Rework `alsa` hw and mixer parameters

playback/src/audio_backend/alsa.rs

@@ -1,20 +1,66 @@
 use super::{Open, Sink};
-use alsa::{Direction, Error, ValueOr};
 use alsa::device_name::HintIter;
-use std::ffi::{CStr, CString};
 use alsa::pcm::{Access, Format, HwParams, PCM};
+use alsa::{Direction, Error, ValueOr};
+use std::env;
+use std::ffi::CString;
 use std::io;
 use std::process::exit;
 
-
 pub struct AlsaSink(Option<PCM>, String);
 
 fn list_outputs() {
     for t in &["pcm", "ctl", "rawmidi", "timer", "seq", "hwdep"] {
-     println!("{} devices:", t);
-     let i = HintIter::new(None, &*CString::new(*t).unwrap()).unwrap();
-     for a in i { println!("  {:?}", a) }
- }
+        println!("{} devices:", t);
+        let i = HintIter::new(None, &*CString::new(*t).unwrap()).unwrap();
+        for a in i {
+            println!("  {:?}", a)
+        }
+    }
+}
+
+fn open_device(dev_name: &str) -> Result<(PCM), Box<Error>> {
+    let pcm = PCM::new(dev_name, Direction::Playback, false)?;
+    // http://www.linuxjournal.com/article/6735?page=0,1#N0x19ab2890.0x19ba78d8
+    // latency = period_size * periods / (rate * bytes_per_frame)
+    // For 16 Bit stereo data, one frame has a length of four bytes.
+    // 500ms  = buffer_size / (44100 * 4)
+    // buffer_size = 0.5 * 44100 = 22050 frames
+    {
+        // Set hardware parameters: 44100 Hz / Stereo / 16 bit
+        let hwp = HwParams::any(&pcm)?;
+
+        hwp.set_access(Access::RWInterleaved)?;
+        hwp.set_format(Format::s16())?;
+        hwp.set_rate(44100, ValueOr::Nearest)?;
+        hwp.set_channels(2)?;
+        // hwp.set_period_size_near(256, ValueOr::Nearest)?;
+        hwp.set_buffer_size_near(11025 * 2)?; // ~ 0.25 x 2 s latency
+
+        pcm.hw_params(&hwp)?;
+    }
+
+    // Additional software paramters + check
+    if env::var("LIBRESPOT_DEBUG").is_ok() {
+        let hwp = pcm.hw_params_current()?;
+        let swp = pcm.sw_params_current()?;
+        let (bufsize, periodsize) = (hwp.get_buffer_size()?, hwp.get_period_size()?);
+        let periods = hwp.get_periods()?;
+        info!(
+            "periods: {:?} buffer_size: {:?} period_size {:?}",
+            periods, bufsize, periodsize
+        );
+        // Not required now that buffer size is set properly
+        // swp.set_start_threshold(bufsize - periodsize)?;
+        // swp.set_avail_min(periodsize)?;
+        // pcm.sw_params(&swp).unwrap();
+        info!(
+            "Opened audio output {:?} with parameters: {:?}, {:?}",
+            dev_name, hwp, swp
+        );
+    }
+
+    Ok(pcm)
 }
 
 impl Open for AlsaSink {
@@ -23,6 +69,7 @@ impl Open for AlsaSink {
 
         let name = match device.as_ref().map(AsRef::as_ref) {
             Some("?") => {
+                println!("Listing available alsa outputs");
                 list_outputs();
                 exit(0)
             }
@@ -37,20 +84,17 @@ impl Open for AlsaSink {
 impl Sink for AlsaSink {
     fn start(&mut self) -> io::Result<()> {
         if self.0.is_none() {
-            let pcm = PCM::new(&*self.1, Direction::Playback, false).unwrap();
-            {
-                // Set hardware parameters: 44100 Hz / Stereo / 16 bit
-                let hwp = HwParams::any(&pcm).unwrap();
-                hwp.set_channels(2).unwrap();
-                hwp.set_rate(44100, ValueOr::Nearest).unwrap();
-                hwp.set_format(Format::s16()).unwrap();
-                hwp.set_access(Access::RWInterleaved).unwrap();
-                pcm.hw_params(&hwp).unwrap();
-                println!("PCM status: {:?}, {:?}", pcm.state(), pcm.hw_params_current().unwrap())
+            let pcm = open_device(&self.1);
+            match pcm {
+                Ok(p) => self.0 = Some(p),
+                Err(e) => {
+                    error!("Alsa error PCM open {}", e);
+                    return Err(io::Error::new(
+                        io::ErrorKind::Other,
+                        "Alsa error: PCM open failed",
+                    ));
                 }
-            PCM::prepare(&pcm).unwrap();
-
-            self.0 = Some(pcm);
+            }
         }
 
         Ok(())
@@ -58,7 +102,7 @@ impl Sink for AlsaSink {
 
     fn stop(&mut self) -> io::Result<()> {
         {
-            let pcm = self.0.as_mut().unwrap();
+            let pcm = self.0.as_ref().unwrap();
             pcm.drain().unwrap();
         }
         self.0 = None;

playback/src/mixer/alsamixer.rs

@@ -1,5 +1,7 @@
-use super::Mixer;
 use super::AudioFilter;
+use super::Mixer;
+use std::env;
+use std::error::Error;
 
 use alsa;
 
@@ -7,27 +9,50 @@ use alsa;
 pub struct AlsaMixer {
     card: String,
     mixer: String,
+    index: u32,
 }
 
-// Doesn't work - Selem is borrowed from Mixer
-// impl AlsaMixer {
-//     fn get_selem(&self ) -> Result<(alsa::mixer::Selem), Box<Error>> {
-//
-//         let selem_id = alsa::mixer::SelemId::new(self.mixer, 0);
-//         let mixer = alsa::mixer::Mixer::new(self.card, false)?;
-//         let selem = mixer.find_selem(&selem_id).unwrap();
-//
-//         Ok((selem))
-//     }
-// }
+impl AlsaMixer {
+
+    fn map_volume(&self, set_volume:Option<u16>) -> Result<(u16),Box<Error>> {
+        let mixer  = alsa::mixer::Mixer::new(&self.card, false)?;
+        let sid    = alsa::mixer::SelemId::new(&*self.mixer, self.index);
+
+        let selem = mixer.find_selem(&sid).expect("Coundn't find SelemId");
+        let (min, max) = selem.get_playback_volume_range();
+        let cur_vol = selem.get_playback_volume(alsa::mixer::SelemChannelId::mono()).expect("Couldn't get current volume");
+        let range = (max - min) as f64;
+
+        let new_vol:u16;
+
+        if let Some(vol) = set_volume {
+            let alsa_volume:i64 = ((vol as f64 / 0xFFFF as f64) * range) as i64 + min;
+            debug!("Maping volume {:?} [u16] ->> Alsa {:?} [i64]",vol,alsa_volume);
+            selem.set_playback_volume_all(alsa_volume).expect("Couldn't set alsa volume");
+            new_vol = vol; // Meh
+        } else {
+            new_vol =  (((cur_vol - min) as f64 / range) * 0xFFFF as f64) as u16;
+            debug!("Maping volume {:?} [u16] <<- Alsa {:?} [i64]",new_vol, cur_vol);
+        }
+
+
+        Ok(new_vol)
+    }
+}
 
 impl Mixer for AlsaMixer {
     fn open(device: Option<String>) -> AlsaMixer {
-        let card = device.unwrap_or(String::from("default"));
-        let mixer = String::from("PCM");
+        let card = env::var("LIBRESPOT_CARD").unwrap_or(device.unwrap_or(String::from("default")));
+        let mixer = env::var("LIBRESPOT_MIXER").unwrap_or(String::from("PCM"));
+        let index: u32 = 0;
+        info!(
+            "Setting up new mixer: card:{} mixer:{} index:{}",
+            card, mixer, index
+        );
         AlsaMixer {
             card: card,
             mixer: mixer,
+            index: index,
         }
     }
 
@@ -38,37 +63,20 @@ impl Mixer for AlsaMixer {
     }
 
     fn volume(&self) -> u16 {
-        let mixer = alsa::mixer::Mixer::new(&self.card, false).unwrap();
-        let selem_id = alsa::mixer::SelemId::new(&self.mixer, 0);
-        let selem = mixer.find_selem(&selem_id).unwrap();
-        let (min, max) = selem.get_playback_volume_range();
-        let volume: i64 = selem.get_playback_volume(alsa::mixer::SelemChannelId::FrontLeft).unwrap();
-
-        // Spotify uses a volume range from 0 to 65535, but the ALSA mixers resolution might
-        // differ, e.g. most ALSA mixers uses a resolution of 256. Therefore, we have to calculate
-        // the multiplier to use, to get the corresponding Spotify volume value from the ALSA
-        // mixers volume.
-        let resolution = max - min + 1;
-        let multiplier: u16 = (((0xFFFF + 1) / resolution) - 1) as u16;
 
-        volume as u16 * multiplier
+        match self.map_volume(None){
+                Ok(vol) => vol,
+                Err(e)  => {
+                        error!("Error getting volume for <{}>, {:?}",self.card, e);
+                        0 }
+        }
     }
 
     fn set_volume(&self, volume: u16) {
-        let mixer = alsa::mixer::Mixer::new(&self.card, false).unwrap();
-        let selem_id = alsa::mixer::SelemId::new(&self.mixer, 0);
-        let selem = mixer.find_selem(&selem_id).unwrap();
-        let (min, max) = selem.get_playback_volume_range();
-
-        // Spotify uses a volume range from 0 to 65535, but the ALSA mixers resolution might
-        // differ, e.g. most ALSA mixers uses a resolution of 256. Therefore, we have to calculate
-        // the factor to use, to get the corresponding ALSA mixers volume value from the Spotify
-        // volume.
-        let resolution = max - min + 1;
-        let factor: u16 = (((0xFFFF + 1) / resolution) - 1) as u16;
-        let volume: i64 = (volume / factor) as i64;
-        info!("Setting volume: {:?}", volume);
-        selem.set_playback_volume_all(volume).unwrap();
+        match self.map_volume(Some(volume)){
+                Ok(_) => (),
+                Err(e)  => error!("Error setting volume for <{}>, {:?}",self.card, e),
+        }
     }
 
     fn get_audio_filter(&self) -> Option<Box<AudioFilter + Send>> {