From d3dd4224463d954691048c3a8ffb64a7e599117f Mon Sep 17 00:00:00 2001
From: Stefan Sayer <stefan.sayer@googlemail.com>
Date: Fri, 10 Jul 2009 14:43:54 +0000
Subject: [PATCH] AmAudio device for playing/sinking silence, optionally a
 certain length

git-svn-id: http://svn.berlios.de/svnroot/repos/sems/trunk@1464 8eb893ce-cfd4-0310-b710-fb5ebe64c474
---
 core/AmAdvancedAudio.cpp | 51 ++++++++++++++++++++++++++++++++++++++++
 core/AmAdvancedAudio.h   | 34 +++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/core/AmAdvancedAudio.cpp b/core/AmAdvancedAudio.cpp
index 106402cc..5fa6c5b9 100644
--- a/core/AmAdvancedAudio.cpp
+++ b/core/AmAdvancedAudio.cpp
@@ -279,3 +279,54 @@ int AmAudioFrontlist::get(unsigned int user_ts, unsigned char* buffer, unsigned
   ba_mut.unlock();
   return res;
 }
+
+
+int AmNullAudio::write(unsigned int user_ts, unsigned int size) {
+  // need to stop at some point? 
+  if (write_msec < 0)
+    return size;
+
+  if (!write_end_ts_i) {
+    write_end_ts_i = true;
+    write_end_ts = user_ts + write_msec*fmt->rate/1000;
+  }
+
+  if (!ts_less()(user_ts, write_end_ts)) {
+    DBG("%dms of silence ended (write)\n", write_msec);
+    return -1;
+  }
+
+  return size;
+}
+
+int AmNullAudio::read(unsigned int user_ts, unsigned int size) {
+  // need to stop at some point? 
+  if (read_msec < 0) {
+    memset((unsigned char*) samples, 0, size);
+    return size;
+  }
+
+  if (!read_end_ts_i) {
+    read_end_ts_i = true;
+    read_end_ts = user_ts + read_msec*fmt->rate/1000; 
+  }
+
+  if (!ts_less()(user_ts, read_end_ts)) {
+    DBG("%dms of silence ended (read)\n", read_msec);
+    return -1;
+  }
+
+  memset((unsigned char*) samples, 0, size);
+  return size;
+}
+
+void AmNullAudio::setReadLength(int n_msec) {
+  read_msec = n_msec;
+  read_end_ts_i = false;
+}
+
+void AmNullAudio::setWriteLength(int n_msec) {
+  write_msec = n_msec;
+  write_end_ts_i = false;
+}
+
diff --git a/core/AmAdvancedAudio.h b/core/AmAdvancedAudio.h
index 97e022d6..d97c6efd 100644
--- a/core/AmAdvancedAudio.h
+++ b/core/AmAdvancedAudio.h
@@ -143,5 +143,39 @@ class AmAudioDelay : public AmAudio {
   int read(unsigned int user_ts, unsigned int size);
 };
 
+/** 
+ * AmNullAudio plays silence, and recording goes to void. 
+ * it can be parametrized with a maximum length (in milliseconds), 
+ * after which it is ended.
+ * Read and write length can also be set after creation (and possibly even
+ * when in use).
+ */
+class AmNullAudio 
+: public AmAudio {
+  int read_msec;
+  int write_msec;
+
+  bool read_end_ts_i;
+  unsigned int read_end_ts;
+
+  bool write_end_ts_i;
+  unsigned int write_end_ts;
+
+ public:
+  AmNullAudio(int read_msec = -1, int write_msec = -1)
+    : read_msec(read_msec), write_msec(write_msec),
+    read_end_ts_i(false), write_end_ts_i(false) { }
+  ~AmNullAudio() { }
+
+  /** (re) set maximum read length*/
+  void setReadLength(int n_msec);
+  /** (re) set maximum write length*/
+  void setWriteLength(int n_msec);
+
+ protected:
+  int write(unsigned int user_ts, unsigned int size);
+  int read(unsigned int user_ts, unsigned int size);
+};
+
 #endif // _AmAdvancedAudio_h_