gstreamer学习笔记：分享几个appsink和appsrc的example

（1）appsink的使用：

#include 
#define HAVE_GTK
#ifdef HAVE_GTK
#include 
#endif

#include 

#define CAPS "video/x-raw,format=RGB,width=160,pixel-aspect-ratio=1/1"

int
main (int argc, char *argv[])
{
  GstElement *pipeline, *sink;
  gint width, height;
  GstSample *sample;
  gchar *descr;
  GError *error = NULL;
  gint64 duration, position;
  GstStateChangeReturn ret;
  gboolean res;
  GstMapInfo map;

  gst_init (&argc, &argv);

  if (argc != 2) {
    g_print ("usage: %s \n Writes snapshot.png in the current directory\n",
        argv[0]);
    exit (-1);
  }

  /* create a new pipeline */
  descr =
      g_strdup_printf ("videotestsrc pattern=%s ! "
      " appsink name=sink caps=\"" CAPS "\"", argv[1]);
  pipeline = gst_parse_launch (descr, &error);

  if (error != NULL) {
    g_print ("could not construct pipeline: %s\n", error->message);
    g_clear_error (&error);
    exit (-1);
  }

  /* get sink */
  sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");

  /* set to PAUSED to make the first frame arrive in the sink */
  ret = gst_element_set_state (pipeline, GST_STATE_PAUSED);
  switch (ret) {
    case GST_STATE_CHANGE_FAILURE:
      g_print ("failed to play the file\n");
      exit (-1);
    case GST_STATE_CHANGE_NO_PREROLL:
      /* for live sources, we need to set the pipeline to PLAYING before we can
       * receive a buffer. We don't do that yet */
      g_print ("live sources not supported yet\n");
      exit (-1);
    default:
      break;
  }
  /* This can block for up to 5 seconds. If your machine is really overloaded,
   * it might time out before the pipeline prerolled and we generate an error. A
   * better way is to run a mainloop and catch errors there. */
  ret = gst_element_get_state (pipeline, NULL, NULL, 5 * GST_SECOND);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    g_print ("failed to play the file\n");
    exit (-1);
  }

  /* get the duration */
  gst_element_query_duration (pipeline, GST_FORMAT_TIME, &duration);

  if (duration != -1)
    /* we have a duration, seek to 5% */
    position = duration * 5 / 100;
  else
    /* no duration, seek to 1 second, this could EOS */
    position = 1 * GST_SECOND;

  /* seek to the a position in the file. Most files have a black first frame so
   * by seeking to somewhere else we have a bigger chance of getting something
   * more interesting. An optimisation would be to detect black images and then
   * seek a little more */
  gst_element_seek_simple (pipeline, GST_FORMAT_TIME,
      GST_SEEK_FLAG_KEY_UNIT | GST_SEEK_FLAG_FLUSH, position);

  /* get the preroll buffer from appsink, this block untils appsink really
   * prerolls */
  g_signal_emit_by_name (sink, "pull-preroll", &sample, NULL);

  /* if we have a buffer now, convert it to a pixbuf. It's possible that we
   * don't have a buffer because we went EOS right away or had an error. */
  if (sample) {
    GstBuffer *buffer;
    GstCaps *caps;
    GstStructure *s;

    /* get the snapshot buffer format now. We set the caps on the appsink so
     * that it can only be an rgb buffer. The only thing we have not specified
     * on the caps is the height, which is dependant on the pixel-aspect-ratio
     * of the source material */
    caps = gst_sample_get_caps (sample);
    if (!caps) {
      g_print ("could not get snapshot format\n");
      exit (-1);
    }
    s = gst_caps_get_structure (caps, 0);

    /* we need to get the final caps on the buffer to get the size */
    res = gst_structure_get_int (s, "width", &width);
    res |= gst_structure_get_int (s, "height", &height);
    if (!res) {
      g_print ("could not get snapshot dimension\n");
      exit (-1);
    }

    /* create pixmap from buffer and save, gstreamer video buffers have a stride
     * that is rounded up to the nearest multiple of 4 */
    buffer = gst_sample_get_buffer (sample);
    
    /* Mapping a buffer can fail (non-readable) */
    if (gst_buffer_map (buffer, &map, GST_MAP_READ)) {
        /* print the buffer data for debug */
        int i = 0, j = 0;
        g_print("width=%d, height = %d\n", width, height);
        for(; i < width; i++){
            for(; j < height; j++){
                g_print("%x ", map.data[i*width + j]);
            }
            g_print("\n");
        }
#ifdef HAVE_GTK
      GdkPixbuf * pixbuf = gdk_pixbuf_new_from_data (map.data,
          GDK_COLORSPACE_RGB, FALSE, 8, width, height,
          GST_ROUND_UP_4 (width * 3), NULL, NULL);

      /* save the pixbuf */
      gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
#endif
      gst_buffer_unmap (buffer, &map);
    }
    gst_sample_unref (sample);
  } else {
    g_print ("could not make snapshot\n");
  }

  /* cleanup and exit */
  gst_element_set_state (pipeline, GST_STATE_NULL);
  gst_object_unref (pipeline);

  exit (0);
}

需要安装gtk：sudo apt-get install libgtk2.0-dev
编译命令：gcc appsink_example.c -o appsink_example $(pkg-config --cflags --libs gstreamer-1.0 gtk+-2.0)

执行： ./appsink_example red

（2）appsrc 例子：

/* 
  I don't know if it is syntax highlighter or blogger, but I can't seem to 
  put angle brackets around header file names properly.
*/
#include 
#include 
#include 
 
typedef struct {
    GstPipeline *pipeline;
    GstAppSrc *src;
    GstElement *sink;
    GstElement *decoder;
    GstElement *ffmpeg;
    GstElement *videosink;
    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);
    //g_print("read data...................\n");

    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)
{
    g_print("start feed...................\n");
    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)
{
    g_print("stop feed...................\n");
    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_WARNING:{
                gchar *debug;
                GError *err;
                gchar *name;

                gst_message_parse_warning(message, &err, &debug);
                g_print("Warning %s\nDebug %s\n", err->message, debug);

                name = GST_MESSAGE_SRC_NAME(message);

                g_print("Name of src %s\n", name ? name : "nil");
                g_error_free(err);
                g_free(debug);
            }
            break;

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

        case GST_MESSAGE_STATE_CHANGED:
            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("decodebin2", "mydecoder");
    app->ffmpeg = gst_element_factory_make("ffmpegcolorspace", "myffmpeg");
    app->videosink = gst_element_factory_make("autovideosink", "myvsink");

    g_assert(app->src);
    g_assert(app->decoder);
    g_assert(app->ffmpeg);
    g_assert(app->videosink);

    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->videosink, 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->videosink)){
        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);

    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;
}

编译：gcc appsrc2.c -o appsrc2 $(pkg-config --cflags --libs gstreamer-0.10 gstreamer-app-0.10)
运行：./appsrc2 xx.avi

（3）appsink和appsrc一起使用的例子：

/* GStreamer
 *
 * appsink-src.c: example for using appsink and appsrc.
 *
 * Copyright (C) 2008 Wim Taymans 
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include 

#include 

#include 
#include 

/* these are the caps we are going to pass through the appsink and appsrc */
const gchar *audio_caps =
    "audio/x-raw,format=S16LE,channels=2,rate=44100,layout=interleaved";

#define DEVICE "alsa_output.pci-0000_00_05.0.analog-stereo.monitor"

#define APPSRC_PULL_MODE (0)  /* appsrc working in pull mode or not */
#define PLAY_FILE (0)     /* play file or get data from pulseaudio */
#define SAVE_FILE (1)     /* save a file or playing directly */
static GstBuffer* s_app_buffer = NULL;

typedef struct
{
    GMainLoop *loop;
    GstElement *sink_pipeline;
    GstElement *src_pipeline;
} ProgramData;

/* called when the appsink notifies us that there is a new buffer ready for
 * processing */
static GstFlowReturn
on_new_sample_from_sink (GstElement * sink_elm, ProgramData * data)
{
    GstSample *sample = NULL;
    GstBuffer *buffer, *app_buffer;
    GstElement *sink, *source;
    GstFlowReturn ret;
    GstMapInfo map;
    
    /* get the sample from appsink */
    //sample = gst_app_sink_pull_sample (GST_APP_SINK (sink_elm));
#if 0
    sink = gst_bin_get_by_name (GST_BIN (data->src_pipeline), "testsink");
    g_signal_emit_by_name (sink, "pull-sample", &sample, &ret);
    gst_object_unref (sink);
#else
    g_signal_emit_by_name(sink_elm, "pull-sample", &sample, &ret);
#endif

    if(sample){
        buffer = gst_sample_get_buffer (sample);
        g_print("on_new_sample_from_sink() call!; size = %d\n", gst_buffer_get_size(buffer));
    }
    else{
        g_print("sample is NULL \n");
        return ret;
    }


    /* 查看pull 到的sample 数据 */
#if 0
    /* Mapping a buffer can fail (non-readable) */
    if (gst_buffer_map (buffer, &map, GST_MAP_READ)) {
        /* print the buffer data for debug */
        int i = 0, j = 0;
        for(; i < 10; i++)         
              g_print("%x ", map.data[i]);
        g_print("\n");
    }
#endif

    /* make a copy */
#if !APPSRC_PULL_MODE
    app_buffer = gst_buffer_copy (buffer);
#else
    s_app_buffer = gst_buffer_copy(buffer);
#endif

    /* we don't need the appsink sample anymore */
    gst_sample_unref (sample);

    /* 如果appsrc 为push 模式，直接将数据注入给appsrc */
    /* get source an push new buffer */
#if !APPSRC_PULL_MODE
    source = gst_bin_get_by_name (GST_BIN (data->sink_pipeline), "testsource");
    //ret = gst_app_src_push_buffer (GST_APP_SRC (source), app_buffer);
    g_signal_emit_by_name( source, "push-buffer", app_buffer, &ret );//数据送入pipeline
    gst_object_unref (source);
    gst_buffer_unref(app_buffer);
#endif

    return ret;
}

/* called when we get a GstMessage from the source pipeline when we get EOS, we
 * notify the appsrc of it. */
static gboolean
on_appsink_message (GstBus * bus, GstMessage * message, ProgramData * data)
{
    GstElement *source;

    switch (GST_MESSAGE_TYPE (message)) {
        case GST_MESSAGE_EOS:
            g_print ("The source got dry\n");
            source = gst_bin_get_by_name (GST_BIN (data->sink_pipeline), "testsource");
            //gst_app_src_end_of_stream (GST_APP_SRC (source));
            g_signal_emit_by_name (source, "end-of-stream", NULL);
            gst_object_unref (source);
            break;
        case GST_MESSAGE_ERROR:
            g_print ("Received error\n");
            g_main_loop_quit (data->loop);
            break;
        default:
            break;
    }
    return TRUE;
}


/* called when we get a GstMessage from the sink pipeline when we get EOS, we
 * exit the mainloop and this testapp. */
static gboolean
on_appsrc_message (GstBus * bus, GstMessage * message, ProgramData * data)
{
    /* nil */
    switch (GST_MESSAGE_TYPE (message)) {
        case GST_MESSAGE_EOS:
            g_print ("Finished playback\n");
            g_main_loop_quit (data->loop);
            break;
        case GST_MESSAGE_ERROR:
            g_print ("Received error\n");
            g_main_loop_quit (data->loop);
            break;
        default:
            break;
    }
    return TRUE;
}

static gboolean read_data(ProgramData* app_data)
{
    GstElement *appsink;
    appsink = gst_bin_get_by_name (GST_BIN (app_data->src_pipeline), "testsink");
    GstFlowReturn ret = on_new_sample_from_sink(appsink, app_data);
    gst_object_unref(appsink);

    GstElement *source = NULL;
    if(s_app_buffer){
        g_print("read data()....\n");
        source = gst_bin_get_by_name (GST_BIN (app_data->sink_pipeline), "testsource");
        //ret = gst_app_src_push_buffer (GST_APP_SRC (source), app_buffer);
        g_signal_emit_by_name( source, "push-buffer", s_app_buffer, &ret );//数据送入pipeline
        gst_object_unref (source);
        gst_buffer_unref(s_app_buffer);
        s_app_buffer = NULL;
    }
    else{
        g_print("read_data() s_app_buffer is NULL\n");
    }
    return TRUE;
}

static void on_appsrc_need_data(GstElement *appsrc,
                                                              guint unused_size,
                                                              ProgramData* app_data)
{
    g_print("on_appsrc_need_data() call !!!\n");
    guint src_id = g_idle_add ((GSourceFunc) read_data, app_data);
    return;
}

int main (int argc, char *argv[])
{
    gchar *filename = NULL;
    ProgramData *data = NULL;
    gchar *string = NULL;
    GstBus *bus = NULL;
    GstElement *testsink = NULL;
    GstElement *testsource = NULL;

    gst_init (&argc, &argv);

    if (argc == 2)
        filename = g_strdup (argv[1]);
    else
        filename = g_strdup ("xxx/xxxx.wav");

    if (!g_file_test (filename, G_FILE_TEST_EXISTS)) {
        g_print ("File %s does not exist\n", filename);
        return -1;
    }

    data = g_new0 (ProgramData, 1);

    data->loop = g_main_loop_new (NULL, FALSE);

    /* setting up source pipeline, we read from a file and convert to our desired
    * caps. */

#if PLAY_FILE  /* 播放wav 歌曲 */
    string =
      g_strdup_printf
      ("filesrc location=\"%s\" ! wavparse ! audioconvert ! appsink caps=\"%s\" name=testsink",
      filename, audio_caps);
#else  /* 从pulseaudio 抓取 */
    string =
      g_strdup_printf
      ("pulsesrc device=%s ! audioconvert ! appsink caps=\"%s\" name=testsink",
      DEVICE, audio_caps);
#endif

    g_free (filename);
    g_print("%s\n", string);
    data->src_pipeline = gst_parse_launch (string, NULL);
    g_free (string);

    if (data->src_pipeline == NULL) {
        g_print ("Bad source\n");
        return -1;
    }

    /* to be notified of messages from this pipeline, mostly EOS */
    bus = gst_element_get_bus (data->src_pipeline);
    gst_bus_add_watch (bus, (GstBusFunc) on_appsink_message, data);
    gst_object_unref (bus);

    /* we use appsink in push mode, it sends us a signal when data is available
    * and we pull out the data in the signal callback. We want the appsink to
    * push as fast as it can, hence the sync=false */
    testsink = gst_bin_get_by_name (GST_BIN (data->src_pipeline), "testsink");
    #if !APPSRC_PULL_MODE
    g_object_set (G_OBJECT (testsink), "emit-signals", TRUE, "sync", FALSE, NULL);
    g_signal_connect (testsink, "new-sample",
      G_CALLBACK (on_new_sample_from_sink), data);
    #endif
    gst_object_unref (testsink);

    /* setting up sink pipeline, we push audio data into this pipeline that will
    * then play it back using the default audio sink. We have no blocking
    * behaviour on the src which means that we will push the entire file into
    * memory. */
#if !SAVE_FILE
    string =
      g_strdup_printf ("appsrc name=testsource caps=\"%s\" ! autoaudiosink",
      audio_caps);
#else
    string =
      g_strdup_printf ("appsrc name=testsource caps=\"%s\" ! avenc_aac ! avmux_adts ! filesink location=sink_src.aac",
      audio_caps);
#endif
    data->sink_pipeline = gst_parse_launch (string, NULL);
    g_free (string);

    if (data->sink_pipeline == NULL) {
        g_print ("Bad sink\n");
        return -1;
    }

    testsource = gst_bin_get_by_name (GST_BIN (data->sink_pipeline), "testsource");
    /* configure for time-based format */
    g_object_set (testsource, "format", GST_FORMAT_TIME, NULL);
    /* uncomment the next line to block when appsrc has buffered enough */
    /* g_object_set (testsource, "block", TRUE, NULL); */
    #if APPSRC_PULL_MODE
    g_signal_connect (testsource, "need-data",
      G_CALLBACK (on_appsrc_need_data), data);
    #endif
    gst_object_unref (testsource);

    bus = gst_element_get_bus (data->sink_pipeline);
    gst_bus_add_watch (bus, (GstBusFunc) on_appsrc_message, data);
    gst_object_unref (bus);

    /* launching things */
    gst_element_set_state (data->src_pipeline, GST_STATE_PLAYING);
    gst_element_set_state (data->sink_pipeline, GST_STATE_PLAYING);

    /* let's run !, this loop will quit when the sink pipeline goes EOS or when an
    * error occurs in the source or sink pipelines. */
    g_print ("Let's run!\n");
    g_main_loop_run (data->loop);
    g_print ("Going out\n");

    gst_element_set_state (data->src_pipeline, GST_STATE_NULL);
    gst_element_set_state (data->sink_pipeline, GST_STATE_NULL);

    gst_object_unref (data->src_pipeline);
    gst_object_unref (data->sink_pipeline);
    g_main_loop_unref (data->loop);
    g_free (data);

    return 0;
}

编译：
//gcc appsink_src_test.c -o appsink_src_test $(pkg-config --cflags --libs gstreamer-1.0)
// or gcc appsink_src_test.c -o appsink_src_test $(pkg-config --cflags --libs gstreamer-1.0 gstreamer-app-1.0)