Method GetFrame

src/FrameMapper.cpp:434–690

Get an openshot::Frame object for a specific frame number of this reader.

// Get an openshot::Frame object for a specific frame number of this reader.
std::shared_ptr<Frame> FrameMapper::GetFrame(int64_t requested_frame)
{
	// Check final cache, and just return the frame (if it's available)
	std::shared_ptr<Frame> final_frame = final_cache.GetFrame(requested_frame);
	if (final_frame) return final_frame;

	// Create a scoped lock, allowing only a single thread to run the following code at one time
	const std::lock_guard<std::recursive_mutex> lock(getFrameMutex);

	// Find parent properties (if any)
	Clip *parent = static_cast<Clip *>(ParentClip());
	bool is_increasing = true;
	bool direction_flipped = false;

	{
		const std::lock_guard<std::recursive_mutex> lock(directionMutex);

		// One-shot: if a hint exists, consume it for THIS call, regardless of frame number.
		if (have_hint) {
			is_increasing = hint_increasing;
			have_hint = false;
		} else if (previous_frame > 0 && std::llabs(requested_frame - previous_frame) == 1) {
			// Infer from request order when adjacent
			is_increasing = (requested_frame > previous_frame);
		} else if (last_dir_initialized) {
			// Reuse last known direction if non-adjacent and no hint
			is_increasing = last_is_increasing;
		} else {
			is_increasing = true; // default on first call
		}

		// Detect flips so we can reset SR context
		if (!last_dir_initialized) {
			last_is_increasing = is_increasing;
			last_dir_initialized = true;
		} else if (last_is_increasing != is_increasing) {
			direction_flipped = true;
			last_is_increasing = is_increasing;
		}
	}
	if (parent) {
		float position = parent->Position();
		float start = parent->Start();
		if (parent_position != position || parent_start != start) {
			// Force dirty if parent clip has moved or been trimmed
			// since this heavily affects frame #s and audio mappings
			is_dirty = true;
		}
	}

	// Check if mappings are dirty (and need to be recalculated)
	if (is_dirty)
		Init();

	// Check final cache a 2nd time (due to potential lock already generating this frame)
	final_frame = final_cache.GetFrame(requested_frame);
	if (final_frame) return final_frame;