Struct bwavfile::WaveFmt

pub struct WaveFmt {
    pub tag: u16,
    pub channel_count: u16,
    pub sample_rate: u32,
    pub bytes_per_second: u32,
    pub block_alignment: u16,
    pub bits_per_sample: u16,
    pub extended_format: Option<WaveFmtExtended>,
}

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.

Resources

Implementation of Wave format fmt chunk

• MSDN WAVEFORMATEX
• MSDN WAVEFORMATEXTENSIBLE

Other resources

• RFC 3261 (June 1998) “WAVE and AVI Codec Registries”
• Sampler Metadata
• Audio File Format Specifications (September 2022) Prof. Peter Kabal, MMSP Lab, ECE, McGill University
• Multimedia Programming Interface and Data Specifications 1.0 (August 1991), IBM Corporation and Microsoft Corporation

Fields

tag: u16

A tag identifying the codec in use.

If this is 0xFFFE, the codec will be identified by a GUID in extended_format.

channel_count: u16

Count of audio channels in each frame

sample_rate: u32

Playback rate of the audio data

In frames per second.

bytes_per_second: u32

Count of bytes per second

By rule, this is block_alignment * sample_rate

block_alignment: u16

Count of bytes per audio frame

By rule, this is channel_count * bits_per_sample / 8

bits_per_sample: u16

Count of bits stored in the file per sample

By rule, bits_per_sample % 8 == 0 for Broadcast-Wave files.

Modern clients will encode unusual sample sizes in normal byte sizes but will set the valid_bits flag in extended format record.

Generally speaking this will be true for all modern wave files, though there was an historical “packed” stereo format of 20 bits per sample, 5 bytes per frame, 5 bytes block alignment.

extended_format: Option<WaveFmtExtended>

Extended format description

Additional format metadata if channel_count is greater than 2, or if certain codecs are used.

Implementations

impl WaveFmt

pub fn valid_bits_per_sample(&self) -> u16

pub fn new_pcm_mono(sample_rate: u32, bits_per_sample: u16) -> Self

Create a new integer PCM format for a monoaural audio stream.

pub fn new_pcm_stereo(sample_rate: u32, bits_per_sample: u16) -> Self

Create a new integer PCM format for a standard Left-Right stereo audio stream.

pub fn new_pcm_ambisonic( sample_rate: u32, bits_per_sample: u16, channel_count: u16 ) -> Self

Create a new integer PCM format for ambisonic b-format.

pub fn new_pcm_multichannel( sample_rate: u32, bits_per_sample: u16, channel_bitmap: u32 ) -> Self

Create a new integer PCM format WaveFmt with a custom channel bitmap.

The order of channels is not important. When reading or writing audio frames you must use the standard multichannel order for Wave files, the numerical order of the cases of ChannelMask.

pub fn common_format(&self) -> CommonFormat

Format or codec of the file’s audio data.

The CommonFormat unifies the format tag and the format extension GUID. Use this method to determine the codec.

pub fn create_frame_buffer<S: Sample>(&self, length: usize) -> Vec<S>

Create a frame buffer sized to hold length frames for a reader or writer

This is a conveneince method that creates a Vec<i32> with as many elements as there are channels in the underlying stream.

pub fn create_raw_buffer(&self, length: usize) -> Vec<u8>

Create a raw byte buffer to hold length blocks from a reader or writer

pub fn unpack_frames(&self, from_bytes: &[u8], into_frames: &mut [i32])

Read bytes into frames

pub fn channels(&self) -> Vec<ChannelDescriptor>

Channel descriptors for each channel.

Trait Implementations

impl Clone for WaveFmt

fn clone(&self) -> WaveFmt

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for WaveFmt

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Copy for WaveFmt