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0000000..6e7bd46 --- /dev/null +++ b/rust/minimqa/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "minimqa" +version = "0.1.0" +edition = "2021" + +[dependencies] +bitstream-io = "2.5.3" +clap = { version = "4.5.20", features = ["derive"] } +color-eyre = { version = "0.6.3", default-features = false } +env_logger = "0.11.5" +log = "0.4.22" +symphonia = { version = "0.5.4", default-features = false, features = ["flac", "pcm", "wav"] } diff --git a/rust/minimqa/src/main.rs b/rust/minimqa/src/main.rs new file mode 100644 index 0000000..56b4472 --- /dev/null +++ b/rust/minimqa/src/main.rs @@ -0,0 +1,161 @@ +use std::{ + collections::VecDeque, + fs::File, + io::Read, + path::{Path, PathBuf}, +}; + +use clap::Parser; +use color_eyre::eyre::{self, OptionExt}; +use symphonia::core::{ + audio::{Channels, SampleBuffer}, + codecs::{Decoder, DecoderOptions}, + formats::FormatReader, + io::MediaSourceStream, +}; + +/// Full 40-bit synchronization, including the packet type and 36-bit magic. +/// Stored as msb-first for easy searching, though MQA packets are lsb-first +const SYNC: u64 = 0xabe0498c88; + +#[derive(Parser)] +#[command(version, about)] +struct Args { + /// Input file + #[arg(short, long)] + input: PathBuf, +} + +fn main() -> eyre::Result<()> { + env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("info")).init(); + color_eyre::install()?; + + let args = Args::parse(); + let reader = MQAReader::open(&args.input)?; + + Ok(()) +} + +pub struct MQAReader { + decoder: Box, + format: Box, + track_id: u32, + + shift: u32, + + decoded: VecDeque, + remaining_bits: u8, + num_remaining_bits: u8, +} + +impl MQAReader { + pub fn open(filename: &Path) -> eyre::Result { + let input_file = Box::new(File::open(filename)?); + let mss = MediaSourceStream::new(input_file, Default::default()); + let probed = symphonia::default::get_probe().format( + &Default::default(), + mss, + &Default::default(), + &Default::default(), + )?; + let format = probed.format; + let track = format + .default_track() + .ok_or_eyre("No default track in file")?; + let track_id = track.id; + let decoder = symphonia::default::get_codecs() + .make(&track.codec_params, &DecoderOptions { verify: true })?; + + let mut result = Self { + decoder, + format, + track_id, + shift: u32::MAX, + decoded: VecDeque::new(), + remaining_bits: 0, + num_remaining_bits: 0, + }; + + let first_packet = result.read_packet_interleaved()?; + let (shift, offset) = + Self::find_sync(first_packet.samples()).ok_or_eyre("No sync packet")?; + log::info!("Found MQA sync at shift {}, offset {}", shift, offset); + + result.shift = shift; + result.decode_interleaved(&first_packet.samples()[offset * 2..]); + + Ok(result) + } + + fn read_packet_interleaved(&mut self) -> eyre::Result> { + loop { + let packet = self.format.next_packet()?; + if packet.track_id() != self.track_id { + continue; + } + let audio_buf = self.decoder.decode(&packet)?; + let spec = audio_buf.spec(); + if spec.channels != Channels::FRONT_LEFT | Channels::FRONT_RIGHT { + eyre::bail!("MQA only supports stereo"); + } + + let mut sample_buf = SampleBuffer::new(audio_buf.capacity() as u64, *spec); + sample_buf.copy_interleaved_ref(audio_buf); + + return Ok(sample_buf); + } + } + + fn decode_interleaved(&mut self, sample_buf: &[u32]) { + self.decoded.reserve(sample_buf.len() / 16); + + let mut accumulator = self.remaining_bits; + let mut num_bits_used = self.num_remaining_bits; + + for pair in sample_buf.chunks_exact(2) { + let bit = (((pair[0] ^ pair[1]) >> self.shift) & 1) as u8; + accumulator = accumulator << 1 | bit; + num_bits_used += 1; + if num_bits_used == 8 { + self.decoded.push_back(accumulator); + num_bits_used = 0; + accumulator = 0; + } + } + self.remaining_bits = accumulator; + self.num_remaining_bits = num_bits_used; + } + + fn find_sync(samples: &[u32]) -> Option<(u32, usize)> { + for shift in 8u32..24 { + let mut accumulator: u64 = 0; + for (idx, pair) in samples.chunks_exact(2).enumerate() { + let bit = (((pair[0] ^ pair[1]) >> shift) & 1) as u64; + accumulator = (accumulator << 1 | bit) & 0xff_ffff_ffff; + + if accumulator == SYNC { + return Some((shift, idx - 39)); + } + } + } + + None + } +} + +impl Read for MQAReader { + fn read(&mut self, buf: &mut [u8]) -> std::io::Result { + while self.decoded.len() < buf.len() { + let Ok(sample_buf) = self.read_packet_interleaved() else { + break; + }; + self.decode_interleaved(sample_buf.samples()); + } + let copy_size = buf.len().min(self.decoded.len()); + for item in buf.iter_mut().take(copy_size) { + *item = self.decoded.pop_front().unwrap(); + } + + Ok(copy_size) + } +}