i try write media stream to buffer and then to file
buf.open(QBuffer::ReadWrite);
file.setFileName("out.mp3");
file.open(QIODevice::WriteOnly|QFile::Truncate);
mp3file.setDevice(&file);
attempts:
1.
void MainWindow::reply_readyRead()
{
QByteArray qa;
qa = reply->read(16 * 1024);
buf.write(qa.data(),qa.size());
}
2.
void MainWindow::reply_readyRead()
{
QByteArray qa;
qa = reply->read(16 * 1024);
buf.write(qa.data(),qa.size());
mp3file.writeRawData(qa.data() ,qa.size());
}
always out-file/buffer is broken(missed parts). you can listen this file here MP3 FILE
writing mp3 from static files(from url) goes well!
You don't read all the data that is available. Either read all the data at once:
QByteArray qa = reply->readAll();
or try doing it in a loop:
QByteArray qa;
while (reply->bytesAvailable() > 0)
qa += reply->read(16 * 1024);
Related
Sometimes I am getting "underrun occured" from ALSA lib and that means the audioouput is not getting the values on time to play. Alsa then repeats the old buffer values on the speaker.
How can I avoid underruns on QAudioOuput?
I am using Qt5.9.1 and ARM Based CPU running on Debian 8.
I tried to change the buffersize:
audioOutput->setBufferSize(144000);
qDebug()<<"buffersize "<<audioOutput->bufferSize()<<" period size" .
<<audioOutput->periodSize();
I get: buffersize 144000 period size 0
and after audiOutput->start() I get: buffersize 19200 period size 3840
Here is what I am doing:
audioOutput->setBufferSize(144000);
qDebug()<<"buffersize "<<audioOutput->bufferSize()<<" period size" .
<<audioOutput->periodSize();
m_audioInput = audioInput->start();
m_audioOutput = audioOutput->start();
qDebug()<<"buffersize "<<audioOutput->bufferSize()<<" period size"<
<<audioOutput->periodSize();
connect(m_audioInput, SIGNAL(readyRead()), SLOT(readBufferSlot()));
Once audio data gets recorded I write to the QIODevice m_audioOutput the values from QIODevice m_audioInput.
So I think I have a timing issue sometimes and the audio interval for both is 1000ms before and after start().
Why cant I increase the buffer size? And how can I avoid underrun?
Based on my experience with QAudioOutput, it's buffer is intended just to keep real-time playing, you can't for example drop 1 minute of sound directly to the QIODevice expecting it gets buffered and played sequentially, but it do not means that you can't buffer sound, just means that you need to do it by yourself.
I made the following example in "C-Style" to make an all-in-one solution, it buffers 1000 milliseconds (1 second) of the input before play it.
The event loop needs to be available to process the Qt SIGNALs.
In my tests, 1 second buffering is fairly enough to avoid under runs.
#include <QtCore>
#include <QtMultimedia>
#define MAX_BUFFERED_TIME 1000
static inline int timeToSize(int ms, const QAudioFormat &format)
{
return ((format.channelCount() * (format.sampleSize() / 8) * format.sampleRate()) * ms / 1000);
}
struct AudioContext
{
QAudioInput *m_audio_input;
QIODevice *m_input_device;
QAudioOutput *m_audio_output;
QIODevice *m_output_device;
QByteArray m_buffer;
QAudioDeviceInfo m_input_device_info;
QAudioDeviceInfo m_output_device_info;
QAudioFormat m_format;
int m_time_to_buffer;
int m_max_size_to_buffer;
int m_size_to_buffer;
bool m_buffer_requested = true; //Needed
bool m_play_called = false;
};
void play(AudioContext *ctx)
{
//Set that last async call was triggered
ctx->m_play_called = false;
if (ctx->m_buffer.isEmpty())
{
//If data is empty set that nothing should be played
//until the buffer has at least the minimum buffered size already set
ctx->m_buffer_requested = true;
return;
}
else if (ctx->m_buffer.size() < ctx->m_size_to_buffer)
{
//If buffer doesn't contains enough data,
//check if exists a already flag telling that the buffer comes
//from a empty state and should not play anything until have the minimum data size
if (ctx->m_buffer_requested)
return;
}
else
{
//Buffer is ready and data can be played
ctx->m_buffer_requested = false;
}
int readlen = ctx->m_audio_output->periodSize();
int chunks = ctx->m_audio_output->bytesFree() / readlen;
//Play data while it's available in the output device
while (chunks)
{
//Get chunk from the buffer
QByteArray samples = ctx->m_buffer.mid(0, readlen);
int len = samples.size();
ctx->m_buffer.remove(0, len);
//Write data to the output device after the volume was applied
if (len)
{
ctx->m_output_device->write(samples);
}
//If chunk is smaller than the output chunk size, exit loop
if (len != readlen)
break;
//Decrease the available number of chunks
chunks--;
}
}
void preplay(AudioContext *ctx)
{
//Verify if exists a pending call to play function
//If not, call the play function async
if (!ctx->m_play_called)
{
ctx->m_play_called = true;
QTimer::singleShot(0, [=]{play(ctx);});
}
}
void init(AudioContext *ctx)
{
/***** INITIALIZE INPUT *****/
//Check if format is supported by the choosen input device
if (!ctx->m_input_device_info.isFormatSupported(ctx->m_format))
{
qDebug() << "Format not supported by the input device";
return;
}
//Initialize the audio input device
ctx->m_audio_input = new QAudioInput(ctx->m_input_device_info, ctx->m_format, qApp);
ctx->m_input_device = ctx->m_audio_input->start();
if (!ctx->m_input_device)
{
qDebug() << "Failed to open input audio device";
return;
}
//Call the readyReadPrivate function when data are available in the input device
QObject::connect(ctx->m_input_device, &QIODevice::readyRead, [=]{
//Read sound samples from input device to buffer
ctx->m_buffer.append(ctx->m_input_device->readAll());
preplay(ctx);
});
/***** INITIALIZE INPUT *****/
/***** INITIALIZE OUTPUT *****/
//Check if format is supported by the choosen output device
if (!ctx->m_output_device_info.isFormatSupported(ctx->m_format))
{
qDebug() << "Format not supported by the output device";
return;
}
int internal_buffer_size;
//Adjust internal buffer size
if (ctx->m_format.sampleRate() >= 44100)
internal_buffer_size = (1024 * 10) * ctx->m_format.channelCount();
else if (ctx->m_format.sampleRate() >= 24000)
internal_buffer_size = (1024 * 6) * ctx->m_format.channelCount();
else
internal_buffer_size = (1024 * 4) * ctx->m_format.channelCount();
//Initialize the audio output device
ctx->m_audio_output = new QAudioOutput(ctx->m_output_device_info, ctx->m_format, qApp);
//Increase the buffer size to enable higher sample rates
ctx->m_audio_output->setBufferSize(internal_buffer_size);
//Compute the size in bytes to be buffered based on the current format
ctx->m_size_to_buffer = int(timeToSize(ctx->m_time_to_buffer, ctx->m_format));
//Define a highest size that the buffer are allowed to have in the given time
//This value is used to discard too old buffered data
ctx->m_max_size_to_buffer = ctx->m_size_to_buffer + int(timeToSize(MAX_BUFFERED_TIME, ctx->m_format));
ctx->m_output_device = ctx->m_audio_output->start();
if (!ctx->m_output_device)
{
qDebug() << "Failed to open output audio device";
return;
}
//Timer that helps to keep playing data while it's available on the internal buffer
QTimer *timer_play = new QTimer(qApp);
timer_play->setTimerType(Qt::PreciseTimer);
QObject::connect(timer_play, &QTimer::timeout, [=]{
preplay(ctx);
});
timer_play->start(10);
//Timer that checks for too old data in the buffer
QTimer *timer_verifier = new QTimer(qApp);
QObject::connect(timer_verifier, &QTimer::timeout, [=]{
if (ctx->m_buffer.size() >= ctx->m_max_size_to_buffer)
ctx->m_buffer.clear();
});
timer_verifier->start(qMax(ctx->m_time_to_buffer, 10));
/***** INITIALIZE OUTPUT *****/
qDebug() << "Playing...";
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
AudioContext ctx;
QAudioFormat format;
format.setCodec("audio/pcm");
format.setSampleRate(44100);
format.setChannelCount(1);
format.setSampleSize(16);
format.setByteOrder(QAudioFormat::LittleEndian);
format.setSampleType(QAudioFormat::SignedInt);
ctx.m_format = format;
ctx.m_input_device_info = QAudioDeviceInfo::defaultInputDevice();
ctx.m_output_device_info = QAudioDeviceInfo::defaultOutputDevice();
ctx.m_time_to_buffer = 1000;
init(&ctx);
return a.exec();
}
I'm creating a socket-based program to send a screenshot from one user to another user. I need to convert a screenshot to a byte array before sending. After I convert my screenshot to a QByteArray I insert 4 bytes to the beginning of the array to mark that it is a picture (it is the number 20 to tell me it is a picture and not text or something else).
After I send the byte array via a socket to other user, when it is received I read the first 4 bytes to know what it is. Since it was a picture I then convert it from a QByteArray to QPixmap to show it on a label. I use secondPixmap.loadFromData(byteArray,"JPEG") to load it but it not load any picture.
This is a sample of my code:
void MainWindow::shootScreen()
{
originalPixmap = QPixmap(); // clear image for low memory situations
// on embedded devices.
originalPixmap = QGuiApplication::primaryScreen()->grabWindow(0);
scaledPixmap = originalPixmap.scaled(500, 500);
QByteArray bArray;
QBuffer buffer(&bArray);
buffer.open(QIODevice::WriteOnly);
originalPixmap.save(&buffer,"JPEG",5);
qDebug() << bArray.size() << "diz0";
byteArray= QByteArray();
QDataStream ds(&byteArray,QIODevice::ReadWrite);
int32_t c = 20;
ds << c;
ds<<bArray;
}
void MainWindow::updateScreenshotLabel()
{
this->ui->label->setPixmap(secondPixmap.scaled(this->ui->label->size(), Qt::KeepAspectRatio, Qt::SmoothTransformation));
}
void MainWindow::on_pushButton_clicked()
{
shootScreen();
}
void MainWindow::on_pushButton_2_clicked()
{
secondPixmap = QPixmap();
QDataStream ds(&byteArray,QIODevice::ReadOnly);
qint32 code;
ds>>code;
secondPixmap.loadFromData(byteArray,"JPEG");
updateScreenshotLabel();
}
Your MainWindow::on_pushButton_2_clicked implementation looks odd. You have...
QDataStream ds(&byteArray,QIODevice::ReadOnly);
which creates a read-only QDataStream that will read it's input data from byteArray. But later you have...
secondPixmap.loadFromData(byteArray,"JPEG");
which attempts to read the QPixmap directly from the same QByteArray -- bypassing the QDataStream completely.
You can also make use of the QPixmap static members that read from/write to a QDataStream. So I think you're looking for something like...
QDataStream ds(&byteArray,QIODevice::ReadOnly);
qint32 code;
ds >> code;
if (code == 20)
ds >> secondPixmap;
And likewise for your MainWindow::shootScreen implementation. You could reduce your code a fair bit by making use of QDataStream & operator<<(QDataStream &stream, const QPixmap &pixmap).
I am downloading an ".apk" file from a Url with Get method.
The file successfully donwload on my disk from the server.
I actually want to add a progressbar to my program. THE problem is : I can show the bytesReceived but I can't show the totalBytes of the file I am downloading (ContentLenth). How can I get it please from the server.
Here is what i get on my qDebug while downloading:
3498 of -1
799062 of -1
1923737 of -1
3037550 of -1
3200231 of 3200231
Here is my code:
void DownloadApk::LaunchDownload()
{
QNetworkProxy proxy;
proxy.setType(QNetworkProxy::HttpProxy);
proxy.setHostName("proxy");
proxy.setPort(8080);
QNetworkProxy::setApplicationProxy(proxy);
QUrl url("I put my Url here");
QNetworkRequest request(url);
_file = new QFile("C:/Users/Desktop/testdownload/downloadedFile.apk");
_file->open(QIODevice::WriteOnly);
QNetworkAccessManager *_manager= new QNetworkAccessManager;
_reply = _manager->get(request);// Manager is my QNetworkAccessManager
_file->write(_reply->readAll());
connect(_reply, SIGNAL(error(QNetworkReply::NetworkError)),
this, SLOT(error(QNetworkReply::NetworkError)));
connect(_reply, SIGNAL(downloadProgress(qint64, qint64)),
this, SLOT(updateProgress(qint64, qint64)));
connect(_reply, SIGNAL(finished()),
this, SLOT(finished()));
}
void DownloadApk::error(QNetworkReply::NetworkError err)
{qDebug() << err;
// Manage error here.
_reply->deleteLater();
}
void DownloadApk::updateProgress(qint64 read, qint64 total)
{
qDebug() << read <<"of"<<total ;
QByteArray b = _reply->readAll();
QDataStream out(_file);
out << b;
}
void DownloadApk::finished()
{
QMessageBox::information(this, tr("Complete"), tr("Successfully Downloaded"));
// Done
_reply->deleteLater();
_file->close();
// probably delete the file object too
}
I fixed the problem. Actually it was not a QT problem. This Qt code works correctly.
The probleme was from the server that wasn't sending ContentLenth on the header of the reply.
Assume that I have executed a QNetworkRequest and got the appropriated QNetworkReply. If it be a large file (say 1 GB) how can I create a say 4k byte array buffer and read data 4k by 4k into that array and write it at same time into an open file stream?
For example the equivalent C# code would be this (I'm familiar with C# not Qt):
public static void CopyStream(Stream input, Stream output)
{
// input is web stream, output is filestream
byte[] buffer = new byte[4096];
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
{
output.Write (buffer, 0, read);
}
}
---- edit
Actually what i am trying to do is a download resume capability on every run of my application. every time i try to resume the download i set the range header of QNetworkRequest and just get the rest of data so need to write data not at once but step by step.
You probably want a solution in c++ as Qt is a library. One possibility is to use QIODevice class, which is inherited by both QFile and QNetworkReply
void copyStream(QIODevice& input, QIODevice& output){
std::vector<char> buffer(4096);
qint64 bytesRead;
while ((bytesRead=input.read(&buffer[0],buffer.size()))>0){
output.write(&buffer[0],bytesRead);
}
}
I am trying to rewrite in c++ an application written in python.
All it does is to open a serial port and read some xml. In python i was using pyserial to read the xml and beautifulsoup to retrieve information. The output was like this.
<file><property>xx32</property></file>
Now i am using qextserialport to read from the serial port and the xml i get is something like this.
<
fil
e>
<prope
rty>xx32
</prop
erty>
</
file>
My problem is that i cant parse an xml like this. I get errors.
EDIT:
Qextserialport reads data from the serial port in set of bytes that are not fixed.
So how do i concatenate my xml into one string? I get an xml string every 4-5 seconds from the serial port.
here is my code
this->port = new QextSerialPort(com_port,QextSerialPort::EventDriven);
port->setBaudRate(BAUD57600);
port->setFlowControl(FLOW_OFF);
port->setParity(PAR_NONE);
port->setDataBits(DATA_8);
port->setStopBits(STOP_1);
port->setTimeout(0);
if (port->open(QIODevice::ReadOnly) == true)
{
//qDebug()<< "hello";
connect(port,SIGNAL(readyRead()),this,SLOT(onReadyRead()));
}
and the function that actually reads from the serial port
void CurrentCost::onReadyRead()
{
QByteArray bytes;
bytes = port->readAll();
//qDebug() << "bytes read:" << bytes.size();
//qDebug() << "bytes:" << bytes;
ui->textBrowser->append(bytes);
}
I mean something like this:
class CurrentCost...{
private:
QByteArray xmlData;
private slots:
void onReadyRead();
};
void CurrentCost::onReadyRead()
{
xmlData.append(port->readAll());
if(xmlData.endsWith(/*what your port sending then xml is over&*/))
{
ui->textBrowser->append(xmlData);
xmlData.clear();
}
}