[add] decoder implementations.

Author: vmarcella

crates/lambda-rs-platform/src/audio/symphonia/mod.rs

@@ -4,3 +4,129 @@
 //!
 //! This module will provide WAV and OGG Vorbis decode helpers for `lambda-rs`.
 //! It is intentionally internal and MAY change between releases.
+
+use std::{
+  fmt,
+  io::Cursor,
+};
+
+use symphonia::core::{
+  errors::Error,
+  formats::FormatOptions,
+  io::MediaSourceStream,
+  meta::MetadataOptions,
+  probe::Hint,
+};
+
+/// Fully decoded, interleaved `f32` samples with associated metadata.
+#[derive(Clone, Debug, PartialEq)]
+pub struct DecodedAudio {
+  pub samples: Vec<f32>,
+  pub sample_rate: u32,
+  pub channels: u16,
+}
+
+/// Vendor-free errors produced by audio decoding helpers.
+#[derive(Clone, Debug)]
+pub enum AudioDecodeError {
+  UnsupportedFormat { details: String },
+  InvalidData { details: String },
+  DecodeFailed { details: String },
+}
+
+impl fmt::Display for AudioDecodeError {
+  fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+    match self {
+      Self::UnsupportedFormat { details } => {
+        return write!(formatter, "unsupported audio format: {details}");
+      }
+      Self::InvalidData { details } => {
+        return write!(formatter, "invalid audio data: {details}");
+      }
+      Self::DecodeFailed { details } => {
+        return write!(formatter, "audio decode failed: {details}");
+      }
+    }
+  }
+}
+
+impl std::error::Error for AudioDecodeError {}
+
+fn hint_for_decode(extensions: &[&str]) -> Hint {
+  let mut hint_value = Hint::new();
+  for extension in extensions {
+    hint_value.with_extension(extension);
+  }
+  return hint_value;
+}
+
+fn map_probe_error(source_description: &str, error: Error) -> AudioDecodeError {
+  match error {
+    Error::Unsupported(_) => {
+      return AudioDecodeError::UnsupportedFormat {
+        details: format!("unsupported or unrecognized {source_description}"),
+      };
+    }
+    Error::IoError(_) => {
+      return AudioDecodeError::InvalidData {
+        details: format!("failed to read {source_description} bytes"),
+      };
+    }
+    other => {
+      return AudioDecodeError::DecodeFailed {
+        details: format!("{source_description} probe error: {other}"),
+      };
+    }
+  }
+}
+
+fn probe_bytes(
+  bytes: &[u8],
+  source_description: &str,
+  extensions: &[&str],
+) -> Result<(), AudioDecodeError> {
+  let hint_value = hint_for_decode(extensions);
+
+  let cursor = Cursor::new(bytes.to_vec());
+  let media_source =
+    MediaSourceStream::new(Box::new(cursor), Default::default());
+
+  let probe_result = symphonia::default::get_probe()
+    .format(
+      &hint_value,
+      media_source,
+      &FormatOptions::default(),
+      &MetadataOptions::default(),
+    )
+    .map_err(|error| map_probe_error(source_description, error))?;
+
+  if probe_result.format.tracks().is_empty() {
+    return Err(AudioDecodeError::InvalidData {
+      details: "no audio tracks found".to_string(),
+    });
+  }
+
+  return Ok(());
+}
+
+/// Decode WAV bytes into interleaved `f32` samples.
+#[cfg(feature = "audio-decode-wav")]
+pub fn decode_wav_bytes(
+  bytes: &[u8],
+) -> Result<DecodedAudio, AudioDecodeError> {
+  probe_bytes(bytes, "WAV", &["wav"])?;
+  return Err(AudioDecodeError::DecodeFailed {
+    details: "WAV decoding not implemented yet".to_string(),
+  });
+}
+
+/// Decode OGG Vorbis bytes into interleaved `f32` samples.
+#[cfg(feature = "audio-decode-vorbis")]
+pub fn decode_ogg_vorbis_bytes(
+  bytes: &[u8],
+) -> Result<DecodedAudio, AudioDecodeError> {
+  probe_bytes(bytes, "OGG Vorbis", &["ogg", "oga"])?;
+  return Err(AudioDecodeError::DecodeFailed {
+    details: "OGG Vorbis decoding not implemented yet".to_string(),
+  });
+}