Merge pull request #44 from AkiyukiOkayasu/develop

Rewrite comments in English

src/imaadpcm.rs

@@ -107,15 +107,15 @@ fn decode_sample(
     (predicted_sample, step_size_table_index)
 }
 
-/// step_sizeの更新
+/// Update step_size of IMA-ADPCM table
 fn compute_step_size(nibble: u4, mut step_size_table_index: i8) -> i8 {
     // adjust index into step_size lookup table using original_sample
     step_size_table_index += INDEX_TABLE[nibble.value() as usize];
     step_size_table_index = step_size_table_index.clamp(0, 88); //check overflow and underflow
     step_size_table_index
 }
 
-/// サンプル数を計算する.
+/// Calculate the number of samples per channel for IMA-ADPCM files.
 pub(crate) fn calc_num_samples_per_channel(
     data_chunk_size_in_bytes: u32,
     spec: &PcmSpecs,
@@ -136,16 +136,17 @@ pub(crate) fn calc_num_samples_per_channel(
 pub struct ImaAdpcmPlayer<'a> {
     /// A reader to access basic information about the PCM file.
     pub reader: PcmReader<'a>,
-    /// 現在読んでいるサンプル位置.
+    /// Frame index of the current block.
     frame_index: u32,
-    /// デコードされた直近の値.
+    /// The last decoded sample value.
     last_predicted_sample: [I1F15; MAX_NUM_CHANNELS],
-    /// STEP_SIZE_TABLEのindex.
+    /// The current index of STEP_SIZE_TABLE.
     step_size_table_index: [i8; MAX_NUM_CHANNELS],
-    /// 現在読み込み中のIMA-ADPCMのブロック.
+    /// The current block of IMA-ADPCM being read.
     reading_block: &'a [u8],
-    /// Data word読み込み時のnibble配列を保管するqueue.
-    nibble_queue: [Queue<u4, 9>; MAX_NUM_CHANNELS], //todo Queueサイズは2の冪乗の方がパフォーマンスよい。
+    /// A queue that stores nibble arrays when reading data words.
+    /// TODO: Queue size is better to be a power of 2 for performance.
+    nibble_queue: [Queue<u4, 9>; MAX_NUM_CHANNELS],
 }
 
 impl<'a> ImaAdpcmPlayer<'a> {

src/lib.rs

@@ -180,21 +180,23 @@ impl<'a> PcmReader<'a> {
         Ok((input, &[]))
     }
 
+    /// PCMReader is a struct that reads PCM data from a byte array.
+    /// It supports Linear PCM and IEEE Float.
     /// * 'input' - PCM data byte array
     pub fn new(input: &'a [u8]) -> Self {
         let file_length = input.len();
 
         let mut reader: PcmReader = Default::default();
 
-        //WAVの場合
+        //WAVE
         if let Ok((input, riff)) = wav::parse_riff_header(input) {
             assert_eq!((file_length - 8) as u32, riff.size);
             if let Ok((_, _)) = reader.parse_wav(input) {
                 return reader;
             }
         };
 
-        //AIFFの場合
+        //AIFF
         if let Ok((input, _aiff)) = aiff::parse_aiff_header(input) {
             // assert_eq!((file_length - 8) as u32, aiff.size);
             if let Ok((_, _)) = reader.parse_aiff(input) {
@@ -203,6 +205,7 @@ impl<'a> PcmReader<'a> {
         };
 
         //WAVでもAIFFでもなかった場合
+
         panic!();
     }
 
@@ -226,11 +229,11 @@ impl<'a> PcmReader<'a> {
     }
 }
 
-/// DATAチャンクを読んでサンプルを読みだす    
-/// フォーマットに関わらず+/-1の範囲に正規化された数を返す
-/// TODO f32以外Q15やQ23, f64などでも返せるようにしたい
-/// もしくはf32かf64を選択できるようにする
-/// 固定小数点の取得はread_raw_sample()的な関数とそのジェネリスクで対応するのがいいかもしれない
+/// Decode a sample from a byte array.
+/// Returns a normalized value in the range +/-1.0 regardless of AudioFormat.
+/// TODO return not only f32 but also Q15, Q23, f64, etc.
+/// Or make it possible to select f32 or f64.
+/// It may be better to use a function like read_raw_sample() to get fixed-point numbers.
 fn decode_sample(specs: &PcmSpecs, data: &[u8]) -> anyhow::Result<f32> {
     match specs.audio_format {
         AudioFormat::Unknown => {