fftools/ffmpeg_opt: merge init_complex_filters() and check_filter_outputs()

The first of these binds inputs of complex filtergraphs to demuxer
streams (with a misleading comment claiming it *creates* complex
filtergraphs).

The second ensures that all filtergraph outputs are connected to an
encoder.

Merge them into a single function, which simplifies the ffmpeg_filter
API, is shorter, and will also be useful in following commits.

Also, rename misleadingly-named init_input_filter() to
fg_complex_bind_input().

fftools/ffmpeg.h

@@ -671,12 +671,11 @@ int find_codec(void *logctx, const char *name,
                enum AVMediaType type, int encoder, const AVCodec **codec);
 int parse_and_set_vsync(const char *arg, int *vsync_var, int file_idx, int st_idx, int is_global);
 
-int check_filter_outputs(void);
 int filtergraph_is_simple(const FilterGraph *fg);
 int init_simple_filtergraph(InputStream *ist, OutputStream *ost,
                             char *graph_desc,
                             Scheduler *sch, unsigned sch_idx_enc);
-int init_complex_filtergraph(FilterGraph *fg);
+int fg_finalise_bindings(FilterGraph *fg);
 
 /**
  * Get our axiliary frame data attached to the frame, allocating it

fftools/ffmpeg_filter.c

@@ -1096,7 +1096,7 @@ int init_simple_filtergraph(InputStream *ist, OutputStream *ost,
     return 0;
 }
 
-static int init_input_filter(FilterGraph *fg, InputFilter *ifilter)
+static int fg_complex_bind_input(FilterGraph *fg, InputFilter *ifilter)
 {
     FilterGraphPriv *fgp = fgp_from_fg(fg);
     InputFilterPriv *ifp = ifp_from_ifilter(ifilter);
@@ -1162,14 +1162,29 @@ static int init_input_filter(FilterGraph *fg, InputFilter *ifilter)
     return 0;
 }
 
-int init_complex_filtergraph(FilterGraph *fg)
+int fg_finalise_bindings(FilterGraph *fg)
 {
     // bind filtergraph inputs to input streams
     for (int i = 0; i < fg->nb_inputs; i++) {
-        int ret = init_input_filter(fg, fg->inputs[i]);
+        InputFilterPriv *ifp = ifp_from_ifilter(fg->inputs[i]);
+        int ret;
+
+        if (ifp->bound)
+            continue;
+
+        ret = fg_complex_bind_input(fg, &ifp->ifilter);
         if (ret < 0)
             return ret;
     }
+
+    for (int i = 0; i < fg->nb_outputs; i++) {
+        OutputFilter *output = fg->outputs[i];
+        if (!output->ost) {
+            av_log(filtergraphs[i], AV_LOG_FATAL,
+                   "Filter %s has an unconnected output\n", output->name);
+            return AVERROR(EINVAL);
+        }
+    }
     return 0;
 }
 
@@ -1436,23 +1451,6 @@ static int configure_output_filter(FilterGraph *fg, AVFilterGraph *graph,
     }
 }
 
-int check_filter_outputs(void)
-{
-    for (int i = 0; i < nb_filtergraphs; i++) {
-        int n;
-        for (n = 0; n < filtergraphs[i]->nb_outputs; n++) {
-            OutputFilter *output = filtergraphs[i]->outputs[n];
-            if (!output->ost) {
-                av_log(filtergraphs[i], AV_LOG_FATAL,
-                       "Filter %s has an unconnected output\n", output->name);
-                return AVERROR(EINVAL);
-            }
-        }
-    }
-
-    return 0;
-}
-
 static void sub2video_prepare(InputFilterPriv *ifp)
 {
     ifp->sub2video.last_pts = INT64_MIN;

fftools/ffmpeg_opt.c

@@ -674,18 +674,6 @@ static int opt_streamid(void *optctx, const char *opt, const char *arg)
     return av_dict_set(&o->streamid, idx_str, p, 0);
 }
 
-static int init_complex_filters(void)
-{
-    int i, ret = 0;
-
-    for (i = 0; i < nb_filtergraphs; i++) {
-        ret = init_complex_filtergraph(filtergraphs[i]);
-        if (ret < 0)
-            return ret;
-    }
-    return 0;
-}
-
 static int opt_target(void *optctx, const char *opt, const char *arg)
 {
     OptionsContext *o = optctx;
@@ -1264,13 +1252,6 @@ int ffmpeg_parse_options(int argc, char **argv, Scheduler *sch)
         goto fail;
     }
 
-    /* create the complex filtergraphs */
-    ret = init_complex_filters();
-    if (ret < 0) {
-        errmsg = "initializing complex filters";
-        goto fail;
-    }
-
     /* open output files */
     ret = open_files(&octx.groups[GROUP_OUTFILE], "output", sch, of_open);
     if (ret < 0) {
@@ -1278,16 +1259,21 @@ int ffmpeg_parse_options(int argc, char **argv, Scheduler *sch)
         goto fail;
     }
 
+    // bind unbound filtegraph inputs/outputs and check consistency
+    for (int i = 0; i < nb_filtergraphs; i++) {
+        ret = fg_finalise_bindings(filtergraphs[i]);
+        if (ret < 0) {
+            errmsg = "binding filtergraph inputs/outputs";
+            goto fail;
+        }
+    }
+
     correct_input_start_times();
 
     ret = apply_sync_offsets();
     if (ret < 0)
         goto fail;
 
-    ret = check_filter_outputs();
-    if (ret < 0)
-        goto fail;
-
 fail:
     uninit_parse_context(&octx);
     if (ret < 0 && ret != AVERROR_EXIT) {