From 1beaea8088ed20b9bd87afa6c1d0adf84b9350bb Mon Sep 17 00:00:00 2001
From: dailz <dailz@192.168.1.254>
Date: Sat, 6 Jun 2026 21:16:55 +0800
Subject: [PATCH] fix(webrtc): use MediaAdded event to discover video mid
 instead of hardcoded iteration (closes #11)

---
 src/webrtc.rs | 47 ++++++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/src/webrtc.rs b/src/webrtc.rs
index 7c7aa8f..a099c2e 100644
--- a/src/webrtc.rs
+++ b/src/webrtc.rs
@@ -311,28 +311,26 @@ impl WebRtcInner {
     }
 
     fn discover_video_params(&mut self) {
-        for s in ["0", "1", "2", "3"] {
-            let mid: Mid = s.into();
-            if let Some(media) = self.rtc.media(mid) {
-                if media.kind() == MediaKind::Video {
-                    tracing::info!("Found video media: mid={mid}");
-                    self.video_mid = Some(mid);
+        let mid = match self.video_mid {
+            Some(m) => m,
+            None => {
+                tracing::warn!("discover_video_params: no video_mid yet");
+                return;
+            }
+        };
+        self.video_pt = None;
+        if let Some(writer) = self.rtc.writer(mid) {
+            for pp in writer.payload_params() {
+                tracing::debug!("Codec: pt={:?} spec={:?}", pp.pt(), pp.spec());
+                if pp.spec().codec.is_video() && pp.spec().codec == Codec::H264 {
+                    self.video_pt = Some(pp.pt());
+                    tracing::info!("H.264 payload type: {:?}", pp.pt());
                     break;
                 }
             }
         }
-
-        if let Some(mid) = self.video_mid {
-            if let Some(writer) = self.rtc.writer(mid) {
-                for pp in writer.payload_params() {
-                    tracing::debug!("Codec: pt={:?} spec={:?}", pp.pt(), pp.spec());
-                    if pp.spec().codec.is_video() && pp.spec().codec == Codec::H264 {
-                        self.video_pt = Some(pp.pt());
-                        tracing::info!("H.264 payload type: {:?}", pp.pt());
-                        break;
-                    }
-                }
-            }
+        if self.video_pt.is_none() {
+            tracing::warn!("discover_video_params: no H.264 codec found for mid={mid}");
         }
     }
 
@@ -360,7 +358,18 @@ impl WebRtcInner {
                             return Ok(true);
                         }
                         Event::MediaAdded(ma) => {
-                            tracing::info!("Media added: mid={:?}", ma.mid);
+                            tracing::info!("Media added: mid={} kind={:?}", ma.mid, ma.kind);
+                            if ma.kind == MediaKind::Video {
+                                if let Some(media) = self.rtc.media(ma.mid) {
+                                    if media.direction().is_sending()
+                                        && self.video_mid.is_none()
+                                    {
+                                        self.video_mid = Some(ma.mid);
+                                        tracing::info!("Captured video mid: {}", ma.mid);
+                                        self.discover_video_params();
+                                    }
+                                }
+                            }
                         }
                         _ => {
                             tracing::debug!("WebRTC event: {:?}", e);