pipewire/src/gst/gstpinossrc.c

/* GStreamer
 * Copyright (C) <2015> Wim Taymans <wim.taymans@gmail.com>
 *
 * 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.
 */

/**
 * SECTION:element-pinossrc
 *
 * <refsect2>
 * <title>Example launch line</title>
 * |[
 * gst-launch -v pinossrc ! videoconvert ! ximagesink
 * ]| Shows pinos output in an X window.
 * </refsect2>
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gstpinossrc.h"

#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <unistd.h>

#include <gio/gunixfdmessage.h>
#include <gst/allocators/gstfdmemory.h>


static GQuark fdpayload_data_quark;

GST_DEBUG_CATEGORY_STATIC (pinos_src_debug);
#define GST_CAT_DEFAULT pinos_src_debug

enum
{
  PROP_0,
  PROP_PATH,
  PROP_CLIENT_NAME,
};


#define PINOSS_VIDEO_CAPS GST_VIDEO_CAPS_MAKE (GST_VIDEO_FORMATS_ALL)

static GstStaticPadTemplate gst_pinos_src_template =
GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS_ANY
    );

#define gst_pinos_src_parent_class parent_class
G_DEFINE_TYPE (GstPinosSrc, gst_pinos_src, GST_TYPE_PUSH_SRC);

static GstStateChangeReturn
gst_pinos_src_change_state (GstElement * element, GstStateChange transition);

static gboolean gst_pinos_src_negotiate (GstBaseSrc * basesrc);
static GstCaps *gst_pinos_src_getcaps (GstBaseSrc * bsrc, GstCaps * filter);
static GstCaps *gst_pinos_src_src_fixate (GstBaseSrc * bsrc,
    GstCaps * caps);

static GstFlowReturn gst_pinos_src_create (GstPushSrc * psrc,
    GstBuffer ** buffer);
static gboolean gst_pinos_src_start (GstBaseSrc * basesrc);
static gboolean gst_pinos_src_stop (GstBaseSrc * basesrc);

static void
gst_pinos_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstPinosSrc *pinossrc = GST_PINOS_SRC (object);

  switch (prop_id) {
    case PROP_PATH:
      g_free (pinossrc->path);
      pinossrc->path = g_value_dup_string (value);
      break;

    case PROP_CLIENT_NAME:
      g_free (pinossrc->client_name);
      pinossrc->client_name = g_value_dup_string (value);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_pinos_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstPinosSrc *pinossrc = GST_PINOS_SRC (object);

  switch (prop_id) {
    case PROP_PATH:
      g_value_set_string (value, pinossrc->path);
      break;

    case PROP_CLIENT_NAME:
      g_value_set_string (value, pinossrc->client_name);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_pinos_src_finalize (GObject * object)
{
  GstPinosSrc *pinossrc = GST_PINOS_SRC (object);

  g_object_unref (pinossrc->fd_allocator);
  g_free (pinossrc->path);
  g_free (pinossrc->client_name);

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static void
gst_pinos_src_class_init (GstPinosSrcClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;
  GstBaseSrcClass *gstbasesrc_class;
  GstPushSrcClass *gstpushsrc_class;

  gobject_class = (GObjectClass *) klass;
  gstelement_class = (GstElementClass *) klass;
  gstbasesrc_class = (GstBaseSrcClass *) klass;
  gstpushsrc_class = (GstPushSrcClass *) klass;

  gobject_class->finalize = gst_pinos_src_finalize;
  gobject_class->set_property = gst_pinos_src_set_property;
  gobject_class->get_property = gst_pinos_src_get_property;

  g_object_class_install_property (gobject_class,
                                   PROP_PATH,
                                   g_param_spec_string ("path",
                                                        "Path",
                                                        "The source path to connect to (NULL = default)",
                                                        NULL,
                                                        G_PARAM_READWRITE |
                                                        G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class,
                                   PROP_CLIENT_NAME,
                                   g_param_spec_string ("client-name",
                                                        "Client Name",
                                                        "The client name to use (NULL = default)",
                                                        NULL,
                                                        G_PARAM_READWRITE |
                                                        G_PARAM_STATIC_STRINGS));

  gstelement_class->change_state = gst_pinos_src_change_state;

  gst_element_class_set_static_metadata (gstelement_class,
      "Pinos source", "Source/Video",
      "Uses pinos to create video", "Wim Taymans <wim.taymans@gmail.com>");

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&gst_pinos_src_template));

  gstbasesrc_class->negotiate = gst_pinos_src_negotiate;
  gstbasesrc_class->get_caps = gst_pinos_src_getcaps;
  gstbasesrc_class->fixate = gst_pinos_src_src_fixate;
  gstbasesrc_class->start = gst_pinos_src_start;
  gstbasesrc_class->stop = gst_pinos_src_stop;

  gstpushsrc_class->create = gst_pinos_src_create;

  GST_DEBUG_CATEGORY_INIT (pinos_src_debug, "pinossrc", 0,
      "Pinos Source");

  fdpayload_data_quark = g_quark_from_static_string ("GstPinosSrcFDPayloadQuark");
}

static void
gst_pinos_src_init (GstPinosSrc * src)
{
  /* we operate in time */
  gst_base_src_set_format (GST_BASE_SRC (src), GST_FORMAT_TIME);
  gst_base_src_set_live (GST_BASE_SRC (src), TRUE);

  src->fd_allocator = gst_fd_allocator_new ();
  src->client_name = pinos_client_name ();
}

static GstCaps *
gst_pinos_src_src_fixate (GstBaseSrc * bsrc, GstCaps * caps)
{
  GstStructure *structure;

  caps = gst_caps_make_writable (caps);

  structure = gst_caps_get_structure (caps, 0);

  if (gst_structure_has_name (structure, "video/x-raw")) {
    gst_structure_fixate_field_nearest_int (structure, "width", 320);
    gst_structure_fixate_field_nearest_int (structure, "height", 240);
    gst_structure_fixate_field_nearest_fraction (structure, "framerate", 30, 1);

    if (gst_structure_has_field (structure, "pixel-aspect-ratio"))
      gst_structure_fixate_field_nearest_fraction (structure,
          "pixel-aspect-ratio", 1, 1);
    else
      gst_structure_set (structure, "pixel-aspect-ratio", GST_TYPE_FRACTION, 1, 1,
          NULL);

    if (gst_structure_has_field (structure, "colorimetry"))
      gst_structure_fixate_field_string (structure, "colorimetry", "bt601");
    if (gst_structure_has_field (structure, "chroma-site"))
      gst_structure_fixate_field_string (structure, "chroma-site", "mpeg2");

    if (gst_structure_has_field (structure, "interlace-mode"))
      gst_structure_fixate_field_string (structure, "interlace-mode",
          "progressive");
    else
      gst_structure_set (structure, "interlace-mode", G_TYPE_STRING,
          "progressive", NULL);
  } else if (gst_structure_has_name (structure, "audio/x-raw")) {
    gst_structure_fixate_field_string (structure, "format", "S16LE");
    gst_structure_fixate_field_nearest_int (structure, "channels", 2);
    gst_structure_fixate_field_nearest_int (structure, "rate", 44100);
  }

  caps = GST_BASE_SRC_CLASS (parent_class)->fixate (bsrc, caps);

  return caps;
}

typedef struct {
  GstPinosSrc *src;
  PinosPacketFDPayload p;
} FDPayloadData;

static void
fdpayload_data_destroy (gpointer user_data)
{
  FDPayloadData *data = user_data;
  GstPinosSrc *pinossrc = data->src;
  PinosBufferBuilder b;
  PinosPacketReleaseFDPayload r;
  PinosBuffer pbuf;

  r.id = data->p.id;

  GST_DEBUG_OBJECT (pinossrc, "destroy %d", r.id);

  pinos_buffer_builder_init (&b);
  pinos_buffer_builder_add_release_fd_payload (&b, &r);
  pinos_buffer_builder_end (&b, &pbuf);

  GST_OBJECT_LOCK (pinossrc);
  if (pinossrc->stream)
    pinos_stream_send_buffer (pinossrc->stream, &pbuf);
  GST_OBJECT_UNLOCK (pinossrc);

  pinos_buffer_clear (&pbuf);

  gst_object_unref (pinossrc);
  g_slice_free (FDPayloadData, data);
}

static void
on_new_buffer (GObject    *gobject,
               gpointer    user_data)
{
  GstPinosSrc *pinossrc = user_data;
  PinosBuffer *pbuf;
  PinosBufferIter it;
  GstBuffer *buf;
  GError *error = NULL;

  GST_LOG_OBJECT (pinossrc, "got new buffer");
  if (!pinos_stream_peek_buffer (pinossrc->stream, &pbuf)) {
    g_warning ("failed to capture buffer");
    return;
  }

  buf = gst_buffer_new ();

  pinos_buffer_iter_init (&it, pbuf);
  while (pinos_buffer_iter_next (&it)) {
    switch (pinos_buffer_iter_get_type (&it)) {
      case PINOS_PACKET_TYPE_HEADER:
      {
        PinosPacketHeader hdr;

        if (!pinos_buffer_iter_parse_header  (&it, &hdr))
          goto no_fds;

        if (GST_CLOCK_TIME_IS_VALID (hdr.pts)) {
          if (hdr.pts > GST_ELEMENT_CAST (pinossrc)->base_time)
            GST_BUFFER_PTS (buf) = hdr.pts - GST_ELEMENT_CAST (pinossrc)->base_time;

          if (GST_BUFFER_PTS (buf) + hdr.dts_offset > 0)
            GST_BUFFER_DTS (buf) = GST_BUFFER_PTS (buf) + hdr.dts_offset;
        }
        GST_BUFFER_OFFSET (buf) = hdr.seq;
        break;
      }
      case PINOS_PACKET_TYPE_FD_PAYLOAD:
      {
        GstMemory *fdmem = NULL;
        FDPayloadData data;
        int fd;

        GST_DEBUG ("got fd payload");
        if (!pinos_buffer_iter_parse_fd_payload  (&it, &data.p))
          goto no_fds;
        fd = pinos_buffer_get_fd (pbuf, data.p.fd_index, &error);
        if (fd == -1)
          goto no_fds;

        fdmem = gst_fd_allocator_alloc (pinossrc->fd_allocator, fd,
                  data.p.offset + data.p.size, GST_FD_MEMORY_FLAG_NONE);
        gst_memory_resize (fdmem, data.p.offset, data.p.size);
        gst_buffer_append_memory (buf, fdmem);

        data.src = gst_object_ref (pinossrc);
        gst_mini_object_set_qdata (GST_MINI_OBJECT_CAST (fdmem),
                                   fdpayload_data_quark,
                                   g_slice_dup (FDPayloadData, &data),
                                   fdpayload_data_destroy);
        break;
      }
      default:
        break;
    }
  }
  if (pinossrc->current)
    gst_buffer_unref (pinossrc->current);
  pinossrc->current = buf;

  pinos_main_loop_signal (pinossrc->loop, FALSE);

  return;

  /* ERRORS */
no_fds:
  {
    gst_buffer_unref (buf);
    GST_ELEMENT_ERROR (pinossrc, RESOURCE, FAILED,
        ("buffer error: %s", error->message), (NULL));
    pinos_main_loop_signal (pinossrc->loop, FALSE);
    return;
  }

}

static void
on_stream_notify (GObject    *gobject,
                  GParamSpec *pspec,
                  gpointer    user_data)
{
  GstPinosSrc *pinossrc = user_data;
  PinosStreamState state = pinos_stream_get_state (pinossrc->stream);

  GST_DEBUG ("got stream state %d", state);

  switch (state) {
    case PINOS_STREAM_STATE_UNCONNECTED:
    case PINOS_STREAM_STATE_CONNECTING:
    case PINOS_STREAM_STATE_STARTING:
    case PINOS_STREAM_STATE_STREAMING:
    case PINOS_STREAM_STATE_READY:
      break;
    case PINOS_STREAM_STATE_ERROR:
      GST_ELEMENT_ERROR (pinossrc, RESOURCE, FAILED,
          ("stream error: %s",
            pinos_stream_get_error (pinossrc->stream)->message), (NULL));
      break;
  }
  pinos_main_loop_signal (pinossrc->loop, FALSE);
}

static gboolean
gst_pinos_src_stream_start (GstPinosSrc *pinossrc, GstCaps * caps)
{
  gchar *str;
  GBytes *format;
  gboolean res;

  str = gst_caps_to_string (caps);
  format = g_bytes_new_take (str, strlen (str) + 1);

  pinos_main_loop_lock (pinossrc->loop);
  res = pinos_stream_start (pinossrc->stream, format, PINOS_STREAM_MODE_BUFFER);
  while (TRUE) {
    PinosStreamState state = pinos_stream_get_state (pinossrc->stream);

    if (state == PINOS_STREAM_STATE_STREAMING)
      break;

    if (state == PINOS_STREAM_STATE_ERROR)
      goto start_error;

    pinos_main_loop_wait (pinossrc->loop);
  }
  pinos_main_loop_unlock (pinossrc->loop);

  return res;

start_error:
  {
    GST_DEBUG_OBJECT (pinossrc, "error starting stream");
    return FALSE;
  }
}

static gboolean
gst_pinos_src_negotiate (GstBaseSrc * basesrc)
{
  GstPinosSrc *pinossrc = GST_PINOS_SRC (basesrc);
  GstCaps *thiscaps;
  GstCaps *caps = NULL;
  GstCaps *peercaps = NULL;
  gboolean result = FALSE;

  /* first see what is possible on our source pad */
  thiscaps = gst_pad_query_caps (GST_BASE_SRC_PAD (basesrc), NULL);
  GST_DEBUG_OBJECT (basesrc, "caps of src: %" GST_PTR_FORMAT, thiscaps);
  /* nothing or anything is allowed, we're done */
  if (thiscaps == NULL)
    goto no_nego_needed;

  if (G_UNLIKELY (gst_caps_is_empty (thiscaps)))
    goto no_caps;

  /* get the peer caps */
  peercaps = gst_pad_peer_query_caps (GST_BASE_SRC_PAD (basesrc), thiscaps);
  GST_DEBUG_OBJECT (basesrc, "caps of peer: %" GST_PTR_FORMAT, peercaps);
  if (peercaps) {
    /* The result is already a subset of our caps */
    caps = peercaps;
    gst_caps_unref (thiscaps);
  } else {
    /* no peer, work with our own caps then */
    caps = thiscaps;
  }
  if (caps && !gst_caps_is_empty (caps)) {
    GBytes *accepted, *possible;
    gchar *str;

    GST_DEBUG_OBJECT (basesrc, "have caps: %" GST_PTR_FORMAT, caps);

    /* open a connection with these caps */
    str = gst_caps_to_string (caps);
    accepted = g_bytes_new_take (str, strlen (str) + 1);

    /* first disconnect */
    pinos_main_loop_lock (pinossrc->loop);
    if (pinos_stream_get_state (pinossrc->stream) != PINOS_STREAM_STATE_UNCONNECTED) {
      GST_DEBUG_OBJECT (basesrc, "disconnect capture");
      pinos_stream_disconnect (pinossrc->stream);
      while (TRUE) {
        PinosStreamState state = pinos_stream_get_state (pinossrc->stream);

        if (state == PINOS_STREAM_STATE_UNCONNECTED)
          break;

        if (state == PINOS_STREAM_STATE_ERROR) {
          g_bytes_unref (accepted);
          goto connect_error;
        }

        pinos_main_loop_wait (pinossrc->loop);
      }
    }

    GST_DEBUG_OBJECT (basesrc, "connect capture with path %s", pinossrc->path);
    pinos_stream_connect_capture (pinossrc->stream, pinossrc->path, 0, accepted);

    while (TRUE) {
      PinosStreamState state = pinos_stream_get_state (pinossrc->stream);

      if (state == PINOS_STREAM_STATE_READY)
        break;

      if (state == PINOS_STREAM_STATE_ERROR)
        goto connect_error;

      pinos_main_loop_wait (pinossrc->loop);
    }
    pinos_main_loop_unlock (pinossrc->loop);

    g_object_get (pinossrc->stream, "possible-formats", &possible, NULL);
    if (possible) {
      GstCaps *newcaps;

      newcaps = gst_caps_from_string (g_bytes_get_data (possible, NULL));
      if (newcaps)
        caps = newcaps;

      g_bytes_unref (possible);
    }
    /* now fixate */
    GST_DEBUG_OBJECT (basesrc, "server fixated caps: %" GST_PTR_FORMAT, caps);
    if (gst_caps_is_any (caps)) {
      GST_DEBUG_OBJECT (basesrc, "any caps, we stop");
      /* hmm, still anything, so element can do anything and
       * nego is not needed */
      result = TRUE;
    } else {
      caps = gst_pinos_src_src_fixate (basesrc, caps);
      GST_DEBUG_OBJECT (basesrc, "fixated to: %" GST_PTR_FORMAT, caps);
      if (gst_caps_is_fixed (caps)) {
        /* yay, fixed caps, use those then, it's possible that the subclass does
         * not accept this caps after all and we have to fail. */
        result = gst_base_src_set_caps (basesrc, caps);
        if (result) {
          result = gst_pinos_src_stream_start (pinossrc, caps);
        }
      }
    }
    gst_caps_unref (caps);
  } else {
    if (caps)
      gst_caps_unref (caps);
    GST_DEBUG_OBJECT (basesrc, "no common caps");
  }
  pinossrc->negotiated = result;

  return result;

no_nego_needed:
  {
    GST_DEBUG_OBJECT (basesrc, "no negotiation needed");
    if (thiscaps)
      gst_caps_unref (thiscaps);
    return TRUE;
  }
no_caps:
  {
    GST_ELEMENT_ERROR (basesrc, STREAM, FORMAT,
        ("No supported formats found"),
        ("This element did not produce valid caps"));
    if (thiscaps)
      gst_caps_unref (thiscaps);
    return TRUE;
  }
connect_error:
  {
    pinos_main_loop_unlock (pinossrc->loop);
    return FALSE;
  }
}

static GstCaps *
gst_pinos_src_getcaps (GstBaseSrc * bsrc, GstCaps * filter)
{
  return GST_BASE_SRC_CLASS (parent_class)->get_caps (bsrc, filter);
}

static GstFlowReturn
gst_pinos_src_create (GstPushSrc * psrc, GstBuffer ** buffer)
{
  GstPinosSrc *pinossrc;

  pinossrc = GST_PINOS_SRC (psrc);

  if (!pinossrc->negotiated)
    goto not_negotiated;

  pinos_main_loop_lock (pinossrc->loop);
  while (TRUE) {
    PinosStreamState state;

    pinos_main_loop_wait (pinossrc->loop);

    state = pinos_stream_get_state (pinossrc->stream);
    if (state == PINOS_STREAM_STATE_ERROR)
      goto streaming_error;

    if (state != PINOS_STREAM_STATE_STREAMING)
      goto streaming_stopped;

    if (pinossrc->current != NULL)
      break;
  }
  pinos_main_loop_unlock (pinossrc->loop);

  *buffer = pinossrc->current;
  pinossrc->current = NULL;

  return GST_FLOW_OK;

not_negotiated:
  {
    return GST_FLOW_NOT_NEGOTIATED;
  }
streaming_error:
  {
    pinos_main_loop_unlock (pinossrc->loop);
    return GST_FLOW_ERROR;
  }
streaming_stopped:
  {
    pinos_main_loop_unlock (pinossrc->loop);
    return GST_FLOW_FLUSHING;
  }
}

static gboolean
gst_pinos_src_start (GstBaseSrc * basesrc)
{
  return TRUE;
}

static gboolean
gst_pinos_src_stop (GstBaseSrc * basesrc)
{
  GstPinosSrc *pinossrc;

  pinossrc = GST_PINOS_SRC (basesrc);
  if (pinossrc->current)
    gst_buffer_unref (pinossrc->current);
  pinossrc->current = NULL;

  return TRUE;
}

static void
on_context_notify (GObject    *gobject,
                   GParamSpec *pspec,
                   gpointer    user_data)
{
  GstPinosSrc *pinossrc = user_data;
  PinosContextState state = pinos_context_get_state (pinossrc->ctx);

  GST_DEBUG ("got context state %d", state);

  switch (state) {
    case PINOS_CONTEXT_STATE_UNCONNECTED:
    case PINOS_CONTEXT_STATE_CONNECTING:
    case PINOS_CONTEXT_STATE_REGISTERING:
    case PINOS_CONTEXT_STATE_READY:
      break;
    case PINOS_CONTEXT_STATE_ERROR:
      GST_ELEMENT_ERROR (pinossrc, RESOURCE, FAILED,
          ("context error: %s",
            pinos_context_get_error (pinossrc->ctx)->message), (NULL));
      break;
  }
  pinos_main_loop_signal (pinossrc->loop, FALSE);
}

static gboolean
gst_pinos_src_open (GstPinosSrc * pinossrc)
{
  GError *error = NULL;

  pinossrc->context = g_main_context_new ();
  GST_DEBUG ("context %p", pinossrc->context);

  pinossrc->loop = pinos_main_loop_new (pinossrc->context, "pinos-main-loop");
  if (!pinos_main_loop_start (pinossrc->loop, &error))
    goto mainloop_failed;

  pinos_main_loop_lock (pinossrc->loop);
  pinossrc->ctx = pinos_context_new (pinossrc->context, g_get_application_name (), NULL);
  g_signal_connect (pinossrc->ctx, "notify::state", (GCallback) on_context_notify, pinossrc);

  pinos_context_connect (pinossrc->ctx, PINOS_CONTEXT_FLAGS_NONE);

  while (TRUE) {
    PinosContextState state = pinos_context_get_state (pinossrc->ctx);

    if (state == PINOS_CONTEXT_STATE_READY)
      break;

    if (state == PINOS_CONTEXT_STATE_ERROR)
      goto connect_error;

    pinos_main_loop_wait (pinossrc->loop);
  }

  pinossrc->stream = pinos_stream_new (pinossrc->ctx, "test", NULL);
  g_signal_connect (pinossrc->stream, "notify::state", (GCallback) on_stream_notify, pinossrc);
  g_signal_connect (pinossrc->stream, "new-buffer", (GCallback) on_new_buffer, pinossrc);
  pinos_main_loop_unlock (pinossrc->loop);

  return TRUE;

  /* ERRORS */
mainloop_failed:
  {
    GST_ELEMENT_ERROR (pinossrc, RESOURCE, FAILED,
        ("mainloop error: %s", error->message), (NULL));
    return FALSE;
  }
connect_error:
  {
    pinos_main_loop_unlock (pinossrc->loop);
    return FALSE;
  }
}

static void
gst_pinos_src_close (GstPinosSrc * pinossrc)
{
  pinos_main_loop_stop (pinossrc->loop);
  g_clear_object (&pinossrc->loop);
  g_clear_object (&pinossrc->ctx);
  g_main_context_unref (pinossrc->context);
  GST_OBJECT_LOCK (pinossrc);
  g_clear_object (&pinossrc->stream);
  GST_OBJECT_UNLOCK (pinossrc);

  if (pinossrc->current)
    gst_buffer_unref (pinossrc->current);
  pinossrc->current = NULL;
}

static GstStateChangeReturn
gst_pinos_src_change_state (GstElement * element, GstStateChange transition)
{
  GstStateChangeReturn ret;
  GstPinosSrc *this = GST_PINOS_SRC_CAST (element);

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      if (!gst_pinos_src_open (this))
        goto open_failed;
      break;
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      break;
    case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
      /* uncork and start recording */
      break;
    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
      /* stop recording ASAP by corking */
      break;
    default:
      break;
  }

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);

  switch (transition) {
    case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
      break;
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      this->negotiated = FALSE;
      break;
    case GST_STATE_CHANGE_READY_TO_NULL:
      gst_pinos_src_close (this);
      break;
    default:
      break;
  }
  return ret;

  /* ERRORS */
open_failed:
  {
    return GST_STATE_CHANGE_FAILURE;
  }
}