GStreamer on Qt for iOS

Question

Created May ’21

Replies 2

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Hello,

I'm trying to develop an iOS application (iPad should be the main target) for controlling a device (Linux embedded) connected to the same network.

Basically it is a remote desktop application.

The application must be multi-platform, so it has be built within a multi-platform framework. This requirement is fulfilled by developing the app with Qt and Qt Creator.

The application should play a stream video stream transmitted over the network from the Linux device. I use GStreamer for that. I already downloaded and succesfully installed the iOS package from the official site.

Now, I have some trouble linking the GStreamer framework in the .pro file.

In desktop environments (Windows, Linux and macOS) all I need to do is to use pkg-config

Code Block mac {
    QT_CONFIG -= no-pkg-config
    PKG_CONFIG = /usr/local/bin/pkg-config
}
CONFIG += link_pkgconfig
PKGCONFIG += gstreamer-1.0
PKGCONFIG += gstreamer-pbutils-1.0

and it works just fine. In iOS I don't have pkg-config (afik), so I manually added the framework:

Code Block LIBS += -F$$PWD/../../Library/Developer/GStreamer/iPhone.sdk/ -framework GStreamer
INCLUDEPATH += $$PWD/../../Library/Developer/GStreamer/iPhone.sdk/GStreamer.framework/Versions/1.0/Headers
DEPENDPATH += $$PWD/../../Library/Developer/GStreamer/iPhone.sdk/GStreamer.framework/Versions/1.0/Headers

When I try to build, it gives me this error:

Code Block GStreamer(libglib-2_0_a-gconvert.c.o):-1: error: Undefined symbols for architecture x86_64:
  "___darwin_check_fd_set_overflow", referenced from:
      _gst_poll_wait in GStreamer(libgstreamer-1_0_a-gstpoll.c.o)
  "_iconv_close", referenced from:
      _g_convert in GStreamer(libglib-2_0_a-gconvert.c.o)
      _g_convert_with_fallback in GStreamer(libglib-2_0_a-gconvert.c.o)
     (maybe you meant: _g_iconv_close)
  "_iconv", referenced from:
      _g_convert_with_iconv in GStreamer(libglib-2_0_a-gconvert.c.o)
      _g_convert_with_fallback in GStreamer(libglib-2_0_a-gconvert.c.o)
     (maybe you meant: _g_iconv_close, _g_iconv , _g_iconv_open , _g_convert_with_iconv )
  "_iconv_open", referenced from:
      _try_conversion in GStreamer(libglib-2_0_a-gconvert.c.o)
     (maybe you meant: _g_iconv_open)

Tried to link the apparently missing liconv, but no luck.

Code Block macx: LIBS += -L$$PWD/../../../../Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr/lib/ -liconv
INCLUDEPATH += $$PWD/../../../../Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr
DEPENDPATH += $$PWD/../../../../Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot/usr

I'm aware of the existence of a similar question on nabble.com but I still couldn't figure out the problem.

Any thoughts?
Thanks

Additional info

The application must be multi-platform, so it must be built in Qt Creator. It already works on Windows, Linux and macOS.
developing machine macOS 11.3.1
Xcode version 11.2.1
Qt version 5.15.2

Boost

Answer 1

FrancescoK OP

May ’21

Some progress:

So far I've managed to correctly link the library and successfully run the project in the Simulator, but when I try to create *GStreamer* elements it fails at runtime.

Here it is my .pro

Code Block #iOS
INCLUDEPATH += /Users/user/Library/Developer/GStreamer/iPhone.sdk/GStreamer.framework/Headers
LIBS += -F /Users/user/Library/Developer/GStreamer/iPhone.sdk -framework GStreamer
LIBS += -L/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/lib -liconv
QMAKE_IOS_DEPLOYMENT_TARGET = 12.0
# Universal target (iPhone and iPad)
QMAKE_APPLE_TARGETED_DEVICE_FAMILY = 1,2
QMAKE_APPLE_DEVICE_ARCHS = arm64
QMAKE_APPLE_SIMULATOR_ARCHS = x86_64

And here it is where it fails:

Code Block data.pipeline = gst_pipeline_new ("pipeline");
        qDebug() << "pipeline" << data.pipeline;
        data.udpsrc = gst_element_factory_make("udpsrc", NULL);
        data.rtph264depay = gst_element_factory_make("rtph264depay", NULL);
        data.avdec_h264 = gst_element_factory_make("avdec_h264", NULL);
        data.videoconvert = gst_element_factory_make("videoconvert", NULL);
        data.videoflip = gst_element_factory_make ("videoflip", NULL);
        qDebug() << "udpsrc" << data.udpsrc;
        qDebug() << "rtph264depay" << data.rtph264depay;
        qDebug() << "avdec_h264" << data.avdec_h264;
        qDebug() << "videoconvert" << data.videoconvert;
        qDebug() << "videoflip" << data.videoflip;

All the calls to *gst_element_factory_make* return null.

Additional Info

Qt 5.15.2
Xcode 12.5
Develop on Big Sur

Any ideas?

Thanks

0

Answer 2

FrancescoK OP

May ’21

Some progress #2

The error shown is:

Code Block 0:00:12.281788000  5678 0x7fbc5cd1c200 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "udpsrc"!
0:00:12.281795000  5678 0x7fbc5cd1c200 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "rtph264depay"!
0:00:12.281801000  5678 0x7fbc5cd1c200 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "avdec_h264"!
0:00:12.281805000  5678 0x7fbc5cd1c200 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "videoconvert"!
0:00:12.281811000  5678 0x7fbc5cd1c200 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "videoflip"!

so clearly it doesn't find the plugins.

I believe that the correct approach to solve the problem is to register such plugins, by writing something like this in main.cpp:

Code Block // Declar plugins
G_BEGIN_DECLS
GST_PLUGIN_STATIC_DECLARE(coreelements);
GST_PLUGIN_STATIC_DECLARE(videotestsrc);
GST_PLUGIN_STATIC_DECLARE(videoconvert);
GST_PLUGIN_STATIC_DECLARE(playback);
GST_PLUGIN_STATIC_DECLARE(x264);
GST_PLUGIN_STATIC_DECLARE(libav);
GST_PLUGIN_STATIC_DECLARE(encoding);
//...
G_END_DECLS
int main(int argc, char *argv[]) {
    // Initialize the GStreamer library
    if (gst_init_check(&argc, &argv, NULL)) {
        qDebug() << "This program is linked against" << gst_version_string();
    }
    // Register plugins
    GST_PLUGIN_STATIC_REGISTER(coreelements);
    GST_PLUGIN_STATIC_REGISTER(videotestsrc);
    GST_PLUGIN_STATIC_REGISTER(videoconvert);
    GST_PLUGIN_STATIC_REGISTER(playback);
    GST_PLUGIN_STATIC_REGISTER(x264);
    GST_PLUGIN_STATIC_REGISTER(libav);
    GST_PLUGIN_STATIC_REGISTER(encoding);
    //...
}

This does in fact give me some positive results, because now some elements are successfully created:

Code Block 0:01:48.471557000  5973 0x7fa450c1ec00 INFO     GST_ELEMENT_FACTORY gstelementfactory.c:361:gst_element_factory_create: creating element "pipeline" named "pipeline"
pipeline 0x7fa452204160
0:01:48.472489000  5973 0x7fa450c1ec00 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "udpsrc"!
0:01:48.472503000  5973 0x7fa450c1ec00 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "rtph264depay"!
0:01:48.472513000  5973 0x7fa450c1ec00 INFO     GST_ELEMENT_FACTORY gstelementfactory.c:363:gst_element_factory_create: creating element "avdec_h264"
0:01:48.474720000  5973 0x7fa450c1ec00 INFO     GST_ELEMENT_FACTORY gstelementfactory.c:363:gst_element_factory_create: creating element "videoconvert"
0:01:48.474936000  5973 0x7fa450c1ec00 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "videoflip"!
0:01:48.475071000  5973 0x7fa450c1ec00 WARN     GST_ELEMENT_FACTORY gstelementfactory.c:467:gst_element_factory_make: no such element factory "glimagesink"!

But if I try to register the others plugins, for example by adding

Code Block GST_PLUGIN_STATIC_DECLARE(udp);

and

Code Block GST_PLUGIN_STATIC_REGISTER(udp);

it gives me this error:

Code Block GStreamer(libgio-2_0_a-gresolver.c.o):-1: error: Undefined symbols for architecture x86_64:
  "_res_9_dn_expand", referenced from:
      _do_lookup_records in GStreamer(libgio-2_0_a-gthreadedresolver.c.o)
  "_res_9_ninit", referenced from:
      _do_lookup_records in GStreamer(libgio-2_0_a-gthreadedresolver.c.o)
  "_res_9_nquery", referenced from:
      _do_lookup_records in GStreamer(libgio-2_0_a-gthreadedresolver.c.o)
  "_res_9_ndestroy", referenced from:
      _do_lookup_records in GStreamer(libgio-2_0_a-gthreadedresolver.c.o)
  "_res_9_init", referenced from:
      _g_resolver_maybe_reload in GStreamer(libgio-2_0_a-gresolver.c.o)

I encountered a similar error before and I solved by adding the missing library (where the symbols were) in the .pro file:

Code Block LIBS += -L/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/lib -liconv

It seems that is missing the gio (or something like that) library, but I don't know where to find it.

[EDIT]

After a quick search

Code Block locate  libgio
         
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/gio/modules/libgioopenssl.a
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/gio/modules/libgioopenssl.so
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/libgio-2.0.0.dylib
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/libgio-2.0.a
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/libgio-2.0.dylib
/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/libgio-2.0.la

I can locate the library for macOS, but not for iOS. In fact if I try to add it

Code Block LIBS += -L/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/ -lgio-2.0

it (rightfully) complains about it:

Code Block :-1: error: building for iOS Simulator, but linking in dylib built for macOS, file '/Library/Frameworks/GStreamer.framework/Versions/1.0/lib/libgio-2.0.dylib' for architecture x86_64

I also tried to include the get_ios_init.h and get_ios_init.m configuration files of the GStreamer tutorials by copying them into the project by adding

Code Block CONFIG += c++11
CONFIG += objective_c
OBJECTIVE_HEADERS = gst_ios_init.h
OBJECTIVE_SOURCES = gst_ios_init.m

but it didn't help.

Any ideas?
Thanks

0