gstreamer/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videodec.c

/*
 * Copyright (C) 2014 Collabora Ltd.
 *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.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.
 *
 */

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

#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#include "gstv4l2object.h"
#include "gstv4l2videodec.h"

#include "gstv4l2h264codec.h"
#include "gstv4l2h265codec.h"
#include "gstv4l2mpeg2codec.h"
#include "gstv4l2mpeg4codec.h"
#include "gstv4l2vp8codec.h"
#include "gstv4l2vp9codec.h"

#include <string.h>
#include <glib/gi18n-lib.h>

GST_DEBUG_CATEGORY_STATIC (gst_v4l2_video_dec_debug);
#define GST_CAT_DEFAULT gst_v4l2_video_dec_debug

typedef struct
{
  gchar *device;
  GstCaps *sink_caps;
  GstCaps *src_caps;
  const gchar *longname;
  const gchar *description;
  const GstV4l2Codec *codec;
} GstV4l2VideoDecCData;

enum
{
  PROP_0,
  V4L2_STD_OBJECT_PROPS
};

#define gst_v4l2_video_dec_parent_class parent_class
G_DEFINE_ABSTRACT_TYPE (GstV4l2VideoDec, gst_v4l2_video_dec,
    GST_TYPE_VIDEO_DECODER);

static GstFlowReturn gst_v4l2_video_dec_finish (GstVideoDecoder * decoder);

static void
gst_v4l2_video_dec_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (object);

  switch (prop_id) {
    case PROP_CAPTURE_IO_MODE:
      if (!gst_v4l2_object_set_property_helper (self->v4l2capture,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;

      /* By default, only set on output */
    default:
      if (!gst_v4l2_object_set_property_helper (self->v4l2output,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;
  }
}

static void
gst_v4l2_video_dec_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (object);

  switch (prop_id) {
    case PROP_CAPTURE_IO_MODE:
      if (!gst_v4l2_object_get_property_helper (self->v4l2capture,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;

      /* By default read from output */
    default:
      if (!gst_v4l2_object_get_property_helper (self->v4l2output,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;
  }
}

static gboolean
gst_v4l2_video_dec_open (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstCaps *codec_caps;

  GST_DEBUG_OBJECT (self, "Opening");

  if (!gst_v4l2_object_open (self->v4l2output, &error))
    goto failure;

  if (!gst_v4l2_object_open_shared (self->v4l2capture, self->v4l2output))
    goto failure;

  codec_caps = gst_pad_get_pad_template_caps (decoder->sinkpad);
  self->probed_sinkcaps = gst_v4l2_object_probe_caps (self->v4l2output,
      codec_caps);
  gst_caps_unref (codec_caps);

  if (gst_caps_is_empty (self->probed_sinkcaps))
    goto no_encoded_format;

  self->supports_source_change =
      gst_v4l2_object_subscribe_event (self->v4l2capture,
      V4L2_EVENT_SOURCE_CHANGE);

  return TRUE;

no_encoded_format:
  GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
      (_("Decoder on device %s has no supported input format"),
          self->v4l2output->videodev), (NULL));
  goto failure;

failure:
  if (GST_V4L2_IS_OPEN (self->v4l2output))
    gst_v4l2_object_close (self->v4l2output);

  if (GST_V4L2_IS_OPEN (self->v4l2capture))
    gst_v4l2_object_close (self->v4l2capture);

  gst_caps_replace (&self->probed_srccaps, NULL);
  gst_caps_replace (&self->probed_sinkcaps, NULL);

  gst_v4l2_error (self, &error);

  return FALSE;
}

static gboolean
gst_v4l2_video_dec_close (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  GST_DEBUG_OBJECT (self, "Closing");

  gst_v4l2_object_close (self->v4l2output);
  gst_v4l2_object_close (self->v4l2capture);
  gst_caps_replace (&self->probed_srccaps, NULL);
  gst_caps_replace (&self->probed_sinkcaps, NULL);

  return TRUE;
}

static gboolean
gst_v4l2_video_dec_start (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  GST_DEBUG_OBJECT (self, "Starting");

  gst_v4l2_object_unlock (self->v4l2output);
  g_atomic_int_set (&self->active, TRUE);
  self->output_flow = GST_FLOW_OK;

  return TRUE;
}

static gboolean
gst_v4l2_video_dec_stop (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  GST_DEBUG_OBJECT (self, "Stopping");

  gst_v4l2_object_unlock (self->v4l2output);
  gst_v4l2_object_unlock (self->v4l2capture);

  /* Wait for capture thread to stop */
  gst_pad_stop_task (decoder->srcpad);

  GST_VIDEO_DECODER_STREAM_LOCK (decoder);
  self->output_flow = GST_FLOW_OK;
  GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);

  /* Should have been flushed already */
  g_assert (g_atomic_int_get (&self->active) == FALSE);

  gst_v4l2_object_stop (self->v4l2output);
  gst_v4l2_object_stop (self->v4l2capture);

  if (self->input_state) {
    gst_video_codec_state_unref (self->input_state);
    self->input_state = NULL;
  }

  GST_DEBUG_OBJECT (self, "Stopped");

  return TRUE;
}

static gboolean
compatible_caps (GstV4l2VideoDec * self, GstCaps * new_caps)
{
  GstCaps *current_caps, *caps1, *caps2;
  GstStructure *s;
  gboolean ret;

  current_caps = gst_v4l2_object_get_current_caps (self->v4l2output);
  if (!current_caps)
    return FALSE;

  caps1 = gst_caps_copy (current_caps);
  s = gst_caps_get_structure (caps1, 0);
  gst_structure_remove_field (s, "framerate");

  caps2 = gst_caps_copy (new_caps);
  s = gst_caps_get_structure (caps2, 0);
  gst_structure_remove_field (s, "framerate");

  ret = gst_caps_is_equal (caps1, caps2);

  gst_caps_unref (caps1);
  gst_caps_unref (caps2);
  gst_caps_unref (current_caps);

  return ret;
}

static gboolean
gst_v4l2_video_dec_set_format (GstVideoDecoder * decoder,
    GstVideoCodecState * state)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  gboolean ret = TRUE;
  gboolean dyn_resolution = self->v4l2output->fmtdesc &&
      (self->v4l2output->fmtdesc->flags & V4L2_FMT_FLAG_DYN_RESOLUTION);

  GST_DEBUG_OBJECT (self, "Setting format: %" GST_PTR_FORMAT, state->caps);

  if (self->input_state && !dyn_resolution) {
    if (compatible_caps (self, state->caps)) {
      GST_DEBUG_OBJECT (self, "Compatible caps");
      goto done;
    }
    gst_video_codec_state_unref (self->input_state);
    self->input_state = NULL;

    gst_v4l2_video_dec_finish (decoder);
    gst_v4l2_object_stop (self->v4l2output);

    /* The renegotiation flow don't blend with the base class flow. To properly
     * stop the capture pool, if the buffers can't be orphaned, we need to
     * reclaim our buffers, which will happend through the allocation query.
     * The allocation query is triggered by gst_video_decoder_negotiate() which
     * requires the output caps to be set, but we can't know this information
     * as we rely on the decoder, which requires the capture queue to be
     * stopped.
     *
     * To workaround this issue, we simply run an allocation query with the
     * old negotiated caps in order to drain/reclaim our buffers. That breaks
     * the complexity and should not have much impact in performance since the
     * following allocation query will happen on a drained pipeline and won't
     * block. */
    if (!gst_v4l2_buffer_pool_orphan (self->v4l2capture)) {
      GstCaps *caps = gst_pad_get_current_caps (decoder->srcpad);
      if (caps) {
        GstQuery *query = gst_query_new_allocation (caps, FALSE);
        gst_pad_peer_query (decoder->srcpad, query);
        gst_query_unref (query);
        gst_caps_unref (caps);
      }
    }

    gst_v4l2_object_stop (self->v4l2capture);
    self->output_flow = GST_FLOW_OK;
  }

  /* No V4L2_FMT_FLAG_DYN_RESOLUTION or no fmtdesc set yet */
  if (!dyn_resolution)
    ret = gst_v4l2_object_set_format (self->v4l2output, state->caps, &error);

  if (ret)
    self->input_state = gst_video_codec_state_ref (state);
  else
    gst_v4l2_error (self, &error);

done:
  return ret;
}

static gboolean
gst_v4l2_video_dec_flush (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  GST_DEBUG_OBJECT (self, "Flushed");

  /* Ensure the processing thread has stopped for the reverse playback
   * discount case */
  if (gst_pad_get_task_state (decoder->srcpad) == GST_TASK_STARTED) {
    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);

    gst_v4l2_object_unlock (self->v4l2output);
    gst_v4l2_object_unlock (self->v4l2capture);
    gst_pad_stop_task (decoder->srcpad);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);
  }

  if (G_UNLIKELY (!g_atomic_int_get (&self->active)))
    return TRUE;

  self->output_flow = GST_FLOW_OK;

  gst_v4l2_object_unlock_stop (self->v4l2output);
  gst_v4l2_object_unlock_stop (self->v4l2capture);

  gst_v4l2_buffer_pool_flush (self->v4l2output);

  /* gst_v4l2_buffer_pool_flush() calls streamon the capture pool and must be
   * called after gst_v4l2_object_unlock_stop() stopped flushing the buffer
   * pool. If the resolution has changed before we stopped the driver we must
   * reallocate the capture pool. We simply discard the pool, and let the
   * capture thread handle re-allocation.*/
  if (gst_v4l2_buffer_pool_flush (self->v4l2capture) ==
      GST_V4L2_FLOW_RESOLUTION_CHANGE || self->draining)
    gst_v4l2_object_stop (self->v4l2capture);

  return TRUE;
}

static gboolean
gst_v4l2_video_remove_padding (GstCapsFeatures * features,
    GstStructure * structure, gpointer user_data)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (user_data);
  GstVideoAlignment *align = &self->v4l2capture->align;
  GstVideoInfo *info = &self->v4l2capture->info;
  int width, height;

  if (!gst_structure_get_int (structure, "width", &width))
    return TRUE;

  if (!gst_structure_get_int (structure, "height", &height))
    return TRUE;

  if (align->padding_left != 0 || align->padding_top != 0 ||
      height != info->height + align->padding_bottom)
    return TRUE;

  if (height == info->height + align->padding_bottom) {
    /* Some drivers may round up width to the padded with */
    if (width == info->width + align->padding_right)
      gst_structure_set (structure,
          "width", G_TYPE_INT, width - align->padding_right,
          "height", G_TYPE_INT, height - align->padding_bottom, NULL);
    /* Some drivers may keep visible width and only round up bytesperline */
    else if (width == info->width)
      gst_structure_set (structure,
          "height", G_TYPE_INT, height - align->padding_bottom, NULL);
  }

  return TRUE;
}

static gboolean
gst_v4l2_video_dec_negotiate (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstVideoInfo info;
  GstVideoCodecState *output_state;
  GstCaps *acquired_caps, *fixation_caps, *available_caps, *caps, *filter;
  GstStructure *st;
  gboolean active;
  GstBufferPool *cpool;
  gboolean ret;

  /* We don't allow renegotiation without careful disabling the pool */
  cpool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
  if (cpool) {
    gboolean is_active = gst_buffer_pool_is_active (cpool);
    gst_object_unref (cpool);
    if (is_active)
      return TRUE;
  }

  /* init capture fps according to output */
  self->v4l2capture->info.fps_d = self->v4l2output->info.fps_d;
  self->v4l2capture->info.fps_n = self->v4l2output->info.fps_n;

  /* For decoders G_FMT returns coded size, G_SELECTION returns visible size
   * in the compose rectangle. gst_v4l2_object_acquire_format() checks both
   * and returns the visible size as with/height and the coded size as
   * padding. */
  if (!gst_v4l2_object_acquire_format (self->v4l2capture, &info))
    goto not_negotiated;

  /* gst_v4l2_object_acquire_format() does not set fps, copy from sink */
  info.fps_n = self->v4l2output->info.fps_n;
  info.fps_d = self->v4l2output->info.fps_d;

  gst_caps_replace (&self->probed_srccaps, NULL);
  self->probed_srccaps = gst_v4l2_object_probe_caps (self->v4l2capture,
      gst_v4l2_object_get_raw_caps ());
  /* Create caps from the acquired format, remove the format field */
  acquired_caps = gst_video_info_to_caps (&info);
  GST_DEBUG_OBJECT (self, "Acquired caps: %" GST_PTR_FORMAT, acquired_caps);
  fixation_caps = gst_caps_copy (acquired_caps);
  st = gst_caps_get_structure (fixation_caps, 0);
  gst_structure_remove_fields (st, "format", "colorimetry", "chroma-site",
      NULL);

  /* Probe currently available pixel formats */
  available_caps = gst_caps_copy (self->probed_srccaps);
  GST_DEBUG_OBJECT (self, "Available caps: %" GST_PTR_FORMAT, available_caps);

  /* Replace coded size with visible size, we want to negotiate visible size
   * with downstream, not coded size. */
  gst_caps_map_in_place (available_caps, gst_v4l2_video_remove_padding, self);

  filter = gst_caps_intersect_full (available_caps, fixation_caps,
      GST_CAPS_INTERSECT_FIRST);
  GST_DEBUG_OBJECT (self, "Filtered caps: %" GST_PTR_FORMAT, filter);
  gst_caps_unref (fixation_caps);
  gst_caps_unref (available_caps);
  caps = gst_pad_peer_query_caps (decoder->srcpad, filter);
  gst_caps_unref (filter);

  GST_DEBUG_OBJECT (self, "Possible decoded caps: %" GST_PTR_FORMAT, caps);
  if (gst_caps_is_empty (caps)) {
    gst_caps_unref (caps);
    goto not_negotiated;
  }

  /* Prefer the acquired caps over anything suggested downstream, this ensure
   * that we preserves the bit depth, as we don't have any fancy fixation
   * process */
  if (gst_caps_is_subset (acquired_caps, caps)) {
    gst_caps_unref (acquired_caps);
    goto use_acquired_caps;
  }

  /* Fixate pixel format */
  caps = gst_caps_fixate (caps);

  GST_DEBUG_OBJECT (self, "Chosen decoded caps: %" GST_PTR_FORMAT, caps);

  /* Try to set negotiated format, on success replace acquired format */
  if (gst_v4l2_object_set_format (self->v4l2capture, caps, &error))
    gst_video_info_from_caps (&info, caps);
  else
    gst_v4l2_clear_error (&error);

use_acquired_caps:
  gst_caps_unref (caps);

  /* catch possible bogus driver that don't enumerate the format it actually
   * returned from G_FMT */
  if (!self->v4l2capture->fmtdesc)
    goto not_negotiated;

  output_state = gst_video_decoder_set_output_state (decoder,
      info.finfo->format, info.width, info.height, self->input_state);

  /* Copy the rest of the information, there might be more in the future */
  output_state->info.interlace_mode = info.interlace_mode;
  output_state->info.colorimetry = info.colorimetry;
  gst_video_codec_state_unref (output_state);

  ret = GST_VIDEO_DECODER_CLASS (parent_class)->negotiate (decoder);
  if (!ret)
    goto not_negotiated;

  /* The pool may be created through gst_video_decoder_negotiate(), so must
   * be kept after */
  cpool = gst_v4l2_object_get_buffer_pool (self->v4l2capture);
  gst_v4l2_buffer_pool_enable_resolution_change (GST_V4L2_BUFFER_POOL (cpool));

  /* Ensure our internal pool is activated */
  active = gst_buffer_pool_set_active (cpool, TRUE);
  if (cpool)
    gst_object_unref (cpool);
  if (!active)
    goto activate_failed;

  return TRUE;

not_negotiated:
  GST_ERROR_OBJECT (self, "not negotiated");
  gst_v4l2_error (self, &error);
  gst_v4l2_object_stop (self->v4l2capture);
  return FALSE;
activate_failed:
  GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
      (_("Failed to allocate required memory.")),
      ("Buffer pool activation failed"));
  gst_v4l2_object_stop (self->v4l2capture);
  return FALSE;
}

static gboolean
gst_v4l2_decoder_cmd (GstV4l2Object * v4l2object, guint cmd, guint flags)
{
  struct v4l2_decoder_cmd dcmd = { 0, };

  GST_DEBUG_OBJECT (v4l2object->element,
      "sending v4l2 decoder command %u with flags %u", cmd, flags);

  if (!GST_V4L2_IS_OPEN (v4l2object))
    return FALSE;

  dcmd.cmd = cmd;
  dcmd.flags = flags;
  if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_DECODER_CMD, &dcmd) < 0)
    goto dcmd_failed;

  return TRUE;

dcmd_failed:
  if (errno == ENOTTY) {
    GST_INFO_OBJECT (v4l2object->element,
        "Failed to send decoder command %u with flags %u for '%s'. (%s)",
        cmd, flags, v4l2object->videodev, g_strerror (errno));
  } else {
    GST_ERROR_OBJECT (v4l2object->element,
        "Failed to send decoder command %u with flags %u for '%s'. (%s)",
        cmd, flags, v4l2object->videodev, g_strerror (errno));
  }
  return FALSE;
}

static GstFlowReturn
gst_v4l2_video_dec_finish (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstFlowReturn ret = GST_FLOW_OK;
  GstBuffer *buffer;
  GList *pending_frames = NULL;

  if (gst_pad_get_task_state (decoder->srcpad) != GST_TASK_STARTED)
    goto done;

  GST_DEBUG_OBJECT (self, "Finishing decoding");

  GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);

  /* If we are in the middle of a source change, cancel it */
  self->draining = FALSE;

  if (gst_v4l2_decoder_cmd (self->v4l2output, V4L2_DEC_CMD_STOP, 0)) {
    GstTask *task;

    GST_OBJECT_LOCK (decoder->srcpad);
    task = GST_PAD_TASK (decoder->srcpad);
    if (task)
      gst_object_ref (task);
    GST_OBJECT_UNLOCK (decoder->srcpad);

    if (task) {
      /* If the decoder stop command succeeded, just wait until processing is
       * finished */
      GST_DEBUG_OBJECT (self, "Waiting for decoder stop");
      GST_OBJECT_LOCK (task);
      while (GST_TASK_STATE (task) == GST_TASK_STARTED)
        GST_TASK_WAIT (task);
      GST_OBJECT_UNLOCK (task);

      ret = GST_FLOW_FLUSHING;
      gst_object_unref (task);
    }
  } else {
    GstBufferPool *opool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
    /* otherwise keep queuing empty buffers until the processing thread has
     * stopped, _pool_process() will return FLUSHING when that happened */
    while (ret == GST_FLOW_OK) {
      buffer = gst_buffer_new ();
      ret =
          gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (opool), &buffer,
          NULL);
      gst_buffer_unref (buffer);
    }
    if (opool)
      gst_object_unref (opool);
  }

  /* and ensure the processing thread has stopped in case another error
   * occurred. */
  gst_v4l2_object_unlock (self->v4l2capture);
  gst_pad_stop_task (decoder->srcpad);
  GST_VIDEO_DECODER_STREAM_LOCK (decoder);

  if (ret == GST_FLOW_FLUSHING)
    ret = self->output_flow;

  GST_DEBUG_OBJECT (decoder, "Done draining buffers");

  /* Draining of the capture buffer has completed.
   * If any pending frames remain at this point there is a decoder error.
   * This has been observed as a driver bug, where eos is sent too early.
   * These frames will never be rendered, so drop them now with a warning */

  pending_frames = gst_video_decoder_get_frames (decoder);
  if (pending_frames) {
    int counter = 0;
    guint32 first, last;
    for (GList * g = pending_frames; g; g = g->next) {
      GstVideoCodecFrame *frame = g->data;
      g->data = NULL;
      last = frame->system_frame_number;
      if (!counter)
        first = last;
      counter++;
      gst_video_decoder_drop_frame (decoder, frame);
    }
    if (self->output_flow == GST_FLOW_OK) {
      g_warning ("%s: %i frames %u-%u left undrained after CMD_STOP, "
          "eos sent too early: bug in decoder -- please file a bug",
          GST_ELEMENT_NAME (decoder), counter, first, last);
    }
    if (pending_frames)
      g_list_free (pending_frames);
  }

done:
  return ret;
}

static GstFlowReturn
gst_v4l2_video_dec_drain (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  GST_DEBUG_OBJECT (self, "Draining...");
  gst_v4l2_video_dec_finish (decoder);
  gst_v4l2_video_dec_flush (decoder);

  return GST_FLOW_OK;
}

static gboolean
check_system_frame_number_too_old (guint32 current, guint32 old)
{
  guint32 absdiff = current > old ? current - old : old - current;

  /* More than 100 frames in the past, or current wrapped around */
  if (absdiff > 100) {
    /* Wraparound and difference is actually smaller than 100 */
    if (absdiff > G_MAXUINT32 - 100)
      return FALSE;
    return TRUE;
  }

  return FALSE;
}

/* Only used initially to wait for a SRC_CH event
 * called with decoder stream lock */
static GstFlowReturn
gst_v4l2_video_dec_wait_for_src_ch (GstV4l2VideoDec * self)
{
  GstFlowReturn flowret;

  if (!self->wait_for_source_change)
    return GST_FLOW_OK;

  GST_DEBUG_OBJECT (self, "Waiting for source change event");

  GST_VIDEO_DECODER_STREAM_UNLOCK (GST_VIDEO_DECODER (self));
  flowret = gst_v4l2_object_poll (self->v4l2capture, GST_CLOCK_TIME_NONE);
  GST_VIDEO_DECODER_STREAM_LOCK (GST_VIDEO_DECODER (self));

  /* Fix the flow return value, as the poll is watching for buffer, but we are
   * looking for the source change event */
  if (flowret == GST_V4L2_FLOW_RESOLUTION_CHANGE) {
    self->wait_for_source_change = FALSE;
    flowret = GST_FLOW_OK;
  } else if (flowret == GST_FLOW_OK) {
    /* A buffer would be unexpected, in this case just terminate */
    flowret = GST_V4L2_FLOW_LAST_BUFFER;
  }

  return flowret;
}

static void
gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstBufferPool *pool;
  GstVideoCodecFrame *frame;
  GstBuffer *buffer = NULL;
  GstFlowReturn ret;

  GST_LOG_OBJECT (self, "Looping.");

  GST_VIDEO_DECODER_STREAM_LOCK (decoder);
  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
    ret = gst_v4l2_video_dec_wait_for_src_ch (self);
    if (ret != GST_FLOW_OK) {
      GST_INFO_OBJECT (decoder, "Polling for source change was interrupted");
      GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
      goto beach;
    }

    GST_DEBUG_OBJECT (decoder, "Setup the capture queue");
    if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
      if (!gst_video_decoder_negotiate (decoder)) {
        /* FIXME not super nice ? */
        if (GST_PAD_IS_FLUSHING (decoder->sinkpad)
            || GST_PAD_IS_FLUSHING (decoder->srcpad)) {
          ret = GST_FLOW_FLUSHING;
        } else {
          ret = GST_FLOW_NOT_NEGOTIATED;
          GST_ERROR_OBJECT (decoder, "Failed to setup capture queue");
        }
        GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
        goto beach;
      }
    }

    /* just a safety, as introducing mistakes in negotiation seems rather
     * easy.*/
    g_return_if_fail (GST_V4L2_IS_ACTIVE (self->v4l2capture));
  }
  GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);

  GST_LOG_OBJECT (decoder, "Acquire output buffer");

  self->output_flow = GST_FLOW_OK;

  do {
    /* We cannot use the base class allotate helper since it taking the internal
     * stream lock. we know that the acquire may need to poll until more frames
     * comes in and holding this lock would prevent that.
     */
    pool = gst_video_decoder_get_buffer_pool (decoder);

    /* Pool may be NULL if we started going to READY state */
    if (pool == NULL) {
      ret = GST_FLOW_FLUSHING;
      goto beach;
    }

    ret = gst_buffer_pool_acquire_buffer (pool, &buffer, NULL);
    g_object_unref (pool);

    if (ret != GST_FLOW_OK)
      goto beach;

    GST_LOG_OBJECT (decoder, "Process output buffer");
    {
      GstV4l2BufferPool *cpool =
          GST_V4L2_BUFFER_POOL (gst_v4l2_object_get_buffer_pool
          (self->v4l2capture));
      ret = gst_v4l2_buffer_pool_process (cpool, &buffer, NULL);
      if (cpool)
        gst_object_unref (cpool);
    }
  } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER);

  if (ret != GST_FLOW_OK)
    goto beach;

  if (GST_BUFFER_TIMESTAMP (buffer) % GST_SECOND != 0)
    GST_ERROR_OBJECT (decoder,
        "Driver bug detected - check driver with v4l2-compliance from http://git.linuxtv.org/v4l-utils.git");
  GST_LOG_OBJECT (decoder, "Got buffer for frame number %u",
      (guint32) (GST_BUFFER_TIMESTAMP (buffer) / GST_SECOND));

  frame =
      gst_video_decoder_get_frame (decoder,
      GST_BUFFER_TIMESTAMP (buffer) / GST_SECOND);
  if (frame) {
    GstVideoCodecFrame *oldest_frame;
    gboolean warned = FALSE;

    /* Garbage collect old frames in case of codec bugs */
    while ((oldest_frame = gst_video_decoder_get_oldest_frame (decoder)) &&
        check_system_frame_number_too_old (frame->system_frame_number,
            oldest_frame->system_frame_number)) {
      if (oldest_frame->system_frame_number > 0) {
        gst_video_decoder_drop_frame (decoder, oldest_frame);
        oldest_frame = NULL;

        if (!warned) {
          g_warning ("%s: Too old frames, bug in decoder -- please file a bug",
              GST_ELEMENT_NAME (decoder));
          warned = TRUE;
        }
      } else {
        /* special treatment when oldest_frame->system_frame_number = 0:
         * if a consecutive sequence 0, 1, 2,..., n < frame->system_frame_number
         * is pending, drop them all at this time. (This has been seen to occur
         * as a driver bug when the initial frame triggered a Caps re-negotiation,
         * and the driver dropped these frames) */
        guint32 counter = 0;
        while (oldest_frame) {
          gst_video_decoder_drop_frame (decoder, oldest_frame);
          counter++;
          oldest_frame = gst_video_decoder_get_oldest_frame (decoder);
          if (oldest_frame &&
              (oldest_frame->system_frame_number > counter ||
                  oldest_frame->system_frame_number >=
                  frame->system_frame_number)) {
            gst_video_codec_frame_unref (oldest_frame);
            oldest_frame = NULL;
          }
        }
        g_warning
            ("%s: %i initial frames were not dequeued: bug in decoder -- please file a bug",
            GST_ELEMENT_NAME (decoder), counter);
      }
    }
    if (oldest_frame)
      gst_video_codec_frame_unref (oldest_frame);

    frame->duration = self->v4l2capture->duration;
    frame->output_buffer = buffer;
    buffer = NULL;
    ret = gst_video_decoder_finish_frame (decoder, frame);

    if (ret != GST_FLOW_OK)
      goto beach;
  } else {
    GST_WARNING_OBJECT (decoder, "Decoder is producing too many buffers");
    gst_buffer_unref (buffer);
  }

  return;

beach:
  if (ret == GST_V4L2_FLOW_RESOLUTION_CHANGE) {
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);
    self->draining = TRUE;
    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    GST_INFO_OBJECT (decoder, "Received resolution change");
    return;
  }

  if (ret == GST_V4L2_FLOW_LAST_BUFFER) {
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);
    if (self->draining) {
      self->draining = FALSE;
      gst_v4l2_object_stop (self->v4l2capture);
      GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
      return;
    }

    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
  }

  GST_DEBUG_OBJECT (decoder, "Leaving output thread: %s",
      gst_flow_get_name (ret));

  gst_buffer_replace (&buffer, NULL);
  self->output_flow = ret;
  gst_v4l2_object_unlock (self->v4l2output);
  gst_pad_pause_task (decoder->srcpad);
}

static GstFlowReturn
gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
    GstVideoCodecFrame * frame)
{
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstBufferPool *pool = NULL;
  GstFlowReturn ret = GST_FLOW_OK;
  gboolean processed = FALSE;
  GstBuffer *tmp;
  GstTaskState task_state;

  GST_DEBUG_OBJECT (self, "Handling frame %d", frame->system_frame_number);

  if (G_UNLIKELY (!g_atomic_int_get (&self->active)))
    goto flushing;

  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2output))) {
    if (!self->input_state)
      goto not_negotiated;
    if (!gst_v4l2_object_set_format (self->v4l2output, self->input_state->caps,
            &error))
      goto not_negotiated;
  }

  pool = gst_v4l2_object_get_buffer_pool (self->v4l2output);
  if (G_UNLIKELY (!gst_buffer_pool_is_active (pool))) {
    GstBuffer *codec_data;
    GstStructure *config = gst_buffer_pool_get_config (pool);
    guint min = MAX (self->v4l2output->min_buffers,
        GST_V4L2_MIN_BUFFERS (self->v4l2output));
    guint max = VIDEO_MAX_FRAME;
    guint32 dummy_frame_number = 0;

    GST_DEBUG_OBJECT (self, "Sending header");
    codec_data = self->input_state->codec_data;

    /* We are running in byte-stream mode, so we don't know the headers, but
     * we need to send something, otherwise the decoder will refuse to
     * initialize.
     */
    if (codec_data) {
      gst_buffer_ref (codec_data);
    } else {
      codec_data = gst_buffer_ref (frame->input_buffer);
      processed = TRUE;
    }

    /* Ensure input internal pool is active */

    gst_buffer_pool_config_set_params (config, self->input_state->caps,
        self->v4l2output->info.size, min, max);

    /* There is no reason to refuse this config */
    if (!gst_buffer_pool_set_config (pool, config)) {
      config = gst_buffer_pool_get_config (pool);

      if (!gst_buffer_pool_config_validate_params (config,
              self->input_state->caps, self->v4l2output->info.size, min, max)) {
        gst_structure_free (config);
        goto activate_failed;
      }

      if (!gst_buffer_pool_set_config (pool, config))
        goto activate_failed;
    }

    /* Ensure to unlock capture, as it may be flushing due to previous
     * unlock/stop calls */
    gst_v4l2_object_unlock_stop (self->v4l2output);
    gst_v4l2_object_unlock_stop (self->v4l2capture);

    if (!gst_buffer_pool_set_active (pool, TRUE))
      goto activate_failed;

    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    GST_LOG_OBJECT (decoder, "Passing buffer with system frame number %u",
        processed ? frame->system_frame_number : 0);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool), &codec_data,
        processed ? &frame->system_frame_number : &dummy_frame_number);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    gst_buffer_unref (codec_data);

    /* Only wait for source change if the formats supports it */
    if (self->v4l2output->fmtdesc->flags & V4L2_FMT_FLAG_DYN_RESOLUTION) {
      gst_v4l2_object_unlock_stop (self->v4l2capture);
      self->wait_for_source_change = TRUE;
    }
  }

  task_state = gst_pad_get_task_state (GST_VIDEO_DECODER_SRC_PAD (self));
  if (task_state == GST_TASK_STOPPED || task_state == GST_TASK_PAUSED) {
    /* It's possible that the processing thread stopped due to an error */
    if (self->output_flow != GST_FLOW_OK &&
        self->output_flow != GST_FLOW_FLUSHING) {
      GST_DEBUG_OBJECT (self, "Processing loop stopped with error, leaving");
      ret = self->output_flow;
      goto drop;
    }

    GST_DEBUG_OBJECT (self, "Starting decoding thread");

    /* Start the processing task, when it quits, the task will disable input
     * processing to unlock input if draining, or prevent potential block */
    self->output_flow = GST_FLOW_FLUSHING;
    self->draining = FALSE;
    if (!gst_pad_start_task (decoder->srcpad,
            (GstTaskFunction) gst_v4l2_video_dec_loop, self, NULL))
      goto start_task_failed;
  }

  if (!processed) {
    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    GST_LOG_OBJECT (decoder, "Passing buffer with system frame number %u",
        frame->system_frame_number);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool),
        &frame->input_buffer, &frame->system_frame_number);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    if (ret == GST_FLOW_FLUSHING) {
      if (gst_pad_get_task_state (GST_VIDEO_DECODER_SRC_PAD (self)) !=
          GST_TASK_STARTED)
        ret = self->output_flow;
      goto drop;
    } else if (ret != GST_FLOW_OK) {
      goto process_failed;
    }
  }

  /* No need to keep input around */
  tmp = frame->input_buffer;
  frame->input_buffer = gst_buffer_new ();
  gst_buffer_copy_into (frame->input_buffer, tmp,
      GST_BUFFER_COPY_FLAGS | GST_BUFFER_COPY_TIMESTAMPS |
      GST_BUFFER_COPY_META, 0, 0);
  gst_buffer_unref (tmp);

  gst_video_codec_frame_unref (frame);
  if (pool)
    gst_object_unref (pool);
  return ret;

  /* ERRORS */
not_negotiated:
  {
    GST_ERROR_OBJECT (self, "not negotiated");
    ret = GST_FLOW_NOT_NEGOTIATED;
    gst_v4l2_error (self, &error);
    goto drop;
  }
activate_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
        (_("Failed to allocate required memory.")),
        ("Buffer pool activation failed"));
    ret = GST_FLOW_ERROR;
    goto drop;
  }
flushing:
  {
    ret = GST_FLOW_FLUSHING;
    goto drop;
  }

start_task_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
        (_("Failed to start decoding thread.")), (NULL));
    ret = GST_FLOW_ERROR;
    goto drop;
  }
process_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
        (_("Failed to process frame.")),
        ("Maybe be due to not enough memory or failing driver"));
    ret = GST_FLOW_ERROR;
    goto drop;
  }
drop:
  {
    if (pool)
      gst_object_unref (pool);
    gst_video_decoder_drop_frame (decoder, frame);
    return ret;
  }
}

static gboolean
gst_v4l2_video_dec_decide_allocation (GstVideoDecoder * decoder,
    GstQuery * query)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstClockTime latency;
  gboolean ret = FALSE;

  if (gst_v4l2_object_decide_allocation (self->v4l2capture, query))
    ret = GST_VIDEO_DECODER_CLASS (parent_class)->decide_allocation (decoder,
        query);

  if (GST_CLOCK_TIME_IS_VALID (self->v4l2capture->duration)) {
    latency = self->v4l2capture->min_buffers * self->v4l2capture->duration;
    GST_DEBUG_OBJECT (self, "Setting latency: %" GST_TIME_FORMAT " (%"
        G_GUINT32_FORMAT " * %" G_GUINT64_FORMAT, GST_TIME_ARGS (latency),
        self->v4l2capture->min_buffers, self->v4l2capture->duration);
    gst_video_decoder_set_latency (decoder, latency, latency);
  } else {
    GST_WARNING_OBJECT (self, "Duration invalid, not setting latency");
  }

  return ret;
}

static gboolean
gst_v4l2_video_dec_src_query (GstVideoDecoder * decoder, GstQuery * query)
{
  gboolean ret = TRUE;
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_CAPS:{
      GstCaps *filter, *result = NULL;
      GstPad *pad = GST_VIDEO_DECODER_SRC_PAD (decoder);

      gst_query_parse_caps (query, &filter);

      if (self->probed_srccaps)
        result = gst_caps_ref (self->probed_srccaps);
      else
        result = gst_pad_get_pad_template_caps (pad);

      if (filter) {
        GstCaps *tmp = result;
        result =
            gst_caps_intersect_full (filter, tmp, GST_CAPS_INTERSECT_FIRST);
        gst_caps_unref (tmp);
      }

      GST_DEBUG_OBJECT (self, "Returning src caps %" GST_PTR_FORMAT, result);

      gst_query_set_caps_result (query, result);
      gst_caps_unref (result);
      break;
    }

    default:
      ret = GST_VIDEO_DECODER_CLASS (parent_class)->src_query (decoder, query);
      break;
  }

  return ret;
}

static GstCaps *
gst_v4l2_video_dec_sink_getcaps (GstVideoDecoder * decoder, GstCaps * filter)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstCaps *result;

  result = gst_video_decoder_proxy_getcaps (decoder, self->probed_sinkcaps,
      filter);

  GST_DEBUG_OBJECT (self, "Returning sink caps %" GST_PTR_FORMAT, result);

  return result;
}

static gboolean
gst_v4l2_video_dec_sink_event (GstVideoDecoder * decoder, GstEvent * event)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  gboolean ret;
  GstEventType type = GST_EVENT_TYPE (event);

  switch (type) {
    case GST_EVENT_FLUSH_START:
      GST_DEBUG_OBJECT (self, "flush start");
      gst_v4l2_object_unlock (self->v4l2output);
      gst_v4l2_object_unlock (self->v4l2capture);
      break;
    default:
      break;
  }

  ret = GST_VIDEO_DECODER_CLASS (parent_class)->sink_event (decoder, event);

  switch (type) {
    case GST_EVENT_FLUSH_START:
      /* The processing thread should stop now, wait for it */
      gst_pad_stop_task (decoder->srcpad);
      GST_DEBUG_OBJECT (self, "flush start done");
      break;
    default:
      break;
  }

  return ret;
}

static GstStateChangeReturn
gst_v4l2_video_dec_change_state (GstElement * element,
    GstStateChange transition)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (element);
  GstVideoDecoder *decoder = GST_VIDEO_DECODER (element);

  if (transition == GST_STATE_CHANGE_PAUSED_TO_READY) {
    g_atomic_int_set (&self->active, FALSE);
    gst_v4l2_object_unlock (self->v4l2output);
    gst_v4l2_object_unlock (self->v4l2capture);
    gst_pad_stop_task (decoder->srcpad);
  }

  return GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
}

static void
gst_v4l2_video_dec_dispose (GObject * object)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (object);

  gst_caps_replace (&self->probed_sinkcaps, NULL);
  gst_caps_replace (&self->probed_srccaps, NULL);

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

static void
gst_v4l2_video_dec_finalize (GObject * object)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (object);

  gst_v4l2_object_destroy (self->v4l2capture);
  gst_v4l2_object_destroy (self->v4l2output);

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

static void
gst_v4l2_video_dec_init (GstV4l2VideoDec * self)
{
  /* V4L2 object are created in subinstance_init */
}

static void
gst_v4l2_video_dec_subinstance_init (GTypeInstance * instance, gpointer g_class)
{
  GstV4l2VideoDecClass *klass = GST_V4L2_VIDEO_DEC_CLASS (g_class);
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (instance);
  GstVideoDecoder *decoder = GST_VIDEO_DECODER (instance);

  gst_video_decoder_set_packetized (decoder, TRUE);

  self->v4l2output = gst_v4l2_object_new (GST_ELEMENT (self),
      GST_OBJECT (GST_VIDEO_DECODER_SINK_PAD (self)),
      V4L2_BUF_TYPE_VIDEO_OUTPUT, klass->default_device,
      gst_v4l2_get_output, gst_v4l2_set_output, NULL);
  self->v4l2output->no_initial_format = TRUE;
  self->v4l2output->keep_aspect = FALSE;

  self->v4l2capture = gst_v4l2_object_new (GST_ELEMENT (self),
      GST_OBJECT (GST_VIDEO_DECODER_SRC_PAD (self)),
      V4L2_BUF_TYPE_VIDEO_CAPTURE, klass->default_device,
      gst_v4l2_get_input, gst_v4l2_set_input, NULL);
}

static void
gst_v4l2_video_dec_class_init (GstV4l2VideoDecClass * klass)
{
  GstElementClass *element_class;
  GObjectClass *gobject_class;
  GstVideoDecoderClass *video_decoder_class;

  parent_class = g_type_class_peek_parent (klass);

  element_class = (GstElementClass *) klass;
  gobject_class = (GObjectClass *) klass;
  video_decoder_class = (GstVideoDecoderClass *) klass;

  GST_DEBUG_CATEGORY_INIT (gst_v4l2_video_dec_debug, "v4l2videodec", 0,
      "V4L2 Video Decoder");

  gobject_class->dispose = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_dispose);
  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_finalize);
  gobject_class->set_property =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_set_property);
  gobject_class->get_property =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_get_property);

  video_decoder_class->open = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_open);
  video_decoder_class->close = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_close);
  video_decoder_class->start = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_start);
  video_decoder_class->stop = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_stop);
  video_decoder_class->finish = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_finish);
  video_decoder_class->flush = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_flush);
  video_decoder_class->drain = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_drain);
  video_decoder_class->set_format =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_set_format);
  video_decoder_class->negotiate =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_negotiate);
  video_decoder_class->decide_allocation =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_decide_allocation);
  /* FIXME propose_allocation or not ? */
  video_decoder_class->handle_frame =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_handle_frame);
  video_decoder_class->getcaps =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_sink_getcaps);
  video_decoder_class->src_query =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_src_query);
  video_decoder_class->sink_event =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_sink_event);

  element_class->change_state =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_change_state);

  gst_v4l2_object_install_m2m_properties_helper (gobject_class);
}

static void
gst_v4l2_video_dec_subclass_init (gpointer g_class, gpointer data)
{
  GstV4l2VideoDecClass *klass = GST_V4L2_VIDEO_DEC_CLASS (g_class);
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
  GstV4l2VideoDecCData *cdata = data;

  klass->default_device = cdata->device;

  gst_element_class_add_pad_template (element_class,
      gst_pad_template_new ("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
          cdata->sink_caps));
  gst_element_class_add_pad_template (element_class,
      gst_pad_template_new ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
          cdata->src_caps));

  gst_element_class_set_metadata (element_class, cdata->longname,
      "Codec/Decoder/Video/Hardware", cdata->description,
      "Nicolas Dufresne <nicolas.dufresne@collabora.com>");

  gst_caps_unref (cdata->sink_caps);
  gst_caps_unref (cdata->src_caps);
  g_free (cdata);
}

/* Probing functions */
gboolean
gst_v4l2_is_video_dec (GstCaps * sink_caps, GstCaps * src_caps)
{
  gboolean ret = FALSE;

  if (gst_caps_is_subset (sink_caps, gst_v4l2_object_get_codec_caps ())
      && gst_caps_is_subset (src_caps, gst_v4l2_object_get_raw_caps ()))
    ret = TRUE;

  return ret;
}

static gchar *
gst_v4l2_video_dec_set_metadata (GstStructure * s, GstV4l2VideoDecCData * cdata,
    const gchar * basename)
{
  gchar *codec_name = NULL;
  gchar *type_name = NULL;

#define SET_META(codec) \
G_STMT_START { \
  cdata->longname = "V4L2 " codec " Decoder"; \
  cdata->description = "Decodes " codec " streams via V4L2 API"; \
  codec_name = g_ascii_strdown (codec, -1); \
} G_STMT_END

  if (gst_structure_has_name (s, "image/jpeg")) {
    SET_META ("JPEG");
  } else if (gst_structure_has_name (s, "video/mpeg")) {
    gint mpegversion = 0;
    gst_structure_get_int (s, "mpegversion", &mpegversion);

    if (mpegversion == 4) {
      SET_META ("MPEG4");
      cdata->codec = gst_v4l2_mpeg4_get_codec ();
    } else {
      /* MPEG 2 decoders supports MPEG 1 format */
      SET_META ("MPEG2");
      cdata->codec = gst_v4l2_mpeg2_get_codec ();
    }
  } else if (gst_structure_has_name (s, "video/x-h263")) {
    SET_META ("H263");
  } else if (gst_structure_has_name (s, "video/x-fwht")) {
    SET_META ("FWHT");
  } else if (gst_structure_has_name (s, "video/x-h264")) {
    SET_META ("H264");
    cdata->codec = gst_v4l2_h264_get_codec ();
  } else if (gst_structure_has_name (s, "video/x-h265")) {
    SET_META ("H265");
    cdata->codec = gst_v4l2_h265_get_codec ();
  } else if (gst_structure_has_name (s, "video/x-wmv")) {
    SET_META ("VC1");
  } else if (gst_structure_has_name (s, "video/x-vp8")) {
    SET_META ("VP8");
    cdata->codec = gst_v4l2_vp8_get_codec ();
  } else if (gst_structure_has_name (s, "video/x-vp9")) {
    SET_META ("VP9");
    cdata->codec = gst_v4l2_vp9_get_codec ();
  } else if (gst_structure_has_name (s, "video/x-bayer")) {
    SET_META ("BAYER");
  } else if (gst_structure_has_name (s, "video/x-sonix")) {
    SET_META ("SONIX");
  } else if (gst_structure_has_name (s, "video/x-pwc1")) {
    SET_META ("PWC1");
  } else if (gst_structure_has_name (s, "video/x-pwc2")) {
    SET_META ("PWC2");
  } else {
    /* This code should be kept on sync with the exposed CODEC type of format
     * from gstv4l2object.c. This warning will only occur in case we forget
     * to also add a format here. */
    gchar *s_str = gst_structure_to_string (s);
    g_warning ("Missing fixed name mapping for caps '%s', this is a GStreamer "
        "bug, please report at https://bugs.gnome.org", s_str);
    g_free (s_str);
  }

  if (codec_name) {
    type_name = g_strdup_printf ("v4l2%sdec", codec_name);
    if (g_type_from_name (type_name) != 0) {
      g_free (type_name);
      type_name = g_strdup_printf ("v4l2%s%sdec", basename, codec_name);
    }

    g_free (codec_name);
  }

  return type_name;
#undef SET_META
}

void
gst_v4l2_video_dec_register (GstPlugin * plugin, const gchar * basename,
    const gchar * device_path, gint video_fd, GstCaps * sink_caps,
    GstCaps * src_caps)
{
  gint i;

  for (i = 0; i < gst_caps_get_size (sink_caps); i++) {
    GstV4l2VideoDecCData *cdata;
    GstStructure *s;
    GTypeQuery type_query;
    GTypeInfo type_info = { 0, };
    GType type, subtype;
    gchar *type_name;

    s = gst_caps_get_structure (sink_caps, i);

    cdata = g_new0 (GstV4l2VideoDecCData, 1);
    cdata->device = g_strdup (device_path);
    cdata->sink_caps = gst_caps_new_empty ();
    gst_caps_append_structure (cdata->sink_caps, gst_structure_copy (s));
    cdata->src_caps = gst_caps_ref (src_caps);
    type_name = gst_v4l2_video_dec_set_metadata (s, cdata, basename);

    /* Skip over if we hit an unmapped type */
    if (!type_name) {
      g_free (cdata);
      continue;
    }

    if (cdata->codec != NULL && cdata->codec != gst_v4l2_vp8_get_codec ()
        && cdata->codec != gst_v4l2_vp9_get_codec ()) {
      GValue value = G_VALUE_INIT;

      if (gst_v4l2_codec_probe_levels (cdata->codec, video_fd, &value)) {
        gst_caps_set_value (cdata->sink_caps, "level", &value);
        g_value_unset (&value);
      }

      if (gst_v4l2_codec_probe_profiles (cdata->codec, video_fd, &value)) {
        gst_caps_set_value (cdata->sink_caps, "profile", &value);
        g_value_unset (&value);
      }
    }

    type = gst_v4l2_video_dec_get_type ();
    g_type_query (type, &type_query);
    memset (&type_info, 0, sizeof (type_info));
    type_info.class_size = type_query.class_size;
    type_info.instance_size = type_query.instance_size;
    type_info.class_init = gst_v4l2_video_dec_subclass_init;
    type_info.class_data = cdata;
    type_info.instance_init = gst_v4l2_video_dec_subinstance_init;

    subtype = g_type_register_static (type, type_name, &type_info, 0);
    if (!gst_element_register (plugin, type_name, GST_RANK_PRIMARY + 1,
            subtype))
      GST_WARNING ("Failed to register plugin '%s'", type_name);

    g_free (type_name);
  }
}