我正在尝试学习 gstreamer appsrc 插件以从我编写的传输流解复用器中播放 AV（我知道插件已经可用，我想自己动手学习）。我从 MPEG 传输流中提取了音频和视频基本流；现在我必须将它推送到appsrc插件并使用gst管道播放它（这部分我还不清楚：至于使用哪些插件 - 任何提示都将受到高度赞赏）。
我找到了一个关于使用 appsrc 的示例代码，但是当我运行它时，没有输出。我验证了确实调用start_feed了read_data函数。在read_data函数中，有一个定时器检查来决定是否推送数据：
ms = g_timer_elapsed(app->timer, NULL);
printf("ms %f\n", ms);
if (ms > 1.0/20.0) {
我不知道这个计时器是做什么用的，但它的值ms总是在 0.035 左右，并且数据永远不会被推送到 appsrc 中。因此，我将 if 条件更改为，if(ms > 0.03)但随后出现内部数据流错误：
ms 0.033747
ms 0.000010
ERROR from element mysource: Internal data flow error.
Debugging info: gstbasesrc.c(2582): gst_base_src_loop (): /GstPipeline:pipeline0/GstAppSrc:mysource:
streaming task paused, reason not-negotiated (-4)
有人可以告诉我如何调整它以查看视频吗？链接网站的代码如下所示。
#include <gst/gst.h>
#include <gst/app/gstappsrc.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <gdk-pixbuf/gdk-pixbuf.h>
GST_DEBUG_CATEGORY (appsrc_pipeline_debug);
#define GST_CAT_DEFAULT appsrc_pipeline_debug
typedef struct _App App;
struct _App
{
GstElement *pipeline;
GstElement *appsrc;
GMainLoop *loop;
guint sourceid;
GTimer *timer;
};
App s_app;
static gboolean
read_data (App * app)
{
guint len;
GstFlowReturn ret;
gdouble ms;
ms = g_timer_elapsed(app->timer, NULL);
printf("ms %f\n", ms);
if (ms > 1.0/20.0) {
GstBuffer *buffer;
GdkPixbuf *pb;
gboolean ok = TRUE;
buffer = gst_buffer_new();
pb = gdk_pixbuf_new(GDK_COLORSPACE_RGB, FALSE, 8, 640, 480);
gdk_pixbuf_fill(pb, 0xffffffff);
GST_BUFFER_DATA (buffer) = gdk_pixbuf_get_pixels(pb);
GST_BUFFER_SIZE (buffer) = 640*480*3*sizeof(guchar);
GST_DEBUG ("feed buffer");
g_signal_emit_by_name (app->appsrc, "push-buffer", buffer, &ret);
gst_buffer_unref (buffer);
if (ret != GST_FLOW_OK) {
/* some error, stop sending data */
GST_DEBUG ("some error");
ok = FALSE;
}
g_timer_start(app->timer);
return ok;
}
// g_signal_emit_by_name (app->appsrc, "end-of-stream", &ret);
return FALSE;
}
/* This signal callback is called when appsrc needs data, we add an idle handler
* to the mainloop to start pushing data into the appsrc */
static void
start_feed (GstElement * pipeline, guint size, App * app)
{
if (app->sourceid == 0) {
GST_DEBUG ("start feeding");
app->sourceid = g_idle_add ((GSourceFunc) read_data, app);
}
}
/* This callback is called when appsrc has enough data and we can stop sending.
* We remove the idle handler from the mainloop */
static void
stop_feed (GstElement * pipeline, App * app)
{
if (app->sourceid != 0) {
GST_DEBUG ("stop feeding");
g_source_remove (app->sourceid);
app->sourceid = 0;
}
}
static gboolean
bus_message (GstBus * bus, GstMessage * message, App * app)
{
GST_DEBUG ("got message %s",
gst_message_type_get_name (GST_MESSAGE_TYPE (message)));
switch (GST_MESSAGE_TYPE (message)) {
case GST_MESSAGE_ERROR: {
GError *err = NULL;
gchar *dbg_info = NULL;
gst_message_parse_error (message, &err, &dbg_info);
g_printerr ("ERROR from element %s: %s\n",
GST_OBJECT_NAME (message->src), err->message);
g_printerr ("Debugging info: %s\n", (dbg_info) ? dbg_info : "none");
g_error_free (err);
g_free (dbg_info);
g_main_loop_quit (app->loop);
break;
}
case GST_MESSAGE_EOS:
g_main_loop_quit (app->loop);
break;
default:
break;
}
return TRUE;
}
int
main (int argc, char *argv[])
{
App *app = &s_app;
GError *error = NULL;
GstBus *bus;
GstCaps *caps;
gst_init (&argc, &argv);
GST_DEBUG_CATEGORY_INIT (appsrc_pipeline_debug, "appsrc-pipeline", 0,
"appsrc pipeline example");
/* create a mainloop to get messages and to handle the idle handler that will
* feed data to appsrc. */
app->loop = g_main_loop_new (NULL, TRUE);
app->timer = g_timer_new();
app->pipeline = gst_parse_launch("appsrc name=mysource ! video/x-raw-rgb,width=640,height=480,bpp=24,depth=24 ! ffmpegcolorspace ! videoscale method=1 ! theoraenc bitrate=150 ! udpsink host=127.0.0.1 port=1234", NULL);
g_assert (app->pipeline);
bus = gst_pipeline_get_bus (GST_PIPELINE (app->pipeline));
g_assert(bus);
/* add watch for messages */
gst_bus_add_watch (bus, (GstBusFunc) bus_message, app);
/* get the appsrc */
app->appsrc = gst_bin_get_by_name (GST_BIN(app->pipeline), "mysource");
g_assert(app->appsrc);
g_assert(GST_IS_APP_SRC(app->appsrc));
g_signal_connect (app->appsrc, "need-data", G_CALLBACK (start_feed), app);
g_signal_connect (app->appsrc, "enough-data", G_CALLBACK (stop_feed), app);
/* set the caps on the source */
caps = gst_caps_new_simple ("video/x-raw-rgb",
"bpp",G_TYPE_INT,24,
"depth",G_TYPE_INT,24,
"width", G_TYPE_INT, 640,
"height", G_TYPE_INT, 480,
NULL);
gst_app_src_set_caps(GST_APP_SRC(app->appsrc), caps);
/* go to playing and wait in a mainloop. */
gst_element_set_state (app->pipeline, GST_STATE_PLAYING);
/* this mainloop is stopped when we receive an error or EOS */
g_main_loop_run (app->loop);
GST_DEBUG ("stopping");
gst_element_set_state (app->pipeline, GST_STATE_NULL);
gst_object_unref (bus);
g_main_loop_unref (app->loop);
return 0;
}
更新：我尝试用普通的 xvimagesink 替换 udpsink 并没有帮助