lavfi: add select filter

Signed-off-by: Anton Khirnov <anton@khirnov.net>

Changelog

@@ -46,6 +46,7 @@ easier to use. The changes are:
 - showinfo filter
 - split filter
 - libcdio-paranoia input device for audio CD grabbing
+- select filter
 
 
 version 0.7:

doc/filters.texi

@@ -1064,6 +1064,122 @@ scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
 scale='min(500\, iw*3/2):-1'
 @end example
 
+@section select
+Select frames to pass in output.
+
+It accepts in input an expression, which is evaluated for each input
+frame. If the expression is evaluated to a non-zero value, the frame
+is selected and passed to the output, otherwise it is discarded.
+
+The expression can contain the following constants:
+
+@table @option
+@item PI
+Greek PI
+
+@item PHI
+golden ratio
+
+@item E
+Euler number
+
+@item n
+the sequential number of the filtered frame, starting from 0
+
+@item selected_n
+the sequential number of the selected frame, starting from 0
+
+@item prev_selected_n
+the sequential number of the last selected frame, NAN if undefined
+
+@item TB
+timebase of the input timestamps
+
+@item pts
+the PTS (Presentation TimeStamp) of the filtered video frame,
+expressed in @var{TB} units, NAN if undefined
+
+@item t
+the PTS (Presentation TimeStamp) of the filtered video frame,
+expressed in seconds, NAN if undefined
+
+@item prev_pts
+the PTS of the previously filtered video frame, NAN if undefined
+
+@item prev_selected_pts
+the PTS of the last previously filtered video frame, NAN if undefined
+
+@item prev_selected_t
+the PTS of the last previously selected video frame, NAN if undefined
+
+@item start_pts
+the PTS of the first video frame in the video, NAN if undefined
+
+@item start_t
+the time of the first video frame in the video, NAN if undefined
+
+@item pict_type
+the type of the filtered frame, can assume one of the following
+values:
+@table @option
+@item I
+@item P
+@item B
+@item S
+@item SI
+@item SP
+@item BI
+@end table
+
+@item interlace_type
+the frame interlace type, can assume one of the following values:
+@table @option
+@item PROGRESSIVE
+the frame is progressive (not interlaced)
+@item TOPFIRST
+the frame is top-field-first
+@item BOTTOMFIRST
+the frame is bottom-field-first
+@end table
+
+@item key
+1 if the filtered frame is a key-frame, 0 otherwise
+
+@item pos
+the position in the file of the filtered frame, -1 if the information
+is not available (e.g. for synthetic video)
+@end table
+
+The default value of the select expression is "1".
+
+Some examples follow:
+
+@example
+# select all frames in input
+select
+
+# the above is the same as:
+select=1
+
+# skip all frames:
+select=0
+
+# select only I-frames
+select='eq(pict_type\,I)'
+
+# select one frame every 100
+select='not(mod(n\,100))'
+
+# select only frames contained in the 10-20 time interval
+select='gte(t\,10)*lte(t\,20)'
+
+# select only I frames contained in the 10-20 time interval
+select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
+
+# select frames with a minimum distance of 10 seconds
+select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
+@end example
+
 @anchor{setdar}
 @section setdar
 

libavfilter/Makefile

@@ -40,6 +40,7 @@ OBJS-$(CONFIG_OVERLAY_FILTER)                += vf_overlay.o
 OBJS-$(CONFIG_PAD_FILTER)                    += vf_pad.o
 OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
 OBJS-$(CONFIG_SCALE_FILTER)                  += vf_scale.o
+OBJS-$(CONFIG_SELECT_FILTER)                 += vf_select.o
 OBJS-$(CONFIG_SETDAR_FILTER)                 += vf_aspect.o
 OBJS-$(CONFIG_SETPTS_FILTER)                 += vf_setpts.o
 OBJS-$(CONFIG_SETSAR_FILTER)                 += vf_aspect.o

libavfilter/allfilters.c

@@ -61,6 +61,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (PAD,         pad,         vf);
     REGISTER_FILTER (PIXDESCTEST, pixdesctest, vf);
     REGISTER_FILTER (SCALE,       scale,       vf);
+    REGISTER_FILTER (SELECT,      select,      vf);
     REGISTER_FILTER (SETDAR,      setdar,      vf);
     REGISTER_FILTER (SETPTS,      setpts,      vf);
     REGISTER_FILTER (SETSAR,      setsar,      vf);

libavfilter/avfilter.h

@@ -29,7 +29,7 @@
 #include "libavutil/rational.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR  6
+#define LIBAVFILTER_VERSION_MINOR  7
 #define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_select.c

@@ -0,0 +1,353 @@
+/*
+ * Copyright (c) 2011 Stefano Sabatini
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * filter for selecting which frame passes in the filterchain
+ */
+
+#include "libavutil/eval.h"
+#include "libavutil/fifo.h"
+#include "libavutil/mathematics.h"
+#include "avfilter.h"
+
+static const char *var_names[] = {
+    "E",                 ///< Euler number
+    "PHI",               ///< golden ratio
+    "PI",                ///< greek pi
+
+    "TB",                ///< timebase
+
+    "pts",               ///< original pts in the file of the frame
+    "start_pts",         ///< first PTS in the stream, expressed in TB units
+    "prev_pts",          ///< previous frame PTS
+    "prev_selected_pts", ///< previous selected frame PTS
+
+    "t",                 ///< first PTS in seconds
+    "start_t",           ///< first PTS in the stream, expressed in seconds
+    "prev_t",            ///< previous frame time
+    "prev_selected_t",   ///< previously selected time
+
+    "pict_type",         ///< the type of picture in the movie
+    "I",
+    "P",
+    "B",
+    "S",
+    "SI",
+    "SP",
+    "BI",
+
+    "interlace_type",    ///< the frame interlace type
+    "PROGRESSIVE",
+    "TOPFIRST",
+    "BOTTOMFIRST",
+
+    "n",                 ///< frame number (starting from zero)
+    "selected_n",        ///< selected frame number (starting from zero)
+    "prev_selected_n",   ///< number of the last selected frame
+
+    "key",               ///< tell if the frame is a key frame
+    "pos",               ///< original position in the file of the frame
+
+    NULL
+};
+
+enum var_name {
+    VAR_E,
+    VAR_PHI,
+    VAR_PI,
+
+    VAR_TB,
+
+    VAR_PTS,
+    VAR_START_PTS,
+    VAR_PREV_PTS,
+    VAR_PREV_SELECTED_PTS,
+
+    VAR_T,
+    VAR_START_T,
+    VAR_PREV_T,
+    VAR_PREV_SELECTED_T,
+
+    VAR_PICT_TYPE,
+    VAR_PICT_TYPE_I,
+    VAR_PICT_TYPE_P,
+    VAR_PICT_TYPE_B,
+    VAR_PICT_TYPE_S,
+    VAR_PICT_TYPE_SI,
+    VAR_PICT_TYPE_SP,
+    VAR_PICT_TYPE_BI,
+
+    VAR_INTERLACE_TYPE,
+    VAR_INTERLACE_TYPE_P,
+    VAR_INTERLACE_TYPE_T,
+    VAR_INTERLACE_TYPE_B,
+
+    VAR_N,
+    VAR_SELECTED_N,
+    VAR_PREV_SELECTED_N,
+
+    VAR_KEY,
+    VAR_POS,
+
+    VAR_VARS_NB
+};
+
+#define FIFO_SIZE 8
+
+typedef struct {
+    AVExpr *expr;
+    double var_values[VAR_VARS_NB];
+    double select;
+    int cache_frames;
+    AVFifoBuffer *pending_frames; ///< FIFO buffer of video frames
+} SelectContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    SelectContext *select = ctx->priv;
+    int ret;
+
+    if ((ret = av_expr_parse(&select->expr, args ? args : "1",
+                             var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Error while parsing expression '%s'\n", args);
+        return ret;
+    }
+
+    select->pending_frames = av_fifo_alloc(FIFO_SIZE*sizeof(AVFilterBufferRef*));
+    if (!select->pending_frames) {
+        av_log(ctx, AV_LOG_ERROR, "Failed to allocate pending frames buffer.\n");
+        return AVERROR(ENOMEM);
+    }
+    return 0;
+}
+
+#define INTERLACE_TYPE_P 0
+#define INTERLACE_TYPE_T 1
+#define INTERLACE_TYPE_B 2
+
+static int config_input(AVFilterLink *inlink)
+{
+    SelectContext *select = inlink->dst->priv;
+
+    select->var_values[VAR_E]   = M_E;
+    select->var_values[VAR_PHI] = M_PHI;
+    select->var_values[VAR_PI]  = M_PI;
+
+    select->var_values[VAR_N]          = 0.0;
+    select->var_values[VAR_SELECTED_N] = 0.0;
+
+    select->var_values[VAR_TB] = av_q2d(inlink->time_base);
+
+    select->var_values[VAR_PREV_PTS]          = NAN;
+    select->var_values[VAR_PREV_SELECTED_PTS] = NAN;
+    select->var_values[VAR_PREV_SELECTED_T]   = NAN;
+    select->var_values[VAR_START_PTS]         = NAN;
+    select->var_values[VAR_START_T]           = NAN;
+
+    select->var_values[VAR_PICT_TYPE_I]  = AV_PICTURE_TYPE_I;
+    select->var_values[VAR_PICT_TYPE_P]  = AV_PICTURE_TYPE_P;
+    select->var_values[VAR_PICT_TYPE_B]  = AV_PICTURE_TYPE_B;
+    select->var_values[VAR_PICT_TYPE_SI] = AV_PICTURE_TYPE_SI;
+    select->var_values[VAR_PICT_TYPE_SP] = AV_PICTURE_TYPE_SP;
+
+    select->var_values[VAR_INTERLACE_TYPE_P] = INTERLACE_TYPE_P;
+    select->var_values[VAR_INTERLACE_TYPE_T] = INTERLACE_TYPE_T;
+    select->var_values[VAR_INTERLACE_TYPE_B] = INTERLACE_TYPE_B;;
+
+    return 0;
+}
+
+#define D2TS(d)  (isnan(d) ? AV_NOPTS_VALUE : (int64_t)(d))
+#define TS2D(ts) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts))
+
+static int select_frame(AVFilterContext *ctx, AVFilterBufferRef *picref)
+{
+    SelectContext *select = ctx->priv;
+    AVFilterLink *inlink = ctx->inputs[0];
+    double res;
+
+    if (isnan(select->var_values[VAR_START_PTS]))
+        select->var_values[VAR_START_PTS] = TS2D(picref->pts);
+    if (isnan(select->var_values[VAR_START_T]))
+        select->var_values[VAR_START_T] = TS2D(picref->pts) * av_q2d(inlink->time_base);
+
+    select->var_values[VAR_PTS] = TS2D(picref->pts);
+    select->var_values[VAR_T  ] = TS2D(picref->pts) * av_q2d(inlink->time_base);
+    select->var_values[VAR_POS] = picref->pos == -1 ? NAN : picref->pos;
+    select->var_values[VAR_PREV_PTS] = TS2D(picref ->pts);
+
+    select->var_values[VAR_INTERLACE_TYPE] =
+        !picref->video->interlaced     ? INTERLACE_TYPE_P :
+        picref->video->top_field_first ? INTERLACE_TYPE_T : INTERLACE_TYPE_B;
+    select->var_values[VAR_PICT_TYPE] = picref->video->pict_type;
+
+    res = av_expr_eval(select->expr, select->var_values, NULL);
+    av_log(inlink->dst, AV_LOG_DEBUG,
+           "n:%d pts:%d t:%f pos:%d interlace_type:%c key:%d pict_type:%c "
+           "-> select:%f\n",
+           (int)select->var_values[VAR_N],
+           (int)select->var_values[VAR_PTS],
+           select->var_values[VAR_T],
+           (int)select->var_values[VAR_POS],
+           select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_P ? 'P' :
+           select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_T ? 'T' :
+           select->var_values[VAR_INTERLACE_TYPE] == INTERLACE_TYPE_B ? 'B' : '?',
+           (int)select->var_values[VAR_KEY],
+           av_get_picture_type_char(select->var_values[VAR_PICT_TYPE]),
+           res);
+
+    select->var_values[VAR_N] += 1.0;
+
+    if (res) {
+        select->var_values[VAR_PREV_SELECTED_N]   = select->var_values[VAR_N];
+        select->var_values[VAR_PREV_SELECTED_PTS] = select->var_values[VAR_PTS];
+        select->var_values[VAR_PREV_SELECTED_T]   = select->var_values[VAR_T];
+        select->var_values[VAR_SELECTED_N] += 1.0;
+    }
+    return res;
+}
+
+static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
+{
+    SelectContext *select = inlink->dst->priv;
+
+    select->select = select_frame(inlink->dst, picref);
+    if (select->select) {
+        /* frame was requested through poll_frame */
+        if (select->cache_frames) {
+            if (!av_fifo_space(select->pending_frames))
+                av_log(inlink->dst, AV_LOG_ERROR,
+                       "Buffering limit reached, cannot cache more frames\n");
+            else
+                av_fifo_generic_write(select->pending_frames, &picref,
+                                      sizeof(picref), NULL);
+            return;
+        }
+        avfilter_start_frame(inlink->dst->outputs[0], avfilter_ref_buffer(picref, ~0));
+    }
+}
+
+static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
+{
+    SelectContext *select = inlink->dst->priv;
+
+    if (select->select && !select->cache_frames)
+        avfilter_draw_slice(inlink->dst->outputs[0], y, h, slice_dir);
+}
+
+static void end_frame(AVFilterLink *inlink)
+{
+    SelectContext *select = inlink->dst->priv;
+    AVFilterBufferRef *picref = inlink->cur_buf;
+
+    if (select->select) {
+        if (select->cache_frames)
+            return;
+        avfilter_end_frame(inlink->dst->outputs[0]);
+    }
+    avfilter_unref_buffer(picref);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    SelectContext *select = ctx->priv;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    select->select = 0;
+
+    if (av_fifo_size(select->pending_frames)) {
+        AVFilterBufferRef *picref;
+        av_fifo_generic_read(select->pending_frames, &picref, sizeof(picref), NULL);
+        avfilter_start_frame(outlink, avfilter_ref_buffer(picref, ~0));
+        avfilter_draw_slice(outlink, 0, outlink->h, 1);
+        avfilter_end_frame(outlink);
+        avfilter_unref_buffer(picref);
+        return 0;
+    }
+
+    while (!select->select) {
+        int ret = avfilter_request_frame(inlink);
+        if (ret < 0)
+            return ret;
+    }
+
+    return 0;
+}
+
+static int poll_frame(AVFilterLink *outlink)
+{
+    SelectContext *select = outlink->src->priv;
+    AVFilterLink *inlink = outlink->src->inputs[0];
+    int count, ret;
+
+    if (!av_fifo_size(select->pending_frames)) {
+        if ((count = avfilter_poll_frame(inlink)) <= 0)
+            return count;
+        /* request frame from input, and apply select condition to it */
+        select->cache_frames = 1;
+        while (count-- && av_fifo_space(select->pending_frames)) {
+            ret = avfilter_request_frame(inlink);
+            if (ret < 0)
+                break;
+        }
+        select->cache_frames = 0;
+    }
+
+    return av_fifo_size(select->pending_frames)/sizeof(AVFilterBufferRef *);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    SelectContext *select = ctx->priv;
+    AVFilterBufferRef *picref;
+
+    av_expr_free(select->expr);
+    select->expr = NULL;
+
+    while (select->pending_frames &&
+           av_fifo_generic_read(select->pending_frames, &picref, sizeof(picref), NULL) == sizeof(picref))
+        avfilter_unref_buffer(picref);
+    av_fifo_free(select->pending_frames);
+    select->pending_frames = NULL;
+}
+
+AVFilter avfilter_vf_select = {
+    .name      = "select",
+    .description = NULL_IF_CONFIG_SMALL("Select frames to pass in output."),
+    .init      = init,
+    .uninit    = uninit,
+
+    .priv_size = sizeof(SelectContext),
+
+    .inputs    = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO,
+                                    .get_video_buffer = avfilter_null_get_video_buffer,
+                                    .config_props     = config_input,
+                                    .start_frame      = start_frame,
+                                    .draw_slice       = draw_slice,
+                                    .end_frame        = end_frame },
+                                  { .name = NULL }},
+    .outputs   = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = AVMEDIA_TYPE_VIDEO,
+                                    .poll_frame       = poll_frame,
+                                    .request_frame    = request_frame, },
+                                  { .name = NULL}},
+};