Add documentation and tests for xact3::adpcm
This also renames variables to be easier to understand (rather than copying the naming scheme of the spec) and moves the calculation of computable fields in the wave format header into the adpcm module.master
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f9c0140100
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@ -1,2 +1,6 @@
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/// Module for writing raw ADPCM data to a RIFF WAVE file.
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///
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/// The WAVE format for ADPCM is specified in the [Microsoft Multimedia Standards Update from 15
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/// April 1994](https://web.archive.org/web/20120917060438if_/http://download.microsoft.com/download/9/8/6/9863C72A-A3AA-4DDB-B1BA-CA8D17EFD2D4/RIFFNEW.pdf).
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mod adpcm;
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pub mod xwb;
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@ -5,6 +5,7 @@ use byteorder::{WriteBytesExt, LE};
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use log::{debug, trace};
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use thiserror::Error;
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/// Standard ADPCM coefficients
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#[rustfmt::skip]
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const COEFFS: &[CoefSet] = &[
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(256, 0),
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@ -18,27 +19,41 @@ const COEFFS: &[CoefSet] = &[
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#[derive(Debug, Error)]
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pub enum Error {
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#[error("unable to create file of size {0} (larger than 2^32)")]
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TooLarge(usize),
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/// WAVE only supports file sizes up to 2<sup>32</sup> bytes (2<sup>32</sup> - 82 bytes of
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/// usable audio data in this case).
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#[error("unable to create file of size {0} (larger than 2^32 - 82 bytes)")]
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TooLargeError(usize),
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}
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/// All wave chunks implement this trait.
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trait WaveChunk {
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/// Serialize to byte vector that is used as a part of the resulting wave file.
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fn to_chunk(&self) -> Vec<u8>;
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}
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/// One set of ADPCM coefficients
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type CoefSet = (i16, i16);
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/// `WAVE_FORMAT_ADPCM` header.
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///
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/// It only includes fields that are usful for usage in conjunction with XACT3. The other fields
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/// are static and defined in the [`to_chunk`] method of this type.
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///
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/// [`to_chunk`]: trait.WaveChunk.html#tymethod.to_chunk
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pub struct WaveFormat {
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// w_format_tag = 2
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pub n_channels: u16,
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pub n_samples_per_sec: u32,
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pub n_avg_bytes_per_sec: u32,
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pub n_block_align: u16,
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// w_bits_per_sample = 4
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// cb_size = 32
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pub n_samples_per_block: u16,
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// w_num_coeff = 7
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// a_coeff = COEFFS
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// wFormatTag = 2
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/// `nChannels`: Number of channels
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pub channels: u16,
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/// `nSamplesPerSec`: Sample rate
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pub sample_rate: u32,
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// nAvgBytesPerSec (calculated),
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/// `nBlockAlign`: Block alignment (in bytes)
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pub block_align: u16,
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// wBitsPerSample = 4
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// cbSize = 32
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// nSamplesPerBlock (calculated)
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// nNumCoeff = 7
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// aCoeff = COEFFS
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}
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impl WaveChunk for WaveFormat {
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@ -48,14 +63,15 @@ impl WaveChunk for WaveFormat {
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buf.write_u32::<LE>(2 + 2 + 4 + 4 + 2 + 2 + 2 + 2 + 2 + 4 * COEFFS.len() as u32)
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.unwrap();
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buf.write_u16::<LE>(2).unwrap(); // WAVE_FORMAT_ADPCM
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buf.write_u16::<LE>(self.n_channels).unwrap();
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buf.write_u32::<LE>(self.n_samples_per_sec).unwrap();
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buf.write_u32::<LE>(self.n_avg_bytes_per_sec).unwrap();
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buf.write_u16::<LE>(self.n_block_align).unwrap();
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buf.write_u16::<LE>(self.channels).unwrap();
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buf.write_u32::<LE>(self.sample_rate).unwrap();
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buf.write_u32::<LE>(self.avg_bytes_per_sec()).unwrap(); // nAvgBytesPerSec
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buf.write_u16::<LE>(self.block_align).unwrap();
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buf.write_u16::<LE>(4).unwrap(); // wBitsPerSample
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buf.write_u16::<LE>(32).unwrap(); // cbSize
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buf.write_u16::<LE>(self.n_samples_per_block).unwrap();
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buf.write_u16::<LE>(7).unwrap(); // wNumCoeff
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buf.write_u16::<LE>(self.samples_per_block()).unwrap();
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buf.write_u16::<LE>(COEFFS.len().try_into().unwrap())
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.unwrap(); // nNumCoeff
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for coef_set in COEFFS {
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buf.write_i16::<LE>(coef_set.0).unwrap();
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buf.write_i16::<LE>(coef_set.1).unwrap();
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@ -64,7 +80,21 @@ impl WaveChunk for WaveFormat {
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}
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}
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impl WaveFormat {
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/// Calculate `nSamplesPerBlock`
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fn samples_per_block(&self) -> u16 {
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(((self.block_align - (7 * self.channels)) * 8) / (4 * self.channels)) + 2
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}
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/// Calculate `nAvgBytesPerSec`
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fn avg_bytes_per_sec(&self) -> u32 {
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(self.sample_rate / u32::from(self.samples_per_block())) * u32::from(self.block_align)
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}
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}
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/// Wave fact chunk
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struct WaveFact {
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/// The length of the audio data in samples
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length_samples: u32,
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}
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@ -72,13 +102,15 @@ impl WaveChunk for WaveFact {
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fn to_chunk(&self) -> Vec<u8> {
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let mut buf = Cursor::new(Vec::new());
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write!(buf, "fact").unwrap();
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buf.write_u32::<LE>(4).unwrap();
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buf.write_u32::<LE>(4).unwrap(); // length of fact chunk
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buf.write_u32::<LE>(self.length_samples).unwrap();
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buf.into_inner()
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}
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}
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/// RIFF header chunk
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struct RIFFHeader {
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/// Size of the file minus 8 bytes (`RIFF` magic number and the file size)
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file_size: u32,
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}
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@ -92,22 +124,30 @@ impl WaveChunk for RIFFHeader {
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}
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}
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/// Builds wave data from a given [`WaveFormat`] and raw ADPCM data.
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///
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/// # Errors
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///
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/// This function returns a [`TooLargeError`] when the length of `data` is greater than or equal to 2<sup>32</sup> - 82
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///
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/// [`WaveFormat`]: struct.WaveFormat.html
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/// [`TooLargeError`]: enum.Error.html#variant.TooLargeError
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pub fn build_wav(format: WaveFormat, data: &[u8]) -> Result<Vec<u8>, Error> {
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debug!("Building file");
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let length: u32 = data
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.len()
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.try_into()
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.map_err(|_| Error::TooLarge(data.len()))?;
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// returning `u32::MAX` will make the next check fail
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let length: u32 = data.len().try_into().unwrap_or(u32::MAX);
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let riff_header = RIFFHeader {
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file_size: 82 + length,
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file_size: length
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.checked_add(82)
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.ok_or_else(|| Error::TooLargeError(data.len()))?,
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};
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let fact = WaveFact {
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length_samples: ((length / u32::from(format.n_block_align))
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* u32::from((format.n_block_align - (7 * format.n_channels)) * 8)
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length_samples: ((length / u32::from(format.block_align))
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* u32::from((format.block_align - (7 * format.channels)) * 8)
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/ 4)
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/ u32::from(format.n_channels),
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/ u32::from(format.channels),
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};
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let mut buf = Cursor::new(Vec::new());
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@ -125,3 +165,70 @@ pub fn build_wav(format: WaveFormat, data: &[u8]) -> Result<Vec<u8>, Error> {
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Ok(buf.into_inner())
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_riff_header_to_chunk() {
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assert_eq!(
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RIFFHeader { file_size: 12345 }.to_chunk(),
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b"RIFF\x39\x30\x00\x00WAVE"
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);
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}
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#[test]
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fn test_wave_fact_to_chunk() {
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assert_eq!(
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WaveFact {
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length_samples: 12345
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}
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.to_chunk(),
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b"fact\x04\x00\x00\x00\x39\x30\x00\x00"
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);
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}
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#[test]
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fn test_wave_format_to_chunk() {
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assert_eq!(
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WaveFormat {
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channels: 2,
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sample_rate: 44100,
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block_align: 140,
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}
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.to_chunk(),
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vec![
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0x66, 0x6d, 0x74, 0x20, 0x32, 0x00, 0x00, 0x00, 0x02, 0x00, 0x02, 0x00, 0x44, 0xac,
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0x00, 0x00, 0x20, 0xbc, 0x00, 0x00, 0x8c, 0x00, 0x04, 0x00, 0x20, 0x00, 0x80, 0x00,
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0x07, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00,
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0xc0, 0x00, 0x40, 0x00, 0xf0, 0x00, 0x00, 0x00, 0xcc, 0x01, 0x30, 0xff, 0x88, 0x01,
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0x18, 0xff
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]
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);
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}
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#[test]
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fn test_build_wav() {
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let built_wav = build_wav(
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WaveFormat {
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channels: 2,
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sample_rate: 44100,
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block_align: 140,
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},
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b"data",
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);
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assert_eq!(
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built_wav.unwrap(),
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vec![
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0x52, 0x49, 0x46, 0x46, 0x56, 0x00, 0x00, 0x00, 0x57, 0x41, 0x56, 0x45, 0x66, 0x6d,
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0x74, 0x20, 0x32, 0x00, 0x00, 0x00, 0x02, 0x00, 0x02, 0x00, 0x44, 0xac, 0x00, 0x00,
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0x20, 0xbc, 0x00, 0x00, 0x8c, 0x00, 0x04, 0x00, 0x20, 0x00, 0x80, 0x00, 0x07, 0x00,
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0x00, 0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x00,
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0x40, 0x00, 0xf0, 0x00, 0x00, 0x00, 0xcc, 0x01, 0x30, 0xff, 0x88, 0x01, 0x18, 0xff,
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0x66, 0x61, 0x63, 0x74, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64, 0x61,
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0x74, 0x61, 0x04, 0x00, 0x00, 0x00, 0x64, 0x61, 0x74, 0x61
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]
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);
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}
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}
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@ -65,18 +65,12 @@ impl TryInto<adpcm::WaveFormat> for Format {
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return Err(Error::UnsupportedFormat(self.tag));
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}
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let n_block_align = (u16::from(self.alignment) + 22) * self.channels;
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let n_samples_per_block =
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(((n_block_align - (7 * self.channels)) * 8) / (4 * self.channels)) + 2;
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let n_avg_bytes_per_sec =
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(self.sample_rate / u32::from(n_samples_per_block)) * u32::from(n_block_align);
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let block_align = (u16::from(self.alignment) + 22) * self.channels;
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Ok(adpcm::WaveFormat {
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n_channels: self.channels,
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n_samples_per_sec: self.sample_rate,
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n_avg_bytes_per_sec,
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n_block_align,
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n_samples_per_block,
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channels: self.channels,
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sample_rate: self.sample_rate,
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block_align,
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})
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}
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}
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