From 6877ca4d6276f5a83cceaa121b3810c3ed41f409 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Tue, 13 May 2025 09:54:07 +0300
Subject: [PATCH] pipeline: Store the actual latency even if no static latency
 was configured

Previously the latency was only stored if a static latency was configured on the
pipeline, which caused gst_pipeline_get_configured_latency() to always return
GST_CLOCK_TIME_NONE in that case.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4429

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8972>
---
 subprojects/gstreamer/gst/gstpipeline.c | 63 +++++++++++++++----------
 1 file changed, 38 insertions(+), 25 deletions(-)

diff --git a/subprojects/gstreamer/gst/gstpipeline.c b/subprojects/gstreamer/gst/gstpipeline.c
index c1418336df..69248df49d 100644
--- a/subprojects/gstreamer/gst/gstpipeline.c
+++ b/subprojects/gstreamer/gst/gstpipeline.c
@@ -693,9 +693,6 @@ gst_pipeline_do_latency (GstBin * bin)
   latency = pipeline->priv->latency;
   GST_OBJECT_UNLOCK (pipeline);
 
-  if (latency == GST_CLOCK_TIME_NONE)
-    return GST_BIN_CLASS (parent_class)->do_latency (bin);
-
   GST_DEBUG_OBJECT (pipeline, "querying latency");
 
   query = gst_query_new_latency ();
@@ -704,10 +701,6 @@ gst_pipeline_do_latency (GstBin * bin)
 
     gst_query_parse_latency (query, &live, &min_latency, &max_latency);
 
-    GST_OBJECT_LOCK (pipeline);
-    pipeline->priv->min_latency = min_latency;
-    GST_OBJECT_UNLOCK (pipeline);
-
     GST_DEBUG_OBJECT (pipeline,
         "got min latency %" GST_TIME_FORMAT ", max latency %"
         GST_TIME_FORMAT ", live %d", GST_TIME_ARGS (min_latency),
@@ -722,13 +715,27 @@ gst_pipeline_do_latency (GstBin * bin)
               GST_TIME_ARGS (max_latency), GST_TIME_ARGS (min_latency)));
     }
 
-    if (latency < min_latency) {
-      /* This is a problematic situation as we will most likely drop lots of
-       * data if we configure a too low latency */
-      GST_ELEMENT_WARNING (pipeline, CORE, CLOCK, (NULL),
-          ("Configured latency is lower than detected minimum latency: configured %"
-              GST_TIME_FORMAT " < min %" GST_TIME_FORMAT,
-              GST_TIME_ARGS (latency), GST_TIME_ARGS (min_latency)));
+    /* If no static latency was configured then select the minimum latency */
+    if (latency == GST_CLOCK_TIME_NONE) {
+      latency = min_latency;
+    } else {
+      if (latency < min_latency) {
+        /* This is a problematic situation as we will most likely drop lots of
+         * data if we configure a too low latency */
+        GST_ELEMENT_WARNING (pipeline, CORE, CLOCK, (NULL),
+            ("Configured latency is lower than detected minimum latency: configured %"
+                GST_TIME_FORMAT " < min %" GST_TIME_FORMAT,
+                GST_TIME_ARGS (latency), GST_TIME_ARGS (min_latency)));
+      }
+      if (max_latency < latency) {
+        /* and this is basically the same check as further above. There is not
+         * enough buffering and the pipeline might not work correctly. */
+        GST_ELEMENT_WARNING (pipeline, CORE, CLOCK, (NULL),
+            ("Impossible to configure latency: max %" GST_TIME_FORMAT
+                " < configured %" GST_TIME_FORMAT
+                ". Add queues or other buffering elements.",
+                GST_TIME_ARGS (max_latency), GST_TIME_ARGS (latency)));
+      }
     }
   } else {
     /* this is not a real problem, we just don't configure any latency. */
@@ -737,17 +744,23 @@ gst_pipeline_do_latency (GstBin * bin)
   gst_query_unref (query);
 
 
-  /* configure latency on elements */
-  res =
-      gst_element_send_event (GST_ELEMENT_CAST (pipeline),
-      gst_event_new_latency (latency));
-  if (res) {
-    GST_INFO_OBJECT (pipeline, "configured latency of %" GST_TIME_FORMAT,
-        GST_TIME_ARGS (latency));
-  } else {
-    GST_WARNING_OBJECT (pipeline,
-        "did not really configure latency of %" GST_TIME_FORMAT,
-        GST_TIME_ARGS (latency));
+  if (latency != GST_CLOCK_TIME_NONE) {
+    GST_OBJECT_LOCK (pipeline);
+    pipeline->priv->min_latency = latency;
+    GST_OBJECT_UNLOCK (pipeline);
+
+    /* configure latency on elements */
+    res =
+        gst_element_send_event (GST_ELEMENT_CAST (pipeline),
+        gst_event_new_latency (latency));
+    if (res) {
+      GST_INFO_OBJECT (pipeline, "configured latency of %" GST_TIME_FORMAT,
+          GST_TIME_ARGS (latency));
+    } else {
+      GST_WARNING_OBJECT (pipeline,
+          "did not really configure latency of %" GST_TIME_FORMAT,
+          GST_TIME_ARGS (latency));
+    }
   }
 
   return res;