This API is intended as a helper for filters that have several video input and need to combine them somehow.

If the inputs have different or variable frame rate, getting the input frames to match requires a rather complex logic and a few user-tunable options.

In this API, when a set of synchronized input frames is ready to be procesed is called a frame event. Frame event can be generated in response to input frames on any or all inputs and the handling of situations where some stream extend beyond the beginning or the end of others can be configured.

The basic working of this API is the following:

• When a frame is available on any input, add it using ff_framesync_add_frame().
• When a frame event is ready to be processed (i.e. after adding a frame or when requested on input):
  • call ff_framesync_next();
  • if fs->frame_ready is true, process the frames;
  • call ff_framesync_drop(). Stream extrapolation mode

Describe how the frames of a stream are extrapolated before the first one and after EOF to keep sync with possibly longer other streams.

Definition at line 62 of file framesync.h.

Initialize a frame sync structure.

The entire structure is expected to be already set to 0.

Parameters

fs frame sync structure to initialize

parent parent object, used for logging

nb_in number of inputs

Definition at line 49 of file framesync.c.

Referenced by config_output(), and ff_dualinput_init().

Configure a frame sync structure.

Must be called after all options are set but before all use.

Returns

>= 0 for success or a negative error code

Definition at line 72 of file framesync.c.

Referenced by config_output(), and ff_dualinput_init().

Free all memory currently allocated.

Definition at line 261 of file framesync.c.

Referenced by ff_dualinput_uninit(), and uninit().

Add a frame to an input.

Typically called from the filter_frame() method.

Parameters

fs frame sync structure

in index of the input

frame input frame, or NULL for EOF

Definition at line 197 of file framesync.c.

Referenced by ff_framesync_filter_frame(), and ff_framesync_request_frame().

Prepare the next frame event.

The status of the operation can be found in fs->frame_ready and fs->eof.

Definition at line 207 of file framesync.c.

Referenced by ff_framesync_process_frame().

Drop the current frame event.

Definition at line 219 of file framesync.c.

Referenced by ff_framesync_process_frame().

Get the current frame in an input.

Parameters

fs frame sync structure

in index of the input

rframe used to return the current frame (or NULL)

get if not zero, the calling code needs to get ownership of the returned frame; the current frame will either be duplicated or removed from the framesync structure

Definition at line 224 of file framesync.c.

Referenced by process_frame().

Process one or several frame using the on_event callback.

Returns

number of frames processed or negative error code

Definition at line 272 of file framesync.c.

Referenced by ff_framesync_filter_frame(), and ff_framesync_request_frame().

Accept a frame on a filter input.

This function can be the complete implementation of all filter_frame methods of a filter using framesync.

Definition at line 293 of file framesync.c.

Referenced by ff_dualinput_filter_frame(), and filter_frame().

Request a frame on the filter output.

This function can be the complete implementation of all filter_frame methods of a filter using framesync if it has only one output.

Definition at line 307 of file framesync.c.

Referenced by ff_dualinput_request_frame(), and request_frame().