gstreamer代碼未能鏈接所有GST元素

Question

Ubuntu 14.04 Gstreamer 0.10 代碼Sdk：Qt。

我對Gstreamer相當陌生。當我在我的終端上使用gst-launch工具時，我可以成功地看到連接到我的工作站的攝像機捕捉到流視頻。

要繼續前進，我已經在Qt中編寫了c代碼。它編譯正確，當我運行它，它打開新的Xterm窗口，並拋出錯誤「Elements could not be linked"我做錯了嗎？或者我需要做別的事情來觀看流媒體

下面是我的代碼（其重點啓發了其他人的代碼）

.pro文件

QT  += core 

QT  -= gui 
QT  += core gui 
QT  += network 
QT   +=core 

QMAKE_CXXFLAGS+= -std=c++11 
QMAKE_LFLAGS += -std=c++11 

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets 



TARGET = justtest 

PKGCONFIG +=glib-2.0 
PKGCONFIG += gstreamer-0.10 
CONFIG += link_pkgconfig 
CONFIG += console 
CONFIG -= app_bundle 


TEMPLATE = app 
INCLUDEPATH += pkg-config --cflags glib-2.0 
INCLUDEPATH += /usr/include/glib-2.0/glib/ 
INCLUDEPATH +=/usr/include/libxml2/ 
INCLUDEPATH += /usr/include/gstreamer-0.10/ 
SOURCES += main.cpp 

的main.cpp

#include <gst/gst.h> 
#include <glib.h> 


static gboolean bus_call (GstBus *bus, GstMessage *msg, gpointer data) 
{ 
    GMainLoop *loop = (GMainLoop *) data; 

    switch (GST_MESSAGE_TYPE (msg)) { 

    case GST_MESSAGE_EOS: 
     g_print ("End of stream\n"); 
     g_main_loop_quit (loop); 
     break; 

    case GST_MESSAGE_ERROR: { 
     gchar *debug; 
     GError *error; 

     gst_message_parse_error (msg, &error, &debug); 
     g_free (debug); 

     g_printerr ("Error: %s\n", error->message); 
     g_error_free (error); 

     g_main_loop_quit (loop); 
     break; 
    } 
    default: 
     break; 
    } 

    return TRUE; 
} 

int main(int argc, char *argv[]) 
{ 
    //QApplication app(argc, argv); 
    GstElement *pipeline, *source, *sink, *convert, *videoenc; 
    GstBus *bus; 
    GstMessage *msg; 
    GstStateChangeReturn ret; 

    GMainLoop *loop; 
    // Initialize GStreamer/
    gst_init (&argc, &argv); 

    loop = g_main_loop_new(NULL, FALSE); 
    // Create the elements 
    source = gst_element_factory_make ("v4l2src", "source"); 
    sink = gst_element_factory_make ("autovideosink", "sink"); 
    convert =gst_element_factory_make("ffmpegcolorspace","convert"); 
    videoenc = gst_element_factory_make ("ffdec_mpeg4", "videoenc"); 
    // Create the empty pipeline 
    pipeline = gst_pipeline_new ("test-pipeline"); 

    if (!pipeline || !source || !sink || !convert) 
    { 
     g_printerr ("Not all elements could be created.\n"); 
     return -1; 
    } 

    //set der source 
     g_object_set (G_OBJECT (source), "device", "/dev/video0", NULL); 

     // we add a message handler 
     bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline)); 
     gst_bus_add_watch (bus, bus_call, loop); 
     gst_object_unref (bus); 


    //Build the pipeline 
    gst_bin_add_many (GST_BIN (pipeline), source, convert,videoenc, sink, NULL); 
    if (gst_element_link (convert, sink) != TRUE) 
    { 
     g_printerr ("Elements could not be linked confert sink.\n"); 
     gst_object_unref (pipeline); 
     return -1; 
    } 


// if (gst_element_link (source, convert) != TRUE) { 
     // g_printerr ("Elements could not be linked source -convert.\n"); 
     // gst_object_unref (pipeline); 
     // return -1; 
    // } 

    if(gst_element_link_many (source, convert, videoenc, sink, 
          NULL) != TRUE) 
    { 
     g_printerr ("Elements could not be linked source -convert.\n"); 
    } 

    g_print("Linked all the Elements together\n"); 
    // Iterate 
     g_print ("Running...\n"); 
     g_main_loop_run (loop); 

     // Out of the main loop, clean up nicely 
     g_print ("Returned, stopping playback\n"); 
     gst_element_set_state (pipeline, GST_STATE_NULL); 

     g_print ("Deleting pipeline\n"); 
     gst_object_unref (GST_OBJECT (pipeline)); 
     return 0; 
} 

OUTPUT：ON新的X詞窗口

"Elements could not be linked" 
Press <Return> to close this window 

Answer 1

你似乎試圖在同一元素重複鏈接，這是不可能的。

將鏈接轉換爲接收器，然後在下面的幾行嘗試鏈接轉換！ videoenc！水槽。

只有當您知道您的相機提供了mpeg4視頻時，才能使用解碼器（您名爲videoenc），否則它將無法進行協商。如果您的相機支持原始格式，只需從管道中移除解碼器即可。

同樣，0.10是多年未知並過時的，請考慮轉向1.x.