Make sending of silence configurable

doc/configuration.md

@@ -138,10 +138,14 @@ output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format
 Captures audio from an alsa device
 
 ```sh
-alsa://?name=<name>&device=<alsa device>
+alsa://?name=<name>&device=<alsa device>[&send_silence=false][&idle_threshold=100]
 ```
 
-`device` is an alsa device name or identifier, e.g. `default` or `hw:0,0`
+#### Available parameters
+
+- `device`: alsa device name or identifier, e.g. `default` or `hw:0,0` or `hw:0,0,0`
+- `idle_threshold`: switch stream state from playing to idle after receiving `idle_threshold` milliseconds of silence
+- `send_silence`: forward silence to clients when stream state is `idle`
 
 The output of any audio player that uses alsa can be redirected to Snapcast by using an alsa loopback device:
 

server/etc/snapserver.conf

@@ -115,7 +115,7 @@ doc_root = /usr/share/snapserver/snapweb
 # Non blocking sources support the dryout_ms parameter: when no new data is read from the source, send silence to the clients
 # Available types are:
 # pipe: pipe:///<path/to/pipe>?name=<name>[&mode=create][&dryout_ms=2000], mode can be "create" or "read"
-# librespot: librespot:///<path/to/librespot>?name=<name>[&dryout_ms=2000][&username=<my username>&password=<my password>][&devicename=Snapcast][&bitrate=320][&wd_timeout=7800][&volume=100][&onevent=""][&nomalize=false][&autoplay=false]
+# librespot: librespot:///<path/to/librespot>?name=<name>[&dryout_ms=2000][&username=<my username>&password=<my password>][&devicename=Snapcast][&bitrate=320][&wd_timeout=7800][&volume=100][&onevent=""][&nomalize=false][&autoplay=false][&params=<generic librepsot process arguments>]
 #  note that you need to have the librespot binary on your machine
 #  sampleformat will be set to "44100:16:2"
 # file: file:///<path/to/PCM/file>?name=<name>
@@ -125,7 +125,7 @@ doc_root = /usr/share/snapserver/snapweb
 #  sampleformat will be set to "44100:16:2"
 # tcp server: tcp://<listen IP, e.g. 127.0.0.1>:<port>?name=<name>[&mode=server]
 # tcp client: tcp://<server IP, e.g. 127.0.0.1>:<port>?name=<name>&mode=client
-# alsa: alsa://?name=<name>&device=<alsa device>
+# alsa: alsa://?name=<name>&device=<alsa device>[&send_silence=false][&idle_threshold=100]
 # meta: meta:///<name of source#1>/<name of source#2>/.../<name of source#N>?name=<name>
 source = pipe:///tmp/snapfifo?name=default
 #source = tcp://127.0.0.1?name=mopidy_tcp

server/streamreader/alsa_stream.cpp

@@ -69,6 +69,8 @@ AlsaStream::AlsaStream(PcmListener* pcmListener, boost::asio::io_context& ioc, c
     : PcmStream(pcmListener, ioc, uri), handle_(nullptr), read_timer_(ioc), silence_(0ms)
 {
     device_ = uri_.getQuery("device", "hw:0");
+    send_silence_ = (uri_.getQuery("send_silence", "false") == "true");
+    idle_threshold_ = std::chrono::milliseconds(std::max(cpt::stoi(uri_.getQuery("idle_threshold", "100")), 10));
     LOG(DEBUG, LOG_TAG) << "Device: " << device_ << "\n";
 }
 
@@ -215,7 +217,7 @@ void AlsaStream::do_read()
         if (std::memcmp(chunk_->payload, silent_chunk_.data(), silent_chunk_.size()) == 0)
         {
             silence_ += chunk_->duration<std::chrono::microseconds>();
-            if (silence_ > 100ms)
+            if (silence_ > idle_threshold_)
             {
                 setState(ReaderState::kIdle);
             }
@@ -223,6 +225,8 @@ void AlsaStream::do_read()
         else
         {
             silence_ = 0ms;
+            if ((state_ == ReaderState::kIdle) && !send_silence_)
+                first_ = true;
             setState(ReaderState::kPlaying);
         }
 
@@ -234,7 +238,10 @@ void AlsaStream::do_read()
             tvEncodedChunk_ = std::chrono::steady_clock::now() - duration;
         }
 
+        if ((state_ == ReaderState::kPlaying) || ((state_ == ReaderState::kIdle) && send_silence_))
+        {
             chunkRead(*chunk_);
+        }
 
         nextTick_ += duration;
         auto currentTick = std::chrono::steady_clock::now();

server/streamreader/alsa_stream.hpp

@@ -56,6 +56,11 @@ protected:
     std::vector<char> silent_chunk_;
     std::chrono::microseconds silence_;
     std::string lastException_;
+
+    /// send silent chunks to clients
+    bool send_silence_;
+    /// silence duration before switching the stream to idle
+    std::chrono::milliseconds idle_threshold_;
 };
 
 } // namespace streamreader