Qt 5.11 QMediaPlayer and custom GStreamer Pipelines

[PhilBot9999]

I am trying to supply a custom gstreamer pipeline to a QMediaPlayer.

The following referenced topic details how one person was able to make it work:

Re: Displaying video stream using Qt Multimedia and GStreamer process

I tried their code exactly on Ubuntu 18.04 with GStreamer 1.14 and Qt 5.11. It fails with the following error:

Error: "Could not determine type of stream."
appsrc: push buffer wrong state
appsrc: push buffer wrong state
appsrc: push buffer wrong state

The entire code is:

#include <QApplication>
#include <QMediaPlayer>
#include <QWidget>
#include <QVideoWidget>
#include <QBoxLayout>
#include <QProcess>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget *window = new QWidget;
    QVideoWidget *videoWidget = new QVideoWidget;
    QBoxLayout *layout = new QVBoxLayout;
    QMediaPlayer *player = new QMediaPlayer;
    QProcess *process = new QProcess;

    layout->addWidget(videoWidget);
    window->setLayout(layout);
    window->show();
    player->setVideoOutput(videoWidget);

    QString program = "gst-launch-1.0";
    QStringList arguments;
    arguments << "videotestsrc" << "!" << "video/x-raw,width=1280,height=720" << "!" << "x264enc" << "!" << "filesink" << "location=/dev/stderr";

    process->start(program, arguments);
    process->waitForReadyRead();

    player->setMedia(QMediaContent(), process);
    player->play();

    return a.exec();
}

How can I get this to work? Thanks.

[SGaist]

Hi,

Why are you using stderr rather than stdout ?

[PhilBot9999]

I have tried STDOUT, but I get the same kind of error, the following is printed constantly:

Error: "Could not determine type of stream."
appsrc: push buffer wrong state
appsrc: push buffer wrong state
appsrc: push buffer wrong state
appsrc: push buffer wrong state
appsrc: push buffer wrong state
appsrc: push buffer wrong state

[SGaist]

Might be a silly question but does it work properly when called on the command line ?

[Pippo]

in my Qt application on console QT application is it continuously printed

0:30:24:279| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:283| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:291| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:297| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:302| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:310| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:315| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:321| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:329| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:333| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:341| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:347| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:352| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:360| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:365| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:371| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:378| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:383| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:389| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:397| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:401| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:411| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:416| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:420| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:426| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:431| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:436| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:445| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:454| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:463| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:468| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:477| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:483| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:490| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:498| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:503| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:512| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:517| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:526| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:532| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:538| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:545| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:550| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:557| Warning | Error: "Could not determine type of stream."
30/01/2019 10:30:24:564| Warning | Error: "Could not determine type of stream."

Does someone know the reason and how can be solved?
Thanks for attention.
Best regards.

[SGaist]

Does that pipeline you use work correctly on the command line ?