Reorganized source, comments

src/fmt.rs

@@ -0,0 +1,143 @@
+
+/**
+ * References:
+ * - http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Docs/multichaudP.pdf
+*/
+#[derive(PartialEq)]
+enum FormatTags {
+    Integer = 0x0001,
+    Float = 0x0003,
+    Extensible = 0xFFFE
+}
+
+const PCM_SUBTYPE_UUID: [u8; 16] = [0x00, 0x00, 0x00, 0x01,
+                                    0x00, 0x00, 0x00, 0x10,
+                                    0x80, 0x00, 0x00, 0xaa,
+                                    0x00, 0x38, 0x9b, 0x71];
+
+const FLOAT_SUBTYPE_UUID: [u8; 16] = [0x00, 0x00, 0x00, 0x03,
+                                      0x00, 0x00, 0x00, 0x10,
+                                      0x80, 0x00, 0x00, 0xaa,
+                                      0x00, 0x38, 0x9b, 0x71];
+
+/*
+https://docs.microsoft.com/en-us/windows-hardware/drivers/audio/subformat-guids-for-compressed-audio-formats
+http://dream.cs.bath.ac.uk/researchdev/wave-ex/bformat.html
+
+These are from http://dream.cs.bath.ac.uk/researchdev/wave-ex/mulchaud.rtf
+*/
+
+#[derive(Debug)]
+pub enum WaveFmtExtendedChannelMask {
+    FrontLeft        = 0x1,
+    FrontRight       = 0x2,
+    FrontCenter      = 0x4,
+    LowFrequency     = 0x8,
+    BackLeft         = 0x10,
+    BackRight        = 0x20,
+    FrontCenterLeft  = 0x40,
+    FrontCenterRight = 0x80,
+    BackCenter       = 0x100,
+    SideLeft         = 0x200,
+    SideRight        = 0x400,
+    TopCenter        = 0x800,
+    TopFrontLeft     = 0x1000,
+    TopFrontCenter   = 0x2000,
+    TopFrontRight    = 0x4000,
+    TopBackLeft      = 0x8000,
+    TopBackCenter    = 0x10000,
+    TopBackRight     = 0x20000 
+}
+
+
+/**
+ * Extended Wave Format
+ * 
+ * https://docs.microsoft.com/en-us/windows/win32/api/mmreg/ns-mmreg-waveformatextensible
+ */
+#[derive(Debug)]
+pub struct WaveFmtExtended {
+
+    /// Valid bits per sample
+    pub valid_bits_per_sample : u16,
+
+    /// Channel mask
+    /// 
+    /// Identifies the speaker assignment for each channel in the file
+    pub channel_mask : WaveFmtExtendedChannelMask,
+
+    /// Codec GUID
+    /// 
+    /// Identifies the codec of the audio stream
+    pub type_guid : [u8; 16],
+}
+
+/**
+ * WAV file data format record.
+ * 
+ * The `fmt` record contains essential information describing the binary
+ * structure of the data segment of the WAVE file, such as sample 
+ * rate, sample binary format, channel count, etc.
+ *
+ */
+#[derive(Debug)]
+pub struct WaveFmt {
+
+    /// A tag identifying the codec in use.
+    /// 
+    /// If this is 0xFFFE, the codec will be identified by a GUID
+    /// in `extended_format`
+    pub tag: u16,
+
+    /// Count of audio channels in each frame
+    pub channel_count: u16,
+
+    /// Sample rate of the audio data
+    pub sample_rate: u32,
+
+    /// Count of bytes per second
+    /// 
+    /// By rule, this is `block_alignment * sample_rate`
+    pub bytes_per_second: u32,
+
+    /// Count of bytes per audio frame
+    /// 
+    /// By rule, this is `channel_count * bits_per_sample / 8`
+    pub block_alignment: u16,
+
+    /// Count of bits stored in the file per sample
+    pub bits_per_sample: u16,
+
+    /// Extended format description
+    /// 
+    /// Additional format metadata if `channel_count` is greater than 2,
+    /// or if certain codecs are used.
+    pub extended_format: Option<WaveFmtExtended>
+}
+
+
+impl WaveFmt {
+
+    /// Create a new integer PCM format `WaveFmt` 
+    pub fn new_pcm(sample_rate: u32, bits_per_sample: u16, channel_count: u16) -> Self {
+        let container_bits_per_sample = bits_per_sample + (bits_per_sample % 8);
+        let container_bytes_per_sample= container_bits_per_sample / 8;
+
+        let tag :u16 = match channel_count {
+            0 => panic!("Error"),
+            1..=2 => FormatTags::Integer as u16,
+            _ => FormatTags::Extensible as u16,
+        };
+
+        WaveFmt {
+            tag, 
+            channel_count,
+            sample_rate,
+            bytes_per_second: container_bytes_per_sample as u32 * sample_rate * channel_count as u32,
+            block_alignment: container_bytes_per_sample * channel_count,
+            bits_per_sample: container_bits_per_sample,
+            extended_format: None
+        }
+    }
+}
+