Add support for AAC (#71)

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
       eagerness and other settings. Previously, when reading a file the only option available was
       `read_properties`, specified with a `bool` in `read_from{_path}`. This will now default to `true`,
       and can be overridden when using `Probe`.
+- **🎉 Support for AAC (ADTS) files** ([issue](https://github.com/Serial-ATA/lofty-rs/issues/58))
 - **FileProperties**: `FileProperties::new`
 - Debug logging via the [log](https://crates.io/crates/log) crate for exposing recoverable errors.
 - **Error**: `ErrorKind::SizeMismatch`

SUPPORTED_FORMATS.md

@@ -1,5 +1,6 @@
 | File Format | Metadata Format(s)                   |
 |-------------|--------------------------------------|
+| AAC (ADTS)  | `ID3v2`, `ID3v1`                     |
 | Ape         | `APEv2`, `APEv1`, `ID3v2`\*, `ID3v1` |
 | AIFF        | `ID3v2`, `Text Chunks`               |
 | FLAC        | `Vorbis Comments`, `ID3v2`\*         |

benches/read_file.rs

@@ -30,6 +30,7 @@ fn content_infer_read(c: &mut Criterion) {
 	test_read_file!(
 		c,
 		[
+			(AAC, "../tests/files/assets/minimal/full_test.aac"),
 			(AIFF, "../tests/files/assets/minimal/full_test.aiff"),
 			(APE, "../tests/files/assets/minimal/full_test.ape"),
 			(FLAC, "../tests/files/assets/minimal/full_test.flac"),

fuzz/Cargo.toml

@@ -26,6 +26,10 @@ path = "fuzz_targets/filetype_from_buffer.rs"
 name = "mp3file_read_from"
 path = "fuzz_targets/mpegfile_read_from.rs"
 
+[[bin]]
+name = "aacfile_read_from"
+path = "fuzz_targets/aacfile_read_from.rs"
+
 [[bin]]
 name = "aifffile_read_from"
 path = "fuzz_targets/aifffile_read_from.rs"

fuzz/fuzz_targets/aacfile_read_from.rs

@@ -0,0 +1,13 @@
+#![no_main]
+
+use std::io::Cursor;
+
+use libfuzzer_sys::fuzz_target;
+use lofty::{AudioFile, ParseOptions};
+
+fuzz_target!(|data: Vec<u8>| {
+	let _ = lofty::aac::AACFile::read_from(
+		&mut Cursor::new(data),
+		ParseOptions::new().read_properties(false),
+	);
+});

lofty_attr/src/internal.rs

@@ -9,8 +9,8 @@ use quote::quote;
 pub(crate) fn opt_internal_file_type(
 	struct_name: String,
 ) -> Option<(proc_macro2::TokenStream, bool)> {
-	const LOFTY_FILE_TYPES: [&str; 10] = [
-		"AIFF", "APE", "FLAC", "MPEG", "MP4", "Opus", "Vorbis", "Speex", "WAV", "WavPack",
+	const LOFTY_FILE_TYPES: [&str; 11] = [
+		"AAC", "AIFF", "APE", "FLAC", "MPEG", "MP4", "Opus", "Vorbis", "Speex", "WAV", "WavPack",
 	];
 
 	const ID3V2_STRIPPABLE: [&str; 1] = ["APE"];

src/aac/header.rs

@@ -0,0 +1,123 @@
+use crate::error::Result;
+use crate::macros::decode_err;
+use crate::mp4::{AudioObjectType, SAMPLE_RATES};
+use crate::mpeg::MpegVersion;
+use crate::probe::ParsingMode;
+
+use std::io::{Read, Seek, SeekFrom};
+
+// Used to compare the headers up to the home bit.
+// If they aren't equal, something is broken.
+pub(super) const HEADER_MASK: u32 = 0xFFFF_FFE0;
+
+#[derive(Copy, Clone)]
+pub(crate) struct ADTSHeader {
+	pub(crate) version: MpegVersion,
+	pub(crate) audio_object_ty: AudioObjectType,
+	pub(crate) sample_rate: u32,
+	pub(crate) channels: u8,
+	pub(crate) copyright: bool,
+	pub(crate) original: bool,
+	pub(crate) len: u16,
+	pub(crate) bitrate: u32,
+	pub(crate) bytes: [u8; 7],
+	pub(crate) has_crc: bool,
+}
+
+impl ADTSHeader {
+	pub(super) fn read<R>(reader: &mut R, _parse_mode: ParsingMode) -> Result<Option<Self>>
+	where
+		R: Read + Seek,
+	{
+		// The ADTS header consists of 7 bytes, or 9 bytes with a CRC
+		let mut needs_crc_skip = false;
+
+		// AAAAAAAA AAAABCCD EEFFFFGH HHIJKLMM MMMMMMMM MMMOOOOO OOOOOOPP (QQQQQQQQ QQQQQQQQ)
+		let mut header = [0; 7];
+		reader.read_exact(&mut header)?;
+
+		// Letter 	Length (bits) 	Description
+		// A 	    12 	Syncword, all bits must be set to 1.
+		// B 	    1 	MPEG Version, set to 0 for MPEG-4 and 1 for MPEG-2.
+		// C 	    2 	Layer, always set to 0.
+		// D 	    1 	Protection absence, set to 1 if there is no CRC and 0 if there is CRC.
+		// E 	    2 	Profile, the MPEG-4 Audio Object Type minus 1.
+		// F 	    4 	MPEG-4 Sampling Frequency Index (15 is forbidden).
+		// G 	    1 	Private bit, guaranteed never to be used by MPEG, set to 0 when encoding, ignore when decoding.
+		// H 	    3 	MPEG-4 Channel Configuration (in the case of 0, the channel configuration is sent via an inband PCE (Program Config Element)).
+		// I 	    1 	Originality, set to 1 to signal originality of the audio and 0 otherwise.
+		// J 	    1 	Home, set to 1 to signal home usage of the audio and 0 otherwise.
+		// K 	    1 	Copyright ID bit, the next bit of a centrally registered copyright identifier. This is transmitted by sliding over the bit-string in LSB-first order and putting the current bit value in this field and wrapping to start if reached end (circular buffer).
+		// L 	    1 	Copyright ID start, signals that this frame's Copyright ID bit is the first one by setting 1 and 0 otherwise.
+		// M 	    13 	Frame length, length of the ADTS frame including headers and CRC check.
+		// O 	    11 	Buffer fullness, states the bit-reservoir per frame.
+		// P 	    2 	Number of AAC frames (RDBs (Raw Data Blocks)) in ADTS frame minus 1. For maximum compatibility always use one AAC frame per ADTS frame.
+		// Q 	    16 	CRC check (as of ISO/IEC 11172-3, subclause 2.4.3.1), if Protection absent is 0.
+
+		// AAAABCCD
+		let byte2 = header[1];
+
+		let version = match (byte2 >> 3) & 0b1 {
+			0 => MpegVersion::V4,
+			1 => MpegVersion::V2,
+			_ => unreachable!(),
+		};
+
+		if byte2 & 0b1 == 0 {
+			needs_crc_skip = true;
+		}
+
+		// EEFFFFGH
+		let byte3 = header[2];
+
+		let audio_object_ty = match ((byte3 >> 6) & 0b11) + 1 {
+			1 => AudioObjectType::AacMain,
+			2 => AudioObjectType::AacLowComplexity,
+			3 => AudioObjectType::AacScalableSampleRate,
+			4 => AudioObjectType::AacLongTermPrediction,
+			_ => unreachable!(),
+		};
+
+		let sample_rate_idx = (byte3 >> 2) & 0b1111;
+		if sample_rate_idx == 15 {
+			// 15 is forbidden
+			decode_err!(@BAIL AAC, "File contains an invalid sample frequency index");
+		}
+
+		let sample_rate = SAMPLE_RATES[sample_rate_idx as usize];
+
+		// HHIJKLMM
+		let byte4 = header[3];
+
+		let channel_configuration = ((byte3 & 0b1) << 2) | ((byte4 >> 6) & 0b11);
+
+		let original = (byte4 >> 5) & 0b1 == 1;
+		let copyright = (byte4 >> 4) & 0b1 == 1;
+
+		// MMMMMMMM
+		let byte5 = header[4];
+
+		// MMMOOOOO
+		let byte6 = header[5];
+
+		let len = (u16::from(byte4 & 0b11) << 11) | u16::from(byte5) << 3 | u16::from(byte6) >> 5;
+		let bitrate = ((u32::from(len) * sample_rate / 1024) * 8) / 1024;
+
+		if needs_crc_skip {
+			reader.seek(SeekFrom::Current(2))?;
+		}
+
+		Ok(Some(ADTSHeader {
+			version,
+			audio_object_ty,
+			sample_rate,
+			channels: channel_configuration,
+			copyright,
+			original,
+			len,
+			bitrate,
+			bytes: header,
+			has_crc: needs_crc_skip,
+		}))
+	}
+}

src/aac/mod.rs

@@ -0,0 +1,30 @@
+//! AAC (ADTS) specific items
+
+// TODO: Currently we only support ADTS, might want to look into ADIF in the future.
+
+mod header;
+mod properties;
+mod read;
+
+use crate::id3::v1::tag::ID3v1Tag;
+use crate::id3::v2::tag::ID3v2Tag;
+
+use lofty_attr::LoftyFile;
+
+// Exports
+
+pub use properties::AACProperties;
+
+/// An AAC (ADTS) file
+#[derive(LoftyFile, Default)]
+#[lofty(read_fn = "read::read_from")]
+#[lofty(internal_write_module_do_not_use_anywhere_else)]
+pub struct AACFile {
+	#[cfg(feature = "id3v2")]
+	#[lofty(tag_type = "ID3v2")]
+	pub(crate) id3v2_tag: Option<ID3v2Tag>,
+	#[cfg(feature = "id3v1")]
+	#[lofty(tag_type = "ID3v1")]
+	pub(crate) id3v1_tag: Option<ID3v1Tag>,
+	pub(crate) properties: AACProperties,
+}

src/aac/properties.rs

@@ -0,0 +1,108 @@
+use crate::aac::header::ADTSHeader;
+use crate::mp4::AudioObjectType;
+use crate::mpeg::header::MpegVersion;
+use crate::properties::FileProperties;
+
+use std::time::Duration;
+
+/// An AAC file's audio properties
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct AACProperties {
+	pub(crate) version: MpegVersion,
+	pub(crate) audio_object_type: AudioObjectType,
+	pub(crate) duration: Duration,
+	pub(crate) overall_bitrate: u32,
+	pub(crate) audio_bitrate: u32,
+	pub(crate) sample_rate: u32,
+	pub(crate) channels: u8,
+	pub(crate) copyright: bool,
+	pub(crate) original: bool,
+}
+
+impl AACProperties {
+	/// MPEG version
+	pub fn version(&self) -> MpegVersion {
+		self.version
+	}
+
+	/// Audio object type
+	///
+	/// The only possible variants are:
+	///
+	/// * [AudioObjectType::AacMain]
+	/// * [AudioObjectType::AacLowComplexity]
+	/// * [AudioObjectType::AacScalableSampleRate]
+	/// * [AudioObjectType::AacLongTermPrediction]
+	pub fn audio_object_type(&self) -> AudioObjectType {
+		self.audio_object_type
+	}
+
+	/// Duration
+	pub fn duration(&self) -> Duration {
+		self.duration
+	}
+
+	/// Overall bitrate (kbps)
+	pub fn overall_bitrate(&self) -> u32 {
+		self.overall_bitrate
+	}
+
+	/// Audio bitrate (kbps)
+	pub fn audio_bitrate(&self) -> u32 {
+		self.audio_bitrate
+	}
+
+	/// Sample rate (Hz)
+	pub fn sample_rate(&self) -> u32 {
+		self.sample_rate
+	}
+
+	/// Channel count
+	pub fn channels(&self) -> u8 {
+		self.channels
+	}
+
+	/// Whether the audio is copyrighted
+	pub fn copyright(&self) -> bool {
+		self.copyright
+	}
+
+	/// Whether the media is original or a copy
+	pub fn original(&self) -> bool {
+		self.original
+	}
+}
+
+impl From<AACProperties> for FileProperties {
+	fn from(input: AACProperties) -> Self {
+		FileProperties {
+			duration: input.duration,
+			overall_bitrate: Some(input.overall_bitrate),
+			audio_bitrate: Some(input.audio_bitrate),
+			sample_rate: Some(input.sample_rate),
+			bit_depth: None,
+			channels: Some(input.channels),
+		}
+	}
+}
+
+pub(super) fn read_properties(
+	properties: &mut AACProperties,
+	first_frame: ADTSHeader,
+	stream_len: u64,
+) {
+	properties.version = first_frame.version;
+	properties.audio_object_type = first_frame.audio_object_ty;
+	properties.sample_rate = first_frame.sample_rate;
+	properties.channels = first_frame.channels;
+	properties.copyright = first_frame.copyright;
+	properties.original = first_frame.original;
+
+	let bitrate = first_frame.bitrate;
+
+	if bitrate > 0 {
+		properties.audio_bitrate = bitrate;
+		properties.overall_bitrate = bitrate;
+		properties.duration = Duration::from_millis((stream_len * 8) / u64::from(bitrate));
+	}
+}

src/aac/read.rs

@@ -0,0 +1,169 @@
+use super::header::{ADTSHeader, HEADER_MASK};
+use super::AACFile;
+use crate::error::Result;
+use crate::id3::v2::read::parse_id3v2;
+use crate::id3::v2::read_id3v2_header;
+use crate::id3::{find_id3v1, ID3FindResults};
+use crate::macros::{decode_err, parse_mode_choice};
+use crate::mpeg::header::{cmp_header, search_for_frame_sync, HeaderCmpResult};
+use crate::probe::{ParseOptions, ParsingMode};
+
+use std::io::{Read, Seek, SeekFrom};
+
+use byteorder::ReadBytesExt;
+
+#[allow(clippy::unnecessary_wraps)]
+pub(super) fn read_from<R>(reader: &mut R, parse_options: ParseOptions) -> Result<AACFile>
+where
+	R: Read + Seek,
+{
+	let parse_mode = parse_options.parsing_mode;
+
+	let mut file = AACFile::default();
+
+	let mut first_frame_header = None;
+	let mut first_frame_end = 0;
+
+	// Skip any invalid padding
+	while reader.read_u8()? == 0 {}
+
+	reader.seek(SeekFrom::Current(-1))?;
+
+	let pos = reader.stream_position()?;
+	let mut stream_len = reader.seek(SeekFrom::End(0))?;
+
+	reader.seek(SeekFrom::Start(pos))?;
+
+	let mut header = [0; 4];
+
+	while let Ok(()) = reader.read_exact(&mut header) {
+		match header {
+			// [I, D, 3, ver_major, ver_minor, flags, size (4 bytes)]
+			[b'I', b'D', b'3', ..] => {
+				// Seek back to read the tag in full
+				reader.seek(SeekFrom::Current(-4))?;
+
+				let header = read_id3v2_header(reader)?;
+				let skip_footer = header.flags.footer;
+
+				stream_len -= u64::from(header.size);
+
+				#[cfg(feature = "id3v2")]
+				{
+					let id3v2 = parse_id3v2(reader, header)?;
+					file.id3v2_tag = Some(id3v2);
+				}
+
+				// Skip over the footer
+				if skip_footer {
+					stream_len -= 10;
+					reader.seek(SeekFrom::Current(10))?;
+				}
+
+				continue;
+			},
+			// Tags might be followed by junk bytes before the first ADTS frame begins
+			_ => {
+				// Seek back the length of the temporary header buffer, to include them
+				// in the frame sync search
+				#[allow(clippy::neg_multiply)]
+				reader.seek(SeekFrom::Current(-1 * header.len() as i64))?;
+
+				if let Some((first_frame_header_, first_frame_end_)) =
+					find_next_frame(reader, parse_mode)?
+				{
+					first_frame_header = Some(first_frame_header_);
+					first_frame_end = first_frame_end_;
+					break;
+				}
+			},
+		}
+	}
+
+	#[allow(unused_variables)]
+	let ID3FindResults(header, id3v1) = find_id3v1(reader, true)?;
+
+	#[cfg(feature = "id3v1")]
+	if header.is_some() {
+		stream_len -= 128;
+		file.id3v1_tag = id3v1;
+	}
+
+	if parse_options.read_properties {
+		let mut first_frame_header = match first_frame_header {
+			Some(header) => header,
+			// The search for sync bits was unsuccessful
+			None => decode_err!(@BAIL MPEG, "File contains an invalid frame"),
+		};
+
+		if first_frame_header.sample_rate == 0 {
+			parse_mode_choice!(
+				parse_mode,
+				STRICT: decode_err!(@BAIL MPEG, "Sample rate is 0"),
+			);
+		}
+
+		if first_frame_header.bitrate == 0 {
+			parse_mode_choice!(parse_mode, STRICT: decode_err!(@BAIL MPEG, "Bitrate is 0"),);
+		}
+
+		// Read as many frames as we can to try and fine the average bitrate
+		reader.seek(SeekFrom::Start(first_frame_end))?;
+
+		let mut frame_count = 1;
+
+		while let Some((header, _)) = find_next_frame(reader, parse_mode)? {
+			first_frame_header.bitrate += header.bitrate;
+			frame_count += 1u32;
+		}
+
+		first_frame_header.bitrate /= frame_count;
+
+		super::properties::read_properties(&mut file.properties, first_frame_header, stream_len);
+	}
+
+	Ok(file)
+}
+
+// Searches for the next frame, comparing it to the following one
+fn find_next_frame<R>(
+	reader: &mut R,
+	parsing_mode: ParsingMode,
+) -> Result<Option<(ADTSHeader, u64)>>
+where
+	R: Read + Seek,
+{
+	let mut pos = reader.stream_position()?;
+
+	while let Ok(Some(first_adts_frame_start_relative)) = search_for_frame_sync(reader) {
+		let first_adts_frame_start_absolute = pos + first_adts_frame_start_relative;
+
+		// Seek back to the start of the frame and read the header
+		reader.seek(SeekFrom::Start(first_adts_frame_start_absolute))?;
+
+		if let Some(first_header) = ADTSHeader::read(reader, parsing_mode)? {
+			let header_len = if first_header.has_crc { 9 } else { 7 };
+
+			match cmp_header(
+				reader,
+				header_len,
+				u32::from(first_header.len),
+				u32::from_be_bytes(first_header.bytes[..4].try_into().unwrap()),
+				HEADER_MASK,
+			) {
+				HeaderCmpResult::Equal => {
+					return Ok(Some((
+						first_header,
+						first_adts_frame_start_absolute + u64::from(header_len),
+					)))
+				},
+				HeaderCmpResult::Undetermined => return Ok(None),
+				HeaderCmpResult::NotEqual => {},
+			}
+		}
+
+		pos = reader.stream_position()?;
+	}
+
+	Ok(None)
+}

src/file.rs

@@ -482,6 +482,7 @@ impl AudioFile for TaggedFile {
 #[non_exhaustive]
 /// The type of file read
 pub enum FileType {
+	AAC,
 	AIFF,
 	APE,
 	FLAC,
@@ -500,7 +501,7 @@ impl FileType {
 	///
 	/// | [`FileType`]                      | [`TagType`]      |
 	/// |-----------------------------------|------------------|
-	/// | `AIFF`, `MP3`, `WAV`              | `ID3v2`          |
+	/// | `AAC`, `AIFF`, `MP3`, `WAV`       | `ID3v2`          |
 	/// | `APE` , `WavPack`                 | `APE`            |
 	/// | `FLAC`, `Opus`, `Vorbis`, `Speex` | `VorbisComments` |
 	/// | `MP4`                             | `MP4ilst`        |
@@ -519,7 +520,7 @@ impl FileType {
 	/// ```
 	pub fn primary_tag_type(&self) -> TagType {
 		match self {
-			FileType::AIFF | FileType::MPEG | FileType::WAV => TagType::ID3v2,
+			FileType::AIFF | FileType::MPEG | FileType::WAV | FileType::AAC => TagType::ID3v2,
 			FileType::APE | FileType::WavPack => TagType::APE,
 			FileType::FLAC | FileType::Opus | FileType::Vorbis | FileType::Speex => {
 				TagType::VorbisComments
@@ -553,7 +554,7 @@ impl FileType {
 	pub fn supports_tag_type(&self, tag_type: TagType) -> bool {
 		match self {
 			#[cfg(feature = "id3v2")]
-			FileType::AIFF | FileType::APE | FileType::MPEG | FileType::WAV
+			FileType::AIFF | FileType::APE | FileType::MPEG | FileType::WAV | FileType::AAC
 				if tag_type == TagType::ID3v2 =>
 			{
 				true
@@ -561,7 +562,11 @@ impl FileType {
 			#[cfg(feature = "aiff_text_chunks")]
 			FileType::AIFF if tag_type == TagType::AIFFText => true,
 			#[cfg(feature = "id3v1")]
-			FileType::APE | FileType::MPEG | FileType::WavPack if tag_type == TagType::ID3v1 => true,
+			FileType::APE | FileType::MPEG | FileType::WavPack | FileType::AAC
+				if tag_type == TagType::ID3v1 =>
+			{
+				true
+			},
 			#[cfg(feature = "ape")]
 			FileType::APE | FileType::MPEG | FileType::WavPack if tag_type == TagType::APE => true,
 			#[cfg(feature = "vorbis_comments")]
@@ -597,6 +602,7 @@ impl FileType {
 		let ext = ext.as_ref().to_str()?.to_ascii_lowercase();
 
 		match ext.as_str() {
+			"aac" => Some(Self::AAC),
 			"ape" => Some(Self::APE),
 			"aiff" | "aif" | "afc" | "aifc" => Some(Self::AIFF),
 			"mp3" | "mp2" | "mp1" => Some(Self::MPEG),
@@ -716,7 +722,40 @@ impl FileType {
 		// Safe to index, since we return early on an empty buffer
 		match buf[0] {
 			77 if buf.starts_with(b"MAC") => Some(Self::APE),
-			255 if buf.len() >= 2 && verify_frame_sync([buf[0], buf[1]]) => Some(Self::MPEG),
+			255 if buf.len() >= 2 && verify_frame_sync([buf[0], buf[1]]) => {
+				// ADTS and MPEG frame headers are way too similar
+
+				// ADTS (https://wiki.multimedia.cx/index.php/ADTS#Header):
+				//
+				// AAAAAAAA AAAABCCX
+				//
+				// Letter 	Length (bits) 	Description
+				// A 	    12 	            Syncword, all bits must be set to 1.
+				// B 	    1 	            MPEG Version, set to 0 for MPEG-4 and 1 for MPEG-2.
+				// C 	    2 	            Layer, always set to 0.
+
+				// MPEG (http://www.mp3-tech.org/programmer/frame_header.html):
+				//
+				// AAAAAAAA AAABBCCX
+				//
+				// Letter 	Length (bits) 	Description
+				// A 	    11              Syncword, all bits must be set to 1.
+				// B 	    2 	            MPEG Audio version ID
+				// C 	    2 	            Layer description
+
+				// The subtle overlap in the ADTS header's frame sync and MPEG's version ID
+				// is the first condition to check. However, since 0b10 and 0b11 are valid versions
+				// in MPEG, we have to also check the layer.
+
+				// So, if we have a version 1 (0b11) or version 2 (0b10) MPEG frame AND a layer of 0b00,
+				// we can assume we have an ADTS header. Awesome!
+
+				if buf[1] & 0b10000 > 0 && buf[1] & 0b110 == 0 {
+					return Some(Self::AAC);
+				}
+
+				Some(Self::MPEG)
+			},
 			70 if buf.len() >= 12 && &buf[..4] == b"FORM" => {
 				let id = &buf[8..12];
 

src/id3/v1/tag.rs

@@ -47,7 +47,10 @@ macro_rules! impl_accessor {
 /// * [`GENRES`] contains the string
 /// * The [`ItemValue`](crate::ItemValue) can be parsed into a `u8`
 #[derive(Default, Debug, PartialEq, Eq, Clone)]
-#[tag(description = "An ID3v1 tag", supported_formats(APE, MPEG, WavPack))]
+#[tag(
+	description = "An ID3v1 tag",
+	supported_formats(AAC, APE, MPEG, WavPack)
+)]
 pub struct ID3v1Tag {
 	/// Track title, 30 bytes max
 	pub title: Option<String>,

src/id3/v2/tag.rs

@@ -92,7 +92,7 @@ macro_rules! impl_accessor {
 #[derive(PartialEq, Eq, Debug, Clone)]
 #[tag(
 	description = "An `ID3v2` tag",
-	supported_formats(AIFF, MPEG, WAV, read_only(FLAC, APE))
+	supported_formats(AAC, AIFF, MPEG, WAV, read_only(FLAC, APE))
 )]
 pub struct ID3v2Tag {
 	flags: ID3v2TagFlags,

src/id3/v2/write/mod.rs

@@ -8,6 +8,7 @@ use crate::id3::find_id3v2;
 use crate::id3::v2::frame::FrameRef;
 use crate::id3::v2::tag::Id3v2TagRef;
 use crate::id3::v2::util::synch_u32;
+use crate::id3::v2::ID3v2Tag;
 use crate::macros::err;
 use crate::probe::Probe;
 
@@ -15,7 +16,6 @@ use std::fs::File;
 use std::io::{Cursor, Read, Seek, SeekFrom, Write};
 use std::ops::Not;
 
-use crate::id3::v2::ID3v2Tag;
 use byteorder::{BigEndian, LittleEndian, WriteBytesExt};
 
 // In the very rare chance someone wants to write a CRC in their extended header

src/lib.rs

@@ -166,6 +166,7 @@
 extern crate self as lofty;
 pub(crate) mod _this_is_internal {}
 
+pub mod aac;
 pub mod ape;
 pub mod error;
 pub(crate) mod file;

src/mp4/mod.rs

@@ -31,6 +31,8 @@ cfg_if::cfg_if! {
 
 pub use crate::mp4::properties::{AudioObjectType, Mp4Codec, Mp4Properties};
 
+pub(crate) use properties::SAMPLE_RATES;
+
 /// An MP4 file
 #[derive(LoftyFile)]
 #[lofty(read_fn = "read::read_from")]

src/mp4/properties.rs

@@ -360,6 +360,11 @@ where
 	Ok(properties)
 }
 
+// https://wiki.multimedia.cx/index.php?title=MPEG-4_Audio#Sampling_Frequencies
+pub(crate) const SAMPLE_RATES: [u32; 15] = [
+	96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350, 0, 0,
+];
+
 fn mp4a_properties<R>(stsd: &mut AtomReader<R>, properties: &mut Mp4Properties) -> Result<()>
 where
 	R: Read + Seek,
@@ -368,12 +373,6 @@ where
 	const DECODER_CONFIG_TAG: u8 = 0x04;
 	const DECODER_SPECIFIC_DESCRIPTOR_TAG: u8 = 0x05;
 
-	// https://wiki.multimedia.cx/index.php?title=MPEG-4_Audio#Sampling_Frequencies
-	const SAMPLE_RATES: [u32; 15] = [
-		96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350, 0,
-		0,
-	];
-
 	// Set the codec to AAC, which is a good guess if we fail before reaching the `esds`
 	properties.codec = Mp4Codec::AAC;
 

src/mpeg/header.rs

@@ -70,39 +70,49 @@ where
 	ret
 }
 
-pub(super) enum HeaderCmpResult {
+pub(crate) enum HeaderCmpResult {
 	Equal,
 	Undetermined,
 	NotEqual,
 }
 
-pub(super) fn cmp_header<R>(
+// Used to compare the versions, layers, and sample rates of two frame headers.
+// If they aren't equal, something is broken.
+pub(super) const HEADER_MASK: u32 = 0xFFFE_0C00;
+
+pub(crate) fn cmp_header<R>(
 	reader: &mut R,
+	header_size: u32,
 	first_header_len: u32,
 	first_header_bytes: u32,
+	header_mask: u32,
 ) -> HeaderCmpResult
 where
 	R: Read + Seek,
 {
-	// Used to compare the versions, layers, and sample rates of two frame headers.
-	// If they aren't equal, something is broken.
-	const HEADER_MASK: u32 = 0xFFFE_0C00;
-
 	// Read the next header and see if they are the same
 	let res = reader.seek(SeekFrom::Current(i64::from(
-		first_header_len.saturating_sub(4),
+		first_header_len.saturating_sub(header_size),
 	)));
 	if res.is_err() {
 		return HeaderCmpResult::Undetermined;
 	}
 
-	match reader.read_u32::<BigEndian>() {
+	let second_header_data = reader.read_u32::<BigEndian>();
+	if second_header_data.is_err() {
+		return HeaderCmpResult::Undetermined;
+	}
+
+	if reader.seek(SeekFrom::Current(-4)).is_err() {
+		return HeaderCmpResult::Undetermined;
+	}
+
+	match second_header_data {
 		Ok(second_header_data)
-			if first_header_bytes & HEADER_MASK == second_header_data & HEADER_MASK =>
+			if first_header_bytes & header_mask == second_header_data & header_mask =>
 		{
 			HeaderCmpResult::Equal
 		},
-		Err(_) => HeaderCmpResult::Undetermined,
 		_ => HeaderCmpResult::NotEqual,
 	}
 }
@@ -114,6 +124,8 @@ pub enum MpegVersion {
 	V1,
 	V2,
 	V2_5,
+	/// Exclusive to AAC
+	V4,
 }
 
 impl Default for MpegVersion {

src/mpeg/properties.rs

@@ -1,6 +1,6 @@
 use super::header::{ChannelMode, Emphasis, Header, Layer, MpegVersion, XingHeader};
 use crate::error::Result;
-use crate::mpeg::header::{cmp_header, rev_search_for_frame_sync, HeaderCmpResult};
+use crate::mpeg::header::{cmp_header, rev_search_for_frame_sync, HeaderCmpResult, HEADER_MASK};
 use crate::properties::FileProperties;
 
 use std::io::{Read, Seek, SeekFrom};
@@ -156,7 +156,13 @@ where
 						let last_frame_data = reader.read_u32::<BigEndian>()?;
 
 						if let Some(last_frame_header) = Header::read(last_frame_data) {
-							match cmp_header(reader, last_frame_header.len, last_frame_data) {
+							match cmp_header(
+								reader,
+								4,
+								last_frame_header.len,
+								last_frame_data,
+								HEADER_MASK,
+							) {
 								HeaderCmpResult::Equal | HeaderCmpResult::Undetermined => {
 									last_frame = Some(last_frame_header);
 									break;

src/mpeg/read.rs

@@ -10,6 +10,7 @@ use crate::id3::v2::read::parse_id3v2;
 use crate::id3::v2::read_id3v2_header;
 use crate::id3::{find_id3v1, find_lyrics3v2, ID3FindResults};
 use crate::macros::{decode_err, err};
+use crate::mpeg::header::HEADER_MASK;
 use crate::probe::ParseOptions;
 
 use std::io::{Read, Seek, SeekFrom};
@@ -187,7 +188,7 @@ where
 		let first_header_data = reader.read_u32::<BigEndian>()?;
 
 		if let Some(first_header) = Header::read(first_header_data) {
-			match cmp_header(reader, first_header.len, first_header_data) {
+			match cmp_header(reader, 4, first_header.len, first_header_data, HEADER_MASK) {
 				HeaderCmpResult::Equal => {
 					return Ok(Some((first_header, first_mp3_frame_start_absolute)))
 				},

src/probe.rs

@@ -1,3 +1,4 @@
+use crate::aac::AACFile;
 use crate::ape::ApeFile;
 use crate::error::Result;
 use crate::file::{AudioFile, FileType, TaggedFile};
@@ -432,7 +433,18 @@ impl<R: Read + Seek> Probe<R> {
 					b"fLaC" => Ok(Some(FileType::FLAC)),
 					// Search for a frame sync, which may be preceded by junk
 					_ if search_for_frame_sync(&mut self.inner)?.is_some() => {
-						Ok(Some(FileType::MPEG))
+						// Seek back to the start of the frame sync to check if we are dealing with
+						// an AAC or MPEG file. See `FileType::quick_type_guess` for explanation.
+						self.inner.seek(SeekFrom::Current(-2))?;
+
+						let mut buf = [0; 2];
+						self.inner.read_exact(&mut buf)?;
+
+						if buf[1] & 0b10000 > 0 && buf[1] & 0b110 == 0 {
+							Ok(Some(FileType::AAC))
+						} else {
+							Ok(Some(FileType::MPEG))
+						}
 					},
 					_ => Ok(None),
 				};
@@ -493,6 +505,7 @@ impl<R: Read + Seek> Probe<R> {
 
 		match self.f_ty {
 			Some(f_type) => Ok(match f_type {
+				FileType::AAC => AACFile::read_from(reader, options)?.into(),
 				FileType::AIFF => AiffFile::read_from(reader, options)?.into(),
 				FileType::APE => ApeFile::read_from(reader, options)?.into(),
 				FileType::FLAC => FlacFile::read_from(reader, options)?.into(),
@@ -621,6 +634,16 @@ mod tests {
 		assert_eq!(probe.file_type(), Some(expected_file_type_guess));
 	}
 
+	#[test]
+	fn probe_aac() {
+		test_probe("tests/files/assets/minimal/untagged.aac", FileType::AAC);
+	}
+
+	#[test]
+	fn probe_aac_with_id3v2() {
+		test_probe("tests/files/assets/minimal/full_test.aac", FileType::AAC);
+	}
+
 	#[test]
 	fn probe_aiff() {
 		test_probe("tests/files/assets/minimal/full_test.aiff", FileType::AIFF);

src/properties.rs

@@ -78,6 +78,7 @@ impl FileProperties {
 
 #[cfg(test)]
 mod tests {
+	use crate::aac::{AACFile, AACProperties};
 	use crate::ape::{ApeFile, ApeProperties};
 	use crate::flac::FlacFile;
 	use crate::iff::aiff::AiffFile;
@@ -98,6 +99,18 @@ mod tests {
 	// There is a chance they will be +/- 1, anything greater (for real world files)
 	// is an issue.
 
+	const AAC_PROPERTIES: AACProperties = AACProperties {
+		version: MpegVersion::V4,
+		audio_object_type: AudioObjectType::AacLowComplexity,
+		duration: Duration::from_millis(1474), /* TODO: This is ~100ms greater than FFmpeg's report, can we do better? */
+		overall_bitrate: 117,                  // 9 less than FFmpeg reports
+		audio_bitrate: 117,                    // 9 less than FFmpeg reports
+		sample_rate: 48000,
+		channels: 2,
+		copyright: false,
+		original: false,
+	};
+
 	const AIFF_PROPERTIES: FileProperties = FileProperties {
 		duration: Duration::from_millis(1428),
 		overall_bitrate: Some(1542),
@@ -281,6 +294,14 @@ mod tests {
 		audio_file.properties().clone()
 	}
 
+	#[test]
+	fn aac_properties() {
+		assert_eq!(
+			get_properties::<AACFile>("tests/files/assets/minimal/full_test.aac"),
+			AAC_PROPERTIES
+		);
+	}
+
 	#[test]
 	fn aiff_properties() {
 		assert_eq!(

src/tag/utils.rs

@@ -2,7 +2,7 @@ use crate::error::Result;
 use crate::file::FileType;
 use crate::macros::err;
 use crate::tag::{Tag, TagType};
-use crate::{ape, flac, iff, mpeg, wavpack};
+use crate::{aac, ape, flac, iff, mpeg, wavpack};
 
 #[cfg(feature = "id3v1")]
 use crate::id3::v1::tag::Id3v1TagRef;
@@ -25,6 +25,7 @@ use std::io::Write;
 #[allow(unreachable_patterns)]
 pub(crate) fn write_tag(tag: &Tag, file: &mut File, file_type: FileType) -> Result<()> {
 	match file_type {
+		FileType::AAC => aac::write::write_to(file, tag),
 		FileType::AIFF => iff::aiff::write::write_to(file, tag),
 		FileType::APE => ape::write::write_to(file, tag),
 		FileType::FLAC => flac::write::write_to(file, tag),

tests/files/aac.rs

@@ -0,0 +1,95 @@
+use crate::{set_artist, temp_file, verify_artist};
+use lofty::{
+	Accessor, FileType, ItemKey, ItemValue, ParseOptions, Probe, TagExt, TagItem, TagType,
+};
+use std::io::{Seek, Write};
+
+#[test]
+fn read() {
+	// Here we have an AAC file with an ID3v2, and an ID3v1 tag
+	let file = Probe::open("tests/files/assets/minimal/full_test.aac")
+		.unwrap()
+		.options(ParseOptions::new().read_properties(false))
+		.read()
+		.unwrap();
+
+	assert_eq!(file.file_type(), FileType::AAC);
+
+	// Verify the ID3v2 tag first
+	crate::verify_artist!(file, primary_tag, "Foo artist", 1);
+
+	// Now verify ID3v1
+	crate::verify_artist!(file, tag, TagType::ID3v1, "Bar artist", 1);
+}
+
+#[test]
+fn read_with_junk_bytes_between_frames() {
+	// Read a file that includes an ID3v2.3 data block followed by four bytes of junk data (0x20)
+
+	// This is the same test as MP3, but it uses the same byte skipping logic, so it should be tested
+	// here too :).
+	let file = Probe::open("tests/files/assets/junk_between_id3_and_adts.aac")
+		.unwrap()
+		.read()
+		.unwrap();
+
+	// note that the file contains ID3v2 and ID3v1 data
+	assert_eq!(file.file_type(), FileType::AAC);
+
+	let id3v2_tag = &file.tags()[0];
+	assert_eq!(id3v2_tag.artist(), Some("artist test"));
+	assert_eq!(id3v2_tag.album(), Some("album test"));
+	assert_eq!(id3v2_tag.title(), Some("title test"));
+	assert_eq!(
+		id3v2_tag.get_string(&ItemKey::EncoderSettings),
+		Some("Lavf58.62.100")
+	);
+
+	let id3v1_tag = &file.tags()[1];
+	assert_eq!(id3v1_tag.artist(), Some("artist test"));
+	assert_eq!(id3v1_tag.album(), Some("album test"));
+	assert_eq!(id3v1_tag.title(), Some("title test"));
+}
+
+#[test]
+fn write() {
+	let mut file = temp_file!("tests/files/assets/minimal/full_test.aac");
+
+	let mut tagged_file = Probe::new(&mut file)
+		.options(ParseOptions::new().read_properties(false))
+		.guess_file_type()
+		.unwrap()
+		.read()
+		.unwrap();
+
+	assert_eq!(tagged_file.file_type(), FileType::AAC);
+
+	// ID3v2
+	crate::set_artist!(tagged_file, primary_tag_mut, "Foo artist", 1 => file, "Bar artist");
+
+	// ID3v1
+	crate::set_artist!(tagged_file, tag_mut, TagType::ID3v1, "Bar artist", 1 => file, "Baz artist");
+
+	// Now reread the file
+	file.rewind().unwrap();
+	let mut tagged_file = Probe::new(&mut file)
+		.options(ParseOptions::new().read_properties(false))
+		.guess_file_type()
+		.unwrap()
+		.read()
+		.unwrap();
+
+	crate::set_artist!(tagged_file, primary_tag_mut, "Bar artist", 1 => file, "Foo artist");
+
+	crate::set_artist!(tagged_file, tag_mut, TagType::ID3v1, "Baz artist", 1 => file, "Bar artist");
+}
+
+#[test]
+fn remove_id3v2() {
+	crate::remove_tag!("tests/files/assets/minimal/full_test.aac", TagType::ID3v2);
+}
+
+#[test]
+fn remove_id3v1() {
+	crate::remove_tag!("tests/files/assets/minimal/full_test.aac", TagType::ID3v1);
+}

tests/files/main.rs

@@ -1,3 +1,4 @@
+mod aac;
 mod aiff;
 mod ape;
 mod mp4;