static GstFlowReturn
gst_base_video_decoder_chain (GstPad * pad, GstBuffer * buf)
{
  GstBaseVideoDecoder *base_video_decoder;
  GstBaseVideoDecoderClass *base_video_decoder_class;
  GstFlowReturn ret;

  GST_DEBUG ("chain %" GST_TIME_FORMAT " duration %" GST_TIME_FORMAT,
      GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)),
      GST_TIME_ARGS (GST_BUFFER_DURATION (buf)));

#if 0
  /* requiring the pad to be negotiated makes it impossible to use
   * oggdemux or filesrc ! decoder */
  if (!gst_pad_is_negotiated (pad)) {
    GST_DEBUG ("not negotiated");
    return GST_FLOW_NOT_NEGOTIATED;
  }
#endif

  base_video_decoder = GST_BASE_VIDEO_DECODER (gst_pad_get_parent (pad));
  base_video_decoder_class =
      GST_BASE_VIDEO_DECODER_GET_CLASS (base_video_decoder);

  GST_DEBUG_OBJECT (base_video_decoder, "chain");

  if (!base_video_decoder->have_segment) {
    GstEvent *event;
    GstFlowReturn ret;

    GST_WARNING
        ("Received buffer without a new-segment. Assuming timestamps start from 0.");

    gst_segment_set_newsegment_full (&base_video_decoder->segment,
        FALSE, 1.0, 1.0, GST_FORMAT_TIME, 0, GST_CLOCK_TIME_NONE, 0);
    base_video_decoder->have_segment = TRUE;

    event = gst_event_new_new_segment (FALSE, 1.0, GST_FORMAT_TIME, 0,
        GST_CLOCK_TIME_NONE, 0);

    ret =
        gst_pad_push_event (GST_BASE_VIDEO_DECODER_SRC_PAD (base_video_decoder),
        event);
    if (!ret) {
      GST_ERROR ("new segment event ret=%d", ret);
      return GST_FLOW_ERROR;
    }
  }

  if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DISCONT))) {
    GST_DEBUG_OBJECT (base_video_decoder, "received DISCONT buffer");
    gst_base_video_decoder_flush (base_video_decoder);
  }

  if (base_video_decoder->current_frame == NULL) {
    base_video_decoder->current_frame =
        gst_base_video_decoder_new_frame (base_video_decoder);
  }

  base_video_decoder->input_offset += GST_BUFFER_SIZE (buf);
  if (GST_BUFFER_TIMESTAMP_IS_VALID (buf)) {
    gst_base_video_decoder_add_timestamp (base_video_decoder, buf);
  }


  if (base_video_decoder->packetized) {
    base_video_decoder->current_frame->sink_buffer = buf;

    ret = gst_base_video_decoder_have_frame (base_video_decoder, TRUE, NULL);
  } else {

    gst_adapter_push (base_video_decoder->input_adapter, buf);

    ret = gst_base_video_decoder_drain (base_video_decoder, FALSE);
  }

  gst_object_unref (base_video_decoder);
  return ret;
}
static GstFlowReturn
gst_base_video_decoder_chain (GstPad * pad, GstBuffer * buf)
{
  GstBaseVideoDecoder *base_video_decoder;
  GstBaseVideoDecoderClass *klass;
  GstFlowReturn ret;

  GST_DEBUG ("chain %" GST_TIME_FORMAT " duration %" GST_TIME_FORMAT,
      GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)),
      GST_TIME_ARGS (GST_BUFFER_DURATION (buf)));

#if 0
  /* requiring the pad to be negotiated makes it impossible to use
   * oggdemux or filesrc ! decoder */
  if (!gst_pad_is_negotiated (pad)) {
    GST_DEBUG ("not negotiated");
    return GST_FLOW_NOT_NEGOTIATED;
  }
#endif

  base_video_decoder = GST_BASE_VIDEO_DECODER (gst_pad_get_parent (pad));
  klass = GST_BASE_VIDEO_DECODER_GET_CLASS (base_video_decoder);

  GST_DEBUG_OBJECT (base_video_decoder, "chain");

  if (!base_video_decoder->have_segment) {
    GstEvent *event;
    GstFlowReturn ret;

    GST_WARNING
        ("Received buffer without a new-segment. Assuming timestamps start from 0.");

    gst_segment_set_newsegment_full (&base_video_decoder->segment,
        FALSE, 1.0, 1.0, GST_FORMAT_TIME, 0, GST_CLOCK_TIME_NONE, 0);
    base_video_decoder->have_segment = TRUE;

    event = gst_event_new_new_segment (FALSE, 1.0, GST_FORMAT_TIME, 0,
        GST_CLOCK_TIME_NONE, 0);

    ret =
        gst_pad_push_event (GST_BASE_VIDEO_CODEC_SRC_PAD (base_video_decoder),
        event);
    if (!ret) {
      GST_ERROR ("new segment event ret=%d", ret);
      return GST_FLOW_ERROR;
    }
  }

  if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DISCONT))) {
    GST_DEBUG_OBJECT (base_video_decoder, "received DISCONT buffer");
    gst_base_video_decoder_reset (base_video_decoder);
  }

  if (!base_video_decoder->started) {
    klass->start (base_video_decoder);
    base_video_decoder->started = TRUE;
  }

  if (base_video_decoder->current_frame == NULL) {
    base_video_decoder->current_frame =
        gst_base_video_decoder_new_frame (base_video_decoder);
  }

  if (GST_BUFFER_TIMESTAMP_IS_VALID (buf)) {
    gst_base_video_decoder_add_timestamp (base_video_decoder, buf);
  }
  base_video_decoder->input_offset += GST_BUFFER_SIZE (buf);

#if 0
  if (base_video_decoder->timestamp_offset == GST_CLOCK_TIME_NONE &&
      GST_BUFFER_TIMESTAMP (buf) != GST_CLOCK_TIME_NONE) {
    GST_DEBUG ("got new offset %" GST_TIME_FORMAT,
        GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)));
    base_video_decoder->timestamp_offset = GST_BUFFER_TIMESTAMP (buf);
  }
#endif

  if (base_video_decoder->packetized) {
    base_video_decoder->current_frame->sink_buffer = buf;

    ret = gst_base_video_decoder_have_frame_2 (base_video_decoder);
  } else {

    gst_adapter_push (base_video_decoder->input_adapter, buf);

    if (!base_video_decoder->have_sync) {
      int n, m;

      GST_DEBUG ("no sync, scanning");

      n = gst_adapter_available (base_video_decoder->input_adapter);
      m = klass->scan_for_sync (base_video_decoder, FALSE, 0, n);
      if (m == -1) {
        gst_object_unref (base_video_decoder);
        return GST_FLOW_OK;
      }

      if (m < 0) {
        g_warning ("subclass returned negative scan %d", m);
      }

      if (m >= n) {
        GST_ERROR ("subclass scanned past end %d >= %d", m, n);
      }

      gst_adapter_flush (base_video_decoder->input_adapter, m);

      if (m < n) {
        GST_DEBUG ("found possible sync after %d bytes (of %d)", m, n);

        /* this is only "maybe" sync */
        base_video_decoder->have_sync = TRUE;
      }

      if (!base_video_decoder->have_sync) {
        gst_object_unref (base_video_decoder);
        return GST_FLOW_OK;
      }
    }

    do {
      ret = klass->parse_data (base_video_decoder, FALSE);
    } while (ret == GST_FLOW_OK);

    if (ret == GST_BASE_VIDEO_DECODER_FLOW_NEED_DATA) {
      gst_object_unref (base_video_decoder);
      return GST_FLOW_OK;
    }
  }

  gst_object_unref (base_video_decoder);
  return ret;
}