static GstFlowReturn
gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
    GstVideoCodecFrame * frame)
{
  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
  GstFlowReturn ret = GST_FLOW_OK;

  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))
      goto not_negotiated;
  }

  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
    GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);
    GstVideoInfo info;
    GstVideoCodecState *output_state;
    GstBuffer *codec_data;

    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
     * intialize.
     */
    if (codec_data) {
      gst_buffer_ref (codec_data);
    } else {
      codec_data = frame->input_buffer;
      frame->input_buffer = NULL;
    }

    /* Ensure input internal pool is active */
    if (!gst_buffer_pool_is_active (pool)) {
      GstStructure *config = gst_buffer_pool_get_config (pool);
      gst_buffer_pool_config_set_params (config, self->input_state->caps,
          self->v4l2output->info.size, 2, 2);

      /* There is no reason to refuse this config */
      if (!gst_buffer_pool_set_config (pool, config))
        goto activate_failed;

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

    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
            v4l2output->pool), &codec_data);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    gst_buffer_unref (codec_data);

    if (!gst_v4l2_object_acquire_format (self->v4l2capture, &info))
      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;
    gst_video_codec_state_unref (output_state);

    if (!gst_video_decoder_negotiate (decoder)) {
      if (GST_PAD_IS_FLUSHING (decoder->srcpad))
        goto flushing;
      else
        goto not_negotiated;
    }

    /* Ensure our internal pool is activated */
    if (!gst_buffer_pool_set_active (GST_BUFFER_POOL (self->v4l2capture->pool),
            TRUE))
      goto activate_failed;
  }

  if (g_atomic_int_get (&self->processing) == FALSE) {
    /* 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 */
    g_atomic_int_set (&self->processing, TRUE);
    if (!gst_pad_start_task (decoder->srcpad,
            (GstTaskFunction) gst_v4l2_video_dec_loop, self,
            (GDestroyNotify) gst_v4l2_video_dec_loop_stopped))
      goto start_task_failed;
  }

  if (frame->input_buffer) {
    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->v4l2output->
            pool), &frame->input_buffer);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    if (ret == GST_FLOW_FLUSHING) {
      if (g_atomic_int_get (&self->processing) == FALSE)
        ret = self->output_flow;
      goto drop;
    } else if (ret != GST_FLOW_OK) {
      goto process_failed;
    }

    /* No need to keep input arround */
    gst_buffer_replace (&frame->input_buffer, NULL);
  }

  gst_video_codec_frame_unref (frame);
  return ret;

  /* ERRORS */
not_negotiated:
  {
    GST_ERROR_OBJECT (self, "not negotiated");
    ret = GST_FLOW_NOT_NEGOTIATED;
    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));
    g_atomic_int_set (&self->processing, FALSE);
    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:
  {
    gst_video_decoder_drop_frame (decoder, frame);
    return ret;
  }
}
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);
  GstFlowReturn ret = GST_FLOW_OK;
  gboolean processed = FALSE;
  GstBuffer *tmp;

  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;
  }

  if (G_UNLIKELY (!GST_V4L2_IS_ACTIVE (self->v4l2capture))) {
    GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);
    GstVideoInfo info;
    GstVideoCodecState *output_state;
    GstBuffer *codec_data;
    GstCaps *acquired_caps, *available_caps, *caps, *filter;
    GstStructure *st;

    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
     * intialize.
     */
    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 */
    if (!gst_buffer_pool_is_active (pool)) {
      GstStructure *config = gst_buffer_pool_get_config (pool);
      gst_buffer_pool_config_set_params (config, self->input_state->caps,
          self->v4l2output->info.size, 2, 2);

      /* There is no reason to refuse this config */
      if (!gst_buffer_pool_set_config (pool, config))
        goto activate_failed;

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

    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
            v4l2output->pool), &codec_data);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    gst_buffer_unref (codec_data);

    /* 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;

    /* Create caps from the acquired format, remove the format field */
    acquired_caps = gst_video_info_to_caps (&info);
    st = gst_caps_get_structure (acquired_caps, 0);
    gst_structure_remove_field (st, "format");

    /* Probe currently available pixel formats */
    available_caps = gst_v4l2_object_probe_caps (self->v4l2capture, NULL);
    available_caps = gst_caps_make_writable (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, acquired_caps,
        GST_CAPS_INTERSECT_FIRST);
    gst_caps_unref (acquired_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;
    }

    /* 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);
    gst_caps_unref (caps);

    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;
    gst_video_codec_state_unref (output_state);

    if (!gst_video_decoder_negotiate (decoder)) {
      if (GST_PAD_IS_FLUSHING (decoder->srcpad))
        goto flushing;
      else
        goto not_negotiated;
    }

    /* Ensure our internal pool is activated */
    if (!gst_buffer_pool_set_active (GST_BUFFER_POOL (self->v4l2capture->pool),
            TRUE))
      goto activate_failed;
  }

  if (g_atomic_int_get (&self->processing) == FALSE) {
    /* 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 */
    g_atomic_int_set (&self->processing, TRUE);
    if (!gst_pad_start_task (decoder->srcpad,
            (GstTaskFunction) gst_v4l2_video_dec_loop, self,
            (GDestroyNotify) gst_v4l2_video_dec_loop_stopped))
      goto start_task_failed;
  }

  if (!processed) {
    GST_VIDEO_DECODER_STREAM_UNLOCK (decoder);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->v4l2output->
            pool), &frame->input_buffer);
    GST_VIDEO_DECODER_STREAM_LOCK (decoder);

    if (ret == GST_FLOW_FLUSHING) {
      if (g_atomic_int_get (&self->processing) == FALSE)
        ret = self->output_flow;
      goto drop;
    } else if (ret != GST_FLOW_OK) {
      goto process_failed;
    }
  }

  /* No need to keep input arround */
  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);
  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));
    g_atomic_int_set (&self->processing, FALSE);
    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:
  {
    gst_video_decoder_drop_frame (decoder, frame);
    return ret;
  }
}