avfilter/f_cue: add cue and acue filters

To delay filtering until a given wallclock timestamp.
Signed-off-by: Marton Balint <cus@passwd.hu>

Changelog

@@ -23,6 +23,7 @@ version <next>:
 - WinCam Motion Video decoder
 - 1D LUT filter (lut1d)
 - RemotelyAnywhere Screen Capture decoder
+- cue and acue filters
 
 
 version 4.0:

doc/filters.texi

@@ -551,6 +551,11 @@ Set LFO range.
 Set LFO rate.
 @end table
 
+@section acue
+
+Delay audio filtering until a given wallclock timestamp. See the @ref{cue}
+filter.
+
 @section adeclick
 Remove impulsive noise from input audio.
 
@@ -6987,6 +6992,37 @@ indicates 'never reset', and returns the largest area encountered during
 playback.
 @end table
 
+@anchor{cue}
+@section cue
+
+Delay video filtering until a given wallclock timestamp. The filter first
+passes on @option{preroll} amount of frames, then it buffers at most
+@option{buffer} amount of frames and waits for the cue. After reaching the cue
+it forwards the buffered frames and also any subsequent frames coming in its
+input.
+
+The filter can be used synchronize the output of multiple ffmpeg processes for
+realtime output devices like decklink. By putting the delay in the filtering
+chain and pre-buffering frames the process can pass on data to output almost
+immediately after the target wallclock timestamp is reached.
+
+Perfect frame accuracy cannot be guaranteed, but the result is good enough for
+some use cases.
+
+@table @option
+
+@item cue
+The cue timestamp expressed in a UNIX timestamp in microseconds. Default is 0.
+
+@item preroll
+The duration of content to pass on as preroll expressed in seconds. Default is 0.
+
+@item buffer
+The maximum duration of content to buffer before waiting for the cue expressed
+in seconds. Default is 0.
+
+@end table
+
 @anchor{curves}
 @section curves
 

libavfilter/Makefile

@@ -36,6 +36,7 @@ OBJS-$(CONFIG_ACONTRAST_FILTER)              += af_acontrast.o
 OBJS-$(CONFIG_ACOPY_FILTER)                  += af_acopy.o
 OBJS-$(CONFIG_ACROSSFADE_FILTER)             += af_afade.o
 OBJS-$(CONFIG_ACRUSHER_FILTER)               += af_acrusher.o
+OBJS-$(CONFIG_ACUE_FILTER)                   += f_cue.o
 OBJS-$(CONFIG_ADECLICK_FILTER)               += af_adeclick.o
 OBJS-$(CONFIG_ADECLIP_FILTER)                += af_adeclick.o
 OBJS-$(CONFIG_ADELAY_FILTER)                 += af_adelay.o
@@ -178,6 +179,7 @@ OBJS-$(CONFIG_COREIMAGE_FILTER)              += vf_coreimage.o
 OBJS-$(CONFIG_COVER_RECT_FILTER)             += vf_cover_rect.o lavfutils.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
+OBJS-$(CONFIG_CUE_FILTER)                    += f_cue.o
 OBJS-$(CONFIG_CURVES_FILTER)                 += vf_curves.o
 OBJS-$(CONFIG_DATASCOPE_FILTER)              += vf_datascope.o
 OBJS-$(CONFIG_DCTDNOIZ_FILTER)               += vf_dctdnoiz.o

libavfilter/allfilters.c

@@ -27,6 +27,7 @@ extern AVFilter ff_af_abench;
 extern AVFilter ff_af_acompressor;
 extern AVFilter ff_af_acontrast;
 extern AVFilter ff_af_acopy;
+extern AVFilter ff_af_acue;
 extern AVFilter ff_af_acrossfade;
 extern AVFilter ff_af_acrusher;
 extern AVFilter ff_af_adeclick;
@@ -167,6 +168,7 @@ extern AVFilter ff_vf_coreimage;
 extern AVFilter ff_vf_cover_rect;
 extern AVFilter ff_vf_crop;
 extern AVFilter ff_vf_cropdetect;
+extern AVFilter ff_vf_cue;
 extern AVFilter ff_vf_curves;
 extern AVFilter ff_vf_datascope;
 extern AVFilter ff_vf_dctdnoiz;

libavfilter/f_cue.c

+/*
+ * Copyright (c) 2018 Marton Balint
+ *
+ * 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/opt.h"
+#include "libavutil/time.h"
+#include "avfilter.h"
+#include "filters.h"
+#include "framequeue.h"
+#include "internal.h"
+
+typedef struct CueContext {
+    const AVClass *class;
+    int64_t first_pts;
+    int64_t cue;
+    int64_t preroll;
+    int64_t buffer;
+    int status;
+    FFFrameQueue queue;
+} CueContext;
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    CueContext *s = ctx->priv;
+    ff_framequeue_init(&s->queue, &ctx->graph->internal->frame_queues);
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    CueContext *s = ctx->priv;
+    ff_framequeue_free(&s->queue);
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    AVFilterLink *inlink = ctx->inputs[0];
+    AVFilterLink *outlink = ctx->outputs[0];
+    CueContext *s = ctx->priv;
+    int64_t pts;
+    AVFrame *frame = NULL;
+
+    FF_FILTER_FORWARD_STATUS_BACK(outlink, inlink);
+
+    if (s->status < 3 || s->status == 5) {
+        int ret = ff_inlink_consume_frame(inlink, &frame);
+        if (ret < 0)
+            return ret;
+        if (frame)
+            pts = av_rescale_q(frame->pts, inlink->time_base, AV_TIME_BASE_Q);
+    }
+
+    if (!s->status && frame) {
+        s->first_pts = pts;
+        s->status++;
+    }
+    if (s->status == 1 && frame) {
+        if (pts - s->first_pts < s->preroll)
+            return ff_filter_frame(outlink, frame);
+        s->first_pts = pts;
+        s->status++;
+    }
+    if (s->status == 2 && frame) {
+        int ret = ff_framequeue_add(&s->queue, frame);
+        if (ret < 0) {
+            av_frame_free(&frame);
+            return ret;
+        }
+        frame = NULL;
+        if (!(pts - s->first_pts < s->buffer && (av_gettime() - s->cue) < 0))
+            s->status++;
+    }
+    if (s->status == 3) {
+        int64_t diff;
+        while ((diff = (av_gettime() - s->cue)) < 0)
+            av_usleep(av_clip(-diff / 2, 100, 1000000));
+        s->status++;
+    }
+    if (s->status == 4) {
+        if (ff_framequeue_queued_frames(&s->queue))
+            return ff_filter_frame(outlink, ff_framequeue_take(&s->queue));
+        s->status++;
+    }
+    if (s->status == 5 && frame)
+        return ff_filter_frame(outlink, frame);
+
+    FF_FILTER_FORWARD_STATUS(inlink, outlink);
+    FF_FILTER_FORWARD_WANTED(outlink, inlink);
+
+    return FFERROR_NOT_READY;
+}
+
+#define OFFSET(x) offsetof(CueContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM
+static const AVOption options[] = {
+    { "cue", "cue unix timestamp in microseconds", OFFSET(cue), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, FLAGS },
+    { "preroll", "preroll duration in seconds", OFFSET(preroll), AV_OPT_TYPE_DURATION, { .i64 = 0 }, 0, INT64_MAX, FLAGS },
+    { "buffer", "buffer duration in seconds", OFFSET(buffer), AV_OPT_TYPE_DURATION, { .i64 = 0 }, 0, INT64_MAX, FLAGS },
+    { NULL }
+};
+
+#if CONFIG_CUE_FILTER
+#define cue_options options
+AVFILTER_DEFINE_CLASS(cue);
+
+static const AVFilterPad cue_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+static const AVFilterPad cue_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_cue = {
+    .name        = "cue",
+    .description = NULL_IF_CONFIG_SMALL("Delay filtering to match a cue."),
+    .priv_size   = sizeof(CueContext),
+    .priv_class  = &cue_class,
+    .init        = init,
+    .uninit      = uninit,
+    .inputs      = cue_inputs,
+    .outputs     = cue_outputs,
+    .activate    = activate,
+};
+#endif /* CONFIG_CUE_FILTER */
+
+#if CONFIG_ACUE_FILTER
+#define acue_options options
+AVFILTER_DEFINE_CLASS(acue);
+
+static const AVFilterPad acue_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_AUDIO,
+    },
+    { NULL }
+};
+
+static const AVFilterPad acue_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_AUDIO,
+    },
+    { NULL }
+};
+
+AVFilter ff_af_acue = {
+    .name        = "acue",
+    .description = NULL_IF_CONFIG_SMALL("Delay filtering to match a cue."),
+    .priv_size   = sizeof(CueContext),
+    .priv_class  = &acue_class,
+    .init        = init,
+    .uninit      = uninit,
+    .inputs      = acue_inputs,
+    .outputs     = acue_outputs,
+    .activate    = activate,
+};
+#endif /* CONFIG_ACUE_FILTER */

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  27
+#define LIBAVFILTER_VERSION_MINOR  28
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \