From e31e5b2c6f002a6dff9cc483b65822eada7e3384 Mon Sep 17 00:00:00 2001
From: Mathieu Duponchelle <mathieu@centricular.com>
Date: Wed, 26 Feb 2025 18:22:34 +0100
Subject: [PATCH] transcriberbin: fix caption-source selection ..

with recent enough cccombiner.

Originally, dropping transcriptions was enough to support
caption-source=inband, as cccombiner did not implement output
scheduling.

However now that it does, even if no captions arrive on the caption pad
the combiner will still output padding.

Recent-enough combiners however expose an `input-meta-processing`
property which lets us achieve the desired behavior, we thus make use of
it when available.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/2115>
---
 video/closedcaption/src/transcriberbin/imp.rs | 20 ++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/video/closedcaption/src/transcriberbin/imp.rs b/video/closedcaption/src/transcriberbin/imp.rs
index d89a09f3..2ce4f8a9 100644
--- a/video/closedcaption/src/transcriberbin/imp.rs
+++ b/video/closedcaption/src/transcriberbin/imp.rs
@@ -2620,7 +2620,25 @@ impl ObjectImpl for TranscriberBin {
 
                 let s = self.state.lock().unwrap();
                 if let Some(state) = s.as_ref() {
-                    if settings.caption_source == CaptionSource::Inband {
+                    if state.cccombiner.has_property("input-meta-processing") {
+                        match settings.caption_source {
+                            CaptionSource::Inband => {
+                                state
+                                    .cccombiner
+                                    .set_property_from_str("input-meta-processing", "force");
+                            }
+                            CaptionSource::Both => {
+                                state
+                                    .cccombiner
+                                    .set_property_from_str("input-meta-processing", "append");
+                            }
+                            CaptionSource::Transcription => {
+                                state
+                                    .cccombiner
+                                    .set_property_from_str("input-meta-processing", "drop");
+                            }
+                        }
+                    } else if settings.caption_source == CaptionSource::Inband {
                         gst::debug!(
                             CAT,
                             imp = self,