From d625010acde36fcf3ac4931ee25184aec06643c3 Mon Sep 17 00:00:00 2001
From: Niklas Haas <git@haasn.dev>
Date: Thu, 15 Jun 2023 16:07:51 +0200
Subject: [PATCH] lavfi/vf_libplacebo: generalize frame update to multiple
 inputs

In the event that some frame mixes are OK while others are not, the
priority goes:

1. Errors in updating any frame -> return error
2. Any input incomplete -> request frames and return
3. Any inputs OK -> ignore EOF streams and render remaining inputs
4. No inputs OK -> set output to most recent status

This logic ensures that we can continue rendering the remaining streams,
no matter which streams reach their end of life, until we have no
streams left at which point we forward the last EOF.
---
 libavfilter/vf_libplacebo.c | 52 ++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
index 753d6f3cc7..6399aae0c6 100644
--- a/libavfilter/vf_libplacebo.c
+++ b/libavfilter/vf_libplacebo.c
@@ -980,9 +980,8 @@ static void drain_input_pts(LibplaceboInput *in, int64_t until)
 
 static int libplacebo_activate(AVFilterContext *ctx)
 {
-    int ret, retry = 0;
+    int ret, ok = 0, retry = 0;
     LibplaceboContext *s = ctx->priv;
-    LibplaceboInput *in = &s->inputs[0];
     AVFilterLink *outlink = ctx->outputs[0];
     int64_t pts, out_pts;
 
@@ -1014,26 +1013,43 @@ static int libplacebo_activate(AVFilterContext *ctx)
                 return 0;
         }
 
-        if (s->status && out_pts >= s->status_pts) {
-            ff_outlink_set_status(outlink, s->status, s->status_pts);
-            return 0;
+        /* Update all input queues to the chosen out_pts */
+        for (int i = 0; i < s->nb_inputs; i++) {
+            LibplaceboInput *in = &s->inputs[i];
+            if (in->status && out_pts >= in->status_pts) {
+                in->qstatus = PL_QUEUE_EOF;
+                continue;
+            }
+
+            in->qstatus = pl_queue_update(in->queue, &in->mix, pl_queue_params(
+                .pts            = out_pts * av_q2d(outlink->time_base),
+                .radius         = pl_frame_mix_radius(&s->params),
+                .vsync_duration = av_q2d(av_inv_q(outlink->frame_rate)),
+            ));
+
+            switch (in->qstatus) {
+            case PL_QUEUE_MORE:
+                ff_inlink_request_frame(in->link);
+                retry = true;
+                break;
+            case PL_QUEUE_OK:
+                ok = true;
+                break;
+            case PL_QUEUE_ERR:
+                return AVERROR_EXTERNAL;
+            }
         }
 
-        in->qstatus = pl_queue_update(in->queue, &in->mix, pl_queue_params(
-            .pts            = out_pts * av_q2d(outlink->time_base),
-            .radius         = pl_frame_mix_radius(&s->params),
-            .vsync_duration = av_q2d(av_inv_q(outlink->frame_rate)),
-        ));
-
-        switch (in->qstatus) {
-        case PL_QUEUE_MORE:
-            ff_inlink_request_frame(in->link);
+        if (retry) {
             return 0;
-        case PL_QUEUE_OK:
-            drain_input_pts(in, out_pts);
+        } else if (ok) {
+            /* Got any valid frame mixes, drain PTS queue and render output */
+            for (int i = 0; i < s->nb_inputs; i++)
+                drain_input_pts(&s->inputs[i], out_pts);
             return output_frame(ctx, out_pts);
-        case PL_QUEUE_ERR:
-            return AVERROR_EXTERNAL;
+        } else if (s->status) {
+            ff_outlink_set_status(outlink, s->status, s->status_pts);
+            return 0;
         }
 
         return AVERROR_BUG;