From d65504aeb88e5b01e4bf34c47ed988899d8449b1 Mon Sep 17 00:00:00 2001
From: "Jan Alexander Steffens (heftig)" <jan.steffens@ltnglobal.com>
Date: Wed, 25 Oct 2023 18:48:50 +0200
Subject: [PATCH] livesync: Keep existing buffer duration in some cases

Resize a repeat buffer only if caps gave us a duration to use, or we
consider its current duration unreasonable.

In particular, for audio streams we should prefer reusing the buffer
size upstream gave us, as we did before 6633cc4046aa1f5a.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1388>
---
 utils/livesync/src/livesync/imp.rs | 55 +++++++++++++++++-------------
 1 file changed, 31 insertions(+), 24 deletions(-)

diff --git a/utils/livesync/src/livesync/imp.rs b/utils/livesync/src/livesync/imp.rs
index ce7a0364..268eb1d7 100644
--- a/utils/livesync/src/livesync/imp.rs
+++ b/utils/livesync/src/livesync/imp.rs
@@ -1302,36 +1302,43 @@ impl LiveSync {
         let buffer = out_buffer.make_mut();
 
         if !duplicate {
-            let duration = state.out_duration.map_or(DEFAULT_DURATION, |dur| {
-                dur.clamp(MINIMUM_DURATION, MAXIMUM_DURATION)
-            });
+            let duration_is_valid =
+                (MINIMUM_DURATION..=MAXIMUM_DURATION).contains(&buffer.duration().unwrap());
 
-            if let Some(audio_info) = &state.out_audio_info {
-                let Some(size) = audio_info
-                    .convert::<Option<gst::format::Bytes>>(duration)
-                    .flatten()
-                    .and_then(|bytes| usize::try_from(bytes).ok())
-                else {
-                    gst::error!(CAT, imp: self, "Failed to calculate size of repeat buffer");
-                    return Err(gst::FlowError::Error);
-                };
+            if state.out_duration.is_some() || !duration_is_valid {
+                // Resize the buffer if caps gave us a duration
+                // or the current duration is unreasonable
 
-                let mut mapped_memory = gst::Memory::with_size(size)
-                    .into_mapped_memory_writable()
-                    .map_err(|_| {
-                        gst::error!(CAT, imp: self, "Failed to map memory");
-                        gst::FlowError::Error
-                    })?;
+                let duration = state.out_duration.map_or(DEFAULT_DURATION, |dur| {
+                    dur.clamp(MINIMUM_DURATION, MAXIMUM_DURATION)
+                });
 
-                audio_info
-                    .format_info()
-                    .fill_silence(mapped_memory.as_mut_slice());
+                if let Some(audio_info) = &state.out_audio_info {
+                    let Some(size) = audio_info
+                        .convert::<Option<gst::format::Bytes>>(duration)
+                        .flatten()
+                        .and_then(|bytes| usize::try_from(bytes).ok())
+                    else {
+                        gst::error!(CAT, imp: self, "Failed to calculate size of repeat buffer");
+                        return Err(gst::FlowError::Error);
+                    };
 
-                buffer.replace_all_memory(mapped_memory.into_memory());
+                    buffer.replace_all_memory(gst::Memory::with_size(size));
+                }
+
+                buffer.set_duration(duration);
+                gst::debug!(CAT, imp: self, "Patched output buffer duration to {duration}");
             }
 
-            buffer.set_duration(duration);
-            gst::debug!(CAT, imp: self, "Patched output buffer duration to {duration}");
+            if let Some(audio_info) = &state.out_audio_info {
+                let mut map_info = buffer.map_writable().map_err(|e| {
+                    gst::error!(CAT, imp: self, "Failed to map buffer: {}", e);
+                    gst::FlowError::Error
+                })?;
+                audio_info
+                    .format_info()
+                    .fill_silence(map_info.as_mut_slice());
+            }
         }
 
         buffer.set_dts(dts);