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authorRonald S. Bultje <rsbultje@gmail.com>2008-11-14 18:37:58 +0000
committerRonald S. Bultje <rsbultje@gmail.com>2008-11-14 18:37:58 +0000
commit9e164392875484daf5dd1a4a63fc3d90cba02760 (patch)
tree5e6bef890f92eddfd6510cdd1926ef41da41447a /libavformat
parent39ded680136edad007db435aba069a8791bfad92 (diff)
downloadffmpeg-9e164392875484daf5dd1a4a63fc3d90cba02760.tar.gz
Add comment describing the RDT packet header. See discussion in "[PATCH]
RDT/Realmedia patches #2" thread on the mailinglist. Originally committed as revision 15823 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavformat')
-rw-r--r--libavformat/rdt.c51
1 files changed, 51 insertions, 0 deletions
diff --git a/libavformat/rdt.c b/libavformat/rdt.c
index c47466397f..daf8cbe21d 100644
--- a/libavformat/rdt.c
+++ b/libavformat/rdt.c
@@ -184,6 +184,57 @@ ff_rdt_parse_header(const uint8_t *buf, int len,
}
if (len < 10)
return -1;
+ /**
+ * Layout of the header (in bits):
+ * 1: len_included
+ * Flag indicating whether this header includes a length field;
+ * this can be used to concatenate multiple RDT packets in a
+ * single UDP/TCP data frame and is used to precede RDT data
+ * by stream status packets
+ * 1: need_reliable
+ * Flag indicating whether this header includes a "reliable
+ * sequence number"; these are apparently sequence numbers of
+ * data packets alone. For data packets, this flag is always
+ * set, according to the Real documentation [1]
+ * 5: set_id
+ * ID of a set of streams of identical content, possibly with
+ * different codecs or bitrates
+ * 1: is_reliable
+ * Flag set for certain streams deemed less tolerable for packet
+ * loss
+ * 16: seq_no
+ * Packet sequence number; if >=0xFF00, this is a non-data packet
+ * containing stream status info, the second byte indicates the
+ * type of status packet (see wireshark docs / source code [2])
+ * if (len_included) {
+ * 16: packet_len
+ * } else {
+ * packet_len = remainder of UDP/TCP frame
+ * }
+ * 1: is_back_to_back
+ * Back-to-Back flag; used for timing, set for one in every 10
+ * packets, according to the Real documentation [1]
+ * 1: is_slow_data
+ * Slow-data flag; currently unused, according to Real docs [1]
+ * 5: stream_id
+ * ID of the stream within this particular set of streams
+ * 1: is_no_keyframe
+ * Non-keyframe flag (unset if packet belongs to a keyframe)
+ * 32: timestamp (PTS)
+ * if (set_id == 0x1F) {
+ * 16: set_id (extended set-of-streams ID; see set_id)
+ * }
+ * if (need_reliable) {
+ * 16: reliable_seq_no
+ * Reliable sequence number (see need_reliable)
+ * }
+ * if (stream_id == 0x3F) {
+ * 16: stream_id (extended stream ID; see stream_id)
+ * }
+ * [1] https://protocol.helixcommunity.org/files/2005/devdocs/RDT_Feature_Level_20.txt
+ * [2] http://www.wireshark.org/docs/dfref/r/rdt.html and
+ * http://anonsvn.wireshark.org/viewvc/trunk/epan/dissectors/packet-rdt.c
+ */
if (sn) *sn = (buf[0]>>1) & 0x1f;
if (seq) *seq = AV_RB16(buf+1);
if (ts) *ts = AV_RB32(buf+4);