appsrc with GST_FORMAT_BYTES cannot query duration

[gyunaev]

Good morning,

I've set up appsrc with format GST_FORMAT_BYTES, use push signal and set the
buffer position via buffer->offset and buffer->offset_end. It works fine,
but the maximum duration is reported.

However if I also set the "size" property of appsrc, querying the duration
fails - gst_element_query_duration() returns 0.

The following example is basically playback-tutorial-3.c with following
modifications:

- "format" is set to GST_FORMAT_BYTES, "stream-type" to 1 (seekable) and
"size" to 40000000
- added seek callback
- added timeout to print position/duration (which fails on querying
duration)
- stream position is set via:
  buffer->offset = data->streampos;
  buffer->offset_end = data->streampos + CHUNK_SIZE - 1;


The sample code (also pasted as http://pastebin.com/ubrWaKQ0 in case mailer
breaks it):

#include <gst/gst.h>
#include <gst/audio/audio.h>
#include <string.h>
  
#define CHUNK_SIZE 1024   /* Amount of bytes we are sending in each buffer
*/
#define SAMPLE_RATE 44100 /* Samples per second we are sending */
  
/* Structure to contain all our information, so we can pass it to callbacks
*/
typedef struct _CustomData {
  GstElement *pipeline;
  GstElement *app_source;
  
  guint64 num_samples;   /* Number of samples generated so far (for
timestamp generation) */
  guint streampos;
  gfloat a, b, c, d;     /* For waveform 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 ide 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;
  GstMapInfo map;
  gint16 *raw;
  gint num_samples = CHUNK_SIZE / 2; /* Because each sample is 16 bits */
  gfloat freq;
  
  /* Create a new empty buffer */
  buffer = gst_buffer_new_and_alloc (CHUNK_SIZE);
   
  /* Generate some psychodelic waveforms */
  gst_buffer_map (buffer, &map, GST_MAP_WRITE);
  raw = (gint16 *)map.data;
  data->c += data->d;
  data->d -= data->c / 1000;
  freq = 1100 + 1000 * data->d;
  for (i = 0; i < num_samples; i++) {
    data->a += data->b;
    data->b -= data->a / freq;
    raw[i] = (gint16)(500 * data->a);
  }
  gst_buffer_unmap (buffer, &map);
  data->num_samples += num_samples;
  
  /* Set its timestamp and duration */
  buffer->offset = data->streampos;
  buffer->offset_end = data->streampos + CHUNK_SIZE - 1;
  data->streampos += CHUNK_SIZE;
  
  /* Push the buffer into the appsrc */
  g_signal_emit_by_name (data->app_source, "push-buffer", buffer, &ret);
  
  /* Free the buffer now that we are done with it */
  gst_buffer_unref (buffer);
  
  if (ret != GST_FLOW_OK) {
    /* We got some error, stop sending data */
    return FALSE;
  }
  
  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);
  }
}
  
/* 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;
  }
}
 
static gboolean seek_feed(GstElement *sourc, guint64 offset, gpointer
user_data)
{
    g_print ("seek called to %d\n", offset);
    return 1;
}

/* 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);
}
  
/* This function is called when playbin has created the appsrc element, so
we have
 * a chance to configure it. */
static void source_setup (GstElement *pipeline, GstElement *source,
CustomData *data) {
  GstAudioInfo info;
  GstCaps *audio_caps;
  
  g_print ("Source has been created. Configuring.\n");
  data->app_source = source;
  
  /* Configure appsrc */
  gst_audio_info_set_format (&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1,
NULL);
  audio_caps = gst_audio_info_to_caps (&info);

  // This does not work
  g_object_set (source, "caps", audio_caps, "format", GST_FORMAT_BYTES,
"stream-type", 1, "size", (gint64) 40000000, NULL);
  
  // This works but the duration is not set
  //g_object_set (source, "caps", audio_caps, "format", GST_FORMAT_BYTES,
"stream-type", 1, NULL);
  g_signal_connect (source, "need-data", G_CALLBACK (start_feed), data);
  g_signal_connect (source, "enough-data", G_CALLBACK (stop_feed), data);
  g_signal_connect (source, "seek-data", G_CALLBACK (seek_feed), &data);
  gst_caps_unref (audio_caps);
}

static gboolean
cb_print_position (GstElement *pipeline)
{
    gint64 pos, len = -1;
    
    if ( !gst_element_query_position (pipeline, GST_FORMAT_TIME, &pos) )
        g_print ("Failed to query position.\n");
    else if ( !gst_element_query_duration (pipeline, GST_FORMAT_TIME, &len)
)
        g_print ("Failed to query duration.\n");
    else
        g_print ("Time: %" GST_TIME_FORMAT " / %" GST_TIME_FORMAT "\r",
GST_TIME_ARGS (pos), GST_TIME_ARGS (len));

    /* call me again */
    return TRUE;
}


int main(int argc, char *argv[]) {
  CustomData data;
  GstBus *bus;
  
  /* Initialize cumstom data structure */
  memset (&data, 0, sizeof (data));
  data.b = 1; /* For waveform generation */
  data.d = 1;
  
  /* Initialize GStreamer */
  gst_init (&argc, &argv);
  
  /* Create the playbin element */
  data.pipeline = gst_parse_launch ("playbin uri=appsrc://", NULL);
  g_signal_connect (data.pipeline, "source-setup", G_CALLBACK
(source_setup), &data);
  
  /* 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);
  
  g_timeout_add (200, (GSourceFunc) cb_print_position, data.pipeline);
  
  /* 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;
}




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