Add some helpful comments

src/ape/constants.rs

@@ -1,3 +1,4 @@
-#[allow(unused)]
 pub(super) const INVALID_KEYS: [&str; 4] = ["ID3", "TAG", "OGGS", "MP+"];
-pub(crate) const APE_PREAMBLE: &[u8; 8] = b"APETAGEX";
+
+// https://wiki.hydrogenaud.io/index.php?title=APE_Tags_Header
+pub(crate) const APE_PREAMBLE: &[u8; 8] = b"APETAGEX";

src/id3/v1/constants.rs

@@ -196,7 +196,7 @@ pub const GENRES: [&str; 192] = [
 	"Psybient",
 ];
 
-pub const VALID_ITEMKEYS: [ItemKey; 7] = [
+pub(crate) const VALID_ITEMKEYS: [ItemKey; 7] = [
 	ItemKey::TrackTitle,
 	ItemKey::TrackArtist,
 	ItemKey::AlbumTitle,

src/id3/v1/read.rs

@@ -19,10 +19,13 @@ pub fn parse_id3v1(reader: [u8; 128]) -> Id3v1Tag {
 	tag.album = decode_text(&reader[60..90]);
 	tag.year = decode_text(&reader[90..94]);
 
-	let range = if reader[119] == 0 && reader[123] != 0 {
+	// Determine the range of the comment (30 bytes for ID3v1 and 28 for ID3v1.1)
+	// We check for the null terminator 28 bytes in, and for a non-zero track number after it.
+	// A track number of 0 is invalid.
+	let range = if reader[122] == 0 && reader[123] != 0 {
 		tag.track_number = Some(reader[123]);
 
-		94_usize..122
+		94_usize..123
 	} else {
 		94..124
 	};

src/ogg/constants.rs

@@ -1,9 +1,11 @@
+// https://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-620004.2.1
 pub const VORBIS_IDENT_HEAD: &[u8] = &[1, 118, 111, 114, 98, 105, 115];
 pub const VORBIS_COMMENT_HEAD: &[u8] = &[3, 118, 111, 114, 98, 105, 115];
-#[allow(unused)]
 pub const VORBIS_SETUP_HEAD: &[u8] = &[5, 118, 111, 114, 98, 105, 115];
 
+// https://datatracker.ietf.org/doc/pdf/rfc7845.pdf#section-5.1
 pub const OPUSTAGS: &[u8] = &[79, 112, 117, 115, 84, 97, 103, 115];
 pub const OPUSHEAD: &[u8] = &[79, 112, 117, 115, 72, 101, 97, 100];
 
+// https://www.speex.org/docs/manual/speex-manual/node8.html
 pub const SPEEXHEADER: &[u8] = &[83, 112, 101, 101, 120, 32, 32, 32];

src/ogg/speex/properties.rs

@@ -20,7 +20,7 @@ pub struct SpeexProperties {
 	vbr: bool,
 	overall_bitrate: u32,
 	audio_bitrate: u32,
-	nominal_bitrate: u32,
+	nominal_bitrate: i32,
 }
 
 impl From<SpeexProperties> for FileProperties {
@@ -47,7 +47,7 @@ impl SpeexProperties {
 		vbr: bool,
 		overall_bitrate: u32,
 		audio_bitrate: u32,
-		nominal_bitrate: u32,
+		nominal_bitrate: i32,
 	) -> Self {
 		Self {
 			duration,
@@ -102,8 +102,8 @@ impl SpeexProperties {
 		self.audio_bitrate
 	}
 
-	/// Audio bitrate (kbps)
-	pub fn nominal_bitrate(&self) -> u32 {
+	/// Audio bitrate (bps)
+	pub fn nominal_bitrate(&self) -> i32 {
 		self.nominal_bitrate
 	}
 }
@@ -149,7 +149,7 @@ where
 	}
 
 	properties.channels = channels as u8;
-	properties.nominal_bitrate = first_page_content.read_u32::<LittleEndian>()?;
+	properties.nominal_bitrate = first_page_content.read_i32::<LittleEndian>()?;
 
 	// The size of the frames in samples
 	let _frame_size = first_page_content.read_u32::<LittleEndian>()?;
@@ -167,7 +167,7 @@ where
 			properties.duration = Duration::from_millis(length as u64);
 
 			properties.overall_bitrate = ((file_length * 8) / length) as u32;
-			properties.audio_bitrate = properties.nominal_bitrate / 1000;
+			properties.audio_bitrate = (properties.nominal_bitrate as u64 / 1000) as u32;
 		}
 	}
 

src/ogg/vorbis/properties.rs

@@ -91,17 +91,17 @@ impl VorbisProperties {
 		self.version
 	}
 
-	/// Maximum bitrate
+	/// Maximum bitrate (bps)
 	pub fn bitrate_max(&self) -> i32 {
 		self.bitrate_maximum
 	}
 
-	/// Nominal bitrate
+	/// Nominal bitrate (bps)
 	pub fn bitrate_nominal(&self) -> i32 {
 		self.bitrate_nominal
 	}
 
-	/// Minimum bitrate
+	/// Minimum bitrate (bps)
 	pub fn bitrate_min(&self) -> i32 {
 		self.bitrate_minimum
 	}