameskip = !strcmp( variable_state.value, "Enabled" );
LOG( string("Automatic frame skip ") + (enable_frameskip? "enabled" : "disabled" ) );

configure_frameskip();
}
}


// =============================================================================
// SETTING UP THE CORE ENVIRONMENT
// =============================================================================
Expand Down Expand Up @@ -172,6 +255,9 @@ void retro_set_environment( retro_environment_t cb )
environ_cb( RETRO_ENVIRONMENT_SET_INPUT_DESCRIPTORS, (void*)controller_descriptor );
environ_cb( RETRO_ENVIRONMENT_SET_CONTROLLER_INFO, (void*)controller_ports );

// define this core's configuration variables
environ_cb( RETRO_ENVIRONMENT_SET_VARIABLES, &config_variables );

// fill callback function for logging
struct retro_log_callback logging;

Expand All @@ -187,44 +273,69 @@ void retro_set_environment( retro_environment_t cb )

void retro_run()
{
input_poll_cb();
// if config variables have changed, update them
bool variables_changed = false;

if( environ_cb( RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE, &variables_changed ) && variables_changed )
update_config_variables();

// read input for all connected gamepads
for( int Port = 0; Port < V32::Constants::GamepadPorts; Port++ )
// determine if this frame will be skipped
bool skip_frame = enable_frameskip && audio_buffer_active && audio_buffer_underrun_likely;

// when possible, run a full frame
if( !skip_frame )
{
if( !Console.HasGamepad( Port ) )
continue;
// read input for all connected gamepads
input_poll_cb();

for( int Port = 0; Port < V32::Constants::GamepadPorts; Port++ )
{
if( !Console.HasGamepad( Port ) )
continue;

// read all controls
Console.SetGamepadControl( Port, V32::GamepadControls::Left, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_LEFT ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Right, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_RIGHT ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Up, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_UP ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Down, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_DOWN ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonStart, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_START ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonA, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_A ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonB, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_B ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonX, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_X ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonY, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_Y ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonL, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonR, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R ) );
}

// run the console
if( !Console.IsPowerOn() )
Console.SetPower( true );

Video.BeginFrame();
Console.RunNextFrame( false );

// read all controls
Console.SetGamepadControl( Port, V32::GamepadControls::Left, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_LEFT ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Right, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_RIGHT ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Up, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_UP ) );
Console.SetGamepadControl( Port, V32::GamepadControls::Down, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_DOWN ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonStart, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_START ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonA, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_A ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonB, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_B ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonX, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_X ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonY, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_Y ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonL, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L ) );
Console.SetGamepadControl( Port, V32::GamepadControls::ButtonR, input_state_cb( Port, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R ) );
// ensure that all queued quads are rendered
Video.RenderQuadQueue();

// send this frame's video signal to libretro
video_cb( RETRO_HW_FRAME_BUFFER_VALID, V32::Constants::ScreenWidth, V32::Constants::ScreenHeight, 0 );

// send this frame's audio signal to libretro
Console.GetFrameSoundOutput( AudioBuffer );
audio_batch_cb( (const int16_t*)AudioBuffer.Samples, V32::Constants::SPUSamplesPerFrame );
}

// run the console
if( !Console.IsPowerOn() )
Console.SetPower( true );

Video.BeginFrame();
Console.RunNextFrame();

// ensure that all queued quads are rendered
Video.RenderQuadQueue();

// send this frame's video signal to libretro
video_cb( RETRO_HW_FRAME_BUFFER_VALID, V32::Constants::ScreenWidth, V32::Constants::ScreenHeight, 0 );

// send this frame's audio signal to libretro
Console.GetFrameSoundOutput( AudioBuffer );
audio_batch_cb( (const int16_t*)AudioBuffer.Samples, V32::Constants::SPUSamplesPerFrame );
// when a frame is skipped, only generate audio
// to avoid a buffer underrun and prevent crackling
else
{
// generate 1 frame's worth of audio
Console.RunNextFrame( false );

// send this frame's audio signal to libretro
Console.GetFrameSoundOutput( AudioBuffer );
audio_batch_cb( (const int16_t*)AudioBuffer.Samples, V32::Constants::SPUSamplesPerFrame );
}
}


Expand Down Expand Up @@ -514,6 +625,9 @@ void retro_reset()

bool retro_load_game( const struct retro_game_info *info )
{
// before loading ensure that config variables are updated
update_config_variables();

// for OpenGL we will normally want 32bpp color format
enum retro_pixel_format fmt = RETRO_PIXEL_FORMAT_XRGB8888;

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