fix: conditionally disable audio track merging

src/ffmpeg.rs

@@ -23,9 +23,10 @@ struct FfprobeOut {
 }
 
 #[derive(serde::Deserialize)]
-struct StreamInfo {
-    width: usize,
-    height: usize,
+#[serde(tag = "codec_type", rename_all = "lowercase")]
+enum StreamInfo {
+    Video { width: usize, height: usize },
+    Audio,
 }
 
 #[derive(serde::Deserialize)]
@@ -37,6 +38,7 @@ struct FormatInfo {
 pub struct VideoMeta {
     pub width: usize,
     pub height: usize,
+    pub audio_streams: usize,
     pub duration_us: usize,
 }
 
@@ -62,10 +64,8 @@ pub async fn get_video_meta(path: &Path) -> Result<VideoMeta> {
         .args([
             "-v",
             "error",
-            "-select_streams",
-            "v:0",
             "-show_entries",
-            "stream=width,height : format=duration",
+            "stream=width,height,codec_type : format=duration",
             "-of",
             "json",
         ])
@@ -77,17 +77,28 @@ pub async fn get_video_meta(path: &Path) -> Result<VideoMeta> {
     let str = String::from_utf8(output.stdout)?;
     let output: FfprobeOut = serde_json::from_str(&str)?;
 
-    let stream = output
+    let (width, height) = output
         .streams
-        .first()
+        .iter()
+        .find_map(|s| match s {
+            StreamInfo::Video { width, height } => Some((*width, *height)),
+            _ => None,
+        })
         .wrap_err("could not get stream information from ffprobe")?;
 
+    let audio_streams = output
+        .streams
+        .iter()
+        .filter(|s| matches!(s, StreamInfo::Audio))
+        .count();
+
     let duration_sec = output.format.duration.parse::<f64>()?;
     let duration_us = (duration_sec * 1_000_000.0).ceil() as usize;
 
     Ok(VideoMeta {
-        width: stream.width,
-        height: stream.height,
+        width,
+        height,
+        audio_streams,
         duration_us,
     })
 }
@@ -115,7 +126,6 @@ pub async fn convert_video(
         Codec::VP9 => &["-c:v", "libvpx-vp9", "-row-mt", "1"],
     };
 
-    // TODO: maybe check if the video has 2 audio tracks? or at least use a "fail-safe" method
     let merge_args: &[&str] = if merge_tracks {
         &["-ac", "2", "-filter_complex", "amerge=inputs=2"]
     } else {

src/main.rs

@@ -94,6 +94,7 @@ struct Tyrolienne {
     step: Step,
     progress: usize,
     total: usize,
+    can_merge: bool,
     video_path: Option<PathBuf>,
     out_filename: Option<String>,
     out_codec: ffmpeg::Codec,
@@ -116,7 +117,7 @@ impl Tyrolienne {
             config: self.config.clone(),
             out_filename: self.out_filename.clone(),
             out_codec: self.out_codec,
-            merge_tracks: self.merge_tracks,
+            merge_tracks: self.can_merge && self.merge_tracks,
             video_path: self.video_path.clone(),
             folder: self.folder.clone(),
         }
@@ -190,7 +191,10 @@ impl AsyncComponent for Tyrolienne {
 
                             adw::SwitchRow {
                                 set_title: "Merge audio tracks",
-                                set_active: true,
+                                #[watch]
+                                set_sensitive: model.can_merge,
+                                #[watch]
+                                set_active: model.can_merge && model.merge_tracks,
                                 connect_active_notify[sender] => move |s| sender.input(Message::SetMergeTracks(s.is_active())),
                             },
 
@@ -246,6 +250,7 @@ impl AsyncComponent for Tyrolienne {
             step: Step::Waiting,
             progress: 0,
             total: 1,
+            can_merge: false,
             video_path: None,
             out_filename: None,
             out_codec: ffmpeg::Codec::VP9,
@@ -306,6 +311,8 @@ impl AsyncComponent for Tyrolienne {
                     .await;
 
                 if let Some(file) = file {
+                    let meta = ffmpeg::get_video_meta(file.path()).await;
+                    self.can_merge = meta.map(|m| m.audio_streams == 2).unwrap_or(false);
                     self.video_path = Some(file.path().to_owned());
                 }
             }