Fix encoder error handling and output locking on Windows

Improves error propagation in MP4 export by mapping encoder errors to strings. Refactors Windows output pipeline to ensure proper locking of output streams and corrects the fallback logic for encoder selection. Also removes an unused import and minor variable cleanup in Windows screen capture source.

Author: richiemcilroy

crates/export/src/mp4.rs

@@ -97,10 +97,12 @@ impl Mp4ExportSettings {
 
             let mut encoded_frames = 0;
             while let Ok(frame) = frame_rx.recv() {
-                encoder.queue_video_frame(
-                    frame.video,
-                    Duration::from_secs_f32(encoded_frames as f32 / fps as f32),
-                );
+                encoder
+                    .queue_video_frame(
+                        frame.video,
+                        Duration::from_secs_f32(encoded_frames as f32 / fps as f32),
+                    )
+                    .map_err(|err| err.to_string())?;
                 encoded_frames += 1;
                 if let Some(audio) = frame.audio {
                     encoder.queue_audio_frame(audio);

crates/recording/src/instant_recording.rs

@@ -224,6 +224,8 @@ async fn create_pipeline(
         mic_feed,
         output_path.clone(),
         output_resolution,
+        #[cfg(windows)]
+        crate::capture_pipeline::EncoderPreferences::new(),
     )
     .await?;
 

crates/recording/src/output_pipeline/win.rs

@@ -75,9 +75,7 @@ impl Muxer for WindowsMuxer {
                 let encoder_preferences = &config.encoder_preferences;
 
                 let encoder = (|| {
-                    let mut output = output.lock().unwrap();
-
-                    let fallback = |reason: Option<String>| {
+                    let mut fallback = |reason: Option<String>| {
                         use tracing::{error, info};
 
                         encoder_preferences.force_software_only();
@@ -98,9 +96,11 @@ impl Muxer for WindowsMuxer {
                             video_config.height
                         };
 
+                        let mut output = output.lock().unwrap();
+
                         cap_enc_ffmpeg::H264Encoder::builder(video_config)
                             .with_output_size(fallback_width, fallback_height)
-                            .and_then(|builder| builder.build(&mut output))
+                            .and_then(|builder| builder.build(&mut *output))
                             .map(either::Right)
                             .map_err(|e| anyhow!("ScreenSoftwareEncoder/{e}"))
                     };
@@ -117,18 +117,25 @@ impl Muxer for WindowsMuxer {
                         config.frame_rate,
                         config.bitrate_multiplier,
                     ) {
-                        Ok(encoder) => match cap_mediafoundation_ffmpeg::H264StreamMuxer::new(
-                            &mut output,
-                            cap_mediafoundation_ffmpeg::MuxerConfig {
-                                width: output_size.Width as u32,
-                                height: output_size.Height as u32,
-                                fps: config.frame_rate,
-                                bitrate: encoder.bitrate(),
-                            },
-                        ) {
-                            Ok(muxer) => Ok(either::Left((encoder, muxer))),
-                            Err(err) => fallback(Some(err.to_string())),
-                        },
+                        Ok(encoder) => {
+                            let muxer = {
+                                let mut output = output.lock().unwrap();
+                                cap_mediafoundation_ffmpeg::H264StreamMuxer::new(
+                                    &mut *output,
+                                    cap_mediafoundation_ffmpeg::MuxerConfig {
+                                        width: output_size.Width as u32,
+                                        height: output_size.Height as u32,
+                                        fps: config.frame_rate,
+                                        bitrate: encoder.bitrate(),
+                                    },
+                                )
+                            };
+
+                            match muxer {
+                                Ok(muxer) => Ok(either::Left((encoder, muxer))),
+                                Err(err) => fallback(Some(err.to_string())),
+                            }
+                        }
                         Err(err) => fallback(Some(err.to_string())),
                     }
                 })();

crates/recording/src/sources/screen_capture/windows.rs

@@ -13,7 +13,6 @@ use futures::{
     FutureExt, SinkExt, StreamExt,
     channel::{mpsc, oneshot},
 };
-use kameo::prelude::*;
 use scap_direct3d::StopCapturerError;
 use scap_ffmpeg::*;
 use scap_targets::{Display, DisplayId};
@@ -179,7 +178,7 @@ impl output_pipeline::VideoSource for VideoSource {
     where
         Self: Sized,
     {
-        let (mut error_tx, mut error_rx) = mpsc::channel(1);
+        let (error_tx, mut error_rx) = mpsc::channel(1);
         let (ctrl_tx, ctrl_rx) = std::sync::mpsc::sync_channel::<VideoControl>(1);
 
         let tokio_rt = tokio::runtime::Handle::current();