avfilter/avfilter: Avoid allocation for AVFilterInternal

To do this, allocate AVFilterInternal jointly with AVFilterContext
and rename it to FFFilterContext in the process (similarly to
AVStream/FFStream).
The AVFilterInternal* will be removed from AVFilterContext
on the next major bump.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/avfilter.c

@@ -159,7 +159,7 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
         src->outputs[srcpad]      || dst->inputs[dstpad])
         return AVERROR(EINVAL);
 
-    if (!src->internal->initialized || !dst->internal->initialized) {
+    if (!fffilterctx(src)->initialized || !fffilterctx(dst)->initialized) {
         av_log(src, AV_LOG_ERROR, "Filters must be initialized before linking.\n");
         return AVERROR(EINVAL);
     }
@@ -668,15 +668,17 @@ static int default_execute(AVFilterContext *ctx, avfilter_action_func *func, voi
 
 AVFilterContext *ff_filter_alloc(const AVFilter *filter, const char *inst_name)
 {
+    FFFilterContext *ctx;
     AVFilterContext *ret;
     int preinited = 0;
 
     if (!filter)
         return NULL;
 
-    ret = av_mallocz(sizeof(AVFilterContext));
-    if (!ret)
+    ctx = av_mallocz(sizeof(*ctx));
+    if (!ctx)
         return NULL;
+    ret = &ctx->p;
 
     ret->av_class = &avfilter_class;
     ret->filter   = filter;
@@ -698,10 +700,7 @@ AVFilterContext *ff_filter_alloc(const AVFilter *filter, const char *inst_name)
         av_opt_set_defaults(ret->priv);
     }
 
-    ret->internal = av_mallocz(sizeof(*ret->internal));
-    if (!ret->internal)
-        goto err;
-    ret->internal->execute = default_execute;
+    ctx->execute = default_execute;
 
     ret->nb_inputs  = filter->nb_inputs;
     if (ret->nb_inputs ) {
@@ -735,7 +734,6 @@ err:
     av_freep(&ret->output_pads);
     ret->nb_outputs = 0;
     av_freep(&ret->priv);
-    av_freep(&ret->internal);
     av_free(ret);
     return NULL;
 }
@@ -807,7 +805,6 @@ void avfilter_free(AVFilterContext *filter)
     av_expr_free(filter->enable);
     filter->enable = NULL;
     av_freep(&filter->var_values);
-    av_freep(&filter->internal);
     av_free(filter);
 }
 
@@ -891,9 +888,10 @@ int ff_filter_process_command(AVFilterContext *ctx, const char *cmd,
 
 int avfilter_init_dict(AVFilterContext *ctx, AVDictionary **options)
 {
+    FFFilterContext *ctxi = fffilterctx(ctx);
     int ret = 0;
 
-    if (ctx->internal->initialized) {
+    if (ctxi->initialized) {
         av_log(ctx, AV_LOG_ERROR, "Filter already initialized\n");
         return AVERROR(EINVAL);
     }
@@ -908,7 +906,7 @@ int avfilter_init_dict(AVFilterContext *ctx, AVDictionary **options)
         ctx->thread_type & ctx->graph->thread_type & AVFILTER_THREAD_SLICE &&
         ctx->graph->internal->thread_execute) {
         ctx->thread_type       = AVFILTER_THREAD_SLICE;
-        ctx->internal->execute = ctx->graph->internal->thread_execute;
+        ctxi->execute    = ctx->graph->internal->thread_execute;
     } else {
         ctx->thread_type = 0;
     }
@@ -924,7 +922,7 @@ int avfilter_init_dict(AVFilterContext *ctx, AVDictionary **options)
             return ret;
     }
 
-    ctx->internal->initialized = 1;
+    ctxi->initialized = 1;
 
     return 0;
 }

libavfilter/graphparser.c

@@ -626,7 +626,7 @@ int avfilter_graph_segment_init(AVFilterGraphSegment *seg, int flags)
 
             if (p->filter_name)
                 return fail_creation_pending(seg, p->filter_name, __func__);
-            if (!p->filter || p->filter->internal->initialized)
+            if (!p->filter || fffilterctx(p->filter)->initialized)
                 continue;
 
             ret = avfilter_init_dict(p->filter, NULL);

libavfilter/internal.h

@@ -133,18 +133,28 @@ struct AVFilterGraphInternal {
     FFFrameQueueGlobal frame_queues;
 };
 
-struct AVFilterInternal {
+typedef struct FFFilterContext {
+    /**
+     * The public AVFilterContext. See avfilter.h for it.
+     */
+    AVFilterContext p;
+
     avfilter_execute_func *execute;
 
     // 1 when avfilter_init_*() was successfully called on this filter
     // 0 otherwise
     int initialized;
-};
+} FFFilterContext;
+
+static inline FFFilterContext *fffilterctx(AVFilterContext *ctx)
+{
+    return (FFFilterContext*)ctx;
+}
 
 static av_always_inline int ff_filter_execute(AVFilterContext *ctx, avfilter_action_func *func,
                                               void *arg, int *ret, int nb_jobs)
 {
-    return ctx->internal->execute(ctx, func, arg, ret, nb_jobs);
+    return fffilterctx(ctx)->execute(ctx, func, arg, ret, nb_jobs);
 }
 
 enum FilterFormatsState {