Revert "libobs: Avoid recycling async frames"

This reverts commit 96c1a7652305784e4bf531933bc82535adcaf320.

Closes obsproject/obs-studio#5474

libobs/obs-source.c

@@ -2852,6 +2852,23 @@ static inline void free_async_cache(struct obs_source *source)
 	source->prev_async_frame = NULL;
 }
 
+#define MAX_UNUSED_FRAME_DURATION 5
+
+/* frees frame allocations if they haven't been used for a specific period
+ * of time */
+static void clean_cache(obs_source_t *source)
+{
+	for (size_t i = source->async_cache.num; i > 0; i--) {
+		struct async_frame *af = &source->async_cache.array[i - 1];
+		if (!af->used) {
+			if (++af->unused_count == MAX_UNUSED_FRAME_DURATION) {
+				obs_source_frame_destroy(af->frame);
+				da_erase(source->async_cache, i - 1);
+			}
+		}
+	}
+}
+
 #define MAX_ASYNC_FRAMES 30
 //if return value is not null then do (os_atomic_dec_long(&output->refs) == 0) && obs_source_frame_destroy(output)
 static inline struct obs_source_frame *
@@ -2861,29 +2878,19 @@ cache_video(struct obs_source *source, const struct obs_source_frame *frame)
 
 	pthread_mutex_lock(&source->async_mutex);
 
+	if (source->async_frames.num >= MAX_ASYNC_FRAMES) {
+		free_async_cache(source);
+		source->last_frame_ts = 0;
+		pthread_mutex_unlock(&source->async_mutex);
+		return NULL;
+	}
+
 	if (async_texture_changed(source, frame)) {
 		free_async_cache(source);
 		source->async_cache_width = frame->width;
 		source->async_cache_height = frame->height;
 	}
 
-	if (source->async_frames.num >= MAX_ASYNC_FRAMES) {
-		bool available = false;
-		for (size_t i = 0; i < source->async_cache.num; i++) {
-			struct async_frame *af = &source->async_cache.array[i];
-			if (!af->used) {
-				available = true;
-				break;
-			}
-		}
-
-		if (!available) {
-			source->last_frame_ts = 0;
-			pthread_mutex_unlock(&source->async_mutex);
-			return NULL;
-		}
-	}
-
 	const enum video_format format = frame->format;
 	source->async_cache_format = format;
 	source->async_cache_full_range = frame->full_range;
@@ -2899,6 +2906,8 @@ cache_video(struct obs_source *source, const struct obs_source_frame *frame)
 		}
 	}
 
+	clean_cache(source);
+
 	if (!new_frame) {
 		struct async_frame new_af;