Add support for S32 output format

While at it, add a small tweak when converting "silent" samples
from float to integer. This ensures 0.0 converts to 0 and vice
versa.

audio/src/lib.rs

@@ -37,6 +37,22 @@ pub enum AudioPacket {
     OggData(Vec<u8>),
 }
 
+// Losslessly represent [-1.0, 1.0] to [$type::MIN, $type::MAX] while maintaining DC linearity.
+macro_rules! convert_samples_to {
+    ($type: ident, $samples: expr) => {
+        $samples
+            .iter()
+            .map(|sample| {
+                if *sample == 0.0 {
+                    0 as $type
+                } else {
+                    (*sample as f64 * (std::$type::MAX as f64 + 0.5) - 0.5) as $type
+                }
+            })
+            .collect()
+    };
+}
+
 impl AudioPacket {
     pub fn samples(&self) -> &[f32] {
         match self {
@@ -59,11 +75,12 @@ impl AudioPacket {
         }
     }
 
+    pub fn f32_to_s32(samples: &[f32]) -> Vec<i32> {
+        convert_samples_to!(i32, samples)
+    }
+
     pub fn f32_to_s16(samples: &[f32]) -> Vec<i16> {
-        samples
-            .iter()
-            .map(|sample| (*sample as f64 * (0x7FFF as f64 + 0.5) - 0.5) as i16)
-            .collect()
+        convert_samples_to!(i16, samples)
     }
 }
 

audio/src/libvorbis_decoder.rs

@@ -45,7 +45,13 @@ where
                         packet
                             .data
                             .iter()
-                            .map(|sample| ((*sample as f64 + 0.5) / (0x7FFF as f64 + 0.5)) as f32)
+                            .map(|sample| {
+                                if *sample == 0 {
+                                    0.0
+                                } else {
+                                    ((*sample as f64 + 0.5) / (0x7FFF as f64 + 0.5)) as f32
+                                }
+                            })
                             .collect(),
                     )));
                 }

playback/src/audio_backend/alsa.rs

@@ -41,6 +41,7 @@ fn open_device(dev_name: &str, format: AudioFormat) -> Result<(PCM, Frames), Box
     let pcm = PCM::new(dev_name, Direction::Playback, false)?;
     let (alsa_format, sample_size) = match format {
         AudioFormat::F32 => (Format::float(), mem::size_of::<f32>()),
+        AudioFormat::S32 => (Format::s32(), mem::size_of::<i32>()),
         AudioFormat::S16 => (Format::s16(), mem::size_of::<i16>()),
     };
 
@@ -157,6 +158,11 @@ impl AlsaSink {
                 let io = pcm.io_f32().unwrap();
                 io.writei(&self.buffer)
             }
+            AudioFormat::S32 => {
+                let io = pcm.io_i32().unwrap();
+                let buf_s32: Vec<i32> = AudioPacket::f32_to_s32(&self.buffer);
+                io.writei(&buf_s32[..])
+            }
             AudioFormat::S16 => {
                 let io = pcm.io_i16().unwrap();
                 let buf_s16: Vec<i16> = AudioPacket::f32_to_s16(&self.buffer);

playback/src/audio_backend/mod.rs

@@ -28,6 +28,10 @@ macro_rules! sink_as_bytes {
             match packet {
                 AudioPacket::Samples(samples) => match self.format {
                     AudioFormat::F32 => self.write_bytes(samples.as_bytes()),
+                    AudioFormat::S32 => {
+                        let samples_s32 = AudioPacket::f32_to_s32(samples);
+                        self.write_bytes(samples_s32.as_bytes())
+                    }
                     AudioFormat::S16 => {
                         let samples_s16 = AudioPacket::f32_to_s16(samples);
                         self.write_bytes(samples_s16.as_bytes())

playback/src/audio_backend/portaudio.rs

@@ -14,6 +14,10 @@ pub enum PortAudioSink<'a> {
         Option<portaudio_rs::stream::Stream<'a, f32, f32>>,
         StreamParameters<f32>,
     ),
+    S32(
+        Option<portaudio_rs::stream::Stream<'a, i32, i32>>,
+        StreamParameters<i32>,
+    ),
     S16(
         Option<portaudio_rs::stream::Stream<'a, i16, i16>>,
         StreamParameters<i16>,
@@ -70,19 +74,20 @@ impl<'a> Open for PortAudioSink<'a> {
         };
 
         macro_rules! open_sink {
-            ($sink: expr, $data: expr) => {{
+            ($sink: expr, $type: ty) => {{
                 let params = StreamParameters {
                     device: device_idx,
                     channel_count: NUM_CHANNELS as u32,
                     suggested_latency: latency,
-                    data: $data,
+                    data: 0.0 as $type,
                 };
                 $sink(None, params)
             }};
         }
         match format {
-            AudioFormat::F32 => open_sink!(PortAudioSink::F32, 0.0),
-            AudioFormat::S16 => open_sink!(PortAudioSink::S16, 0),
+            AudioFormat::F32 => open_sink!(PortAudioSink::F32, f32),
+            AudioFormat::S32 => open_sink!(PortAudioSink::S32, i32),
+            AudioFormat::S16 => open_sink!(PortAudioSink::S16, i16),
         }
     }
 }
@@ -109,6 +114,7 @@ impl<'a> Sink for PortAudioSink<'a> {
         }
         match self {
             PortAudioSink::F32(stream, parameters) => start_sink!(stream, parameters),
+            PortAudioSink::S32(stream, parameters) => start_sink!(stream, parameters),
             PortAudioSink::S16(stream, parameters) => start_sink!(stream, parameters),
         };
 
@@ -124,6 +130,7 @@ impl<'a> Sink for PortAudioSink<'a> {
         }
         match self {
             PortAudioSink::F32(stream, _parameters) => stop_sink!(stream),
+            PortAudioSink::S32(stream, _parameters) => stop_sink!(stream),
             PortAudioSink::S16(stream, _parameters) => stop_sink!(stream),
         };
 
@@ -141,6 +148,10 @@ impl<'a> Sink for PortAudioSink<'a> {
                 let samples = packet.samples();
                 write_sink!(stream, &samples)
             }
+            PortAudioSink::S32(stream, _parameters) => {
+                let samples_s32: Vec<i32> = AudioPacket::f32_to_s32(packet.samples());
+                write_sink!(stream, &samples_s32)
+            }
             PortAudioSink::S16(stream, _parameters) => {
                 let samples_s16: Vec<i16> = AudioPacket::f32_to_s16(packet.samples());
                 write_sink!(stream, &samples_s16)

playback/src/audio_backend/pulseaudio.rs

@@ -22,6 +22,7 @@ impl Open for PulseAudioSink {
 
         let pulse_format = match format {
             AudioFormat::F32 => pulse::sample::Format::F32le,
+            AudioFormat::S32 => pulse::sample::Format::S32le,
             AudioFormat::S16 => pulse::sample::Format::S16le,
         };
 

playback/src/audio_backend/rodio.rs

@@ -7,6 +7,8 @@ use cpal::traits::{DeviceTrait, HostTrait};
 use std::process::exit;
 use std::{io, thread, time};
 
+const FORMAT_NOT_SUPPORTED: &'static str = "Rodio currently does not support that output format";
+
 // most code is shared between RodioSink and JackRodioSink
 macro_rules! rodio_sink {
     ($name: ident) => {
@@ -27,12 +29,13 @@ macro_rules! rodio_sink {
                     AudioFormat::F32 => {
                         let source = rodio::buffer::SamplesBuffer::new(2, 44100, samples);
                         self.rodio_sink.append(source)
-                    }
+                    },
                     AudioFormat::S16 => {
                         let samples_s16: Vec<i16> = AudioPacket::f32_to_s16(samples);
                         let source = rodio::buffer::SamplesBuffer::new(2, 44100, samples_s16);
                         self.rodio_sink.append(source)
-                    }
+                    },
+                    _ => panic!(FORMAT_NOT_SUPPORTED),
                 };
 
                 // Chunk sizes seem to be about 256 to 3000 ish items long.
@@ -48,12 +51,16 @@ macro_rules! rodio_sink {
 
         impl $name {
             fn open_sink(host: &cpal::Host, device: Option<String>, format: AudioFormat) -> $name {
-                if format != AudioFormat::S16 {
+                match format  {
+                    AudioFormat::F32 => {
                         #[cfg(target_os = "linux")]
                         {
                             warn!("Rodio output to Alsa is known to cause garbled sound on output formats other than 16-bit signed integer.");
                             warn!("Consider using `--backend alsa` OR `--format {:?}`", AudioFormat::S16);
                         }
+                    },
+                    AudioFormat::S16 => {},
+                    _ => panic!(FORMAT_NOT_SUPPORTED),
                 }
 
                 let rodio_device = match_device(&host, device);

playback/src/audio_backend/sdl.rs

@@ -7,6 +7,7 @@ use std::{io, mem, thread, time};
 
 pub enum SdlSink {
     F32(AudioQueue<f32>),
+    S32(AudioQueue<i32>),
     S16(AudioQueue<i16>),
 }
 
@@ -39,6 +40,7 @@ impl Open for SdlSink {
         }
         match format {
             AudioFormat::F32 => open_sink!(SdlSink::F32, f32),
+            AudioFormat::S32 => open_sink!(SdlSink::S32, i32),
             AudioFormat::S16 => open_sink!(SdlSink::S16, i16),
         }
     }
@@ -54,6 +56,7 @@ impl Sink for SdlSink {
         }
         match self {
             SdlSink::F32(queue) => start_sink!(queue),
+            SdlSink::S32(queue) => start_sink!(queue),
             SdlSink::S16(queue) => start_sink!(queue),
         };
         Ok(())
@@ -68,6 +71,7 @@ impl Sink for SdlSink {
         }
         match self {
             SdlSink::F32(queue) => stop_sink!(queue),
+            SdlSink::S32(queue) => stop_sink!(queue),
             SdlSink::S16(queue) => stop_sink!(queue),
         };
         Ok(())
@@ -87,6 +91,11 @@ impl Sink for SdlSink {
                 drain_sink!(queue, mem::size_of::<f32>());
                 queue.queue(packet.samples())
             }
+            SdlSink::S32(queue) => {
+                drain_sink!(queue, mem::size_of::<i32>());
+                let samples_s32: Vec<i32> = AudioPacket::f32_to_s32(packet.samples());
+                queue.queue(&samples_s32)
+            }
             SdlSink::S16(queue) => {
                 drain_sink!(queue, mem::size_of::<i16>());
                 let samples_s16: Vec<i16> = AudioPacket::f32_to_s16(packet.samples());

playback/src/config.rs

@@ -29,6 +29,7 @@ impl Default for Bitrate {
 #[derive(Clone, Copy, Debug, Hash, PartialOrd, Ord, PartialEq, Eq)]
 pub enum AudioFormat {
     F32,
+    S32,
     S16,
 }
 
@@ -37,6 +38,7 @@ impl TryFrom<&String> for AudioFormat {
     fn try_from(s: &String) -> Result<Self, Self::Error> {
         match s.to_uppercase().as_str() {
             "F32" => Ok(AudioFormat::F32),
+            "S32" => Ok(AudioFormat::S32),
             "S16" => Ok(AudioFormat::S16),
             _ => unimplemented!(),
         }

src/main.rs

@@ -156,7 +156,7 @@ fn setup(args: &[String]) -> Setup {
         .optopt(
             "",
             "format",
-            "Output format (F32 or S16). Defaults to F32",
+            "Output format (F32, S32 or S16). Defaults to F32",
             "FORMAT",
         )
         .optopt("", "mixer", "Mixer to use (alsa or softvol)", "MIXER")