Add --ffmpeg-threads flag to control the ffmpeg thread number

crunchy-cli-core/src/archive/command.rs

@@ -90,6 +90,16 @@ pub struct Archive {
     #[arg(long)]
     #[arg(value_parser = FFmpegPreset::parse)]
     pub(crate) ffmpeg_preset: Option<FFmpegPreset>,
+    #[arg(
+        help = "The number of threads used by ffmpeg to generate the output file. Does not work with every codec/preset"
+    )]
+    #[arg(
+        long_help = "The number of threads used by ffmpeg to generate the output file. \
+    Does not work with every codec/preset and is skipped entirely when specifying custom ffmpeg output arguments instead of a preset for `--ffmpeg-preset`. \
+    By default, ffmpeg chooses the thread count which works best for the output codec"
+    )]
+    #[arg(long)]
+    pub(crate) ffmpeg_threads: Option<usize>,
 
     #[arg(
         help = "Set which subtitle language should be set as default / auto shown when starting a video"
@@ -182,6 +192,7 @@ impl Execute for Archive {
             let download_builder = DownloadBuilder::new()
                 .default_subtitle(self.default_subtitle.clone())
                 .ffmpeg_preset(self.ffmpeg_preset.clone().unwrap_or_default())
+                .ffmpeg_threads(self.ffmpeg_threads)
                 .output_format(Some("matroska".to_string()))
                 .audio_sort(Some(self.audio.clone()))
                 .subtitle_sort(Some(self.subtitle.clone()))

crunchy-cli-core/src/download/command.rs

@@ -74,6 +74,16 @@ pub struct Download {
     #[arg(long)]
     #[arg(value_parser = FFmpegPreset::parse)]
     pub(crate) ffmpeg_preset: Option<FFmpegPreset>,
+    #[arg(
+        help = "The number of threads used by ffmpeg to generate the output file. Does not work with every codec/preset"
+    )]
+    #[arg(
+        long_help = "The number of threads used by ffmpeg to generate the output file. \
+    Does not work with every codec/preset and is skipped entirely when specifying custom ffmpeg output arguments instead of a preset for `--ffmpeg-preset`. \
+    By default, ffmpeg chooses the thread count which works best for the output codec"
+    )]
+    #[arg(long)]
+    pub(crate) ffmpeg_threads: Option<usize>,
 
     #[arg(help = "Skip files which are already existing")]
     #[arg(long, default_value_t = false)]
@@ -203,6 +213,7 @@ impl Execute for Download {
                     None
                 })
                 .ffmpeg_preset(self.ffmpeg_preset.clone().unwrap_or_default())
+                .ffmpeg_threads(self.ffmpeg_threads)
                 .threads(self.threads);
 
             for mut single_formats in single_format_collection.into_iter() {

crunchy-cli-core/src/utils/download.rs

@@ -51,6 +51,7 @@ pub struct DownloadBuilder {
     subtitle_sort: Option<Vec<Locale>>,
     force_hardsub: bool,
     threads: usize,
+    ffmpeg_threads: Option<usize>,
 }
 
 impl DownloadBuilder {
@@ -63,6 +64,7 @@ impl DownloadBuilder {
             subtitle_sort: None,
             force_hardsub: false,
             threads: num_cpus::get(),
+            ffmpeg_threads: None,
         }
     }
 
@@ -75,7 +77,9 @@ impl DownloadBuilder {
             subtitle_sort: self.subtitle_sort,
 
             force_hardsub: self.force_hardsub,
-            threads: self.threads,
+
+            download_threads: self.threads,
+            ffmpeg_threads: self.ffmpeg_threads,
 
             formats: vec![],
         }
@@ -102,7 +106,9 @@ pub struct Downloader {
     subtitle_sort: Option<Vec<Locale>>,
 
     force_hardsub: bool,
-    threads: usize,
+
+    download_threads: usize,
+    ffmpeg_threads: Option<usize>,
 
     formats: Vec<DownloadFormat>,
 }
@@ -343,6 +349,7 @@ impl Downloader {
             }
         }
 
+        let preset_custom = matches!(self.ffmpeg_preset, FFmpegPreset::Custom(_));
         let (input_presets, mut output_presets) = self.ffmpeg_preset.into_input_output_args();
         let fifo = temp_named_pipe()?;
 
@@ -356,6 +363,11 @@ impl Downloader {
         command_args.extend(input);
         command_args.extend(maps);
         command_args.extend(metadata);
+        if !preset_custom {
+            if let Some(ffmpeg_threads) = self.ffmpeg_threads {
+                command_args.extend(vec!["-threads".to_string(), ffmpeg_threads.to_string()])
+            }
+        }
 
         // set default subtitle
         if let Some(default_subtitle) = self.default_subtitle {
@@ -618,7 +630,7 @@ impl Downloader {
             None
         };
 
-        let cpus = self.threads;
+        let cpus = self.download_threads;
         let mut segs: Vec<Vec<VariantSegment>> = Vec::with_capacity(cpus);
         for _ in 0..cpus {
             segs.push(vec![])