alsa backend for low-level audio doesn't pass new unit tests

New unit tests have identified issues with alsa backend. These issues
need to be resolved before new unit tests are added.

  * stateChanged() signal should only be emitted on change of state
    currently signals can be emitted multiple times.
  * elapsedUSecs() currently uses alsa to provide this value but
    this is not reliable enough and this time is reset when
    suspend/resuming. This is not correct operation.
  * for output data is being lost when input cant be read
    from QIODevice but cannot be written to audio sub system.

Task-number:QTBUG-8440
Reviewed-by:Dmytro Poplavskiy

2 files changed, 67 insertions, 118 deletions

diff --git a/src/multimedia/audio/qaudioinput_alsa_p.cpp b/src/multimedia/audio/qaudioinput_alsa_p.cpp
index 26e46b3..6010f3c 100644
--- a/src/multimedia/audio/qaudioinput_alsa_p.cpp
+++ b/src/multimedia/audio/qaudioinput_alsa_p.cpp
@@ -217,9 +217,11 @@ QIODevice* QAudioInputPrivate::start(QIODevice* device)
         //set to pull mode
         pullMode = true;
         audioSource = device;
+        deviceState = QAudio::ActiveState;
     } else {
         //set to push mode
         pullMode = false;
+        deviceState = QAudio::IdleState;
         audioSource = new InputPrivate(this);
         audioSource->open(QIODevice::ReadOnly | QIODevice::Unbuffered);
     }
@@ -413,7 +415,6 @@ bool QAudioInputPrivate::open()
     timer->start(period_time*chunks/2000);
 
     errorState  = QAudio::NoError;
-    deviceState = QAudio::ActiveState;
 
     totalTimeValue = 0;
 
@@ -439,7 +440,7 @@ int QAudioInputPrivate::bytesReady() const
     if(resuming)
         return period_size;
 
-    if(deviceState != QAudio::ActiveState)
+    if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState)
         return 0;
     int frames = snd_pcm_avail_update(handle);
     if((int)frames > (int)buffer_frames)
@@ -450,8 +451,8 @@ int QAudioInputPrivate::bytesReady() const
 
 qint64 QAudioInputPrivate::read(char* data, qint64 len)
 {
-    Q_UNUSED(data)
     Q_UNUSED(len)
+
     // Read in some audio data and write it to QIODevice, pull mode
     if ( !handle )
         return 0;
@@ -468,7 +469,7 @@ qint64 QAudioInputPrivate::read(char* data, qint64 len)
         if (readFrames >= 0) {
             err = snd_pcm_frames_to_bytes(handle, readFrames);
 #ifdef DEBUG_AUDIO
-            qDebug()<<QString::fromLatin1("PULL: read in bytes = %1 (frames=%2)").arg(err).arg(readFrames).toLatin1().constData();
+            qDebug()<<QString::fromLatin1("read in bytes = %1 (frames=%2)").arg(err).arg(readFrames).toLatin1().constData();
 #endif
             break;
         } else if((readFrames == -EAGAIN) || (readFrames == -EINTR)) {
@@ -489,28 +490,46 @@ qint64 QAudioInputPrivate::read(char* data, qint64 len)
     if(err > 0) {
         // got some send it onward
 #ifdef DEBUG_AUDIO
-        qDebug()<<"PULL: frames to write to QIODevice = "<<
+        qDebug()<<"frames to write to QIODevice = "<<
             snd_pcm_bytes_to_frames( handle, (int)err )<<" ("<<err<<") bytes";
 #endif
-        if(deviceState != QAudio::ActiveState)
+        if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState)
             return 0;
+        if (pullMode) {
+            qint64 l = audioSource->write(audioBuffer,err);
+            if(l < 0) {
+                close();
+                errorState = QAudio::IOError;
+                deviceState = QAudio::StoppedState;
+                emit stateChanged(deviceState);
+            } else if(l == 0) {
+                if (deviceState != QAudio::IdleState) {
+                    errorState = QAudio::NoError;
+                    deviceState = QAudio::IdleState;
+                    emit stateChanged(deviceState);
+                }
+            } else {
+                totalTimeValue += err;
+                resuming = false;
+                if (deviceState != QAudio::ActiveState) {
+                    errorState = QAudio::NoError;
+                    deviceState = QAudio::ActiveState;
+                    emit stateChanged(deviceState);
+                }
+            }
+            return l;
 
-        qint64 l = audioSource->write(audioBuffer,err);
-        if(l < 0) {
-            close();
-            errorState = QAudio::IOError;
-            deviceState = QAudio::StoppedState;
-            emit stateChanged(deviceState);
-        } else if(l == 0) {
-            errorState = QAudio::NoError;
-            deviceState = QAudio::IdleState;
         } else {
-            totalTimeValue += snd_pcm_bytes_to_frames(handle, err)*1000000/settings.frequency();
+            memcpy(data,audioBuffer,err);
+            totalTimeValue += err;
             resuming = false;
-            errorState = QAudio::NoError;
-            deviceState = QAudio::ActiveState;
+            if (deviceState != QAudio::ActiveState) {
+                errorState = QAudio::NoError;
+                deviceState = QAudio::ActiveState;
+                emit stateChanged(deviceState);
+            }
+            return err;
         }
-        return l;
     }
     return 0;
 }
@@ -569,7 +588,7 @@ int QAudioInputPrivate::notifyInterval() const
 
 qint64 QAudioInputPrivate::processedUSecs() const
 {
-    return totalTimeValue;
+    return qint64(1000000) * totalTimeValue / settings.frequency();
 }
 
 void QAudioInputPrivate::suspend()
@@ -617,34 +636,10 @@ bool QAudioInputPrivate::deviceReady()
 
 qint64 QAudioInputPrivate::elapsedUSecs() const
 {
-    if(!handle)
-        return 0;
-
     if (deviceState == QAudio::StoppedState)
         return 0;
 
-#if(SND_LIB_MAJOR == 1 && SND_LIB_MINOR == 0 && SND_LIB_SUBMINOR >= 14)
-    snd_pcm_status_t* status;
-    snd_pcm_status_alloca(&status);
-
-    snd_timestamp_t t1,t2;
-    if( snd_pcm_status(handle, status) >= 0) {
-        snd_pcm_status_get_tstamp(status,&t1);
-        snd_pcm_status_get_trigger_tstamp(status,&t2);
-        t1.tv_sec-=t2.tv_sec;
-
-        signed long l = (signed long)t1.tv_usec - (signed long)t2.tv_usec;
-        if(l < 0) {
-            t1.tv_sec--;
-            l = -l;
-            l %= 1000000;
-        }
-        return ((t1.tv_sec * 1000000)+l);
-    } else
-        return 0;
-#else
     return clockStamp.elapsed()*1000;
-#endif
 }
 
 void QAudioInputPrivate::reset()
@@ -670,43 +665,7 @@ InputPrivate::~InputPrivate()
 
 qint64 InputPrivate::readData( char* data, qint64 len)
 {
-    // push mode, user read() called
-    if((audioDevice->state() != QAudio::ActiveState) && !audioDevice->resuming)
-        return 0;
-
-    int readFrames;
-    int count=0, err = 0;
-
-    while(count < 5) {
-        int frames = snd_pcm_bytes_to_frames(audioDevice->handle, len);
-        readFrames = snd_pcm_readi(audioDevice->handle, data, frames);
-        if (readFrames >= 0) {
-            err = snd_pcm_frames_to_bytes(audioDevice->handle, readFrames);
-#ifdef DEBUG_AUDIO
-            qDebug()<<QString::fromLatin1("PUSH: read in bytes = %1 (frames=%2)").arg(err).arg(readFrames).toLatin1().constData();
-#endif
-            break;
-        } else if((readFrames == -EAGAIN) || (readFrames == -EINTR)) {
-            audioDevice->errorState = QAudio::IOError;
-            err = 0;
-            break;
-        } else {
-            if(readFrames == -EPIPE) {
-                audioDevice->errorState = QAudio::UnderrunError;
-                err = snd_pcm_prepare(audioDevice->handle);
-            } else if(readFrames == -ESTRPIPE) {
-                err = snd_pcm_prepare(audioDevice->handle);
-            }
-            if(err != 0) break;
-        }
-        count++;
-    }
-    if(err > 0 && readFrames > 0) {
-        audioDevice->totalTimeValue += readFrames*1000/audioDevice->settings.frequency()*1000;
-        audioDevice->deviceState = QAudio::ActiveState;
-        return err;
-    }
-    return 0;
+    return audioDevice->read(data,len);
 }
 
 qint64 InputPrivate::writeData(const char* data, qint64 len)
diff --git a/src/multimedia/audio/qaudiooutput_alsa_p.cpp b/src/multimedia/audio/qaudiooutput_alsa_p.cpp
index 7b89cef..b127103 100644
--- a/src/multimedia/audio/qaudiooutput_alsa_p.cpp
+++ b/src/multimedia/audio/qaudiooutput_alsa_p.cpp
@@ -259,6 +259,7 @@ void QAudioOutputPrivate::stop()
 {
     if(deviceState == QAudio::StoppedState)
         return;
+    errorState = QAudio::NoError;
     deviceState = QAudio::StoppedState;
     close();
     emit stateChanged(deviceState);
@@ -494,10 +495,13 @@ qint64 QAudioOutputPrivate::write( const char *data, qint64 len )
         err = snd_pcm_writei( handle, data, frames );
     }
     if(err > 0) {
-        totalTimeValue += err*1000000/settings.frequency();
+        totalTimeValue += err;
         resuming = false;
         errorState = QAudio::NoError;
-        deviceState = QAudio::ActiveState;
+        if (deviceState != QAudio::ActiveState) {
+            deviceState = QAudio::ActiveState;
+            emit stateChanged(deviceState);
+        }
         return snd_pcm_frames_to_bytes( handle, err );
     } else
         err = xrun_recovery(err);
@@ -542,7 +546,7 @@ int QAudioOutputPrivate::notifyInterval() const
 
 qint64 QAudioOutputPrivate::processedUSecs() const
 {
-    return totalTimeValue;
+    return qint64(1000000) * totalTimeValue / settings.frequency();
 }
 
 void QAudioOutputPrivate::resume()
@@ -562,10 +566,8 @@ void QAudioOutputPrivate::resume()
             bytesAvailable = (int)snd_pcm_frames_to_bytes(handle, buffer_frames);
         }
         resuming = true;
-        if(pullMode)
-            deviceState = QAudio::ActiveState;
-        else
-            deviceState = QAudio::IdleState;
+
+        deviceState = QAudio::ActiveState;
 
         errorState = QAudio::NoError;
         timer->start(period_time/1000);
@@ -637,7 +639,9 @@ bool QAudioOutputPrivate::deviceReady()
             // Got some data to output
             if(deviceState != QAudio::ActiveState)
                 return true;
-            write(audioBuffer,l);
+            qint64 bytesWritten = write(audioBuffer,l);
+            if (bytesWritten != l)
+                audioSource->seek(audioSource->pos()-(l-bytesWritten));
             bytesAvailable = bytesFree();
 
         } else if(l == 0) {
@@ -645,9 +649,11 @@ bool QAudioOutputPrivate::deviceReady()
             bytesAvailable = bytesFree();
             if(bytesAvailable > snd_pcm_frames_to_bytes(handle, buffer_frames-period_frames)) {
                 // Underrun
-                errorState = QAudio::UnderrunError;
-                deviceState = QAudio::IdleState;
-                emit stateChanged(deviceState);
+                if (deviceState != QAudio::IdleState) {
+                    errorState = QAudio::UnderrunError;
+                    deviceState = QAudio::IdleState;
+                    emit stateChanged(deviceState);
+                }
             }
 
         } else if(l < 0) {
@@ -655,8 +661,17 @@ bool QAudioOutputPrivate::deviceReady()
             errorState = QAudio::IOError;
             emit stateChanged(deviceState);
         }
-    } else
+    } else {
         bytesAvailable = bytesFree();
+        if(bytesAvailable > snd_pcm_frames_to_bytes(handle, buffer_frames-period_frames)) {
+            // Underrun
+            if (deviceState != QAudio::IdleState) {
+                errorState = QAudio::UnderrunError;
+                deviceState = QAudio::IdleState;
+                emit stateChanged(deviceState);
+            }
+        }
+    }
 
     if(deviceState != QAudio::ActiveState)
         return true;
@@ -671,35 +686,10 @@ bool QAudioOutputPrivate::deviceReady()
 
 qint64 QAudioOutputPrivate::elapsedUSecs() const
 {
-    if(!handle)
-        return 0;
-
     if (deviceState == QAudio::StoppedState)
         return 0;
 
-#if(SND_LIB_MAJOR == 1 && SND_LIB_MINOR == 0 && SND_LIB_SUBMINOR >= 14)
-    snd_pcm_status_t* status;
-    snd_pcm_status_alloca(&status);
-
-    snd_timestamp_t t1,t2;
-    if( snd_pcm_status(handle, status) >= 0) {
-        snd_pcm_status_get_tstamp(status,&t1);
-        snd_pcm_status_get_trigger_tstamp(status,&t2);
-        t1.tv_sec-=t2.tv_sec;
-
-        signed long l = (signed long)t1.tv_usec - (signed long)t2.tv_usec;
-        if(l < 0) {
-            t1.tv_sec--;
-            l = -l;
-            l %= 1000000;
-        }
-        return ((t1.tv_sec * 1000000)+l);
-    } else
-        return 0;
-#else
     return clockStamp.elapsed()*1000;
-#endif
-    return 0;
 }
 
 void QAudioOutputPrivate::reset()