From 1e205c842e6834de18e80c3d5136fb55d2e01174 Mon Sep 17 00:00:00 2001
From: Jakub Adam <jakub.adam@collabora.com>
Date: Wed, 21 May 2025 23:31:25 +0200
Subject: [PATCH] webrtcsink: Don't require encoder element for pre-encoded
 streams

When webrtcsink takes as an input a stream that is already encoded, it
errors out when there is no encoder element available for the codec in
question.

This change makes it possible to stream an output from a camera that
already produces e.g. video/x-h264 without bloating the GStreamer
installation with a redundant H.264 encoder element.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/2273>
---
 net/webrtc/src/utils.rs          | 27 ++++++++++++++++++++++-----
 net/webrtc/src/webrtcsink/imp.rs |  3 ++-
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/net/webrtc/src/utils.rs b/net/webrtc/src/utils.rs
index 382f338ea..85e52bbaf 100644
--- a/net/webrtc/src/utils.rs
+++ b/net/webrtc/src/utils.rs
@@ -464,9 +464,9 @@ impl Codec {
         let encoder = Self::get_encoder_for_caps(caps, encoders);
         let payloader = Self::get_payloader_for_codec(name, payloaders);
 
-        let encoding_info = if let (Some(encoder), Some(payloader)) = (encoder, payloader) {
+        let encoding_info = if let (encoder, Some(payloader)) = (encoder, payloader) {
             Some(EncodingInfo {
-                encoder: Some(encoder),
+                encoder,
                 payloader,
                 output_filter: None,
             })
@@ -828,6 +828,20 @@ impl Codecs {
         Self(codecs.values().cloned().collect())
     }
 
+    pub fn list_encoders(&self) -> Codecs {
+        Codecs(
+            self.iter()
+                .filter(|codec| {
+                    codec
+                        .encoding_info
+                        .as_ref()
+                        .is_some_and(|info| info.encoder.is_some())
+                })
+                .cloned()
+                .collect(),
+        )
+    }
+
     pub fn find_for_payloadable_caps(&self, caps: &gst::Caps) -> Option<Codec> {
         self.iter()
             .find(|codec| codec.caps.can_intersect(caps) && codec.encoding_info.is_some())
@@ -938,9 +952,12 @@ impl Codecs {
             .filter(|codec| codec.stream_type == gst::StreamType::AUDIO)
     }
 
-    /// List all codecs that can be used for encoding the given caps and assign
-    /// a payload type to each of them. This is useful to initiate SDP negotiation.
-    pub fn list_encoders<'a>(caps: impl IntoIterator<Item = &'a gst::StructureRef>) -> Codecs {
+    /// List all codecs that can be used for encoding and/or payloading the given
+    /// caps and assign a payload type to each of them. This is useful to initiate
+    /// SDP negotiation.
+    pub fn list_encoders_and_payloaders<'a>(
+        caps: impl IntoIterator<Item = &'a gst::StructureRef>,
+    ) -> Codecs {
         let mut payload = 96..128;
 
         Codecs(
diff --git a/net/webrtc/src/webrtcsink/imp.rs b/net/webrtc/src/webrtcsink/imp.rs
index 8d98376d1..bae4ad760 100644
--- a/net/webrtc/src/webrtcsink/imp.rs
+++ b/net/webrtc/src/webrtcsink/imp.rs
@@ -4080,6 +4080,7 @@ impl BaseWebRTCSink {
         codecs: &Codecs,
     ) -> Result<(), Error> {
         let futs = if has_raw_caps(&discovery_info.caps) {
+            let codecs = codecs.list_encoders();
             if codecs.is_empty() {
                 return Err(anyhow!(
                     "No codec available for encoding stream {}, \
@@ -4331,7 +4332,7 @@ impl BaseWebRTCSink {
             } else {
                 drop(state);
                 let settings = self.settings.lock().unwrap();
-                let codecs = Codecs::list_encoders(
+                let codecs = Codecs::list_encoders_and_payloaders(
                     settings.video_caps.iter().chain(settings.audio_caps.iter()),
                 );