我正在尝试学习gstreamer appsrc插件，以便从我写的传输流解复用器播放AV（我知道插件已经可用，我想自己动手去学习）。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（这部分我还不清楚：关于使用哪些插件 - 任何提示都将受到高度赞赏）。
我找到了sample code on using appsrc，但是当我运行它时，没有输出。我确认确实调用了start_feed和read_data函数。在read_data函数中，有一个计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的用途，但ms的值总是大约为0.035，数据永远不会被推送到appsrc。所以我将if条件更改为if(ms > 0.03)，但后来出现了内部数据流错误：
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此视频吗？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，但没有帮助
答案 0 :(得分：9)
由于没有人愿意回答，我会发布一个针对appsrc插件的工作测试代码 - 虽然这不能解答为什么问题中的代码不起作用，这将有助于人们在搜索时从Google登陆对于appsrc测试代码。
#include <stdio.h>
#include <gst/gst.h>
#include <gst/app/gstappsrc.h>
typedef struct {
GstPipeline *pipeline;
GstAppSrc *src;
GstElement *sink;
GstElement *decoder;
GstElement *ffmpeg;
GstElement *xvimagesink;
GMainLoop *loop;
guint sourceid;
FILE *file;
}gst_app_t;
static gst_app_t gst_app;
#define BUFF_SIZE (1024)
static gboolean read_data(gst_app_t *app)
{
GstBuffer *buffer;
guint8 *ptr;
gint size;
GstFlowReturn ret;
ptr = g_malloc(BUFF_SIZE);
g_assert(ptr);
size = fread(ptr, 1, BUFF_SIZE, app->file);
if(size == 0){
ret = gst_app_src_end_of_stream(app->src);
g_debug("eos returned %d at %d\n", ret, __LINE__);
return FALSE;
}
buffer = gst_buffer_new();
GST_BUFFER_MALLOCDATA(buffer) = ptr;
GST_BUFFER_SIZE(buffer) = size;
GST_BUFFER_DATA(buffer) = GST_BUFFER_MALLOCDATA(buffer);
ret = gst_app_src_push_buffer(app->src, buffer);
if(ret != GST_FLOW_OK){
g_debug("push buffer returned %d for %d bytes \n", ret, size);
return FALSE;
}
if(size != BUFF_SIZE){
ret = gst_app_src_end_of_stream(app->src);
g_debug("eos returned %d at %d\n", ret, __LINE__);
return FALSE;
}
return TRUE;
}
static void start_feed (GstElement * pipeline, guint size, gst_app_t *app)
{
if (app->sourceid == 0) {
GST_DEBUG ("start feeding");
app->sourceid = g_idle_add ((GSourceFunc) read_data, app);
}
}
static void stop_feed (GstElement * pipeline, gst_app_t *app)
{
if (app->sourceid != 0) {
GST_DEBUG ("stop feeding");
g_source_remove (app->sourceid);
app->sourceid = 0;
}
}
static void on_pad_added(GstElement *element, GstPad *pad)
{
GstCaps *caps;
GstStructure *str;
gchar *name;
GstPad *ffmpegsink;
GstPadLinkReturn ret;
g_debug("pad added");
caps = gst_pad_get_caps(pad);
str = gst_caps_get_structure(caps, 0);
g_assert(str);
name = (gchar*)gst_structure_get_name(str);
g_debug("pad name %s", name);
if(g_strrstr(name, "video")){
ffmpegsink = gst_element_get_pad(gst_app.ffmpeg, "sink");
g_assert(ffmpegsink);
ret = gst_pad_link(pad, ffmpegsink);
g_debug("pad_link returned %d\n", ret);
gst_object_unref(ffmpegsink);
}
gst_caps_unref(caps);
}
static gboolean bus_callback(GstBus *bus, GstMessage *message, gpointer *ptr)
{
gst_app_t *app = (gst_app_t*)ptr;
switch(GST_MESSAGE_TYPE(message)){
case GST_MESSAGE_ERROR:{
gchar *debug;
GError *err;
gst_message_parse_error(message, &err, &debug);
g_print("Error %s\n", err->message);
g_error_free(err);
g_free(debug);
g_main_loop_quit(app->loop);
}
break;
case GST_MESSAGE_EOS:
g_print("End of stream\n");
g_main_loop_quit(app->loop);
break;
default:
g_print("got message %s\n", \
gst_message_type_get_name (GST_MESSAGE_TYPE (message)));
break;
}
return TRUE;
}
int main(int argc, char *argv[])
{
gst_app_t *app = &gst_app;
GstBus *bus;
GstStateChangeReturn state_ret;
if(argc != 2){
printf("File name not specified\n");
return 1;
}
app->file = fopen(argv[1], "r");
g_assert(app->file);
gst_init(NULL, NULL);
app->pipeline = (GstPipeline*)gst_pipeline_new("mypipeline");
bus = gst_pipeline_get_bus(app->pipeline);
gst_bus_add_watch(bus, (GstBusFunc)bus_callback, app);
gst_object_unref(bus);
app->src = (GstAppSrc*)gst_element_factory_make("appsrc", "mysrc");
app->decoder = gst_element_factory_make("decodebin", "mydecoder");
app->ffmpeg = gst_element_factory_make("ffmpegcolorspace", "myffmpeg");
app->xvimagesink = gst_element_factory_make("xvimagesink", "myvsink");
g_assert(app->src);
g_assert(app->decoder);
g_assert(app->ffmpeg);
g_assert(app->xvimagesink);
g_signal_connect(app->src, "need-data", G_CALLBACK(start_feed), app);
g_signal_connect(app->src, "enough-data", G_CALLBACK(stop_feed), app);
g_signal_connect(app->decoder, "pad-added", G_CALLBACK(on_pad_added), app->decoder);
gst_bin_add_many(GST_BIN(app->pipeline), (GstElement*)app->src, app->decoder, app->ffmpeg, app->xvimagesink, NULL);
if(!gst_element_link((GstElement*)app->src, app->decoder)){
g_warning("failed to link src anbd decoder");
}
if(!gst_element_link(app->ffmpeg, app->xvimagesink)){
g_warning("failed to link ffmpeg and xvsink");
}
state_ret = gst_element_set_state((GstElement*)app->pipeline, GST_STATE_PLAYING);
g_warning("set state returned %d\n", state_ret);
app->loop = g_main_loop_new(NULL, FALSE);
printf("Running main loop\n");
g_main_loop_run(app->loop);
state_ret = gst_element_set_state((GstElement*)app->pipeline, GST_STATE_NULL);
g_warning("set state null returned %d\n", state_ret);
return 0;
}
答案 1 :(得分：2)
非常感谢IRC / freenode /＃gstreamer（尤其是__tim！）上的专家，我已经找到了如何修复示例代码中的错误。
错误1. read_data（）的最后一行应该“返回TRUE”，以便此函数保留在总线上，并将被重复调用。只有在想要完全停止发送数据时才返回FALSE。
错误2.用gst_video_format_new_caps（）替换gst_caps_new_simple（）。您还需要包含gst / video / video.h，并链接到-lgstvideo-0.10。
这是我的代码版本，展示了如何显示图像以及如何通过UDP流式传输theora编码版本。请注意后一种情况下videorate的用法，因为theora需要一个恒定的帧速率源。
#include <gst/gst.h>
#include <gst/app/gstappsrc.h>
#include <gst/video/video.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);
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 TRUE;
}
/* 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();
// Option 1: Display on screen via xvimagesink
app->pipeline = gst_parse_launch("appsrc name=mysource ! video/x-raw-rgb,width=640,height=480 ! ffmpegcolorspace ! videoscale method=1 ! xvimagesink", NULL);
// Option 2: Encode using Theora and stream through UDP
// NOTE: first launch receiver by executing:
// gst-launch udpsrc port=5000 ! theoradec ! ffmpegcolorspace ! xvimagesink
//app->pipeline = gst_parse_launch("appsrc name=mysource ! videorate ! ffmpegcolorspace ! videoscale method=1 ! video/x-raw-yuv,width=640,height=480,framerate=\(fraction\)15/1 ! theoraenc bitrate=700 ! udpsink host=127.0.0.1 port=5000", 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_video_format_new_caps(GST_VIDEO_FORMAT_RGB, 640, 480, 0, 1, 4, 3);
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;
}