我一直在关注将图像推送到Gstreamer管道的许多示例，但我仍然无法使代码正常工作。
任何建议（除了告诉我尝试使用Gstreamer1.0而不是0.10）都将非常感激。我想了解以下脚本中的错误，该脚本使用jpeg图像提供appsrc元素。稍后我将使用相同的代码来提供从相机中获取的openCv图像，但首先我想通过使这个简单的示例工作来理解基础知识。
#include <gst/gst.h>
#include <string.h>
#include <cv.h>
#include <highgui.h>
#include <stdio.h>
#define VIDEO_CAPS "video/x-raw-rgb,bpp=8,depth=8,width=640,height=360,framerate=5/1,red_mask=224,green_mask=28,blue_mask=3,endianness=1234;"
/* Structure to contain all our information, so we can pass it to callbacks */
guint64 imagecounter=1;
typedef struct _CustomData {
GstElement *pipeline, *app_source;
GstElement *video_convert, *video_sink;
GstElement *image_manage;
guint64 num_samples; /* Number of samples generated so far (for timestamp generation) */
guint sourceid; /* To control the GSource */
GMainLoop *main_loop; /* GLib's Main Loop */
} CustomData;
/* This method is called by the idle GSource in the mainloop, to feed CHUNK_SIZE bytes into appsrc.
* The idle handler is added to the mainloop when appsrc requests us to start sending data (need-data signal)
* and is removed when appsrc has enough data (enough-data signal).
*/
static gboolean push_data (CustomData *data) {
GstBuffer *buffer;
GstFlowReturn ret;
int i;
gint8 *raw;
gint num_samples;
gfloat freq;
int size,depth,height,width,step,channels;
guchar *data1;
IplImage* img;
g_print("push_data is beginning\n");
img=cvLoadImage("frame1.jpg",CV_LOAD_IMAGE_COLOR);
height = img->height;
width = img->width;
step = img->widthStep;
channels = img->nChannels;
depth = img->depth;
data1 = (guchar *)img->imageData;
num_samples = height*width*channels;
g_print("height %d\n",height);
g_print("width %d\n",width);
g_print("widthStep %d\n",step);
g_print("nChannels %d\n",channels);
g_print("depth %d\n",depth);
g_print("image_number %" G_GUINT64_FORMAT "\n", imagecounter);
g_print("sizeof guchar: %lu\n",sizeof(guchar));
/* Create a new empty buffer */
buffer = gst_buffer_new_and_alloc (num_samples); // guint size :the size in bytes of the new buffer's data.
size = GST_BUFFER_SIZE(buffer);
g_print("nSize %d\n",size);
g_print("buffer initialized\n");
/* Set its timestamp and duration */
GST_BUFFER_TIMESTAMP (buffer) = gst_util_uint64_scale (imagecounter, GST_SECOND, 5 );
imagecounter += 1;
GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale (num_samples, GST_SECOND,5);
memcpy( (guchar *)GST_BUFFER_DATA( buffer ), data1, GST_BUFFER_SIZE( buffer ) );
g_print("image data copied into buffer\n");
data->num_samples += num_samples;
/* Push the buffer into the appsrc */
g_signal_emit_by_name (data->app_source, "push-buffer", buffer, &ret);
g_print("buffer pushed\n");
/* Free the buffer now that we are done with it */
gst_buffer_unref (buffer);
g_print("buffer unreferenced\n");
if (ret != GST_FLOW_OK) {
g_printerr("something wrong in sending data");
/* We got some error, stop sending data */
return FALSE;
}
g_print("push_data is ending\n");
return TRUE;
}
/* This signal callback triggers when appsrc needs data. Here, we add an idle handler
* to the mainloop to start pushing data into the appsrc */
static void start_feed (GstElement *source, guint size, CustomData *data) {
if (data->sourceid == 0) {
g_print ("Start feeding\n");
data->sourceid = g_idle_add ((GSourceFunc) push_data, data);
g_print ("push_data started\n");
}
}
/* This callback triggers when appsrc has enough data and we can stop sending.
* We remove the idle handler from the mainloop */
static void stop_feed (GstElement *source, CustomData *data) {
if (data->sourceid != 0) {
g_print ("Stop feeding\n");
g_source_remove (data->sourceid);
data->sourceid = 0;
}
}
/* This function is called when an error message is posted on the bus */
static void error_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
GError *err;
gchar *debug_info;
/* Print error details on the screen */
gst_message_parse_error (msg, &err, &debug_info);
g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
g_main_loop_quit (data->main_loop);
}
int main(int argc, char *argv[]) {
CustomData data;
gchar *video_caps_text;
GstCaps *video_caps;
GstBus *bus;
/* Initialize cumstom data structure */
memset (&data, 0, sizeof (data));
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create the elements */
data.app_source = gst_element_factory_make ("appsrc", "video_source");
data.video_convert = gst_element_factory_make ("ffmpegcolorspace", "csp");
data.video_sink = gst_element_factory_make ("v4l2sink", "video_sink");
data.image_manage= gst_element_factory_make("imagefreeze","image_manage");
/* Create the empty pipeline */
data.pipeline = gst_pipeline_new ("test-pipeline");
if (!data.pipeline || !data.app_source || !data.video_convert || !data.video_sink || !data.image_manage) {
g_printerr ("Not all elements could be created.\n");
return -1;
}
/* Configure appsrc */
video_caps_text = g_strdup_printf (VIDEO_CAPS);
video_caps = gst_caps_from_string (video_caps_text);
if( !GST_IS_CAPS(video_caps) ) {
g_printerr("Error creating Caps for OpenCV-Source, exiting...");
exit( 1 );
}
g_object_set (data.app_source, "caps", video_caps, NULL);
g_signal_connect (data.app_source, "need-data", G_CALLBACK (start_feed), &data);
g_signal_connect (data.app_source, "enough-data", G_CALLBACK (stop_feed), &data);
/* Configure v4l2loopback videosink*/
//g_object_set (data.video_sink, "device", "/dev/video0", NULL);
/* Link all elements that can be automatically linked because they have "Always" pads */
gst_bin_add_many (GST_BIN (data.pipeline), data.app_source, data.image_manage, data.video_convert, data.video_sink, NULL);
if ( gst_element_link_many ( data.app_source, data.video_convert,data.video_sink, NULL) != TRUE) {
g_printerr ("Elements could not be linked.\n");
gst_object_unref (data.pipeline);
return -1;}
/*
/* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
bus = gst_element_get_bus (data.pipeline);
gst_bus_add_signal_watch (bus);
g_signal_connect (G_OBJECT (bus), "message::error", (GCallback)error_cb, &data);
gst_object_unref (bus);
/* Start playing the pipeline */
gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
/* Create a GLib Main Loop and set it to run */
data.main_loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (data.main_loop);
/* Free resources */
gst_element_set_state (data.pipeline, GST_STATE_NULL);
gst_object_unref (data.pipeline);
return 0;
}
发送几个缓冲区后，我收到以下输出：
Error received from element video_source: Internal data flow error。
Debugging information: gstbasesrc.c(2625): gst_base_src_loop (): /GstPipeline:test-pipeline/GstAppSrc:video_source:
streaming task paused, reason not-negotiated (-4)
答案 0 :(得分：1)
我找到了让它发挥作用的方法。我切换到Gstreamer1.0，一切都变得容易了。我仍然不知道旧代码中的问题是什么，但是由于这个新代码没问题，所以不需要浪费其他时间。
#include <gst/gst.h>
#include <cv.h>
#include <highgui.h>
static GMainLoop *loop;
static void
cb_need_data (GstElement *appsrc,
guint unused_size,
gpointer user_data)
{
static gboolean white = FALSE;
static GstClockTime timestamp = 0;
GstBuffer *buffer;
guint size,depth,height,width,step,channels;
GstFlowReturn ret;
IplImage* img;
guchar *data1;
GstMapInfo map;
img=cvLoadImage("frame1.jpg",CV_LOAD_IMAGE_COLOR);
height = img->height;
width = img->width;
step = img->widthStep;
channels = img->nChannels;
depth = img->depth;
data1 = (guchar *)img->imageData;
size = height*width*channels;
buffer = gst_buffer_new_allocate (NULL, size, NULL);
gst_buffer_map (buffer, &map, GST_MAP_WRITE);
memcpy( (guchar *)map.data, data1, gst_buffer_get_size( buffer ) );
/* this makes the image black/white */
//gst_buffer_memset (buffer, 0, white ? 0xff : 0x0, size);
white = !white;
GST_BUFFER_PTS (buffer) = timestamp;
GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale_int (1, GST_SECOND, 2);
timestamp += GST_BUFFER_DURATION (buffer);
g_signal_emit_by_name (appsrc, "push-buffer", buffer, &ret);
if (ret != GST_FLOW_OK) {
/* something wrong, stop pushing */
g_main_loop_quit (loop);
}
}
gint
main (gint argc,
gchar *argv[])
{
GstElement *pipeline, *appsrc, *conv, *videosink;
/* init GStreamer */
gst_init (&argc, &argv);
loop = g_main_loop_new (NULL, FALSE);
/* setup pipeline */
pipeline = gst_pipeline_new ("pipeline");
appsrc = gst_element_factory_make ("appsrc", "source");
conv = gst_element_factory_make ("videoconvert", "conv");
videosink = gst_element_factory_make ("autovideosink", "videosink");
/* setup */
g_object_set (G_OBJECT (appsrc), "caps",
gst_caps_new_simple ("video/x-raw",
"format", G_TYPE_STRING, "RGB",
"width", G_TYPE_INT, 640,
"height", G_TYPE_INT, 360,
"framerate", GST_TYPE_FRACTION, 1, 1,
NULL), NULL);
gst_bin_add_many (GST_BIN (pipeline), appsrc, conv, videosink, NULL);
gst_element_link_many (appsrc, conv, videosink, NULL);
//g_object_set (videosink, "device", "/dev/video0", NULL);
/* setup appsrc */
g_object_set (G_OBJECT (appsrc),
"stream-type", 0,
"format", GST_FORMAT_TIME, NULL);
g_signal_connect (appsrc, "need-data", G_CALLBACK (cb_need_data), NULL);
/* play */
gst_element_set_state (pipeline, GST_STATE_PLAYING);
g_main_loop_run (loop);
/* clean up */
gst_element_set_state (pipeline, GST_STATE_NULL);
gst_object_unref (GST_OBJECT (pipeline));
g_main_loop_unref (loop);
return 0;
}