Realtime Audio Disk Stream

Realtime disk streaming IO for audio files

This crate is currently experimental and incomplete.

How it Works

The stream has two types of buffers: a cache buffer and look-ahead buffer.

A cache buffer is a user-defined range (of a fixed user-defined number of blocks) starting from any frame in the file. Caches must be loaded before they can be used. The default size for a block is 16384 frames in length.

There are a number of look-ahead blocks ahead of the currently used cache block/playhead. These automatically load-in to ensure that data will always be ready even in the worse-case IO latency scenerio. A number of look-ahead blocks are added to the end of every cache buffer to ensure enough data is always available.

The stream can have as many cache buffers as desired. When seeking to a frame in the file, the stream searches for a cache that contains that frame. If one does, then it uses it and playback can resume immediately. A common use case is to cache the start of a file or loop region for seamless looping.

If a suitable cache is not found (or the cache is not loaded yet), then the look-ahead buffer will need to fill-up before any more data can be read. In this case, you may choose to either continue playback (which will output silence) or to temporarily pause playback.

Format and Codec Support Roadmap

Default decoding of files is provided by the Symphonia crate. (So far only wav is verified to work).

In addition to the default decoders, you may define your own using the Decoder trait.

Formats (Demux)

Codecs (Decode)

Codecs (Encode)

Examples

Simple Usage Example

use rt_audio_disk_stream::{Decoder, SymphoniaDecoder, SeekMode};

// Open the read stream.
let mut read_disk_stream = rt_audio_disk_stream::open_read::<SymphoniaDecoder, _>(
    "./test_files/wav_i24_stereo.wav",  // Path to file.
    0,  // The frame in the file to start reading from.
    Default::default(),  // Use default read stream options.
).unwrap();

// Cache the start of the file into cache with index `0`.
let _ = read_disk_stream.cache(0, 0);

// Tell the stream to seek to the beginning of file. This will also alert the stream to the existence
// of the cache with index `0`.
read_disk_stream.seek(0, Default::default()).unwrap();

// Wait until the buffer is filled before sending it to the process thread.
//
// NOTE: Do ***not*** use this method in a real-time thread.
read_disk_stream.block_until_ready().unwrap();

// (Send `read_stream` to the audio processing thread)


// -------------------------------------------------------------

// In the realtime audio processing thread:


// Update client and check if it is ready.
//
// NOTE: You should avoid using `unwrap()` in realtime code.
if !read_disk_stream.is_ready().unwrap() {
    // If the look-ahead buffer is still buffering, We can choose to either continue
    // reading (which will return silence), or pause playback until the buffer is filled.
}

let read_data = read_disk_stream.read(num_frames_in_output_buffer).unwrap();

println!("{}", read_data.num_frames());
println!("{}", read_data.num_channels());

// Seek to a new position in the file.
read_disk_stream.seek(50000, SeekMode::Auto};

assert_eq!(read_dist_stream.playhead(), 50000);

Demo Audio Player

Here is a basic looping demo player that plays a single wav file with adjustable loop regions.