133 lines
4.3 KiB
Rust
133 lines
4.3 KiB
Rust
//! Audio streaming transformer built on pmoflac.
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//!
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//! This module wires the generic `pmocache` download pipeline with the new
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//! streaming transcode helper provided by `pmoflac`. Any supported codec
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//! (FLAC, MP3, OGG/Vorbis, Opus, WAV, AIFF) is converted to FLAC on the fly,
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//! while native FLAC input is forwarded byte-for-byte without re-encoding.
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use bytes::Bytes;
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use pmocache::StreamTransformer;
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use pmoflac::{transcode_to_flac_stream, AudioCodec, TranscodeOptions};
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use tokio::io::{AsyncReadExt, AsyncWriteExt};
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/// Creates the transformer consumed by the audio cache.
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pub fn create_streaming_flac_transformer() -> StreamTransformer {
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Box::new(|input, mut file, progress| {
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Box::pin(async move {
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let byte_stream = input.into_byte_stream();
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let reader = StreamToAsyncRead::new(byte_stream);
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let transcode = transcode_to_flac_stream(reader, TranscodeOptions::default())
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.await
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.map_err(|e| format!("Audio transcode error: {}", e))?;
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log_stream_info(transcode.input_codec(), transcode.input_stream_info());
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let mut flac_stream = transcode.into_stream();
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let mut buffer = vec![0u8; 64 * 1024];
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let mut total_written = 0u64;
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loop {
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let read = flac_stream
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.read(&mut buffer)
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.await
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.map_err(|e| format!("Failed to read FLAC data: {}", e))?;
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if read == 0 {
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break;
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}
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file.write_all(&buffer[..read])
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.await
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.map_err(|e| format!("Failed to write FLAC file: {}", e))?;
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total_written += read as u64;
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progress(total_written);
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}
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file.flush()
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.await
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.map_err(|e| format!("Failed to flush FLAC file: {}", e))?;
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flac_stream
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.wait()
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.await
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.map_err(|e| format!("FLAC encoder error: {}", e))?;
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Ok(())
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})
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})
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}
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fn log_stream_info(codec: AudioCodec, info: &pmoflac::StreamInfo) {
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tracing::debug!(
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"Detected codec {:?}: {} Hz, {} channels, {} bits/sample (passthrough={})",
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codec,
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info.sample_rate,
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info.channels,
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info.bits_per_sample,
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codec == AudioCodec::Flac
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);
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}
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/// Adapter exposing a byte stream as `AsyncRead`.
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struct StreamToAsyncRead {
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stream: futures_util::stream::BoxStream<'static, Result<Bytes, String>>,
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current_chunk: Option<Bytes>,
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offset: usize,
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}
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impl StreamToAsyncRead {
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fn new(
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stream: std::pin::Pin<Box<dyn futures_util::Stream<Item = Result<Bytes, String>> + Send>>,
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) -> Self {
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use futures_util::StreamExt;
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Self {
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stream: stream.boxed(),
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current_chunk: None,
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offset: 0,
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}
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}
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}
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impl tokio::io::AsyncRead for StreamToAsyncRead {
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fn poll_read(
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mut self: std::pin::Pin<&mut Self>,
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cx: &mut std::task::Context<'_>,
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buf: &mut tokio::io::ReadBuf<'_>,
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) -> std::task::Poll<std::io::Result<()>> {
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use futures_util::StreamExt;
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use std::task::Poll;
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loop {
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if let Some(chunk) = &self.current_chunk {
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if self.offset < chunk.len() {
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let available = chunk.len() - self.offset;
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let to_copy = available.min(buf.remaining());
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buf.put_slice(&chunk[self.offset..self.offset + to_copy]);
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self.offset += to_copy;
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return Poll::Ready(Ok(()));
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}
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self.current_chunk = None;
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self.offset = 0;
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}
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match self.stream.poll_next_unpin(cx) {
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Poll::Ready(Some(Ok(chunk))) => {
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if chunk.is_empty() {
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continue;
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}
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self.current_chunk = Some(chunk);
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}
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Poll::Ready(Some(Err(e))) => {
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return Poll::Ready(Err(std::io::Error::new(std::io::ErrorKind::Other, e)));
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}
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Poll::Ready(None) => return Poll::Ready(Ok(())),
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Poll::Pending => return Poll::Pending,
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}
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}
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}
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}
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impl Unpin for StreamToAsyncRead {}
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