rtpmanager: update for rtp header extensions

Provide an implementation of the transport-wide-cc header extension and
use it in rtpfunnel.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/808>

docs/gst_plugins_cache.json

@@ -17001,6 +17001,38 @@
                 },
                 "rank": "none"
             },
+            "rtphdrexttwcc": {
+                "RTP-Header-Extension-URI": "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01",
+                "author": "Matthew Waters <matthew@centricular.com>",
+                "description": "Extends RTP packets to add sequence number transport wide.",
+                "hierarchy": [
+                    "GstRTPHeaderExtensionTWCC",
+                    "GstRTPHeaderExtension",
+                    "GstElement",
+                    "GstObject",
+                    "GInitiallyUnowned",
+                    "GObject"
+                ],
+                "klass": "Network/Extension/RTPHeader",
+                "long-name": "Transport Wide Congestion Control",
+                "properties": {
+                    "n-streams": {
+                        "blurb": "The number of separate RTP streams this header applies to",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "1",
+                        "max": "-1",
+                        "min": "1",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "guint",
+                        "writable": true
+                    }
+                },
+                "rank": "marginal"
+            },
             "rtpjitterbuffer": {
                 "author": "Philippe Kalaf <philippe.kalaf@collabora.co.uk>, Wim Taymans <wim.taymans@gmail.com>",
                 "description": "A buffer that deals with network jitter and other transmission faults",

gst/rtpmanager/gstrtpfunnel.c

@@ -67,14 +67,13 @@
 #endif
 
 #include <gst/rtp/gstrtpbuffer.h>
+#include <gst/rtp/gstrtphdrext.h>
 
 #include "gstrtpfunnel.h"
 
 GST_DEBUG_CATEGORY_STATIC (gst_rtp_funnel_debug);
 #define GST_CAT_DEFAULT gst_rtp_funnel_debug
 
-#define TWCC_EXTMAP_STR "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01"
-
 /**************** GstRTPFunnelPad ****************/
 
 struct _GstRtpFunnelPadClass
@@ -127,9 +126,8 @@ struct _GstRtpFunnel
   /* The last pad data was chained on */
   GstPad *current_pad;
 
-  guint8 twcc_ext_id;           /* the negotiated twcc extmap id */
-  guint16 twcc_seqnum;          /* our internal twcc seqnum */
   guint twcc_pads;              /* numer of sinkpads with negotiated twcc */
+  GstRTPHeaderExtension *twcc_ext;
 
   /* properties */
   gint common_ts_offset;
@@ -222,36 +220,40 @@ gst_rtp_funnel_set_twcc_seqnum (GstRtpFunnel * funnel,
     GstPad * pad, GstBuffer ** buf)
 {
   GstRtpFunnelPad *fpad = GST_RTP_FUNNEL_PAD_CAST (pad);
+  guint8 twcc_seq[2] = { 0, };
   GstRTPBuffer rtp = GST_RTP_BUFFER_INIT;
+  guint ext_id = gst_rtp_header_extension_get_id (funnel->twcc_ext);
+  guint8 *existing;
+  guint size;
 
-  if (!funnel->twcc_ext_id || !fpad->has_twcc)
+  if (!funnel->twcc_ext || !fpad->has_twcc)
     return;
 
   *buf = gst_buffer_make_writable (*buf);
 
-  if (gst_rtp_buffer_map (*buf, GST_MAP_READWRITE, &rtp)) {
-    gpointer data;
+  gst_rtp_header_extension_write (funnel->twcc_ext, *buf,
+      GST_RTP_HEADER_EXTENSION_ONE_BYTE, *buf, twcc_seq, sizeof (twcc_seq));
 
-    /* if there already is a twcc-seqnum inside the packet */
-    if (gst_rtp_buffer_get_extension_onebyte_header (&rtp, funnel->twcc_ext_id,
-            0, &data, NULL)) {
+  if (!gst_rtp_buffer_map (*buf, GST_MAP_READWRITE, &rtp))
+    goto map_failed;
 
-      /* with only one pad, we read the twcc-seqnum instead of writing it */
-      if (funnel->twcc_pads == 1) {
-        funnel->twcc_seqnum = GST_READ_UINT16_BE (data);
-      } else {
-        GST_WRITE_UINT16_BE (data, funnel->twcc_seqnum);
-      }
-    } else {
-      guint16 seq_be;
-      GST_WRITE_UINT16_BE (&seq_be, funnel->twcc_seqnum);
-      gst_rtp_buffer_add_extension_onebyte_header (&rtp, funnel->twcc_ext_id,
-          &seq_be, 2);
+  if (gst_rtp_buffer_get_extension_onebyte_header (&rtp, ext_id,
+          0, (gpointer) & existing, &size)) {
+    if (size >= gst_rtp_header_extension_get_max_size (funnel->twcc_ext, *buf)) {
+      existing[0] = twcc_seq[0];
+      existing[1] = twcc_seq[1];
     }
   }
+  /* TODO: two-byte variant */
+
   gst_rtp_buffer_unmap (&rtp);
 
-  funnel->twcc_seqnum++;
+  return;
+
+map_failed:
+  {
+    GST_ERROR ("failed to map buffer %p", *buf);
+  }
 }
 
 static GstFlowReturn
@@ -302,24 +304,25 @@ static void
 gst_rtp_funnel_set_twcc_ext_id (GstRtpFunnel * funnel, guint8 twcc_ext_id)
 {
   gchar *name;
+  guint current_ext_id;
 
-  if (funnel->twcc_ext_id == twcc_ext_id)
+  current_ext_id = gst_rtp_header_extension_get_id (funnel->twcc_ext);
+  g_object_set (funnel->twcc_ext, "n-streams", funnel->twcc_pads, NULL);
+
+  if (current_ext_id == twcc_ext_id)
     return;
 
   name = g_strdup_printf ("extmap-%u", twcc_ext_id);
 
-  GST_OBJECT_LOCK (funnel);
-  gst_caps_set_simple (funnel->srccaps, name, G_TYPE_STRING, TWCC_EXTMAP_STR,
-      NULL);
-  GST_OBJECT_UNLOCK (funnel);
+  gst_caps_set_simple (funnel->srccaps, name, G_TYPE_STRING,
+      gst_rtp_header_extension_get_uri (funnel->twcc_ext), NULL);
 
   g_free (name);
 
   /* make sure we update the sticky with the new caps */
   funnel->send_sticky_events = TRUE;
 
-  GST_INFO_OBJECT (funnel, "Setting twcc-ext-id to %u", twcc_ext_id);
-  funnel->twcc_ext_id = twcc_ext_id;
+  gst_rtp_header_extension_set_id (funnel->twcc_ext, twcc_ext_id);
 }
 
 static guint8
@@ -345,6 +348,8 @@ _get_extmap_id_for_attribute (const GstStructure * s, const gchar * ext_name)
   return extmap_id;
 }
 
+#define TWCC_EXTMAP_STR "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01"
+
 static gboolean
 gst_rtp_funnel_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
 {
@@ -376,22 +381,25 @@ gst_rtp_funnel_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
             caps);
         g_assert_not_reached ();
       }
-      GST_OBJECT_UNLOCK (funnel);
 
       s = gst_caps_get_structure (caps, 0);
       if (gst_structure_get_uint (s, "ssrc", &ssrc)) {
         fpad->ssrc = ssrc;
         GST_DEBUG_OBJECT (pad, "Got ssrc: %u", ssrc);
-        GST_OBJECT_LOCK (funnel);
         g_hash_table_insert (funnel->ssrc_to_pad, GUINT_TO_POINTER (ssrc), pad);
-        GST_OBJECT_UNLOCK (funnel);
       }
+
+      if (!funnel->twcc_ext)
+        funnel->twcc_ext =
+            gst_rtp_header_extension_create_from_uri (TWCC_EXTMAP_STR);
+
       ext_id = _get_extmap_id_for_attribute (s, TWCC_EXTMAP_STR);
       if (ext_id > 0) {
         fpad->has_twcc = TRUE;
         funnel->twcc_pads++;
         gst_rtp_funnel_set_twcc_ext_id (funnel, ext_id);
       }
+      GST_OBJECT_UNLOCK (funnel);
 
       forward = FALSE;
       break;
@@ -625,6 +633,8 @@ gst_rtp_funnel_finalize (GObject * object)
   gst_caps_unref (funnel->srccaps);
   g_hash_table_destroy (funnel->ssrc_to_pad);
 
+  gst_clear_object (&funnel->twcc_ext);
+
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }
 

gst/rtpmanager/gstrtphdrext-twcc.c

@@ -0,0 +1,232 @@
+/* GStreamer
+ * Copyright (C) <2020> Matthew Waters <matthew@centricular.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:rtphdrexttwcc
+ * @title: GstRtphdrext-TWCC
+ * @short_description: Helper methods for dealing with RTP header extensions
+ * in the Audio/Video RTP Profile for transport-wide-cc
+ * @see_also: #GstRTPHeaderExtension, #GstRTPBasePayload, #GstRTPBaseDepayload, gstrtpbuffer
+ *
+ * Since: 1.20
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gst/rtp/gstrtpbuffer.h>
+
+#include "gstrtphdrext-twcc.h"
+
+GST_DEBUG_CATEGORY_STATIC (rtphdrext_twcc_debug);
+#define GST_CAT_DEFAULT (rtphdrext_twcc_debug)
+
+#define gst_gl_base_filter_parent_class parent_class
+G_DEFINE_TYPE_WITH_CODE (GstRTPHeaderExtensionTWCC,
+    gst_rtp_header_extension_twcc, GST_TYPE_RTP_HEADER_EXTENSION,
+    GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "rtphdrexttwcc", 0,
+        "RTP TWCC Header Extensions");
+    );
+
+#define TWCC_EXTMAP_STR "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01"
+
+static void gst_rtp_header_extension_twcc_set_property (GObject * object,
+    guint prop_id, const GValue * value, GParamSpec * pspec);
+static void gst_rtp_header_extension_twcc_get_property (GObject * object,
+    guint prop_id, GValue * value, GParamSpec * pspec);
+
+static GstRTPHeaderExtensionFlags
+gst_rtp_header_extension_twcc_get_supported_flags (GstRTPHeaderExtension * ext);
+static gsize gst_rtp_header_extension_twcc_get_max_size (GstRTPHeaderExtension *
+    ext, const GstBuffer * buffer);
+static gsize gst_rtp_header_extension_twcc_write (GstRTPHeaderExtension * ext,
+    const GstBuffer * input_meta, GstRTPHeaderExtensionFlags write_flags,
+    GstBuffer * output, guint8 * data, gsize size);
+static gboolean gst_rtp_header_extension_twcc_read (GstRTPHeaderExtension * ext,
+    GstRTPHeaderExtensionFlags read_flags, const guint8 * data, gsize size,
+    GstBuffer * buffer);
+
+enum
+{
+  PROP_0,
+  PROP_N_STREAMS,
+};
+
+static void
+gst_rtp_header_extension_twcc_class_init (GstRTPHeaderExtensionTWCCClass *
+    klass)
+{
+  GstRTPHeaderExtensionClass *rtp_hdr_class;
+  GstElementClass *gstelement_class;
+  GObjectClass *gobject_class;
+
+  rtp_hdr_class = (GstRTPHeaderExtensionClass *) klass;
+  gobject_class = (GObjectClass *) klass;
+  gstelement_class = (GstElementClass *) klass;
+
+  gobject_class->set_property = gst_rtp_header_extension_twcc_set_property;
+  gobject_class->get_property = gst_rtp_header_extension_twcc_get_property;
+
+  /**
+   * rtphdrexttwcc:n-streams:
+   *
+   * The number of independant RTP streams that are being used for the transport
+   * wide counter for TWCC.  If set to 1 (the default), then any existing
+   * transport wide counter is kept.
+   *
+   * Since: 1.20
+   */
+  g_object_class_install_property (gobject_class, PROP_N_STREAMS,
+      g_param_spec_uint ("n-streams", "N Streams",
+          "The number of separate RTP streams this header applies to",
+          1, G_MAXUINT32, 1, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
+  rtp_hdr_class->get_supported_flags =
+      gst_rtp_header_extension_twcc_get_supported_flags;
+  rtp_hdr_class->get_max_size = gst_rtp_header_extension_twcc_get_max_size;
+  rtp_hdr_class->write = gst_rtp_header_extension_twcc_write;
+  rtp_hdr_class->read = gst_rtp_header_extension_twcc_read;
+  rtp_hdr_class->set_attributes_from_caps =
+      gst_rtp_header_extension_set_attributes_from_caps_simple_sdp;
+  rtp_hdr_class->set_caps_from_attributes =
+      gst_rtp_header_extension_set_caps_from_attributes_simple_sdp;
+
+  gst_element_class_set_static_metadata (gstelement_class,
+      "Transport Wide Congestion Control", GST_RTP_HDREXT_ELEMENT_CLASS,
+      "Extends RTP packets to add sequence number transport wide.",
+      "Matthew Waters <matthew@centricular.com>");
+  gst_rtp_header_extension_class_set_uri (rtp_hdr_class, TWCC_EXTMAP_STR);
+}
+
+static void
+gst_rtp_header_extension_twcc_init (GstRTPHeaderExtensionTWCC * twcc)
+{
+  twcc->n_streams = 1;
+}
+
+static void
+gst_rtp_header_extension_twcc_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstRTPHeaderExtensionTWCC *twcc = GST_RTP_HEADER_EXTENSION_TWCC (object);
+
+  switch (prop_id) {
+    case PROP_N_STREAMS:
+      twcc->n_streams = g_value_get_uint (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_rtp_header_extension_twcc_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstRTPHeaderExtensionTWCC *twcc = GST_RTP_HEADER_EXTENSION_TWCC (object);
+
+  switch (prop_id) {
+    case PROP_N_STREAMS:
+      g_value_set_uint (value, twcc->n_streams);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static GstRTPHeaderExtensionFlags
+gst_rtp_header_extension_twcc_get_supported_flags (GstRTPHeaderExtension * ext)
+{
+  return GST_RTP_HEADER_EXTENSION_ONE_BYTE;
+}
+
+static gsize
+gst_rtp_header_extension_twcc_get_max_size (GstRTPHeaderExtension * ext,
+    const GstBuffer * buffer)
+{
+  return 2;
+}
+
+static gsize
+gst_rtp_header_extension_twcc_write (GstRTPHeaderExtension * ext,
+    const GstBuffer * input_meta, GstRTPHeaderExtensionFlags write_flags,
+    GstBuffer * output, guint8 * data, gsize size)
+{
+  GstRTPHeaderExtensionTWCC *twcc = GST_RTP_HEADER_EXTENSION_TWCC (ext);
+  GstRTPBuffer rtp = { NULL, };
+  gpointer ext_data;
+  guint ext_size;
+  gsize written = 0;
+
+  g_return_val_if_fail (size >= gst_rtp_header_extension_twcc_get_max_size (ext,
+          NULL), -1);
+  g_return_val_if_fail (write_flags &
+      gst_rtp_header_extension_twcc_get_supported_flags (ext), -1);
+
+  if (!gst_rtp_buffer_map (output, GST_MAP_READWRITE, &rtp))
+    goto map_failed;
+
+  /* if there already is a twcc-seqnum inside the packet */
+  if (gst_rtp_buffer_get_extension_onebyte_header (&rtp, ext->ext_id, 0,
+          &ext_data, &ext_size)) {
+    if (ext_size < gst_rtp_header_extension_twcc_get_max_size (ext, NULL))
+      goto existing_too_small;
+
+    /* with only one stream, we read the twcc-seqnum */
+    if (twcc->n_streams == 1)
+      twcc->seqnum = GST_READ_UINT16_BE (ext_data);
+  } else {
+    /* with only one stream, we read the existing seqnum */
+    if (twcc->n_streams == 1)
+      twcc->seqnum = gst_rtp_buffer_get_seq (&rtp);
+
+    written = 2;
+  }
+  GST_WRITE_UINT16_BE (data, twcc->seqnum);
+
+  gst_rtp_buffer_unmap (&rtp);
+
+  twcc->seqnum++;
+
+  return written;
+
+  /* ERRORS */
+map_failed:
+  {
+    GST_ERROR ("failed to map buffer %p", output);
+    return 0;
+  }
+
+existing_too_small:
+  {
+    GST_ERROR ("Cannot rewrite twcc data of smaller size (%u)", ext_size);
+    return 0;
+  }
+}
+
+static gboolean
+gst_rtp_header_extension_twcc_read (GstRTPHeaderExtension * ext,
+    GstRTPHeaderExtensionFlags read_flags, const guint8 * data, gsize size,
+    GstBuffer * buffer)
+{
+  /* TODO: does this need an extra GstMeta? */
+  return TRUE;
+}

gst/rtpmanager/gstrtphdrext-twcc.h

@@ -0,0 +1,82 @@
+/* GStreamer
+ * Copyright (C) 2020 Matthew Waters <matthew@centricular.com>
+ *
+ * gstrtphdrexttwcc.h: transport-wide-cc RTP header extensions for the
+ *   Audio/Video RTP Profile
+ *
+ * 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.
+ */
+
+#ifndef __GST_RTPHDREXT_TWCC_H__
+#define __GST_RTPHDREXT_TWCC_H__
+
+#include <gst/gst.h>
+#include <gst/rtp/gstrtphdrext.h>
+
+G_BEGIN_DECLS
+
+GST_RTP_API
+GType gst_rtp_header_extension_twcc_get_type (void);
+#define GST_TYPE_RTP_HEADER_EXTENSION_TWCC (gst_rtp_header_extension_twcc_get_type())
+#define GST_RTP_HEADER_EXTENSION_TWCC(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_RTP_HEADER_EXTENSION_TWCC,GstRTPHeaderExtensionTWCC))
+#define GST_RTP_HEADER_EXTENSION_TWCC_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_RTP_HEADER_EXTENSION_TWCC,GstRTPHeaderExtensionTWCCClass))
+#define GST_RTP_HEADER_EXTENSION_TWCC_GET_CLASS(obj) \
+        (G_TYPE_INSTANCE_GET_CLASS ((obj),GST_TYPE_RTP_HEADER_EXTENSION_TWCC,GstRTPHeaderExtensionTWCCClass))
+#define GST_IS_RTP_HEADER_EXTENSION_TWCC(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_RTP_HEADER_EXTENSION_TWCC))
+#define GST_IS_RTP_HEADER_EXTENSION_TWCC_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_RTP_HEADER_EXTENSION_TWCC))
+#define GST_RTP_HEADER_EXTENSION_TWCC_CAST(obj) ((GstRTPHeaderExtensionTWCC *)(obj))
+
+typedef struct _GstRTPHeaderExtensionTWCC      GstRTPHeaderExtensionTWCC;
+typedef struct _GstRTPHeaderExtensionTWCCClass GstRTPHeaderExtensionTWCCClass;
+
+/**
+ * GstRTPHeaderExtensionTWCC:
+ * @parent: the parent #GstRTPHeaderExtension
+ *
+ * Instance struct for a transport-wide-cc RTP Audio/Video header extension.
+ *
+ * http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
+ */
+struct _GstRTPHeaderExtensionTWCC
+{
+  GstRTPHeaderExtension parent;
+
+  guint16 seqnum;
+  guint n_streams;
+
+  /*< private >*/
+  gpointer _gst_reserved[GST_PADDING];
+};
+
+/**
+ * GstRTPHeaderExtensionTWCCClass:
+ * @parent_class: the parent class
+ */
+struct _GstRTPHeaderExtensionTWCCClass
+{
+  GstRTPHeaderExtensionClass parent_class;
+
+  /*< private >*/
+  gpointer _gst_reserved[GST_PADDING];
+};
+
+G_END_DECLS
+
+#endif /* __GST_RTPHDREXT_TWCC_H__ */

gst/rtpmanager/gstrtpmanager.c

@@ -34,6 +34,7 @@
 #include "gstrtpfunnel.h"
 #include "gstrtpst2022-1-fecdec.h"
 #include "gstrtpst2022-1-fecenc.h"
+#include "gstrtphdrext-twcc.h"
 
 static gboolean
 plugin_init (GstPlugin * plugin)
@@ -84,6 +85,10 @@ plugin_init (GstPlugin * plugin)
           GST_TYPE_RTPST_2022_1_FECENC))
     return FALSE;
 
+  if (!gst_element_register (plugin, "rtphdrexttwcc", GST_RANK_MARGINAL,
+          GST_TYPE_RTP_HEADER_EXTENSION_TWCC))
+    return FALSE;
+
   return TRUE;
 }
 

gst/rtpmanager/meson.build

@@ -3,6 +3,7 @@ rtpmanager_sources = [
   'gstrtpbin.c',
   'gstrtpdtmfmux.c',
   'gstrtpjitterbuffer.c',
+  'gstrtphdrext-twcc.c',
   'gstrtpmux.c',
   'gstrtpptdemux.c',
   'gstrtprtxqueue.c',