gstreamer/subprojects/gst-plugins-bad/ext/avtp/gstavtpvfdepaybase.c

/*
 * GStreamer AVTP Plugin
 * Copyright (c) 2021, Fastree3D
 * Adrian Fiergolski <Adrian.Fiergolski@fastree3d.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301 USA
 */

#include <avtp.h>

#include "gstavtpvfdepaybase.h"

GST_DEBUG_CATEGORY_STATIC (avtpvfdepaybase_debug);
#define GST_CAT_DEFAULT avtpvfdepaybase_debug

static GstStateChangeReturn gst_avtp_vf_depay_change_state (GstElement *
    element, GstStateChange transition);

#define gst_avtp_vf_depay_base_parent_class parent_class
G_DEFINE_TYPE_EXTENDED (GstAvtpVfDepayBase, gst_avtp_vf_depay_base,
    GST_TYPE_AVTP_BASE_DEPAYLOAD, G_TYPE_FLAG_ABSTRACT, {
    });

static void
gst_avtp_vf_depay_base_class_init (GstAvtpVfDepayBaseClass * klass)
{
  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);

  element_class->change_state =
      GST_DEBUG_FUNCPTR (gst_avtp_vf_depay_change_state);

  klass->depay_push_caps = NULL;

  GST_DEBUG_CATEGORY_INIT (avtpvfdepaybase_debug, "avtpvfdepaybase",
      0, "debug category for avtpvfdepay element");
}

static void
gst_avtp_vf_depay_base_init (GstAvtpVfDepayBase * avtpvfdepaybase)
{
  avtpvfdepaybase->out_buffer = NULL;
}

static GstStateChangeReturn
gst_avtp_vf_depay_change_state (GstElement * element, GstStateChange transition)
{
  GstAvtpVfDepayBase *avtpvfdepaybase = GST_AVTP_VF_DEPAY_BASE (element);
  GstStateChangeReturn ret;

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    return ret;
  }

  if (transition == GST_STATE_CHANGE_READY_TO_NULL) {
    if (avtpvfdepaybase->out_buffer) {
      gst_buffer_unref (avtpvfdepaybase->out_buffer);
      avtpvfdepaybase->out_buffer = NULL;
    }
  }

  return ret;
}

GstFlowReturn
gst_avtp_vf_depay_base_push (GstAvtpVfDepayBase * avtpvfdepaybase)
{
  GstAvtpBaseDepayload *avtpbasedepayload =
      GST_AVTP_BASE_DEPAYLOAD (avtpvfdepaybase);
  GstFlowReturn ret;

  if (G_UNLIKELY (!gst_pad_has_current_caps (avtpbasedepayload->srcpad))) {
    guint64 pts_m;
    guint32 dts, pts;

    if (gst_debug_category_get_threshold (GST_CAT_DEFAULT) >= GST_LEVEL_DEBUG) {
      GstClock *clock =
          gst_element_get_clock (GST_ELEMENT_CAST (avtpvfdepaybase));
      if (clock == NULL) {
        GST_DEBUG_OBJECT (avtpvfdepaybase,
            "Sending initial CAPS and SEGMENT, no pipeline time.");
      } else {
        GST_DEBUG_OBJECT (avtpvfdepaybase,
            "Sending initial CAPS and SEGMENT, pipeline time: %"
            GST_TIME_FORMAT, GST_TIME_ARGS (gst_clock_get_time (clock)));
      }
    }

    g_assert (GST_AVTP_VF_DEPAY_BASE_GET_CLASS
        (avtpvfdepaybase)->depay_push_caps != NULL);
    if (!GST_AVTP_VF_DEPAY_BASE_GET_CLASS (avtpvfdepaybase)->depay_push_caps
        (avtpvfdepaybase)) {
      GST_ELEMENT_ERROR (avtpvfdepaybase, CORE, CAPS, (NULL), (NULL));
      return GST_FLOW_ERROR;
    }

    if (!gst_avtp_base_depayload_push_segment_event (avtpbasedepayload,
            GST_BUFFER_PTS (avtpvfdepaybase->out_buffer))) {
      GST_ELEMENT_ERROR (avtpvfdepaybase, CORE, EVENT,
          ("Could not send SEGMENT event"), (NULL));
    }

    /* Now that we sent our segment starting on the first Presentation
     * time available, `avtpbasedepayload->prev_ptime` saves that value,
     * to be a reference for calculating future buffer timestamps from
     * the AVTP timestamps.
     *
     * However, decode timestamps can be smaller than presentation
     * timestamps. So we can't use `avtpbasedepayload->prev_time` as
     * reference to calculate them. Instead, here, we calculate the
     * first decode timestamp and save it on `avtpvfdepaybase->prev_ptime`.
     *
     * The method used to calculate the "absolute" decode timestamp (DTS)
     * from presentation timestamp is as follows:
     *
     *   DTS = dts > pts ? (PTSm - 1) | dts : PTSm | dts
     *
     * Where:
     *   dts: 32 bits gPTP decode timestamp
     *   pts: 32 bits gPTP presentation timestamp
     *   PTSm: 32 most signifactive bits of the "absolute" presentation
     *   timestamp
     *
     * This allow us to handle cases where the pts ends up being smaller
     * than dts due pts falling after an AVTP timestamp wrapping.
     */

    pts = GST_BUFFER_PTS (avtpvfdepaybase->out_buffer);
    dts = GST_BUFFER_DTS (avtpvfdepaybase->out_buffer);
    pts_m = avtpbasedepayload->prev_ptime & 0xFFFFFFFF00000000ULL;

    avtpbasedepayload->prev_ptime = dts > pts ? (pts_m -=
        (1ULL << 32)) | dts : pts_m | dts;
    GST_DEBUG_OBJECT (avtpvfdepaybase, "prev_ptime set to %" GST_TIME_FORMAT,
        GST_TIME_ARGS (avtpbasedepayload->prev_ptime));
  }

  /* At this point, we're sure segment was sent, so we can properly calc
   * buffer timestamps */
  GST_DEBUG_OBJECT (avtpvfdepaybase, "Converting %" GST_TIME_FORMAT " to PTS",
      GST_TIME_ARGS (GST_BUFFER_PTS (avtpvfdepaybase->out_buffer)));
  GST_BUFFER_PTS (avtpvfdepaybase->out_buffer) =
      gst_avtp_base_depayload_tstamp_to_ptime (avtpbasedepayload, GST_BUFFER_PTS
      (avtpvfdepaybase->out_buffer), avtpbasedepayload->prev_ptime);

  GST_DEBUG_OBJECT (avtpvfdepaybase, "Converting %" GST_TIME_FORMAT " to DTS",
      GST_TIME_ARGS (GST_BUFFER_DTS (avtpvfdepaybase->out_buffer)));
  GST_BUFFER_DTS (avtpvfdepaybase->out_buffer) =
      gst_avtp_base_depayload_tstamp_to_ptime (avtpbasedepayload, GST_BUFFER_DTS
      (avtpvfdepaybase->out_buffer), avtpbasedepayload->prev_ptime);

  /* Use DTS as prev_ptime as it is smaller or equal to PTS, so that
   * next calculations of PTS/DTS won't wrap too early */
  avtpbasedepayload->prev_ptime = GST_BUFFER_DTS (avtpvfdepaybase->out_buffer);

  ret = gst_pad_push (GST_AVTP_BASE_DEPAYLOAD (avtpvfdepaybase)->srcpad,
      avtpvfdepaybase->out_buffer);
  avtpvfdepaybase->out_buffer = NULL;

  return ret;
}