gstreamer/gst-libs/gst/video/gstbasevideoencoder.c

/* GStreamer
 * Copyright (C) 2008 David Schleef <ds@schleef.org>
 * Copyright (C) 2011 Mark Nauwelaerts <mark.nauwelaerts@collabora.co.uk>.
 * Copyright (C) 2011 Nokia Corporation. All rights reserved.
 *   Contact: Stefan Kost <stefan.kost@nokia.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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/**
 * SECTION:gstbasevideoencoder
 * @short_description: Base class for video encoders
 * @see_also: #GstBaseTransform
 *
 * This base class is for video encoders turning raw video into
 * encoded video data.
 *
 * GstBaseVideoEncoder and subclass should cooperate as follows.
 * <orderedlist>
 * <listitem>
 *   <itemizedlist><title>Configuration</title>
 *   <listitem><para>
 *     Initially, GstBaseVideoEncoder calls @start when the encoder element
 *     is activated, which allows subclass to perform any global setup.
 *   </para></listitem>
 *   <listitem><para>
 *     GstBaseVideoEncoder calls @set_format to inform subclass of the format
 *     of input video data that it is about to receive.  Subclass should
 *     setup for encoding and configure base class as appropriate
 *     (e.g. latency). While unlikely, it might be called more than once,
 *     if changing input parameters require reconfiguration.  Baseclass
 *     will ensure that processing of current configuration is finished.
 *   </para></listitem>
 *   <listitem><para>
 *     GstBaseVideoEncoder calls @stop at end of all processing.
 *   </para></listitem>
 *   </itemizedlist>
 * </listitem>
 * <listitem>
 *   <itemizedlist>
 *   <title>Data processing</title>
 *     <listitem><para>
 *       Base class collects input data and metadata into a frame and hands
 *       this to subclass' @handle_frame.
 *     </para></listitem>
 *     <listitem><para>
 *       If codec processing results in encoded data, subclass should call
 *       @gst_base_video_encoder_finish_frame to have encoded data pushed
 *       downstream.
 *     </para></listitem>
 *     <listitem><para>
 *       If implemented, baseclass calls subclass @shape_output which then sends
 *       data downstream in desired form.  Otherwise, it is sent as-is.
 *     </para></listitem>
 *     <listitem><para>
 *       GstBaseVideoEncoderClass will handle both srcpad and sinkpad events.
 *       Sink events will be passed to subclass if @event callback has been
 *       provided.
 *     </para></listitem>
 *   </itemizedlist>
 * </listitem>
 * <listitem>
 *   <itemizedlist><title>Shutdown phase</title>
 *   <listitem><para>
 *     GstBaseVideoEncoder class calls @stop to inform the subclass that data
 *     parsing will be stopped.
 *   </para></listitem>
 *   </itemizedlist>
 * </listitem>
 * </orderedlist>
 *
 * Subclass is responsible for providing pad template caps for
 * source and sink pads. The pads need to be named "sink" and "src". It should
 * also be able to provide fixed src pad caps in @getcaps by the time it calls
 * @gst_base_video_encoder_finish_frame.
 *
 * Things that subclass need to take care of:
 * <itemizedlist>
 *   <listitem><para>Provide pad templates</para></listitem>
 *   <listitem><para>
 *      Provide source pad caps before pushing the first buffer
 *   </para></listitem>
 *   <listitem><para>
 *      Accept data in @handle_frame and provide encoded results to
 *      @gst_base_video_encoder_finish_frame.
 *   </para></listitem>
 * </itemizedlist>
 *
 */

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

#include "gstbasevideoencoder.h"
#include "gstbasevideoutils.h"

#include <string.h>

GST_DEBUG_CATEGORY (basevideoencoder_debug);
#define GST_CAT_DEFAULT basevideoencoder_debug

static void gst_base_video_encoder_finalize (GObject * object);

static gboolean gst_base_video_encoder_sink_setcaps (GstPad * pad,
    GstCaps * caps);
static GstCaps *gst_base_video_encoder_sink_getcaps (GstPad * pad);
static gboolean gst_base_video_encoder_src_event (GstPad * pad,
    GstEvent * event);
static gboolean gst_base_video_encoder_sink_event (GstPad * pad,
    GstEvent * event);
static GstFlowReturn gst_base_video_encoder_chain (GstPad * pad,
    GstBuffer * buf);
static GstStateChangeReturn gst_base_video_encoder_change_state (GstElement *
    element, GstStateChange transition);
static const GstQueryType *gst_base_video_encoder_get_query_types (GstPad *
    pad);
static gboolean gst_base_video_encoder_src_query (GstPad * pad,
    GstQuery * query);


static void
_do_init (GType object_type)
{
  const GInterfaceInfo preset_interface_info = {
    NULL,                       /* interface_init */
    NULL,                       /* interface_finalize */
    NULL                        /* interface_data */
  };

  g_type_add_interface_static (object_type, GST_TYPE_PRESET,
      &preset_interface_info);
}

GST_BOILERPLATE_FULL (GstBaseVideoEncoder, gst_base_video_encoder,
    GstBaseVideoCodec, GST_TYPE_BASE_VIDEO_CODEC, _do_init);

static void
gst_base_video_encoder_base_init (gpointer g_class)
{
  GST_DEBUG_CATEGORY_INIT (basevideoencoder_debug, "basevideoencoder", 0,
      "Base Video Encoder");

}

static void
gst_base_video_encoder_class_init (GstBaseVideoEncoderClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

  gobject_class = G_OBJECT_CLASS (klass);
  gstelement_class = GST_ELEMENT_CLASS (klass);

  gobject_class->finalize = gst_base_video_encoder_finalize;

  gstelement_class->change_state =
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_change_state);

  parent_class = g_type_class_peek_parent (klass);
}

static void
gst_base_video_encoder_reset (GstBaseVideoEncoder * base_video_encoder)
{
  base_video_encoder->presentation_frame_number = 0;
  base_video_encoder->distance_from_sync = 0;
  base_video_encoder->force_keyframe = FALSE;

  base_video_encoder->drained = TRUE;
  base_video_encoder->min_latency = 0;
  base_video_encoder->max_latency = 0;

  if (base_video_encoder->force_keyunit_event) {
    gst_event_unref (base_video_encoder->force_keyunit_event);
    base_video_encoder->force_keyunit_event = NULL;
  }

  g_list_foreach (base_video_encoder->current_frame_events,
      (GFunc) gst_event_unref, NULL);
  g_list_free (base_video_encoder->current_frame_events);
  base_video_encoder->current_frame_events = NULL;
}

static void
gst_base_video_encoder_init (GstBaseVideoEncoder * base_video_encoder,
    GstBaseVideoEncoderClass * klass)
{
  GstPad *pad;

  GST_DEBUG_OBJECT (base_video_encoder, "gst_base_video_encoder_init");

  pad = GST_BASE_VIDEO_CODEC_SINK_PAD (base_video_encoder);

  gst_pad_set_chain_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_chain));
  gst_pad_set_event_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_sink_event));
  gst_pad_set_setcaps_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_sink_setcaps));
  gst_pad_set_getcaps_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_sink_getcaps));

  pad = GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_encoder);

  gst_pad_set_query_type_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_get_query_types));
  gst_pad_set_query_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_src_query));
  gst_pad_set_event_function (pad,
      GST_DEBUG_FUNCPTR (gst_base_video_encoder_src_event));

  base_video_encoder->a.at_eos = FALSE;

  /* encoder is expected to do so */
  base_video_encoder->sink_clipping = TRUE;
}

static gboolean
gst_base_video_encoder_drain (GstBaseVideoEncoder * enc)
{
  GstBaseVideoCodec *codec;
  GstBaseVideoEncoderClass *enc_class;
  gboolean ret = TRUE;

  codec = GST_BASE_VIDEO_CODEC (enc);
  enc_class = GST_BASE_VIDEO_ENCODER_GET_CLASS (enc);

  GST_DEBUG_OBJECT (enc, "draining");

  if (enc->drained) {
    GST_DEBUG_OBJECT (enc, "already drained");
    return TRUE;
  }

  if (enc_class->reset) {
    GST_DEBUG_OBJECT (enc, "requesting subclass to finish");
    ret = enc_class->reset (enc);
  }
  /* everything should be away now */
  if (codec->frames) {
    /* not fatal/impossible though if subclass/codec eats stuff */
    GST_WARNING_OBJECT (enc, "still %d frames left after draining",
        g_list_length (codec->frames));
#if 0
    /* FIXME should do this, but subclass may come up with it later on ?
     * and would then need refcounting or so on frames */
    g_list_foreach (codec->frames,
        (GFunc) gst_base_video_codec_free_frame, NULL);
#endif
  }

  return ret;
}

static gboolean
gst_base_video_encoder_sink_setcaps (GstPad * pad, GstCaps * caps)
{
  GstBaseVideoEncoder *base_video_encoder;
  GstBaseVideoEncoderClass *base_video_encoder_class;
  GstStructure *structure;
  GstVideoState *state, tmp_state;
  gboolean ret;
  gboolean changed = FALSE;

  base_video_encoder = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));
  base_video_encoder_class =
      GST_BASE_VIDEO_ENCODER_GET_CLASS (base_video_encoder);

  /* subclass should do something here ... */
  g_return_val_if_fail (base_video_encoder_class->set_format != NULL, FALSE);

  GST_DEBUG_OBJECT (base_video_encoder, "setcaps %" GST_PTR_FORMAT, caps);

  state = &GST_BASE_VIDEO_CODEC (base_video_encoder)->state;
  memset (&tmp_state, 0, sizeof (tmp_state));

  tmp_state.caps = gst_caps_ref (caps);
  structure = gst_caps_get_structure (caps, 0);

  ret =
      gst_video_format_parse_caps (caps, &tmp_state.format, &tmp_state.width,
      &tmp_state.height);
  if (!ret)
    goto exit;

  changed = (tmp_state.format != state->format
      || tmp_state.width != state->width || tmp_state.height != state->height);

  if (!gst_video_parse_caps_framerate (caps, &tmp_state.fps_n,
          &tmp_state.fps_d)) {
    tmp_state.fps_n = 0;
    tmp_state.fps_d = 1;
  }
  changed = changed || (tmp_state.fps_n != state->fps_n
      || tmp_state.fps_d != state->fps_d);

  if (!gst_video_parse_caps_pixel_aspect_ratio (caps, &tmp_state.par_n,
          &tmp_state.par_d)) {
    tmp_state.par_n = 1;
    tmp_state.par_d = 1;
  }
  changed = changed || (tmp_state.par_n != state->par_n
      || tmp_state.par_d != state->par_d);

  tmp_state.have_interlaced =
      gst_structure_get_boolean (structure, "interlaced",
      &tmp_state.interlaced);
  changed = changed || (tmp_state.have_interlaced != state->have_interlaced
      || tmp_state.interlaced != state->interlaced);

  tmp_state.bytes_per_picture =
      gst_video_format_get_size (tmp_state.format, tmp_state.width,
      tmp_state.height);
  tmp_state.clean_width = tmp_state.width;
  tmp_state.clean_height = tmp_state.height;
  tmp_state.clean_offset_left = 0;
  tmp_state.clean_offset_top = 0;

  if (changed) {
    /* arrange draining pending frames */
    gst_base_video_encoder_drain (base_video_encoder);

    /* and subclass should be ready to configure format at any time around */
    if (base_video_encoder_class->set_format)
      ret =
          base_video_encoder_class->set_format (base_video_encoder, &tmp_state);
    if (ret) {
      gst_caps_replace (&state->caps, NULL);
      *state = tmp_state;
    }
  } else {
    /* no need to stir things up */
    GST_DEBUG_OBJECT (base_video_encoder,
        "new video format identical to configured format");
    gst_caps_unref (tmp_state.caps);
    ret = TRUE;
  }

exit:
  g_object_unref (base_video_encoder);

  if (!ret) {
    GST_WARNING_OBJECT (base_video_encoder, "rejected caps %" GST_PTR_FORMAT,
        caps);
  }

  return ret;
}

static GstCaps *
gst_base_video_encoder_sink_getcaps (GstPad * pad)
{
  GstBaseVideoEncoder *base_video_encoder;
  const GstCaps *templ_caps;
  GstCaps *allowed;
  GstCaps *fcaps, *filter_caps;
  gint i, j;

  base_video_encoder = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));

  /* FIXME: Allow subclass to override this? */

  /* Allow downstream to specify width/height/framerate/PAR constraints
   * and forward them upstream for video converters to handle
   */
  templ_caps =
      gst_pad_get_pad_template_caps (GST_BASE_VIDEO_CODEC_SINK_PAD
      (base_video_encoder));
  allowed =
      gst_pad_get_allowed_caps (GST_BASE_VIDEO_CODEC_SRC_PAD
      (base_video_encoder));
  if (!allowed || gst_caps_is_empty (allowed) || gst_caps_is_any (allowed)) {
    fcaps = gst_caps_copy (templ_caps);
    goto done;
  }

  GST_LOG_OBJECT (base_video_encoder, "template caps %" GST_PTR_FORMAT,
      templ_caps);
  GST_LOG_OBJECT (base_video_encoder, "allowed caps %" GST_PTR_FORMAT, allowed);

  filter_caps = gst_caps_new_empty ();

  for (i = 0; i < gst_caps_get_size (templ_caps); i++) {
    GQuark q_name =
        gst_structure_get_name_id (gst_caps_get_structure (templ_caps, i));

    for (j = 0; j < gst_caps_get_size (allowed); j++) {
      const GstStructure *allowed_s = gst_caps_get_structure (allowed, j);
      const GValue *val;
      GstStructure *s;

      s = gst_structure_id_empty_new (q_name);
      if ((val = gst_structure_get_value (allowed_s, "width")))
        gst_structure_set_value (s, "width", val);
      if ((val = gst_structure_get_value (allowed_s, "height")))
        gst_structure_set_value (s, "height", val);
      if ((val = gst_structure_get_value (allowed_s, "framerate")))
        gst_structure_set_value (s, "framerate", val);
      if ((val = gst_structure_get_value (allowed_s, "pixel-aspect-ratio")))
        gst_structure_set_value (s, "pixel-aspect-ratio", val);

      gst_caps_merge_structure (filter_caps, s);
    }
  }

  fcaps = gst_caps_intersect (filter_caps, templ_caps);
  gst_caps_unref (filter_caps);

done:

  gst_caps_replace (&allowed, NULL);

  GST_LOG_OBJECT (base_video_encoder, "Returning caps %" GST_PTR_FORMAT, fcaps);

  return fcaps;
}

static void
gst_base_video_encoder_finalize (GObject * object)
{
  GST_DEBUG_OBJECT (object, "finalize");

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

static gboolean
gst_base_video_encoder_sink_eventfunc (GstBaseVideoEncoder * base_video_encoder,
    GstEvent * event)
{
  GstBaseVideoEncoderClass *base_video_encoder_class;
  gboolean ret = FALSE;

  base_video_encoder_class =
      GST_BASE_VIDEO_ENCODER_GET_CLASS (base_video_encoder);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_EOS:
    {
      GstFlowReturn flow_ret;

      base_video_encoder->a.at_eos = TRUE;

      if (base_video_encoder_class->finish) {
        flow_ret = base_video_encoder_class->finish (base_video_encoder);
      } else {
        flow_ret = GST_FLOW_OK;
      }

      ret = (flow_ret == GST_BASE_VIDEO_ENCODER_FLOW_DROPPED);
      break;
    }
    case GST_EVENT_NEWSEGMENT:
    {
      gboolean update;
      double rate;
      double applied_rate;
      GstFormat format;
      gint64 start;
      gint64 stop;
      gint64 position;

      gst_event_parse_new_segment_full (event, &update, &rate, &applied_rate,
          &format, &start, &stop, &position);

      GST_DEBUG_OBJECT (base_video_encoder, "newseg rate %g, applied rate %g, "
          "format %d, start = %" GST_TIME_FORMAT ", stop = %" GST_TIME_FORMAT
          ", pos = %" GST_TIME_FORMAT, rate, applied_rate, format,
          GST_TIME_ARGS (start), GST_TIME_ARGS (stop),
          GST_TIME_ARGS (position));

      if (format != GST_FORMAT_TIME) {
        GST_DEBUG_OBJECT (base_video_encoder, "received non TIME newsegment");
        break;
      }

      base_video_encoder->a.at_eos = FALSE;

      gst_segment_set_newsegment_full (&GST_BASE_VIDEO_CODEC
          (base_video_encoder)->segment, update, rate, applied_rate, format,
          start, stop, position);
      break;
    }
    case GST_EVENT_CUSTOM_DOWNSTREAM:
    {
      const GstStructure *s;

      s = gst_event_get_structure (event);

      if (gst_structure_has_name (s, "GstForceKeyUnit")) {
        GST_OBJECT_LOCK (base_video_encoder);
        base_video_encoder->force_keyframe = TRUE;
        if (base_video_encoder->force_keyunit_event)
          gst_event_unref (base_video_encoder->force_keyunit_event);
        base_video_encoder->force_keyunit_event = gst_event_copy (event);
        GST_OBJECT_UNLOCK (base_video_encoder);
        gst_event_unref (event);
        ret = TRUE;
      }
      break;
    }
    default:
      break;
  }

  return ret;
}

static gboolean
gst_base_video_encoder_sink_event (GstPad * pad, GstEvent * event)
{
  GstBaseVideoEncoder *enc;
  GstBaseVideoEncoderClass *klass;
  gboolean handled = FALSE;
  gboolean ret = TRUE;

  enc = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));
  klass = GST_BASE_VIDEO_ENCODER_GET_CLASS (enc);

  GST_DEBUG_OBJECT (enc, "received event %d, %s", GST_EVENT_TYPE (event),
      GST_EVENT_TYPE_NAME (event));

  if (klass->event)
    handled = klass->event (enc, event);

  if (!handled)
    handled = gst_base_video_encoder_sink_eventfunc (enc, event);

  if (!handled) {
    /* Forward non-serialized events and EOS/FLUSH_STOP immediately.
     * For EOS this is required because no buffer or serialized event
     * will come after EOS and nothing could trigger another
     * _finish_frame() call.   *
     * If the subclass handles sending of EOS manually it can return
     * _DROPPED from ::finish() and all other subclasses should have
     * decoded/flushed all remaining data before this
     *
     * For FLUSH_STOP this is required because it is expected
     * to be forwarded immediately and no buffers are queued anyway.
     */
    if (!GST_EVENT_IS_SERIALIZED (event)
        || GST_EVENT_TYPE (event) == GST_EVENT_EOS
        || GST_EVENT_TYPE (event) == GST_EVENT_FLUSH_STOP) {
      ret = gst_pad_push_event (enc->base_video_codec.srcpad, event);
    } else {
      enc->current_frame_events =
          g_list_prepend (enc->current_frame_events, event);
    }
  }

  GST_DEBUG_OBJECT (enc, "event handled");

  gst_object_unref (enc);
  return ret;
}

static gboolean
gst_base_video_encoder_src_event (GstPad * pad, GstEvent * event)
{
  GstBaseVideoEncoder *base_video_encoder;
  gboolean ret = FALSE;

  base_video_encoder = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));

  GST_LOG_OBJECT (base_video_encoder, "handling event: %" GST_PTR_FORMAT,
      event);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_CUSTOM_UPSTREAM:
    {
      const GstStructure *s;

      s = gst_event_get_structure (event);

      if (gst_structure_has_name (s, "GstForceKeyUnit")) {
        GST_OBJECT_LOCK (base_video_encoder);
        base_video_encoder->force_keyframe = TRUE;
        GST_OBJECT_UNLOCK (base_video_encoder);

        gst_event_unref (event);
        ret = TRUE;
      } else {
        ret =
            gst_pad_push_event (GST_BASE_VIDEO_CODEC_SINK_PAD
            (base_video_encoder), event);
      }
      break;
    }
    default:
      ret =
          gst_pad_push_event (GST_BASE_VIDEO_CODEC_SINK_PAD
          (base_video_encoder), event);
      break;
  }

  gst_object_unref (base_video_encoder);
  return ret;
}

static const GstQueryType *
gst_base_video_encoder_get_query_types (GstPad * pad)
{
  static const GstQueryType query_types[] = {
    GST_QUERY_CONVERT,
    GST_QUERY_LATENCY,
    0
  };

  return query_types;
}

static gboolean
gst_base_video_encoder_src_query (GstPad * pad, GstQuery * query)
{
  GstBaseVideoEncoder *enc;
  gboolean res;
  GstPad *peerpad;

  enc = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));
  peerpad = gst_pad_get_peer (GST_BASE_VIDEO_CODEC_SINK_PAD (enc));

  GST_LOG_OBJECT (enc, "handling query: %" GST_PTR_FORMAT, query);

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_CONVERT:
    {
      GstBaseVideoCodec *codec = GST_BASE_VIDEO_CODEC (enc);
      GstFormat src_fmt, dest_fmt;
      gint64 src_val, dest_val;

      gst_query_parse_convert (query, &src_fmt, &src_val, &dest_fmt, &dest_val);
      res = gst_base_video_encoded_video_convert (&codec->state,
          codec->bytes, codec->time, src_fmt, src_val, &dest_fmt, &dest_val);
      if (!res)
        goto error;
      gst_query_set_convert (query, src_fmt, src_val, dest_fmt, dest_val);
      break;
    }
    case GST_QUERY_LATENCY:
    {
      gboolean live;
      GstClockTime min_latency, max_latency;

      res = gst_pad_query (peerpad, query);
      if (res) {
        gst_query_parse_latency (query, &live, &min_latency, &max_latency);
        GST_DEBUG_OBJECT (enc, "Peer latency: live %d, min %"
            GST_TIME_FORMAT " max %" GST_TIME_FORMAT, live,
            GST_TIME_ARGS (min_latency), GST_TIME_ARGS (max_latency));

        GST_OBJECT_LOCK (enc);
        min_latency += enc->min_latency;
        if (max_latency != GST_CLOCK_TIME_NONE) {
          max_latency += enc->max_latency;
        }
        GST_OBJECT_UNLOCK (enc);

        gst_query_set_latency (query, live, min_latency, max_latency);
      }
    }
      break;
    default:
      res = gst_pad_query_default (pad, query);
  }
  gst_object_unref (peerpad);
  gst_object_unref (enc);
  return res;

error:
  GST_DEBUG_OBJECT (enc, "query failed");
  gst_object_unref (peerpad);
  gst_object_unref (enc);
  return res;
}

static GstFlowReturn
gst_base_video_encoder_chain (GstPad * pad, GstBuffer * buf)
{
  GstBaseVideoEncoder *base_video_encoder;
  GstBaseVideoEncoderClass *klass;
  GstVideoFrame *frame;
  GstFlowReturn ret = GST_FLOW_OK;

  base_video_encoder = GST_BASE_VIDEO_ENCODER (gst_pad_get_parent (pad));
  klass = GST_BASE_VIDEO_ENCODER_GET_CLASS (base_video_encoder);

  g_return_val_if_fail (klass->handle_frame != NULL, GST_FLOW_ERROR);

  if (!GST_PAD_CAPS (pad)) {
    return GST_FLOW_NOT_NEGOTIATED;
  }

  GST_LOG_OBJECT (base_video_encoder,
      "received buffer of size %d with ts %" GST_TIME_FORMAT
      ", duration %" GST_TIME_FORMAT, GST_BUFFER_SIZE (buf),
      GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)),
      GST_TIME_ARGS (GST_BUFFER_DURATION (buf)));

  if (base_video_encoder->a.at_eos) {
    return GST_FLOW_UNEXPECTED;
  }

  if (base_video_encoder->sink_clipping) {
    gint64 start = GST_BUFFER_TIMESTAMP (buf);
    gint64 stop = start + GST_BUFFER_DURATION (buf);
    gint64 clip_start;
    gint64 clip_stop;

    if (!gst_segment_clip (&GST_BASE_VIDEO_CODEC (base_video_encoder)->segment,
            GST_FORMAT_TIME, start, stop, &clip_start, &clip_stop)) {
      GST_DEBUG_OBJECT (base_video_encoder,
          "clipping to segment dropped frame");
      goto done;
    }
  }

  if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DISCONT))) {
    GST_LOG_OBJECT (base_video_encoder, "marked discont");
    GST_BASE_VIDEO_CODEC (base_video_encoder)->discont = TRUE;
  }

  frame =
      gst_base_video_codec_new_frame (GST_BASE_VIDEO_CODEC
      (base_video_encoder));
  frame->events = base_video_encoder->current_frame_events;
  base_video_encoder->current_frame_events = NULL;
  frame->sink_buffer = buf;
  frame->presentation_timestamp = GST_BUFFER_TIMESTAMP (buf);
  frame->presentation_duration = GST_BUFFER_DURATION (buf);
  frame->presentation_frame_number =
      base_video_encoder->presentation_frame_number;
  base_video_encoder->presentation_frame_number++;
  frame->force_keyframe = base_video_encoder->force_keyframe;
  base_video_encoder->force_keyframe = FALSE;

  GST_OBJECT_LOCK (base_video_encoder);
  GST_BASE_VIDEO_CODEC (base_video_encoder)->frames =
      g_list_append (GST_BASE_VIDEO_CODEC (base_video_encoder)->frames, frame);
  GST_OBJECT_UNLOCK (base_video_encoder);

  /* new data, more finish needed */
  base_video_encoder->drained = FALSE;

  GST_LOG_OBJECT (base_video_encoder, "passing frame pfn %d to subclass",
      frame->presentation_frame_number);

  ret = klass->handle_frame (base_video_encoder, frame);

done:
  g_object_unref (base_video_encoder);

  return ret;
}

static GstStateChangeReturn
gst_base_video_encoder_change_state (GstElement * element,
    GstStateChange transition)
{
  GstBaseVideoEncoder *base_video_encoder;
  GstBaseVideoEncoderClass *base_video_encoder_class;
  GstStateChangeReturn ret;

  base_video_encoder = GST_BASE_VIDEO_ENCODER (element);
  base_video_encoder_class = GST_BASE_VIDEO_ENCODER_GET_CLASS (element);

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      gst_base_video_encoder_reset (base_video_encoder);
      gst_base_video_encoder_reset (base_video_encoder);
      if (base_video_encoder_class->start) {
        base_video_encoder_class->start (base_video_encoder);
      }
      break;
    default:
      break;
  }

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

  switch (transition) {
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      gst_base_video_encoder_reset (base_video_encoder);
      if (base_video_encoder_class->stop) {
        base_video_encoder_class->stop (base_video_encoder);
      }
      break;
    default:
      break;
  }

  return ret;
}

/**
 * gst_base_video_encoder_finish_frame:
 * @base_video_encoder: a #GstBaseVideoEncoder
 * @frame: an encoded #GstVideoFrame 
 *
 * @frame must have a valid encoded data buffer, whose metadata fields
 * are then appropriately set according to frame data or no buffer at
 * all if the frame should be dropped.
 * It is subsequently pushed downstream or provided to @shape_output.
 * In any case, the frame is considered finished and released.
 *
 * Returns: a #GstFlowReturn resulting from sending data downstream
 */
GstFlowReturn
gst_base_video_encoder_finish_frame (GstBaseVideoEncoder * base_video_encoder,
    GstVideoFrame * frame)
{
  GstFlowReturn ret = GST_FLOW_OK;
  GstBaseVideoEncoderClass *base_video_encoder_class;
  GList *l;

  base_video_encoder_class =
      GST_BASE_VIDEO_ENCODER_GET_CLASS (base_video_encoder);

  GST_LOG_OBJECT (base_video_encoder,
      "finish frame fpn %d", frame->presentation_frame_number);

  /* Push all pending events that arrived before this frame */
  for (l = base_video_encoder->base_video_codec.frames; l; l = l->next) {
    GstVideoFrame *tmp = l->data;

    if (tmp->events) {
      GList *k;

      for (k = g_list_last (tmp->events); k; k = k->prev)
        gst_pad_push_event (GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_encoder),
            k->data);
      g_list_free (tmp->events);
      tmp->events = NULL;
    }

    if (tmp == frame)
      break;
  }

  if (frame->force_keyframe) {
    GstClockTime stream_time;
    GstClockTime running_time;
    GstEvent *ev;

    running_time =
        gst_segment_to_running_time (&GST_BASE_VIDEO_CODEC
        (base_video_encoder)->segment, GST_FORMAT_TIME,
        frame->presentation_timestamp);
    stream_time =
        gst_segment_to_stream_time (&GST_BASE_VIDEO_CODEC
        (base_video_encoder)->segment, GST_FORMAT_TIME,
        frame->presentation_timestamp);

    /* re-use upstream event if any so it also conveys any additional
     * info upstream arranged in there */
    GST_OBJECT_LOCK (base_video_encoder);
    if (base_video_encoder->force_keyunit_event) {
      ev = base_video_encoder->force_keyunit_event;
      base_video_encoder->force_keyunit_event = NULL;
    } else {
      ev = gst_event_new_custom (GST_EVENT_CUSTOM_DOWNSTREAM,
          gst_structure_new ("GstForceKeyUnit", NULL));
    }
    GST_OBJECT_UNLOCK (base_video_encoder);

    gst_structure_set (ev->structure,
        "timestamp", G_TYPE_UINT64, frame->presentation_timestamp,
        "stream-time", G_TYPE_UINT64, stream_time,
        "running-time", G_TYPE_UINT64, running_time, NULL);

    gst_pad_push_event (GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_encoder), ev);
  }

  /* no buffer data means this frame is skipped/dropped */
  if (!frame->src_buffer) {
    GST_DEBUG_OBJECT (base_video_encoder, "skipping frame %" GST_TIME_FORMAT,
        GST_TIME_ARGS (frame->presentation_timestamp));
    goto done;
  }

  if (frame->is_sync_point) {
    GST_LOG_OBJECT (base_video_encoder, "key frame");
    base_video_encoder->distance_from_sync = 0;
    GST_BUFFER_FLAG_UNSET (frame->src_buffer, GST_BUFFER_FLAG_DELTA_UNIT);
  } else {
    GST_BUFFER_FLAG_SET (frame->src_buffer, GST_BUFFER_FLAG_DELTA_UNIT);
  }

  frame->distance_from_sync = base_video_encoder->distance_from_sync;
  base_video_encoder->distance_from_sync++;

  frame->decode_frame_number = frame->system_frame_number - 1;
  if (frame->decode_frame_number < 0) {
    frame->decode_timestamp = 0;
  } else {
    frame->decode_timestamp = gst_util_uint64_scale (frame->decode_frame_number,
        GST_SECOND * GST_BASE_VIDEO_CODEC (base_video_encoder)->state.fps_d,
        GST_BASE_VIDEO_CODEC (base_video_encoder)->state.fps_n);
  }

  GST_BUFFER_TIMESTAMP (frame->src_buffer) = frame->presentation_timestamp;
  GST_BUFFER_DURATION (frame->src_buffer) = frame->presentation_duration;
  GST_BUFFER_OFFSET (frame->src_buffer) = frame->decode_timestamp;

  /* update rate estimate */
  GST_BASE_VIDEO_CODEC (base_video_encoder)->bytes +=
      GST_BUFFER_SIZE (frame->src_buffer);
  if (GST_CLOCK_TIME_IS_VALID (frame->presentation_duration)) {
    GST_BASE_VIDEO_CODEC (base_video_encoder)->time +=
        frame->presentation_duration;
  } else {
    /* better none than nothing valid */
    GST_BASE_VIDEO_CODEC (base_video_encoder)->time = GST_CLOCK_TIME_NONE;
  }

  if (G_UNLIKELY (GST_BASE_VIDEO_CODEC (base_video_encoder)->discont)) {
    GST_LOG_OBJECT (base_video_encoder, "marking discont");
    GST_BUFFER_FLAG_SET (frame->src_buffer, GST_BUFFER_FLAG_DISCONT);
    GST_BASE_VIDEO_CODEC (base_video_encoder)->discont = FALSE;
  }

  gst_buffer_set_caps (GST_BUFFER (frame->src_buffer),
      GST_PAD_CAPS (GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_encoder)));

  if (base_video_encoder_class->shape_output) {
    ret = base_video_encoder_class->shape_output (base_video_encoder, frame);
  } else {
    ret =
        gst_pad_push (GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_encoder),
        frame->src_buffer);
  }
  frame->src_buffer = NULL;

done:
  /* handed out */
  GST_OBJECT_LOCK (base_video_encoder);
  GST_BASE_VIDEO_CODEC (base_video_encoder)->frames =
      g_list_remove (GST_BASE_VIDEO_CODEC (base_video_encoder)->frames, frame);
  GST_OBJECT_UNLOCK (base_video_encoder);

  gst_base_video_codec_free_frame (frame);

  return ret;
}

/**
 * gst_base_video_encoder_get_state:
 * @base_video_encoder: a #GstBaseVideoEncoder
 *
 * Returns: #GstVideoState describing format of video data.
 */
const GstVideoState *
gst_base_video_encoder_get_state (GstBaseVideoEncoder * base_video_encoder)
{
  return &GST_BASE_VIDEO_CODEC (base_video_encoder)->state;
}

/**
 * gst_base_video_encoder_set_latency:
 * @base_video_encoder: a #GstBaseVideoEncoder
 * @min_latency: minimum latency
 * @max_latency: maximum latency
 *
 * Informs baseclass of encoding latency.
 */
void
gst_base_video_encoder_set_latency (GstBaseVideoEncoder * base_video_encoder,
    GstClockTime min_latency, GstClockTime max_latency)
{
  g_return_if_fail (min_latency >= 0);
  g_return_if_fail (max_latency >= min_latency);

  GST_OBJECT_LOCK (base_video_encoder);
  base_video_encoder->min_latency = min_latency;
  base_video_encoder->max_latency = max_latency;
  GST_OBJECT_UNLOCK (base_video_encoder);

  gst_element_post_message (GST_ELEMENT_CAST (base_video_encoder),
      gst_message_new_latency (GST_OBJECT_CAST (base_video_encoder)));
}

/**
 * gst_base_video_encoder_set_latency_fields:
 * @base_video_encoder: a #GstBaseVideoEncoder
 * @fields: latency in fields
 *
 * Informs baseclass of encoding latency in terms of fields (both min
 * and max latency).
 */
void
gst_base_video_encoder_set_latency_fields (GstBaseVideoEncoder *
    base_video_encoder, int n_fields)
{
  gint64 latency;

  latency = gst_util_uint64_scale (n_fields,
      GST_BASE_VIDEO_CODEC (base_video_encoder)->state.fps_d * GST_SECOND,
      2 * GST_BASE_VIDEO_CODEC (base_video_encoder)->state.fps_n);

  gst_base_video_encoder_set_latency (base_video_encoder, latency, latency);

}

/**
 * gst_base_video_encoder_get_oldest_frame:
 * @base_video_encoder: a #GstBaseVideoEncoder
 *
 * Returns: oldest unfinished pending #GstVideoFrame
 */
GstVideoFrame *
gst_base_video_encoder_get_oldest_frame (GstBaseVideoEncoder *
    base_video_encoder)
{
  GList *g;

  GST_OBJECT_LOCK (base_video_encoder);
  g = g_list_first (GST_BASE_VIDEO_CODEC (base_video_encoder)->frames);
  GST_OBJECT_UNLOCK (base_video_encoder);

  if (g == NULL)
    return NULL;
  return (GstVideoFrame *) (g->data);
}

/* FIXME there could probably be more of these;
 * get by presentation_number, by presentation_time ? */