gstreamer/gst/rtp/gstrtpulpfecdec.h
Mathieu Duponchelle 90f5ae8f45 ulpfecdec: output perfect seqnums
ULP FEC, as defined in RFC 5109, has the protected and protection
packets sharing the same ssrc, and a different payload type, and
implies rewriting the seqnums of the protected stream when encoding
the protection packets. This has the unfortunate drawback of not
being able to tell whether a lost packet was a protection packet.

rtpbasedepayload relies on gaps in the seqnums to set the DISCONT
flag on buffers it outputs. Before that commit, this created two
problems:

* The protection packets don't make it as far as the depayloader,
  which means it will mark buffers as DISCONT every time the previous
  packets were protected

* While we could work around the previous issue by looking at
  the protection packets ignored and dropped in rtpptdemux, we
  would still mark buffers as DISCONT when a FEC packet was lost,
  as we cannot know that it was indeed a FEC packet, even though
  this should have no impact on the decoding of the stream

With this commit, we consider that when using ULPFEC, gaps in
the seqnums are not a reliable indicator of whether buffers should
be marked as DISCONT or not, and thus rewrite the seqnums on
the decoding side as well to form a perfect sequence, this
obviously doesn't prevent the jitterbuffer from doing its job
as the ulpfec decoder is downstream from it.

https://bugzilla.gnome.org/show_bug.cgi?id=794909
2018-04-19 18:17:39 +02:00

84 lines
2.4 KiB
C

/* GStreamer plugin for forward error correction
* Copyright (C) 2017 Pexip
*
* 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
*
* Author: Mikhail Fludkov <misha@pexip.com>
*/
#ifndef __GST_RTP_ULPFEC_DEC_H__
#define __GST_RTP_ULPFEC_DEC_H__
#include <gst/gst.h>
#include "rtpstorage.h"
G_BEGIN_DECLS
#define GST_TYPE_RTP_ULPFEC_DEC \
(gst_rtp_ulpfec_dec_get_type())
#define GST_RTP_ULPFEC_DEC(obj) \
(G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_RTP_ULPFEC_DEC,GstRtpUlpFecDec))
#define GST_RTP_ULPFEC_DEC_CLASS(klass) \
(G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_RTP_ULPFEC_DEC,GstRtpUlpFecDecClass))
#define GST_IS_RTP_ULPFEC_DEC(obj) \
(G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_RTP_ULPFEC_DEC))
#define GST_IS_RTP_ULPFEC_DEC_CLASS(klass) \
(G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_RTP_ULPFEC_DEC))
typedef struct _GstRtpUlpFecDec GstRtpUlpFecDec;
typedef struct _GstRtpUlpFecDecClass GstRtpUlpFecDecClass;
struct _GstRtpUlpFecDecClass {
GstElementClass parent_class;
};
struct _GstRtpUlpFecDec {
GstElement parent;
GstPad *srcpad;
GstPad *sinkpad;
/* properties */
guint8 fec_pt;
RtpStorage *storage;
gsize packets_recovered;
gsize packets_unrecovered;
/* internal stuff */
GstFlowReturn chain_return_val;
gboolean unset_discont_flag;
gboolean have_caps_ssrc;
gboolean have_caps_pt;
guint32 caps_ssrc;
guint8 caps_pt;
GList *info_media;
GPtrArray *info_fec;
GArray *info_arr;
GArray *scratch_buf;
gboolean lost_packet_from_storage;
gboolean lost_packet_returned;
guint16 next_seqnum;
/* stats */
gsize fec_packets_received;
gsize fec_packets_rejected;
gsize packets_rejected;
};
GType gst_rtp_ulpfec_dec_get_type (void);
G_END_DECLS
#endif /* __GST_RTP_ULPFEC_DEC_H__ */