Add function to get audio file duration

src/util/audio.rs

@@ -0,0 +1,33 @@
+use symphonia::core::formats::FormatOptions;
+use symphonia::core::io::MediaSourceStream;
+use symphonia::core::meta::MetadataOptions;
+use symphonia::core::probe::Hint;
+use std::fs::File;
+
+/// Measure the duration (in seconds) of an audio file
+pub fn measure_duration(file: File) -> Result<u64, Box<dyn std::error::Error>> {
+	let source_stream = MediaSourceStream::new(Box::new(file), Default::default());
+
+	let hint = Hint::new();
+	let format_opts = FormatOptions::default();
+	let metadata_opts = MetadataOptions::default();
+
+	let probe = symphonia::default::get_probe().format(&hint, source_stream, &format_opts, &metadata_opts)?;
+	let reader = probe.format;
+
+	if reader.tracks().len() != 1 {
+		return Err(format!("Expected 1 track, found {}", reader.tracks().len()).into())
+	}
+
+	let track = &reader.tracks()[0];
+
+	let time_base = track.codec_params.time_base.ok_or("Missing time base")?;
+	let duration = track.codec_params.n_frames
+		.map(|frames| track.codec_params.start_ts + frames)
+		.ok_or("Missing number of frames")?;
+
+	duration
+		.checked_mul(time_base.numer as u64)
+		.and_then(|v| v.checked_div(time_base.denom as u64))
+		.ok_or("Overflow while computing duration".into())
+}

src/util/mod.rs

@@ -0,0 +1,7 @@
+use cfg_if::cfg_if;
+
+cfg_if! {
+	if #[cfg(feature = "ssr")] {
+		pub mod audio;
+	}
+}