diff --git a/modules/taglib/src/impls/file.rs b/modules/taglib/src/impls/file.rs
index 81c542b..d2b56ac 100644
--- a/modules/taglib/src/impls/file.rs
+++ b/modules/taglib/src/impls/file.rs
@@ -51,6 +51,7 @@ impl TagLibFile {
 				| TagLibFileType::OggOpus
 				| TagLibFileType::OggSpeex
 				| TagLibFileType::OggVorbis => true,
+				_ => false,
 			};
 
 			if !supported {
diff --git a/modules/taglib/src/lib.rs b/modules/taglib/src/lib.rs
index 23870cc..d882ca4 100644
--- a/modules/taglib/src/lib.rs
+++ b/modules/taglib/src/lib.rs
@@ -17,6 +17,7 @@ pub enum TagLibFileType {
 	OggOpus = 2,
 	OggSpeex = 3,
 	OggVorbis = 4,
+	MP4 = 5,
 }
 
 pub use impls::file::*;
diff --git a/modules/taglib/src/wrapper.cxx b/modules/taglib/src/wrapper.cxx
index e990124..37c74e5 100644
--- a/modules/taglib/src/wrapper.cxx
+++ b/modules/taglib/src/wrapper.cxx
@@ -5,6 +5,7 @@
 #include <taglib/vorbisfile.h>
 #include <taglib/oggflacfile.h>
 #include <taglib/opusfile.h>
+#include <taglib/mp4file.h>
 #include <taglib/speexfile.h>
 
 #include <string.h>
@@ -39,6 +40,9 @@ TagLib_File *wrap_taglib_file_new_with_type(const char *filename, short taglib_t
   if (taglib_type == 4) {
     return reinterpret_cast<TagLib_File *>(new TagLib::Ogg::Vorbis::File(filename));
   }
+  if (taglib_type == 5) {
+    return reinterpret_cast<TagLib_File *>(new TagLib::MP4::File(filename));
+  }
   return reinterpret_cast<TagLib_File *>(TagLib::FileRef::create(filename));
 }
 
diff --git a/src/commands/copy.rs b/src/commands/copy.rs
index 3f735b8..2744113 100644
--- a/src/commands/copy.rs
+++ b/src/commands/copy.rs
@@ -222,7 +222,7 @@ fn transcode_files(
 	)
 	.expect("transcode config error");
 
-	let threads = copy_args.threads.unwrap_or(1);
+	let threads = copy_args.threads.unwrap_or(2);
 
 	if threads > 1 {
 		let files_copy = files.to_vec();
diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index 3aad189..026bb1d 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -1,7 +1,7 @@
 pub mod copy;
 #[cfg(feature = "command_genhtml")]
 pub mod genhtml;
+pub mod presets;
 pub mod process;
 pub mod tags;
 pub mod transcode;
-pub mod presets;
diff --git a/src/commands/presets.rs b/src/commands/presets.rs
index eadf471..caaa768 100644
--- a/src/commands/presets.rs
+++ b/src/commands/presets.rs
@@ -42,9 +42,9 @@ pub fn presets_command(
 			let preset = match crate::utils::transcoder::presets::get_preset(x.preset) {
 				Some(preset) => preset,
 				None => {
-          println!("invalid preset specified");
-          std::process::exit(1);
-        },
+					println!("invalid preset specified");
+					std::process::exit(1);
+				}
 			};
 
 			match x.format {
diff --git a/src/commands/process.rs b/src/commands/process.rs
index fa96a7b..579bd43 100644
--- a/src/commands/process.rs
+++ b/src/commands/process.rs
@@ -215,7 +215,7 @@ pub fn process_command(
 	for file in files.iter_mut() {
 		rename_file(process_args, file);
 	}
-	
+
 	#[cfg(feature = "replaygain")]
 	if !process_args.skip_replaygain && !process_args.dry_run {
 		println!("Adding ReplayGain Tags to Files");
diff --git a/src/utils/format_detection.rs b/src/utils/format_detection.rs
index 5c8b10e..af9eca1 100644
--- a/src/utils/format_detection.rs
+++ b/src/utils/format_detection.rs
@@ -22,6 +22,7 @@ pub enum FileFormat {
 	AIFF,
 	Wav,
 	WavPack,
+	M4A,
 }
 
 impl ToString for FileFormat {
@@ -37,6 +38,7 @@ impl ToString for FileFormat {
 			FileFormat::AIFF => "AIFF".to_string(),
 			FileFormat::Wav => "Wav".to_string(),
 			FileFormat::WavPack => "WavPack".to_string(),
+			FileFormat::M4A => "M4A (Unknown)".to_string(),
 		}
 	}
 }
@@ -104,6 +106,9 @@ pub fn detect_format(path: &Path) -> Result<FileFormat, FormatDetectionError> {
 		"audio/mpeg" => {
 			return Ok(FileFormat::MP3);
 		}
+		"audio/m4a" => {
+			return Ok(FileFormat::M4A);
+		}
 		"audio/x-wav" => {
 			return Ok(FileFormat::Wav);
 		}
diff --git a/src/utils/formats/handlers/mod.rs b/src/utils/formats/handlers/mod.rs
index 3dfe7a9..8c04893 100644
--- a/src/utils/formats/handlers/mod.rs
+++ b/src/utils/formats/handlers/mod.rs
@@ -92,6 +92,8 @@ lazy_static! {
 				"wav".to_string(),
 				"wv".to_string(),
 				"aiff".to_string(),
+				"m4a".to_string(),
+				"alac".to_string(),
 			],
 			supported_formats: vec![
 				FileFormat::MP3,
@@ -104,6 +106,7 @@ lazy_static! {
 				FileFormat::Wav,
 				FileFormat::WavPack,
 				FileFormat::AIFF,
+				FileFormat::M4A,
 			],
 			new: |path, file_format| -> NewHandlerFuncReturn {
 				let handler = taglib::new_handler(path, file_format)?;
@@ -122,6 +125,8 @@ lazy_static! {
 				"wav".to_string(),
 				"wv".to_string(),
 				"aiff".to_string(),
+				"m4a".to_string(),
+				"alac".to_string(),
 			],
 			supported_formats: vec![
 				FileFormat::MP3,
@@ -134,6 +139,7 @@ lazy_static! {
 				FileFormat::Wav,
 				FileFormat::WavPack,
 				FileFormat::AIFF,
+				FileFormat::M4A,
 			],
 			new: |path, file_format| -> NewHandlerFuncReturn {
 				let handler = ffprobe::new_handler(path, file_format)?;
diff --git a/src/utils/formats/handlers/taglib.rs b/src/utils/formats/handlers/taglib.rs
index 14cb715..1bc8072 100644
--- a/src/utils/formats/handlers/taglib.rs
+++ b/src/utils/formats/handlers/taglib.rs
@@ -74,10 +74,11 @@ impl FormatHandler for TaglibAudioFormat {
 				FileFormat::OggVorbis
 					| FileFormat::OggOpus
 					| FileFormat::OggFLAC
-					| FileFormat::OggSpeex // Both "support" ReplayGain but not implemented yet
-				                       // FileFormat::Wav |
-				                       // FileFormat::WavPack
+					| FileFormat::OggSpeex
 			);
+			// Both "support" ReplayGain but not implemented yet
+			// FileFormat::Wav |
+			// FileFormat::WavPack
 		}
 
 		false
@@ -99,20 +100,27 @@ impl FormatHandler for TaglibAudioFormat {
 
 	fn set_replaygain_data(&mut self, data: ReplayGainRawData) -> Result<(), BoxedError> {
 		if let Some(format) = self.file_format {
-			let oggtag = self.file.oggtag().expect("oggtag not available?");
+			match format {
+				FileFormat::OggOpus
+				| FileFormat::OggVorbis
+				| FileFormat::OggFLAC
+				| FileFormat::OggSpeex => {
+					let oggtag = self.file.oggtag().expect("oggtag not available?");
 
-			if format == FileFormat::OggOpus {
-				let data = data.to_normal(true);
+					if format == FileFormat::OggOpus {
+						let data = data.to_normal(true);
 
-				oggtag.add_field("R128_TRACK_GAIN".to_string(), data.track_gain);
-			} else if matches!(
-				format,
-				FileFormat::OggVorbis | FileFormat::OggFLAC | FileFormat::OggSpeex
-			) {
-				let data = data.to_normal(false);
+						oggtag.add_field("R128_TRACK_GAIN".to_string(), data.track_gain);
+					} else {
+						let data = data.to_normal(false);
 
-				oggtag.add_field("REPLAYGAIN_TRACK_GAIN".to_string(), data.track_gain);
-				oggtag.add_field("REPLAYGAIN_TRACK_PEAK".to_string(), data.track_peak);
+						oggtag.add_field("REPLAYGAIN_TRACK_GAIN".to_string(), data.track_gain);
+						oggtag.add_field("REPLAYGAIN_TRACK_PEAK".to_string(), data.track_peak);
+					}
+				}
+				_ => {
+					panic!("setting replaygain not supported on this format");
+				}
 			}
 		}
 
@@ -152,6 +160,7 @@ pub fn new_handler(
 			FileFormat::OggOpus => Some(TagLibFileType::OggOpus),
 			FileFormat::OggFLAC => Some(TagLibFileType::OggFLAC),
 			FileFormat::OggSpeex => Some(TagLibFileType::OggSpeex),
+			FileFormat::M4A => Some(TagLibFileType::MP4),
 			_ => None,
 		}
 	}
diff --git a/src/utils/transcoder/presets/flac.rs b/src/utils/transcoder/presets/flac.rs
index cb79e2d..63afa5c 100644
--- a/src/utils/transcoder/presets/flac.rs
+++ b/src/utils/transcoder/presets/flac.rs
@@ -15,4 +15,4 @@ pub fn add_preset(preset_categories: &mut Vec<PresetCategory>) {
 			},
 		}]),
 	})
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/presets/g726.rs b/src/utils/transcoder/presets/g726.rs
index 883c7a4..c361b2d 100644
--- a/src/utils/transcoder/presets/g726.rs
+++ b/src/utils/transcoder/presets/g726.rs
@@ -24,4 +24,4 @@ pub fn add_presets(preset_categories: &mut Vec<PresetCategory>) {
 		name: "g726".to_string(),
 		presets,
 	});
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/presets/mod.rs b/src/utils/transcoder/presets/mod.rs
index 59fab65..1efefd3 100644
--- a/src/utils/transcoder/presets/mod.rs
+++ b/src/utils/transcoder/presets/mod.rs
@@ -4,12 +4,12 @@ use string_error::into_err;
 use crate::utils::transcoder::types::PresetCategory;
 use crate::utils::transcoder::types::TranscodeConfig;
 
+mod flac;
+mod g726;
 mod mp3;
 mod opus;
-mod vorbis;
-mod g726;
 mod speex;
-mod flac;
+mod vorbis;
 mod wav;
 
 lazy_static! {
diff --git a/src/utils/transcoder/presets/mp3.rs b/src/utils/transcoder/presets/mp3.rs
index 779eea3..17acd2a 100644
--- a/src/utils/transcoder/presets/mp3.rs
+++ b/src/utils/transcoder/presets/mp3.rs
@@ -36,4 +36,4 @@ pub fn add_presets(preset_categories: &mut Vec<PresetCategory>) {
 		name: "mp3".to_string(),
 		presets,
 	});
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/presets/opus.rs b/src/utils/transcoder/presets/opus.rs
index 23768cd..0ba3cf1 100644
--- a/src/utils/transcoder/presets/opus.rs
+++ b/src/utils/transcoder/presets/opus.rs
@@ -21,4 +21,4 @@ pub fn add_presets(preset_categories: &mut Vec<PresetCategory>) {
 		name: "opus".to_string(),
 		presets,
 	});
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/presets/vorbis.rs b/src/utils/transcoder/presets/vorbis.rs
index 812eb9a..6e9e3fe 100644
--- a/src/utils/transcoder/presets/vorbis.rs
+++ b/src/utils/transcoder/presets/vorbis.rs
@@ -21,4 +21,4 @@ pub fn add_presets(preset_categories: &mut Vec<PresetCategory>) {
 		name: "vorbis".to_string(),
 		presets,
 	});
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/presets/wav.rs b/src/utils/transcoder/presets/wav.rs
index 48c169c..6186a48 100644
--- a/src/utils/transcoder/presets/wav.rs
+++ b/src/utils/transcoder/presets/wav.rs
@@ -2,7 +2,6 @@ use crate::utils::transcoder::types::Preset;
 use crate::utils::transcoder::types::PresetCategory;
 use crate::utils::transcoder::types::TranscodeConfig;
 
-
 pub fn add_preset(preset_categories: &mut Vec<PresetCategory>) {
 	preset_categories.push(PresetCategory {
 		name: "wav".to_string(),
@@ -15,4 +14,4 @@ pub fn add_preset(preset_categories: &mut Vec<PresetCategory>) {
 			},
 		}]),
 	})
-}
\ No newline at end of file
+}
diff --git a/src/utils/transcoder/transcoder.rs b/src/utils/transcoder/transcoder.rs
index 8d36f08..0da64d2 100644
--- a/src/utils/transcoder/transcoder.rs
+++ b/src/utils/transcoder/transcoder.rs
@@ -57,9 +57,11 @@ pub fn transcode(
 				width = -1;
 			}
 
-			command_args.extend(vec!["-vf".to_string(), format!("scale={}:{}", width, height)]);
+			command_args.extend(vec![
+				"-vf".to_string(),
+				format!("scale={}:{}", width, height),
+			]);
 		}
-
 	}
 
 	command_args.push(dest);