- /* Before we `re-write' the frame indexes of these incoming data we need to check for
- the case where the user has some 2D content which they have marked as 3D. With 3D
- we should get two frames for each frame index, but in this `bad' case we only get
- one. We need to throw an exception if this happens.
- */
-
- if (_content->video->frame_type() == VIDEO_FRAME_TYPE_3D) {
- if (_last_threed_frames.size() > 4) {
- _last_threed_frames.erase (_last_threed_frames.begin());
- }
- _last_threed_frames.push_back (decoder_frame);
- if (_last_threed_frames.size() == 4) {
- if (_last_threed_frames[0] != _last_threed_frames[1] || _last_threed_frames[2] != _last_threed_frames[3]) {
- boost::throw_exception (
- DecodeError(
- String::compose(
- _("The content file %1 is set as 3D but does not appear to contain 3D images. Please set it to 2D. "
- "You can still make a 3D DCP from this content by ticking the 3D option in the DCP video tab."),
- _content->path(0)
- )
+ double const afr = _content->active_video_frame_rate(film);
+ VideoFrameType const vft = _content->video->frame_type();
+
+ ContentTime frame_time = ContentTime::from_frames (decoder_frame, afr);
+
+ /* Do some heuristics to try and spot the case where the user sets content to 3D
+ * when it is not. We try to tell this by looking at the differences in time between
+ * the first few frames. Real 3D content should have two frames for each timestamp.
+ */
+ if (_frame_interval_checker) {
+ _frame_interval_checker->feed (frame_time, afr);
+ if (_frame_interval_checker->guess() == FrameIntervalChecker::PROBABLY_NOT_3D && vft == VIDEO_FRAME_TYPE_3D) {
+ boost::throw_exception (
+ DecodeError(
+ String::compose(
+ _("The content file %1 is set as 3D but does not appear to contain 3D images. Please set it to 2D. "
+ "You can still make a 3D DCP from this content by ticking the 3D option in the DCP video tab."),
+ _content->path(0)