avfilter/vf_libplacebo: refactor status handling

Instead of having a single s->status field to track the most recently
EOF'd stream, track the number of active streams directly and only query
the most recent status at the end.

The reason this worked before is because we implicitly relied on the
assumption that `ok` would always be true until all streams are EOF, but
because it's possible to have gaps in the timeline when mixing multiple
streams, this is not always the case in principle.

In practice, this fixes a bug where the filter would early-exit (EOF)
too soon, when any input reached EOF and there is a gap in the timeline.

1 files changed, 15 insertions, 9 deletions

diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
index 70aa746e80..e3761bead8 100644
--- a/libavfilter/vf_libplacebo.c
+++ b/libavfilter/vf_libplacebo.c
@@ -170,8 +170,7 @@ typedef struct LibplaceboContext {
     /* input state */
     LibplaceboInput *inputs;
     int nb_inputs;
-    int64_t status_pts; ///< tracks status of most recently used input
-    int status;
+    int nb_active;
 
     /* settings */
     char *out_format_string;
@@ -768,6 +767,7 @@ static int init_vulkan(AVFilterContext *avctx, const AVVulkanDeviceContext *hwct
         return AVERROR(ENOMEM);
     for (int i = 0; i < s->nb_inputs; i++)
         RET(input_init(avctx, &s->inputs[i], i));
+    s->nb_active = s->nb_inputs;
     s->linear_rr = pl_renderer_create(s->log, s->gpu);
 
     /* fall through */
@@ -1166,11 +1166,7 @@ static int handle_input(AVFilterContext *ctx, LibplaceboInput *input)
         pl_queue_push(input->queue, NULL); /* Signal EOF to pl_queue */
         input->status = status;
         input->status_pts = pts;
-        if (!s->status || pts >= s->status_pts) {
-            /* Also propagate to output unless overwritten by later status change */
-            s->status = status;
-            s->status_pts = pts;
-        }
+        s->nb_active--;
     }
 
     return 0;
@@ -1254,8 +1250,18 @@ static int libplacebo_activate(AVFilterContext *ctx)
             for (int i = 0; i < s->nb_inputs; i++)
                 drain_input_pts(&s->inputs[i], out_pts);
             return output_frame(ctx, out_pts);
-        } else if (s->status) {
-            ff_outlink_set_status(outlink, s->status, s->status_pts);
+        } else if (s->nb_active == 0) {
+            /* Forward most recent status */
+            int status = s->inputs[0].status;
+            int64_t status_pts = s->inputs[0].status_pts;
+            for (int i = 1; i < s->nb_inputs; i++) {
+                const LibplaceboInput *in = &s->inputs[i];
+                if (in->status_pts > status_pts) {
+                    status = s->inputs[i].status;
+                    status_pts = s->inputs[i].status_pts;
+                }
+            }
+            ff_outlink_set_status(outlink, status, status_pts);
             return 0;
         }