lavfi: copy framesync into framesync2.

framesync2 will be the base for the version using activate.
Most of the logic will be the same, but the code cannot be shared.
Copying the file initially without change will make the diff
easier to read.

libavfilter/framesync2.h

+/*
+ * Copyright (c) 2013 Nicolas George
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVFILTER_FRAMESYNC2_H
+#define AVFILTER_FRAMESYNC2_H
+
+#include "bufferqueue.h"
+
+/*
+ * TODO
+ * Callback-based API similar to dualinput.
+ * Export convenient options.
+ */
+
+/**
+ * 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.
+ */
+enum FFFrameSyncExtMode {
+
+    /**
+     * Completely stop all streams with this one.
+     */
+    EXT_STOP,
+
+    /**
+     * Ignore this stream and continue processing the other ones.
+     */
+    EXT_NULL,
+
+    /**
+     * Extend the frame to infinity.
+     */
+    EXT_INFINITY,
+};
+
+/**
+ * Input stream structure
+ */
+typedef struct FFFrameSyncIn {
+
+    /**
+     * Queue of incoming AVFrame, and NULL to mark EOF
+     */
+    struct FFBufQueue queue;
+
+    /**
+     * Extrapolation mode for timestamps before the first frame
+     */
+    enum FFFrameSyncExtMode before;
+
+    /**
+     * Extrapolation mode for timestamps after the last frame
+     */
+    enum FFFrameSyncExtMode after;
+
+    /**
+     * Time base for the incoming frames
+     */
+    AVRational time_base;
+
+    /**
+     * Current frame, may be NULL before the first one or after EOF
+     */
+    AVFrame *frame;
+
+    /**
+     * Next frame, for internal use
+     */
+    AVFrame *frame_next;
+
+    /**
+     * PTS of the current frame
+     */
+    int64_t pts;
+
+    /**
+     * PTS of the next frame, for internal use
+     */
+    int64_t pts_next;
+
+    /**
+     * Boolean flagging the next frame, for internal use
+     */
+    uint8_t have_next;
+
+    /**
+     * State: before first, in stream or after EOF, for internal use
+     */
+    uint8_t state;
+
+    /**
+     * Synchronization level: frames on input at the highest sync level will
+     * generate output frame events.
+     *
+     * For example, if inputs #0 and #1 have sync level 2 and input #2 has
+     * sync level 1, then a frame on either input #0 or #1 will generate a
+     * frame event, but not a frame on input #2 until both inputs #0 and #1
+     * have reached EOF.
+     *
+     * If sync is 0, no frame event will be generated.
+     */
+    unsigned sync;
+
+} FFFrameSyncIn;
+
+/**
+ * Frame sync structure.
+ */
+typedef struct FFFrameSync {
+    const AVClass *class;
+    void *parent;
+
+    /**
+     * Number of input streams
+     */
+    unsigned nb_in;
+
+    /**
+     * Time base for the output events
+     */
+    AVRational time_base;
+
+    /**
+     * Timestamp of the current event
+     */
+    int64_t pts;
+
+    /**
+     * Callback called when a frame event is ready
+     */
+    int (*on_event)(struct FFFrameSync *fs);
+
+    /**
+     * Opaque pointer, not used by the API
+     */
+    void *opaque;
+
+    /**
+     * Index of the input that requires a request
+     */
+    unsigned in_request;
+
+    /**
+     * Synchronization level: only inputs with the same sync level are sync
+     * sources.
+     */
+    unsigned sync_level;
+
+    /**
+     * Flag indicating that a frame event is ready
+     */
+    uint8_t frame_ready;
+
+    /**
+     * Flag indicating that output has reached EOF.
+     */
+    uint8_t eof;
+
+    /**
+     * Pointer to array of inputs.
+     */
+    FFFrameSyncIn *in;
+
+} FFFrameSync;
+
+/**
+ * Initialize a frame sync structure.
+ *
+ * The entire structure is expected to be already set to 0.
+ *
+ * @param  fs      frame sync structure to initialize
+ * @param  parent  parent object, used for logging
+ * @param  nb_in   number of inputs
+ * @return  >= 0 for success or a negative error code
+ */
+int ff_framesync_init(FFFrameSync *fs, void *parent, unsigned nb_in);
+
+/**
+ * Configure a frame sync structure.
+ *
+ * Must be called after all options are set but before all use.
+ *
+ * @return  >= 0 for success or a negative error code
+ */
+int ff_framesync_configure(FFFrameSync *fs);
+
+/**
+ * Free all memory currently allocated.
+ */
+void ff_framesync_uninit(FFFrameSync *fs);
+
+/**
+ * Add a frame to an input
+ *
+ * Typically called from the filter_frame() method.
+ *
+ * @param fs     frame sync structure
+ * @param in     index of the input
+ * @param frame  input frame, or NULL for EOF
+ */
+int ff_framesync_add_frame(FFFrameSync *fs, unsigned in, AVFrame *frame);
+
+/**
+ * Prepare the next frame event.
+ *
+ * The status of the operation can be found in fs->frame_ready and fs->eof.
+ */
+void ff_framesync_next(FFFrameSync *fs);
+
+/**
+ * Drop the current frame event.
+ */
+void ff_framesync_drop(FFFrameSync *fs);
+
+/**
+ * Get the current frame in an input.
+ *
+ * @param fs      frame sync structure
+ * @param in      index of the input
+ * @param rframe  used to return the current frame (or NULL)
+ * @param 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
+ */
+int ff_framesync_get_frame(FFFrameSync *fs, unsigned in, AVFrame **rframe,
+                           unsigned get);
+
+/**
+ * Process one or several frame using the on_event callback.
+ *
+ * @return  number of frames processed or negative error code
+ */
+int ff_framesync_process_frame(FFFrameSync *fs, unsigned all);
+
+
+/**
+ * Accept a frame on a filter input.
+ *
+ * This function can be the complete implementation of all filter_frame
+ * methods of a filter using framesync.
+ */
+int ff_framesync_filter_frame(FFFrameSync *fs, AVFilterLink *inlink,
+                              AVFrame *in);
+
+/**
+ * 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.
+ */
+int ff_framesync_request_frame(FFFrameSync *fs, AVFilterLink *outlink);
+
+#endif /* AVFILTER_FRAMESYNC2_H */