lavfi: add an API to synchronize multiple video inputs.

Compared to dualinput, this API can handle more than two
inputs and can generate frames synchronized to any or all
input streams.

2 files changed, 625 insertions, 0 deletions

diff --git a/libavfilter/framesync.c b/libavfilter/framesync.c
new file mode 100644
index 0000000000..12db50cb77
--- /dev/null
+++ b/libavfilter/framesync.c
@@ -0,0 +1,329 @@
+/*
+ * 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
+ */
+
+#include "libavutil/avassert.h"
+#include "avfilter.h"
+#include "bufferqueue.h"
+#include "framesync.h"
+#include "internal.h"
+
+#define OFFSET(member) offsetof(FFFrameSync, member)
+
+static const char *framesync_name(void *ptr)
+{
+    return "framesync";
+}
+
+static const AVClass framesync_class = {
+    .version                   = LIBAVUTIL_VERSION_INT,
+    .class_name                = "framesync",
+    .item_name                 = framesync_name,
+    .category                  = AV_CLASS_CATEGORY_FILTER,
+    .option                    = NULL,
+    .parent_log_context_offset = OFFSET(parent),
+};
+
+enum {
+    STATE_BOF,
+    STATE_RUN,
+    STATE_EOF,
+};
+
+void ff_framesync_init(FFFrameSync *fs, void *parent, unsigned nb_in)
+{
+    fs->class  = &framesync_class;
+    fs->parent = parent;
+    fs->nb_in  = nb_in;
+}
+
+static void framesync_sync_level_update(FFFrameSync *fs)
+{
+    unsigned i, level = 0;
+
+    for (i = 0; i < fs->nb_in; i++)
+        if (fs->in[i].state != STATE_EOF)
+            level = FFMAX(level, fs->in[i].sync);
+    av_assert0(level <= fs->sync_level);
+    if (level < fs->sync_level)
+        av_log(fs, AV_LOG_VERBOSE, "Sync level %u\n", level);
+    if (level)
+        fs->sync_level = level;
+    else
+        fs->eof = 1;
+}
+
+int ff_framesync_configure(FFFrameSync *fs)
+{
+    unsigned i;
+    int64_t gcd, lcm;
+
+    if (!fs->time_base.num) {
+        for (i = 0; i < fs->nb_in; i++) {
+            if (fs->in[i].sync) {
+                if (fs->time_base.num) {
+                    gcd = av_gcd(fs->time_base.den, fs->in[i].time_base.den);
+                    lcm = (fs->time_base.den / gcd) * fs->in[i].time_base.den;
+                    if (lcm < AV_TIME_BASE / 2) {
+                        fs->time_base.den = lcm;
+                        fs->time_base.num = av_gcd(fs->time_base.num,
+                                                   fs->in[i].time_base.num);
+                    } else {
+                        fs->time_base.num = 1;
+                        fs->time_base.den = AV_TIME_BASE;
+                        break;
+                    }
+                } else {
+                    fs->time_base = fs->in[i].time_base;
+                }
+            }
+        }
+        if (!fs->time_base.num) {
+            av_log(fs, AV_LOG_ERROR, "Impossible to set time base\n");
+            return AVERROR(EINVAL);
+        }
+        av_log(fs, AV_LOG_VERBOSE, "Selected %d/%d time base\n",
+               fs->time_base.num, fs->time_base.den);
+    }
+
+    for (i = 0; i < fs->nb_in; i++)
+        fs->in[i].pts = fs->in[i].pts_next = AV_NOPTS_VALUE;
+    fs->sync_level = UINT_MAX;
+    framesync_sync_level_update(fs);
+
+    return 0;
+}
+
+static void framesync_advance(FFFrameSync *fs)
+{
+    int latest;
+    unsigned i;
+    int64_t pts;
+
+    if (fs->eof)
+        return;
+    while (!fs->frame_ready) {
+        latest = -1;
+        for (i = 0; i < fs->nb_in; i++) {
+            if (!fs->in[i].have_next) {
+                if (latest < 0 || fs->in[i].pts < fs->in[latest].pts)
+                    latest = i;
+            }
+        }
+        if (latest >= 0) {
+            fs->in_request = latest;
+            break;
+        }
+
+        pts = fs->in[0].pts_next;
+        for (i = 1; i < fs->nb_in; i++)
+            if (fs->in[i].pts_next < pts)
+                pts = fs->in[i].pts_next;
+        if (pts == INT64_MAX) {
+            fs->eof = 1;
+            break;
+        }
+        for (i = 0; i < fs->nb_in; i++) {
+            if (fs->in[i].pts_next == pts ||
+                (fs->in[i].before == EXT_INFINITY &&
+                 fs->in[i].state == STATE_BOF)) {
+                av_frame_free(&fs->in[i].frame);
+                fs->in[i].frame      = fs->in[i].frame_next;
+                fs->in[i].pts        = fs->in[i].pts_next;
+                fs->in[i].frame_next = NULL;
+                fs->in[i].pts_next   = AV_NOPTS_VALUE;
+                fs->in[i].have_next  = 0;
+                fs->in[i].state      = fs->in[i].frame ? STATE_RUN : STATE_EOF;
+                if (fs->in[i].sync == fs->sync_level && fs->in[i].frame)
+                    fs->frame_ready = 1;
+                if (fs->in[i].state == STATE_EOF &&
+                    fs->in[i].after == EXT_STOP)
+                    fs->eof = 1;
+            }
+        }
+        if (fs->eof)
+            fs->frame_ready = 0;
+        if (fs->frame_ready)
+            for (i = 0; i < fs->nb_in; i++)
+                if ((fs->in[i].state == STATE_BOF &&
+                     fs->in[i].before == EXT_STOP))
+                    fs->frame_ready = 0;
+        fs->pts = pts;
+    }
+}
+
+static int64_t framesync_pts_extrapolate(FFFrameSync *fs, unsigned in,
+                                         int64_t pts)
+{
+    /* Possible enhancement: use the link's frame rate */
+    return pts + 1;
+}
+
+static void framesync_inject_frame(FFFrameSync *fs, unsigned in, AVFrame *frame)
+{
+    int64_t pts;
+
+    av_assert0(!fs->in[in].have_next);
+    if (frame) {
+        pts = av_rescale_q(frame->pts, fs->in[in].time_base, fs->time_base);
+        frame->pts = pts;
+    } else {
+        pts = fs->in[in].state != STATE_RUN || fs->in[in].after == EXT_INFINITY
+            ? INT64_MAX : framesync_pts_extrapolate(fs, in, fs->in[in].pts);
+        fs->in[in].sync = 0;
+        framesync_sync_level_update(fs);
+    }
+    fs->in[in].frame_next = frame;
+    fs->in[in].pts_next   = pts;
+    fs->in[in].have_next  = 1;
+}
+
+int ff_framesync_add_frame(FFFrameSync *fs, unsigned in, AVFrame *frame)
+{
+    av_assert1(in < fs->nb_in);
+    if (!fs->in[in].have_next)
+        framesync_inject_frame(fs, in, frame);
+    else
+        ff_bufqueue_add(fs, &fs->in[in].queue, frame);
+    return 0;
+}
+
+void ff_framesync_next(FFFrameSync *fs)
+{
+    unsigned i;
+
+    av_assert0(!fs->frame_ready);
+    for (i = 0; i < fs->nb_in; i++)
+        if (!fs->in[i].have_next && fs->in[i].queue.available)
+            framesync_inject_frame(fs, i, ff_bufqueue_get(&fs->in[i].queue));
+    fs->frame_ready = 0;
+    framesync_advance(fs);
+}
+
+void ff_framesync_drop(FFFrameSync *fs)
+{
+    fs->frame_ready = 0;
+}
+
+int ff_framesync_get_frame(FFFrameSync *fs, unsigned in, AVFrame **rframe,
+                           unsigned get)
+{
+    AVFrame *frame;
+    unsigned need_copy = 0, i;
+    int64_t pts_next;
+    int ret;
+
+    if (!fs->in[in].frame) {
+        *rframe = NULL;
+        return 0;
+    }
+    frame = fs->in[in].frame;
+    if (get) {
+        /* Find out if we need to copy the frame: is there another sync
+           stream, and do we know if its current frame will outlast this one? */
+        pts_next = fs->in[in].have_next ? fs->in[in].pts_next : INT64_MAX;
+        for (i = 0; i < fs->nb_in && !need_copy; i++)
+            if (i != in && fs->in[i].sync &&
+                (!fs->in[i].have_next || fs->in[i].pts_next < pts_next))
+                need_copy = 1;
+        if (need_copy) {
+            if (!(frame = av_frame_clone(frame)))
+                return AVERROR(ENOMEM);
+            if ((ret = av_frame_make_writable(frame)) < 0) {
+                av_frame_free(&frame);
+                return ret;
+            }
+        } else {
+            fs->in[in].frame = NULL;
+        }
+        fs->frame_ready = 0;
+    }
+    *rframe = frame;
+    return 0;
+}
+
+void ff_framesync_uninit(FFFrameSync *fs)
+{
+    unsigned i;
+
+    for (i = 0; i < fs->nb_in; i++) {
+        av_frame_free(&fs->in[i].frame);
+        av_frame_free(&fs->in[i].frame_next);
+        ff_bufqueue_discard_all(&fs->in[i].queue);
+    }
+}
+
+int ff_framesync_process_frame(FFFrameSync *fs, unsigned all)
+{
+    int ret, count = 0;
+
+    av_assert0(fs->on_event);
+    while (1) {
+        ff_framesync_next(fs);
+        if (fs->eof || !fs->frame_ready)
+            break;
+        if ((ret = fs->on_event(fs)) < 0)
+            return ret;
+        ff_framesync_drop(fs);
+        count++;
+        if (!all)
+            break;
+    }
+    if (!count && fs->eof)
+        return AVERROR_EOF;
+    return count;
+}
+
+int ff_framesync_filter_frame(FFFrameSync *fs, AVFilterLink *inlink,
+                              AVFrame *in)
+{
+    int ret;
+
+    if ((ret = ff_framesync_process_frame(fs, 1)) < 0)
+        return ret;
+    if ((ret = ff_framesync_add_frame(fs, FF_INLINK_IDX(inlink), in)) < 0)
+        return ret;
+    if ((ret = ff_framesync_process_frame(fs, 0)) < 0)
+        return ret;
+    return 0;
+}
+
+int ff_framesync_request_frame(FFFrameSync *fs, AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    int input, ret;
+
+    if ((ret = ff_framesync_process_frame(fs, 0)) < 0)
+        return ret;
+    if (ret > 0)
+        return 0;
+    if (fs->eof)
+        return AVERROR_EOF;
+    outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
+    input = fs->in_request;
+    ret = ff_request_frame(ctx->inputs[input]);
+    if (ret == AVERROR_EOF) {
+        if ((ret = ff_framesync_add_frame(fs, input, NULL)) < 0)
+            return ret;
+        if ((ret = ff_framesync_process_frame(fs, 0)) < 0)
+            return ret;
+        ret = 0;
+    }
+    return ret;
+}
diff --git a/libavfilter/framesync.h b/libavfilter/framesync.h
new file mode 100644
index 0000000000..2072781054
--- /dev/null
+++ b/libavfilter/framesync.h
@@ -0,0 +1,296 @@
+/*
+ * 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_FRAMESYNC_H
+#define AVFILTER_FRAMESYNC_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;
+
+    /**
+     * Array of inputs; all inputs must be in consecutive memory
+     */
+    FFFrameSyncIn in[1]; /* must be the last field */
+
+} 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
+ */
+void 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_FRAMESYNC_H */