double out_pts = out_pts_origin + TIMEBASE * frameno / global_flags.output_framerate;
next_frame_start =
origin + microseconds(lrint((out_pts - out_pts_origin) * 1e6 / TIMEBASE));
double out_pts = out_pts_origin + TIMEBASE * frameno / global_flags.output_framerate;
next_frame_start =
origin + microseconds(lrint((out_pts - out_pts_origin) * 1e6 / TIMEBASE));