gstreamer/subprojects/gst-plugins-bad/sys/winks/gstksvideosrc.c

/*
 * Copyright (C) 2008 Ole André Vadla Ravnås <ole.andre.ravnas@tandberg.com>
 *               2009 Andres Colubri <andres.colubri@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-ksvideosrc
 * @title: ksvideosrc
 *
 * Provides low-latency video capture from WDM cameras on Windows.
 *
 * ## Example pipelines
 * |[
 * gst-launch-1.0 -v ksvideosrc do-stats=TRUE ! videoconvert ! dshowvideosink
 * ]| Capture from a camera and render using dshowvideosink.
 * |[
 * gst-launch-1.0 -v ksvideosrc do-stats=TRUE ! image/jpeg, width=640, height=480
 * ! jpegdec ! videoconvert ! dshowvideosink
 * ]| Capture from an MJPEG camera and render using dshowvideosink.
 *
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "gstksvideosrc.h"

#include "gstksclock.h"
#include "gstksvideodevice.h"
#include "kshelpers.h"
#include "ksvideohelpers.h"
#include "ksdeviceprovider.h"

#include <versionhelpers.h>

#define DEFAULT_DEVICE_PATH     NULL
#define DEFAULT_DEVICE_NAME     NULL
#define DEFAULT_DEVICE_INDEX    -1
#define DEFAULT_DO_STATS        FALSE
#define DEFAULT_ENABLE_QUIRKS   TRUE

enum
{
  PROP_0,
  PROP_DEVICE_PATH,
  PROP_DEVICE_NAME,
  PROP_DEVICE_INDEX,
  PROP_DO_STATS,
  PROP_FPS,
  PROP_ENABLE_QUIRKS,
};

GST_DEBUG_CATEGORY (gst_ks_debug);
#define GST_CAT_DEFAULT gst_ks_debug

#define KS_WORKER_LOCK(priv) g_mutex_lock (&priv->worker_lock)
#define KS_WORKER_UNLOCK(priv) g_mutex_unlock (&priv->worker_lock)
#define KS_WORKER_WAIT(priv) \
    g_cond_wait (&priv->worker_notify_cond, &priv->worker_lock)
#define KS_WORKER_NOTIFY(priv) g_cond_signal (&priv->worker_notify_cond)
#define KS_WORKER_WAIT_FOR_RESULT(priv) \
    g_cond_wait (&priv->worker_result_cond, &priv->worker_lock)
#define KS_WORKER_NOTIFY_RESULT(priv) \
    g_cond_signal (&priv->worker_result_cond)

typedef enum
{
  KS_WORKER_STATE_STARTING,
  KS_WORKER_STATE_READY,
  KS_WORKER_STATE_STOPPING,
  KS_WORKER_STATE_ERROR,
} KsWorkerState;

struct _GstKsVideoSrcPrivate
{
  /* Properties */
  gchar *device_path;
  gchar *device_name;
  gint device_index;
  gboolean do_stats;
  gboolean enable_quirks;

  /* State */
  GstKsClock *ksclock;
  GstKsVideoDevice *device;

  gboolean running;

  /* Worker thread */
  GThread *worker_thread;
  GMutex worker_lock;
  GCond worker_notify_cond;
  GCond worker_result_cond;
  KsWorkerState worker_state;

  GstCaps *worker_pending_caps;
  gboolean worker_setcaps_result;

  gboolean worker_pending_run;
  gboolean worker_run_result;

  gulong worker_error_code;

  /* Statistics */
  GstClockTime last_sampling;
  guint count;
  guint fps;
};

#define GST_KS_VIDEO_SRC_GET_PRIVATE(o) ((o)->priv)

static void gst_ks_video_src_finalize (GObject * object);
static void gst_ks_video_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static void gst_ks_video_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);

G_GNUC_UNUSED static GArray
    * gst_ks_video_src_get_device_name_values (GstKsVideoSrc * self);
static void gst_ks_video_src_reset (GstKsVideoSrc * self);

static GstStateChangeReturn gst_ks_video_src_change_state (GstElement * element,
    GstStateChange transition);
static gboolean gst_ks_video_src_set_clock (GstElement * element,
    GstClock * clock);

static GstCaps *gst_ks_video_src_get_caps (GstBaseSrc * basesrc,
    GstCaps * filter);
static gboolean gst_ks_video_src_set_caps (GstBaseSrc * basesrc,
    GstCaps * caps);
static GstCaps *gst_ks_video_src_fixate (GstBaseSrc * basesrc, GstCaps * caps);
static gboolean gst_ks_video_src_query (GstBaseSrc * basesrc, GstQuery * query);
static gboolean gst_ks_video_src_unlock (GstBaseSrc * basesrc);
static gboolean gst_ks_video_src_unlock_stop (GstBaseSrc * basesrc);

static GstFlowReturn gst_ks_video_src_create (GstPushSrc * pushsrc,
    GstBuffer ** buffer);
static GstBuffer *gst_ks_video_src_alloc_buffer (guint size, guint alignment,
    gpointer user_data);

G_DEFINE_TYPE_WITH_PRIVATE (GstKsVideoSrc, gst_ks_video_src, GST_TYPE_PUSH_SRC);

static GstKsVideoSrcClass *parent_class = NULL;

static void
gst_ks_video_src_class_init (GstKsVideoSrcClass * klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  GstBaseSrcClass *gstbasesrc_class = GST_BASE_SRC_CLASS (klass);
  GstPushSrcClass *gstpushsrc_class = GST_PUSH_SRC_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  gst_element_class_set_static_metadata (gstelement_class, "KsVideoSrc",
      "Source/Video/Hardware",
      "Stream data from a video capture device through Windows kernel streaming",
      "Ole André Vadla Ravnås <ole.andre.ravnas@tandberg.com>, "
      "Haakon Sporsheim <hakon.sporsheim@tandberg.com>, "
      "Andres Colubri <andres.colubri@gmail.com>");

  gst_element_class_add_pad_template (gstelement_class,
      gst_pad_template_new ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
          ks_video_get_all_caps ()));

  gobject_class->finalize = gst_ks_video_src_finalize;
  gobject_class->get_property = gst_ks_video_src_get_property;
  gobject_class->set_property = gst_ks_video_src_set_property;

  gstelement_class->change_state =
      GST_DEBUG_FUNCPTR (gst_ks_video_src_change_state);
  gstelement_class->set_clock = GST_DEBUG_FUNCPTR (gst_ks_video_src_set_clock);

  gstbasesrc_class->get_caps = GST_DEBUG_FUNCPTR (gst_ks_video_src_get_caps);
  gstbasesrc_class->set_caps = GST_DEBUG_FUNCPTR (gst_ks_video_src_set_caps);
  gstbasesrc_class->fixate = GST_DEBUG_FUNCPTR (gst_ks_video_src_fixate);
  gstbasesrc_class->query = GST_DEBUG_FUNCPTR (gst_ks_video_src_query);
  gstbasesrc_class->unlock = GST_DEBUG_FUNCPTR (gst_ks_video_src_unlock);
  gstbasesrc_class->unlock_stop =
      GST_DEBUG_FUNCPTR (gst_ks_video_src_unlock_stop);

  gstpushsrc_class->create = GST_DEBUG_FUNCPTR (gst_ks_video_src_create);

  g_object_class_install_property (gobject_class, PROP_DEVICE_PATH,
      g_param_spec_string ("device-path", "Device Path",
          "The device path", DEFAULT_DEVICE_PATH,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DEVICE_NAME,
      g_param_spec_string ("device-name", "Device Name",
          "The human-readable device name", DEFAULT_DEVICE_NAME,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DEVICE_INDEX,
      g_param_spec_int ("device-index", "Device Index",
          "The zero-based device index", -1, G_MAXINT, DEFAULT_DEVICE_INDEX,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DO_STATS,
      g_param_spec_boolean ("do-stats", "Enable statistics",
          "Enable logging of statistics", DEFAULT_DO_STATS,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_FPS,
      g_param_spec_int ("fps", "Frames per second",
          "Last measured framerate, if statistics are enabled",
          -1, G_MAXINT, -1, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_ENABLE_QUIRKS,
      g_param_spec_boolean ("enable-quirks", "Enable quirks",
          "Enable driver-specific quirks", DEFAULT_ENABLE_QUIRKS,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
}

static void
gst_ks_video_src_init (GstKsVideoSrc * self)
{
  GstBaseSrc *basesrc = GST_BASE_SRC (self);
  GstKsVideoSrcPrivate *priv;

  self->priv = gst_ks_video_src_get_instance_private (self);
  priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  gst_base_src_set_live (basesrc, TRUE);
  gst_base_src_set_format (basesrc, GST_FORMAT_TIME);

  gst_ks_video_src_reset (self);

  priv->device_path = DEFAULT_DEVICE_PATH;
  priv->device_name = DEFAULT_DEVICE_NAME;
  priv->device_index = DEFAULT_DEVICE_INDEX;
  priv->do_stats = DEFAULT_DO_STATS;
  priv->enable_quirks = DEFAULT_ENABLE_QUIRKS;

  /* MediaFoundation does not support MinGW build */
#ifdef _MSC_VER
  {
    static gsize deprecated_warn = 0;

    if (g_once_init_enter (&deprecated_warn)) {
      if (IsWindows8OrGreater ()) {
        g_warning ("\"ksvideosrc\" is deprecated and will be removed"
            "in the future. Use \"mfvideosrc\" element instead");
      }
      g_once_init_leave (&deprecated_warn, 1);
    }
  }
#endif
}

static void
gst_ks_video_src_finalize (GObject * object)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (object);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  g_free (priv->device_name);
  g_free (priv->device_path);

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

static void
gst_ks_video_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (object);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  switch (prop_id) {
    case PROP_DEVICE_PATH:
      g_value_set_string (value, priv->device_path);
      break;
    case PROP_DEVICE_NAME:
      g_value_set_string (value, priv->device_name);
      break;
    case PROP_DEVICE_INDEX:
      g_value_set_int (value, priv->device_index);
      break;
    case PROP_DO_STATS:
      GST_OBJECT_LOCK (object);
      g_value_set_boolean (value, priv->do_stats);
      GST_OBJECT_UNLOCK (object);
      break;
    case PROP_FPS:
      GST_OBJECT_LOCK (object);
      g_value_set_int (value, priv->fps);
      GST_OBJECT_UNLOCK (object);
      break;
    case PROP_ENABLE_QUIRKS:
      g_value_set_boolean (value, priv->enable_quirks);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_ks_video_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (object);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  switch (prop_id) {
    case PROP_DEVICE_PATH:
    {
      const gchar *device_path = g_value_get_string (value);
      g_free (priv->device_path);
      priv->device_path = NULL;
      if (device_path && strlen (device_path) != 0)
        priv->device_path = g_value_dup_string (value);
    }
      break;
    case PROP_DEVICE_NAME:
    {
      const gchar *device_name = g_value_get_string (value);
      g_free (priv->device_name);
      priv->device_name = NULL;
      if (device_name && strlen (device_name) != 0)
        priv->device_name = g_strdup (device_name);
    }
      break;
    case PROP_DEVICE_INDEX:
      priv->device_index = g_value_get_int (value);
      break;
    case PROP_DO_STATS:
      GST_OBJECT_LOCK (object);
      priv->do_stats = g_value_get_boolean (value);
      GST_OBJECT_UNLOCK (object);
      break;
    case PROP_ENABLE_QUIRKS:
      priv->enable_quirks = g_value_get_boolean (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_ks_video_src_reset (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  /* Reset statistics */
  priv->last_sampling = GST_CLOCK_TIME_NONE;
  priv->count = 0;
  priv->fps = -1;

  priv->running = FALSE;
}

static void
gst_ks_video_src_apply_driver_quirks (GstKsVideoSrc * self)
{
  HMODULE mod;

  /*
   * Logitech's driver software injects the following DLL into all processes
   * spawned. This DLL does some nasty tricks, sitting in between the
   * application and the low-level ntdll API (NtCreateFile, NtClose,
   * NtDeviceIoControlFile, NtDuplicateObject, etc.), making all sorts
   * of assumptions.
   *
   * The only regression that this quirk causes is that the video effects
   * feature doesn't work.
   */
  mod = GetModuleHandle ("LVPrcInj.dll");
  if (mod != NULL) {
    GST_DEBUG_OBJECT (self, "Logitech DLL detected, neutralizing it");

    /*
     * We know that no-one's actually keeping this handle around to decrement
     * its reference count, so we'll take care of that job. The DLL's DllMain
     * implementation takes care of rolling back changes when it gets unloaded,
     * so this seems to be the cleanest and most future-proof way that we can
     * get rid of it...
     */
    FreeLibrary (mod);

    /* Paranoia: verify that it's no longer there */
    mod = GetModuleHandle ("LVPrcInj.dll");
    if (mod != NULL)
      GST_WARNING_OBJECT (self, "failed to neutralize Logitech DLL");
  }
}

/*FIXME: when we have a devices API replacement */
G_GNUC_UNUSED static GArray *
gst_ks_video_src_get_device_name_values (GstKsVideoSrc * self)
{
  GList *devices, *cur;
  GArray *array = g_array_new (TRUE, TRUE, sizeof (GValue));

  devices = ks_enumerate_devices (&KSCATEGORY_VIDEO, &KSCATEGORY_CAPTURE);
  if (devices == NULL)
    return array;

  devices = ks_video_device_list_sort_cameras_first (devices);

  for (cur = devices; cur != NULL; cur = cur->next) {
    GValue value = { 0, };
    KsDeviceEntry *entry = cur->data;

    g_value_init (&value, G_TYPE_STRING);
    g_value_set_string (&value, entry->name);
    g_array_append_val (array, value);
    g_value_unset (&value);

    ks_device_entry_free (entry);
  }

  g_list_free (devices);
  return array;
}

static gboolean
gst_ks_video_src_open_device (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  GstKsVideoDevice *device = NULL;
  GList *devices, *cur;

  g_assert (priv->device == NULL);

  devices = ks_enumerate_devices (&KSCATEGORY_VIDEO, &KSCATEGORY_CAPTURE);
  if (devices == NULL)
    goto error_no_devices;

  devices = ks_video_device_list_sort_cameras_first (devices);

  for (cur = devices; cur != NULL; cur = cur->next) {
    KsDeviceEntry *entry = cur->data;

    GST_DEBUG_OBJECT (self, "device %d: name='%s' path='%s'",
        entry->index, entry->name, entry->path);
  }

  for (cur = devices; cur != NULL; cur = cur->next) {
    KsDeviceEntry *entry = cur->data;
    gboolean match;

    if (device != NULL) {
      ks_device_entry_free (entry);
      continue;
    }
    if (priv->device_path != NULL) {
      match = g_ascii_strcasecmp (entry->path, priv->device_path) == 0;
    } else if (priv->device_name != NULL) {
      match = g_ascii_strcasecmp (entry->name, priv->device_name) == 0;
    } else if (priv->device_index >= 0) {
      match = entry->index == priv->device_index;
    } else {
      match = TRUE;             /* pick the first entry */
    }

    if (match) {
      priv->ksclock = g_object_new (GST_TYPE_KS_CLOCK, NULL);
      if (priv->ksclock != NULL && gst_ks_clock_open (priv->ksclock)) {
        GstClock *clock = GST_ELEMENT_CLOCK (self);
        if (clock != NULL)
          gst_ks_clock_provide_master_clock (priv->ksclock, clock);
      } else {
        GST_WARNING_OBJECT (self, "failed to create/open KsClock");
        g_object_unref (priv->ksclock);
        priv->ksclock = NULL;
      }

      device = gst_ks_video_device_new (entry->path, priv->ksclock,
          gst_ks_video_src_alloc_buffer, self);
    }

    ks_device_entry_free (entry);
  }

  g_list_free (devices);

  if (device == NULL)
    goto error_no_match;

  if (!gst_ks_video_device_open (device))
    goto error_open;

  priv->device = device;

  return TRUE;

  /* ERRORS */
error_no_devices:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
        ("No video capture devices found"), (NULL));
    return FALSE;
  }
error_no_match:
  {
    if (priv->device_path != NULL) {
      GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
          ("Specified video capture device with path '%s' not found",
              priv->device_path), (NULL));
    } else if (priv->device_name != NULL) {
      GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
          ("Specified video capture device with name '%s' not found",
              priv->device_name), (NULL));
    } else {
      GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
          ("Specified video capture device with index %d not found",
              priv->device_index), (NULL));
    }
    return FALSE;
  }
error_open:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, OPEN_READ,
        ("Failed to open device"), (NULL));
    g_object_unref (device);
    return FALSE;
  }
}

static void
gst_ks_video_src_close_device (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  g_assert (priv->device != NULL);

  gst_ks_video_device_close (priv->device);
  g_object_unref (priv->device);
  priv->device = NULL;

  if (priv->ksclock != NULL) {
    gst_ks_clock_close (priv->ksclock);
    g_object_unref (priv->ksclock);
    priv->ksclock = NULL;
  }

  gst_ks_video_src_reset (self);
}

/*
 * Worker thread that takes care of starting, configuring and stopping things.
 *
 * This is needed because Logitech's driver software injects a DLL that
 * intercepts API functions like NtCreateFile, NtClose, NtDeviceIoControlFile
 * and NtDuplicateObject so that they can provide in-place video effects to
 * existing applications. Their assumption is that at least one thread tainted
 * by their code stays around for the lifetime of the capture.
 */
static gpointer
gst_ks_video_src_worker_func (gpointer data)
{
  GstKsVideoSrc *self = data;
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  if (!gst_ks_video_src_open_device (self))
    goto open_failed;

  KS_WORKER_LOCK (priv);
  priv->worker_state = KS_WORKER_STATE_READY;
  KS_WORKER_NOTIFY_RESULT (priv);

  while (priv->worker_state != KS_WORKER_STATE_STOPPING) {
    KS_WORKER_WAIT (priv);

    if (priv->worker_pending_caps != NULL) {
      priv->worker_setcaps_result =
          gst_ks_video_device_set_caps (priv->device,
          priv->worker_pending_caps);

      priv->worker_pending_caps = NULL;
      KS_WORKER_NOTIFY_RESULT (priv);
    } else if (priv->worker_pending_run) {
      if (priv->ksclock != NULL)
        gst_ks_clock_start (priv->ksclock);
      priv->worker_run_result = gst_ks_video_device_set_state (priv->device,
          KSSTATE_RUN, &priv->worker_error_code);

      priv->worker_pending_run = FALSE;
      KS_WORKER_NOTIFY_RESULT (priv);
    }
  }

  KS_WORKER_UNLOCK (priv);

  gst_ks_video_src_close_device (self);

  return NULL;

  /* ERRORS */
open_failed:
  {
    KS_WORKER_LOCK (priv);
    priv->worker_state = KS_WORKER_STATE_ERROR;
    KS_WORKER_NOTIFY_RESULT (priv);
    KS_WORKER_UNLOCK (priv);

    return NULL;
  }
}

static gboolean
gst_ks_video_src_start_worker (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  gboolean result;

  g_mutex_init (&priv->worker_lock);
  g_cond_init (&priv->worker_notify_cond);
  g_cond_init (&priv->worker_result_cond);

  priv->worker_pending_caps = NULL;
  priv->worker_pending_run = FALSE;

  priv->worker_state = KS_WORKER_STATE_STARTING;
  priv->worker_thread =
      g_thread_new ("ks-worker", gst_ks_video_src_worker_func, self);

  KS_WORKER_LOCK (priv);
  while (priv->worker_state < KS_WORKER_STATE_READY)
    KS_WORKER_WAIT_FOR_RESULT (priv);
  result = priv->worker_state == KS_WORKER_STATE_READY;
  KS_WORKER_UNLOCK (priv);

  return result;
}

static void
gst_ks_video_src_stop_worker (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  KS_WORKER_LOCK (priv);
  priv->worker_state = KS_WORKER_STATE_STOPPING;
  KS_WORKER_NOTIFY (priv);
  KS_WORKER_UNLOCK (priv);

  g_thread_join (priv->worker_thread);
  priv->worker_thread = NULL;

  g_cond_clear (&priv->worker_result_cond);
  g_cond_clear (&priv->worker_notify_cond);
  g_mutex_clear (&priv->worker_lock);
}

static GstStateChangeReturn
gst_ks_video_src_change_state (GstElement * element, GstStateChange transition)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (element);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  GstStateChangeReturn ret;

  switch (transition) {
    case GST_STATE_CHANGE_NULL_TO_READY:
      if (priv->enable_quirks)
        gst_ks_video_src_apply_driver_quirks (self);
      if (!gst_ks_video_src_start_worker (self))
        goto open_failed;
      break;
    default:
      break;
  }

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

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_NULL:
      gst_ks_video_src_stop_worker (self);
      break;
    default:
      break;
  }

  return ret;

  /* ERRORS */
open_failed:
  {
    gst_ks_video_src_stop_worker (self);
    return GST_STATE_CHANGE_FAILURE;
  }
}

static gboolean
gst_ks_video_src_set_clock (GstElement * element, GstClock * clock)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (element);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  GST_OBJECT_LOCK (element);
  if (clock != NULL && priv->ksclock != NULL)
    gst_ks_clock_provide_master_clock (priv->ksclock, clock);
  GST_OBJECT_UNLOCK (element);

  return GST_ELEMENT_CLASS (parent_class)->set_clock (element, clock);
}

static GstCaps *
gst_ks_video_src_get_caps (GstBaseSrc * basesrc, GstCaps * filter)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (basesrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  if (priv->device != NULL)
    return gst_ks_video_device_get_available_caps (priv->device);
  else
    return NULL;                /* BaseSrc will return template caps */
}

static gboolean
gst_ks_video_src_set_caps (GstBaseSrc * basesrc, GstCaps * caps)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (basesrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  if (priv->device == NULL)
    return FALSE;

  KS_WORKER_LOCK (priv);
  priv->worker_pending_caps = caps;
  KS_WORKER_NOTIFY (priv);
  while (priv->worker_pending_caps == caps)
    KS_WORKER_WAIT_FOR_RESULT (priv);
  KS_WORKER_UNLOCK (priv);

  GST_DEBUG ("Result is %d", priv->worker_setcaps_result);
  return priv->worker_setcaps_result;
}

static GstCaps *
gst_ks_video_src_fixate (GstBaseSrc * basesrc, GstCaps * caps)
{
  GstStructure *structure;
  GstCaps *fixated_caps;
  gint i;

  fixated_caps = gst_caps_make_writable (caps);

  for (i = 0; i < gst_caps_get_size (fixated_caps); ++i) {
    structure = gst_caps_get_structure (fixated_caps, i);
    gst_structure_fixate_field_nearest_int (structure, "width", G_MAXINT);
    gst_structure_fixate_field_nearest_int (structure, "height", G_MAXINT);
    gst_structure_fixate_field_nearest_fraction (structure, "framerate",
        G_MAXINT, 1);
  }

  return gst_caps_fixate (fixated_caps);
}

static gboolean
gst_ks_video_src_query (GstBaseSrc * basesrc, GstQuery * query)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (basesrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  gboolean result = FALSE;

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_LATENCY:{
      GstClockTime min_latency, max_latency;

      if (priv->device == NULL)
        goto beach;

      result = gst_ks_video_device_get_latency (priv->device, &min_latency,
          &max_latency);
      if (!result)
        goto beach;

      GST_DEBUG_OBJECT (self, "reporting latency of min %" GST_TIME_FORMAT
          " max %" GST_TIME_FORMAT,
          GST_TIME_ARGS (min_latency), GST_TIME_ARGS (max_latency));

      gst_query_set_latency (query, TRUE, min_latency, max_latency);
      break;
    }
    default:
      result = GST_BASE_SRC_CLASS (parent_class)->query (basesrc, query);
      break;
  }

beach:
  return result;
}

static gboolean
gst_ks_video_src_unlock (GstBaseSrc * basesrc)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (basesrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  GST_DEBUG_OBJECT (self, "%s", G_STRFUNC);

  gst_ks_video_device_cancel (priv->device);
  return TRUE;
}

static gboolean
gst_ks_video_src_unlock_stop (GstBaseSrc * basesrc)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (basesrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);

  GST_DEBUG_OBJECT (self, "%s", G_STRFUNC);

  gst_ks_video_device_cancel_stop (priv->device);
  return TRUE;
}

static gboolean
gst_ks_video_src_timestamp_buffer (GstKsVideoSrc * self, GstBuffer * buf,
    GstClockTime presentation_time)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  GstClockTime duration;
  GstClock *clock;
  GstClockTime timestamp, base_time;

  /* Don't timestamp muxed streams */
  if (gst_ks_video_device_stream_is_muxed (priv->device)) {
    duration = timestamp = GST_CLOCK_TIME_NONE;
    goto timestamp;
  }

  duration = gst_ks_video_device_get_duration (priv->device);

  GST_OBJECT_LOCK (self);
  clock = GST_ELEMENT_CLOCK (self);
  if (clock != NULL) {
    gst_object_ref (clock);
    base_time = GST_ELEMENT (self)->base_time;
  } else {
    timestamp = GST_CLOCK_TIME_NONE;
  }
  GST_OBJECT_UNLOCK (self);

  if (clock != NULL) {
    /* The time according to the current clock */
    timestamp = gst_clock_get_time (clock) - base_time;
    if (timestamp > duration)
      timestamp -= duration;
    else
      timestamp = 0;

    gst_object_unref (clock);
    clock = NULL;
  }

timestamp:
  GST_BUFFER_PTS (buf) = timestamp;
  GST_BUFFER_DTS (buf) = GST_CLOCK_TIME_NONE;
  GST_BUFFER_DURATION (buf) = duration;

  return TRUE;
}

static void
gst_ks_video_src_update_statistics (GstKsVideoSrc * self)
{
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  GstClock *clock;

  GST_OBJECT_LOCK (self);
  clock = GST_ELEMENT_CLOCK (self);
  if (clock != NULL)
    gst_object_ref (clock);
  GST_OBJECT_UNLOCK (self);

  if (clock != NULL) {
    GstClockTime now = gst_clock_get_time (clock);
    gst_object_unref (clock);

    priv->count++;

    if (GST_CLOCK_TIME_IS_VALID (priv->last_sampling)) {
      if (now - priv->last_sampling >= GST_SECOND) {
        GST_OBJECT_LOCK (self);
        priv->fps = priv->count;
        GST_OBJECT_UNLOCK (self);

        g_object_notify (G_OBJECT (self), "fps");

        priv->last_sampling = now;
        priv->count = 0;
      }
    } else {
      priv->last_sampling = now;
    }
  }
}

static GstFlowReturn
gst_ks_video_src_create (GstPushSrc * pushsrc, GstBuffer ** buf)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (pushsrc);
  GstKsVideoSrcPrivate *priv = GST_KS_VIDEO_SRC_GET_PRIVATE (self);
  GstFlowReturn result;
  GstClockTime presentation_time;
  gulong error_code;
  gchar *error_str;

  g_assert (priv->device != NULL);

  if (!gst_ks_video_device_has_caps (priv->device))
    goto error_no_caps;

  if (G_UNLIKELY (!priv->running)) {
    KS_WORKER_LOCK (priv);
    priv->worker_pending_run = TRUE;
    KS_WORKER_NOTIFY (priv);
    while (priv->worker_pending_run)
      KS_WORKER_WAIT_FOR_RESULT (priv);
    priv->running = priv->worker_run_result;
    error_code = priv->worker_error_code;
    KS_WORKER_UNLOCK (priv);

    if (!priv->running)
      goto error_start_capture;
  }

  do {
    if (*buf != NULL) {
      gst_buffer_unref (*buf);
      *buf = NULL;
    }

    result = gst_ks_video_device_read_frame (priv->device, buf,
        &presentation_time, &error_code, &error_str);
    if (G_UNLIKELY (result != GST_FLOW_OK))
      goto error_read_frame;
  }
  while (!gst_ks_video_src_timestamp_buffer (self, *buf, presentation_time));

  if (G_UNLIKELY (priv->do_stats))
    gst_ks_video_src_update_statistics (self);

  if (!gst_ks_video_device_postprocess_frame (priv->device, buf)) {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED, ("Postprocessing failed"),
        ("Postprocessing failed"));
    return GST_FLOW_ERROR;
  }

  return GST_FLOW_OK;

  /* ERRORS */
error_no_caps:
  {
    GST_ELEMENT_ERROR (self, CORE, NEGOTIATION,
        ("not negotiated"), ("maybe setcaps failed?"));

    return GST_FLOW_ERROR;
  }
error_start_capture:
  {
    const gchar *debug_str = "failed to change pin state to KSSTATE_RUN";

    switch (error_code) {
      case ERROR_FILE_NOT_FOUND:
        GST_ELEMENT_ERROR (self, RESOURCE, NOT_FOUND,
            ("failed to start capture (device unplugged)"), ("%s", debug_str));
        break;
      case ERROR_NO_SYSTEM_RESOURCES:
        GST_ELEMENT_ERROR (self, RESOURCE, BUSY,
            ("failed to start capture (device already in use)"), ("%s",
                debug_str));
        break;
      default:
        GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
            ("failed to start capture (0x%08x)", (guint) error_code), ("%s",
                debug_str));
        break;
    }

    return GST_FLOW_ERROR;
  }
error_read_frame:
  {
    if (result == GST_FLOW_ERROR) {
      if (error_str != NULL) {
        GST_ELEMENT_ERROR (self, RESOURCE, READ,
            ("read failed: %s [0x%08x]", error_str, (guint) error_code),
            ("gst_ks_video_device_read_frame failed"));
      }
    } else if (result == GST_FLOW_CUSTOM_ERROR) {
      GST_ELEMENT_ERROR (self, RESOURCE, READ,
          ("read failed"), ("gst_ks_video_device_read_frame failed"));
    }

    g_free (error_str);

    return result;
  }
}

static GstBuffer *
gst_ks_video_src_alloc_buffer (guint size, guint alignment, gpointer user_data)
{
  GstKsVideoSrc *self = GST_KS_VIDEO_SRC (user_data);
  GstBuffer *buf;
  GstAllocationParams params = { 0, alignment - 1, 0, 0, };

  buf = gst_buffer_new_allocate (NULL, size, &params);
  if (buf == NULL)
    goto error_alloc_buffer;

  return buf;

error_alloc_buffer:
  {
    GST_ELEMENT_ERROR (self, CORE, PAD, ("alloc_buffer failed"), (NULL));

    return NULL;
  }
}

static gboolean
plugin_init (GstPlugin * plugin)
{
  GST_DEBUG_CATEGORY_INIT (gst_ks_debug, "ksvideosrc",
      0, "Kernel streaming video source");

  if (!gst_element_register (plugin, "ksvideosrc",
          GST_RANK_PRIMARY, GST_TYPE_KS_VIDEO_SRC))
    return FALSE;

  if (!gst_device_provider_register (plugin, "ksdeviceprovider",
          GST_RANK_PRIMARY, GST_TYPE_KS_DEVICE_PROVIDER))
    return FALSE;

  return TRUE;
}

GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
    GST_VERSION_MINOR,
    winks,
    "Windows kernel streaming plugin",
    plugin_init, VERSION, "LGPL", GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN)