Fix output on big-endian systems (#778)

Author: roderickvd

CHANGELOG.md

@@ -36,8 +36,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [connect] Fix step size on volume up/down events
 - [playback] Incorrect `PlayerConfig::default().normalisation_threshold` caused distortion when using dynamic volume normalisation downstream 
 - [playback] Fix `log` and `cubic` volume controls to be mute at zero volume
+- [playback] Fix `S24_3` format on big-endian systems
 - [playback] `alsamixer`: make `cubic` consistent between cards that report minimum volume as mute, and cards that report some dB value
 - [playback] `alsamixer`: make `--volume-ctrl {linear|log}` work as expected
+- [playback] `alsa`, `gstreamer`, `pulseaudio`: always output in native endianness
 
 ## [0.2.0] - 2021-05-04
 

playback/src/audio_backend/alsa.rs

@@ -45,8 +45,12 @@ fn open_device(dev_name: &str, format: AudioFormat) -> Result<(PCM, Frames), Box
         AudioFormat::F32 => Format::float(),
         AudioFormat::S32 => Format::s32(),
         AudioFormat::S24 => Format::s24(),
-        AudioFormat::S24_3 => Format::S243LE,
         AudioFormat::S16 => Format::s16(),
+
+        #[cfg(target_endian = "little")]
+        AudioFormat::S24_3 => Format::S243LE,
+        #[cfg(target_endian = "big")]
+        AudioFormat::S24_3 => Format::S243BE,
     };
 
     // http://www.linuxjournal.com/article/6735?page=0,1#N0x19ab2890.0x19ba78d8

playback/src/audio_backend/gstreamer.rs

@@ -34,9 +34,14 @@ impl Open for GstreamerSink {
         let sample_size = format.size();
         let gst_bytes = 2048 * sample_size;
 
+        #[cfg(target_endian = "little")]
+        const ENDIANNESS: &str = "LE";
+        #[cfg(target_endian = "big")]
+        const ENDIANNESS: &str = "BE";
+
         let pipeline_str_preamble = format!(
-            "appsrc caps=\"audio/x-raw,format={}LE,layout=interleaved,channels={},rate={}\" block=true max-bytes={} name=appsrc0 ",
-            gst_format, NUM_CHANNELS, SAMPLE_RATE, gst_bytes
+            "appsrc caps=\"audio/x-raw,format={}{},layout=interleaved,channels={},rate={}\" block=true max-bytes={} name=appsrc0 ",
+            gst_format, ENDIANNESS, NUM_CHANNELS, SAMPLE_RATE, gst_bytes
         );
         // no need to dither twice; use librespot dithering instead
         let pipeline_str_rest = r#" ! audioconvert dithering=none ! autoaudiosink"#;

playback/src/audio_backend/pulseaudio.rs

@@ -23,11 +23,11 @@ impl Open for PulseAudioSink {
 
         // PulseAudio calls S24 and S24_3 different from the rest of the world
         let pulse_format = match format {
-            AudioFormat::F32 => pulse::sample::Format::F32le,
-            AudioFormat::S32 => pulse::sample::Format::S32le,
-            AudioFormat::S24 => pulse::sample::Format::S24_32le,
-            AudioFormat::S24_3 => pulse::sample::Format::S24le,
-            AudioFormat::S16 => pulse::sample::Format::S16le,
+            AudioFormat::F32 => pulse::sample::Format::FLOAT32NE,
+            AudioFormat::S32 => pulse::sample::Format::S32NE,
+            AudioFormat::S24 => pulse::sample::Format::S24_32NE,
+            AudioFormat::S24_3 => pulse::sample::Format::S24NE,
+            AudioFormat::S16 => pulse::sample::Format::S16NE,
             _ => {
                 unimplemented!("PulseAudio currently does not support {:?} output", format)
             }

playback/src/convert.rs

@@ -8,8 +8,12 @@ pub struct i24([u8; 3]);
 impl i24 {
     fn from_s24(sample: i32) -> Self {
         // trim the padding in the most significant byte
-        let [a, b, c, _d] = sample.to_le_bytes();
-        i24([a, b, c])
+        #[allow(unused_variables)]
+        let [a, b, c, d] = sample.to_ne_bytes();
+        #[cfg(target_endian = "little")]
+        return Self([a, b, c]);
+        #[cfg(target_endian = "big")]
+        return Self([b, c, d]);
     }
 }