lavfi: add a closed field to AVFilerLink.

It will help forward errors and maintain consistency.

libavfilter/audio.c

@@ -172,6 +172,11 @@ int ff_filter_samples_framed(AVFilterLink *link, AVFilterBufferRef *samplesref)
 
     FF_TPRINTF_START(NULL, filter_samples); ff_tlog_link(NULL, link, 1);
 
+    if (link->closed) {
+        avfilter_unref_buffer(samplesref);
+        return AVERROR_EOF;
+    }
+
     if (!(filter_samples = dst->filter_samples))
         filter_samples = default_filter_samples;
 

libavfilter/avfilter.c

@@ -159,6 +159,11 @@ void avfilter_link_free(AVFilterLink **link)
     av_freep(link);
 }
 
+void avfilter_link_set_closed(AVFilterLink *link, int closed)
+{
+    link->closed = closed;
+}
+
 int avfilter_insert_filter(AVFilterLink *link, AVFilterContext *filt,
                            unsigned filt_srcpad_idx, unsigned filt_dstpad_idx)
 {
@@ -325,6 +330,8 @@ int ff_request_frame(AVFilterLink *link)
     int ret = -1;
     FF_TPRINTF_START(NULL, request_frame); ff_tlog_link(NULL, link, 1);
 
+    if (link->closed)
+        return AVERROR_EOF;
     if (link->srcpad->request_frame)
         ret = link->srcpad->request_frame(link);
     else if (link->src->inputs[0])
@@ -335,6 +342,8 @@ int ff_request_frame(AVFilterLink *link)
         ff_filter_samples_framed(link, pbuf);
         return 0;
     }
+    if (ret == AVERROR_EOF)
+        link->closed = 1;
     return ret;
 }
 

libavfilter/avfilter.h

@@ -697,6 +697,18 @@ struct AVFilterLink {
      * by the filters.
      */
     AVFilterBufferRef *cur_buf_copy;
+
+    /**
+     * True if the link is closed.
+     * If set, all attemps of start_frame, filter_samples or request_frame
+     * will fail with AVERROR_EOF, and if necessary the reference will be
+     * destroyed.
+     * If request_frame returns AVERROR_EOF, this flag is set on the
+     * corresponding link.
+     * It can be set also be set by either the source or the destination
+     * filter.
+     */
+    int closed;
 };
 
 /**
@@ -716,6 +728,11 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
  */
 void avfilter_link_free(AVFilterLink **link);
 
+/**
+ * Set the closed field of a link.
+ */
+void avfilter_link_set_closed(AVFilterLink *link, int closed);
+
 /**
  * Negotiate the media format, dimensions, etc of all inputs to a filter.
  *

libavfilter/video.c

@@ -248,6 +248,11 @@ int ff_start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
 
     FF_TPRINTF_START(NULL, start_frame); ff_tlog_link(NULL, link, 0); ff_tlog(NULL, " "); ff_tlog_ref(NULL, picref, 1);
 
+    if (link->closed) {
+        avfilter_unref_buffer(picref);
+        return AVERROR_EOF;
+    }
+
     if (!(start_frame = dst->start_frame))
         start_frame = default_start_frame;