accurate video capture timestep

// client.h

typedef struct {
// ...
    float       aviDemoRemain;      // Used for accurate fps recording
} clientConnection_t;



// cl_main.cpp -> CL_Frame

void CL_Frame ( int msec ) {
// ...
if ( CL_VideoRecording( ) && cl_aviFrameRate->integer && msec) {
    // save the current screen
    if ( cls.state == CA_ACTIVE || cl_forceavidemo->integer) {
        float frameTime, fps;
        CL_TakeVideoFrame( );
        // fixed time for next frame'
        fps = cl_aviFrameRate->value * com_timescale->value;
        if ( fps > 1000.0f)
            fps = 1000.0f;
        frameTime = (1000.0f / fps);
        if (frameTime < 1) {
            frameTime = 1;
        }
        frameTime += clc.aviDemoRemain;
        msec = (int)frameTime;
        clc.aviDemoRemain = frameTime - msec;
    }
}