Qt Audio in Linux and Windows: different behaviour

[janK]

That is true, but that does not explain why the Audiosink opens without error and then goes into state Idle. especially when the QIODevice reports that opening is fine, The result is that in the end no bytes are read.
If I understand the documentation, then the Audiosink goes into state Idle if there is no input, but I ensured that a buffer is filled, and then no element of the buffer is read
And again, using Linux, it works fine, so either the Windows version should have worked, or the Linux version works while it should not

I think the basic quesiton is
if the creation of a QIODevice and the creation of an QAudioSink is also without errors,
under what conditions changes the AudioSink the state to "Idle"

I checked again btw that while sthe "start" of the QIODevice is - according to the QIODevice = without problems, the "readData" function
is not called at all. So, it seems that the AudioSink does not see that the readData function can be called

Anyway, in the documentation I do not find any clue of why this behavious happens under Windows

[janK]

Implementing the (virtual) bytesAvailable function for the derives QUIDevice class did the trick. It remains a mystery why the Linux implementation apaprently does not require that and rhe windows ine does
(Both are 6.8.1)

[d_stranz]

Implementing the (virtual) bytesAvailable function for the derives QUIDevice class did the trick.

I assume you meant QIODevice. It would be nice if you could post your code for that to help others who might experience the same problem in the future and come across this thread looking for an answer.

[janK]

I assume you meant QIODevice. It would be nice if you could post your code for that to help others who might experience the same problem in the future and come across this thread looking for an answer.

The siruation was roughly as sketched below, a derived class from QIODevice was used and sound was output under Linux and silence was output under Windows
Under windows, the AudioSink that was use to embed the derived QIODevice class gave state Idle under Window and Active under Linux
The read function implemented in the derived QIOdevice class always gives the required amount of bytes back, taken from abuffer and a shortage, if appearing, filled with o bytes.
The original version differs from the one given below by not having impmented the "bytesAvailable" function and the "sze" function.
After implementing the bytesAvailable function itworked fine. Appparently the Windows version of AudioSink - when started- first looks at the bytesAvailable function, while the
same class in the Linux version does not.

The amount returned by the bytesAvailable function did not matter, as long as the (virtual) function is reimplemented and returns a value > 0 it works fine (again, given that the read function always returns the
requested amount

In both cases it was version 6.8.1.

Qt_AudioDevice::~Qt_AudioDevice () {
        close ();
}
 
void    Qt_AudioDevice::start () {
        bool b = open (QIODevice::ReadOnly);
}
 
//      we always return "maxSize" bytes
qint64  Qt_AudioDevice::readData (char* buffer, qint64 maxSize) {
//      "maxSize" is the requested size in bytes
//      "amount" is in uint8_t's
        amount = Buffer -> getDataFromBuffer (buffer, maxSize);
        if (amount < maxSize) {
           for (int i = amount; i < maxSize; i ++)
              buffer [i] = (char)(0);
        }
}
 
//      usused here
qint64  Qt_AudioDevice::writeData (const char* data, qint64 len) {
        Q_UNUSED (data);
        Q_UNUSED (len);
        return 0;
}
 
 
qint64  Qt_AudioDevice::bytesAvailable  () const {
        return  32768;
}

Qt_AudioDevice::~Qt_AudioDevice () {
        close ();
}

void    Qt_AudioDevice::start () {
        bool b = open (QIODevice::ReadOnly);
}

//      we always return "maxSize" bytes
qint64  Qt_AudioDevice::readData (char* buffer, qint64 maxSize) {
//      "maxSize" is the requested size in bytes
//      "amount" is in uint8_t's
        amount = Buffer -> getDataFromBuffer (buffer, maxSize);
        if (amount < maxSize) {
           for (int i = amount; i < maxSize; i ++)
              buffer [i] = (char)(0);
        }
}

//      usused here
qint64  Qt_AudioDevice::writeData (const char* data, qint64 len) {
        Q_UNUSED (data);
        Q_UNUSED (len);
        return 0;
}


qint64  Qt_AudioDevice::bytesAvailable  () const {
        return  32768;
}

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