draft-ietf-avt-rtp-mpeg4-es-00.txt   draft-ietf-avt-rtp-mpeg4-es-01.txt 
Internet Engineering Task Force Yoshihiro Kikuchi - Toshiba Internet Engineering Task Force Yoshihiro Kikuchi - Toshiba
Internet Draft Toshiyuki Nomura - NEC Internet Draft Toshiyuki Nomura - NEC
Document: draft-ietf-avt-rtp-mpeg4-es-00.txt Shigeru Fukunaga - Oki Document: draft-ietf-avt-rtp-mpeg4-es-01.txt Shigeru Fukunaga - Oki
Yoshinori Matsui - Matsushita Yoshinori Matsui - Matsushita
Hideaki Kimata - NTT Hideaki Kimata - NTT
February 1, 2000 May 31, 2000
RTP payload format for MPEG-4 Audio/Visual streams RTP payload format for MPEG-4 Audio/Visual streams
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026 [1]. provisions of Section 10 of RFC2026 [1].
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups Force (IETF), its areas, and its working groups. Note that other groups
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This document describes RTP payload formats for the carriage of MPEG-4 This document describes RTP payload formats for the carriage of MPEG-4
Audio and Visual streams[2][3], and an RTCP format for MPEG-4 upstream Audio and Visual streams[2][3], and an RTCP format for MPEG-4 upstream
messages functionalities[4]. In this specification, MPEG-4 Audio/Visual messages functionalities[4]. In this specification, MPEG-4 Audio/Visual
bitstreams are directly mapped into RTP packets without using MPEG-4 bitstreams are directly mapped into RTP packets. The RTP header fields
Systems[6]. The RTP header fields usage and the fragmentation rule for usage and the fragmentation rule for MPEG-4 Visual and Audio bitstreams
MPEG-4 Visual and Audio bitstreams are specified. It also specifies an are specified. It also specifies an RTCP packet usage to carry the MPEG-4
RTCP packet usage to carry the MPEG-4 upstream messages. upstream messages. In addition, MIME type registrations and SDP usages
for the MPEG-4 Audio and Visual streams are defined in this document.
1. Introduction 1. Introduction
1.1 Why MPEG-4 Audio/Visual RTP format needed? 1.1 Why MPEG-4 Audio/Visual RTP format needed?
The RTP payload formats described in this Internet-Draft specify the The RTP payload formats described in this Internet-Draft specify a way of
normative way on how MPEG-4 Audio/Visual streams are fragmented and how MPEG-4 Audio and Visual streams are fragmented and mapped directly
mapped directly onto RTP packets. No extra header field is used for such onto RTP packets.
functionality as error protection or grouping of streams.
H.323 terminals could be the case. MPEG-4 Audio/Visual streams are not H.323 terminals could be an example where such RTP payload formats are
managed by Object Descriptors[6] but H.245, and directly mapped into RTP used. MPEG-4 Audio/Visual streams are not managed by Object Descriptors
packets without Sync Layer[6]. The semantics of RTP headers in this case of MPEG-4 Systems[6] but by H.245. The streams are directly mapped onto
need to be clearly defined including the association with the MPEG-4 RTP packets without using the synchronization functionality of MPEG-4
Audio/Visual data elements. In addition, it would be beneficial to Systems [6].
define the fragmentation rule of RTP packets for MPEG-4 Video streams to
enhance error resiliency by utilizing the error resilience tools provided
inside the MPEG-4 Video stream. However, they have not been studied
until now.
1.2 Consideration on the MPEG-4 Visual RTP payload format The semantics of RTP headers in such cases need to be clearly defined,
including the association with the MPEG-4 Audio/Visual data elements. In
addition, it would be beneficial to define the fragmentation rule of RTP
packets for MPEG-4 Video streams so as to enhance error resiliency by
utilizing the error resilience tools provided inside the MPEG-4 Video
stream. However, these items are not covered by other RTP payload format
proposals.
1.2 MPEG-4 Visual RTP payload format
MPEG-4 Visual is a visual coding standard with many new functionalities: MPEG-4 Visual is a visual coding standard with many new functionalities:
high coding efficiency, high error resiliency, multiple arbitrary shaped high coding efficiency, high error resiliency, multiple arbitrary shaped
object based coding, etc. [2]. It covers a wide range of bitrate from object based coding, etc. [2]. It covers a wide range of bitrate from
several Kbps to many Mbps. It also covers a wide variety of networks from several Kbps to many Mbps. It also covers a wide variety of networks
guarantied with almost error-free to mobile with high error rate by its ranging from guarantied to be almost error-free to mobile networks with
error resilience functionalities. high error rate due to its error resilience functionalities.
A fragmentation rule for an MPEG-4 visual bitstream into RTP packets is
defined in this document. Since MPEG-4 Visual is used for a wide variety
of networks, it is desirable not to apply too much restriction to the
fragmentation. A fragmentation rule like "a single video packet shall
always be mapped on a single RTP packet" may be inappropriate. On the
other hand, a careless media unaware fragmentation may cause degradation
of the error resiliency and the bandwidth efficiency. The fragmentation
rule described in this document is flexible but to define the minimum
rules and guidelines for preventing the meaningless fragmentation and to
utilizing the error resilience functionality of MPEG-4 visual.
A normative way of fragmentation of an MPEG-4 visual bitstream into RTP
packets is defined in this Internet draft. Since MPEG-4 Visual is used
for a wide variety of networks, it is not desired to apply too much
restriction on the fragmentation like a single video packet shall always
be mapped on a single RTP packet. On the other hand, a careless media
unaware fragmentation may cause degradation of the error resiliency and
the bandwidth efficiency. The fragmentation rule described in this
Internet draft is flexible but to define the minimum rules to prevent the
meaningless fragmentation of e.g. splitting a header into packets.
For video coding media such as H.261 or MPEG-1/2, the additional media For video coding media such as H.261 or MPEG-1/2, the additional media
specific RTP header works effectively for recovering e.g. a picture specific RTP header works effectively for recovering. e.g., of a picture
header corrupt by packet losses. However, there are error resilience header corrupted by packet losses. However, there are error resilience
functionalities inside MPEG-4 Visual to recover corrupt headers. These functionalities inside MPEG-4 Visual to recover corrupt headers. These
functionalities can commonly be used on RTP/IP network as well as other functionalities can commonly be used on RTP/IP network as well as other
networks. (H.223/mobile, MPEG-2/TS, etc.) Therefore, no extra RTP header networks. (H.223/mobile, MPEG-2/TS, etc.) Therefore, no extra RTP header
fields are defined in the MPEG-4 Visual RTP payload format. fields are defined in the MPEG-4 Visual RTP payload format.
1.3 Consideration on the MPEG-4 Audio RTP payload format 1.3 Consideration on the MPEG-4 Audio RTP payload format
MPEG-4 Audio is a new kind of audio standard that integrates many MPEG-4 Audio is a new kind of audio standard that integrates many
different types of audio coding tools. It also supports a mechanism different types of audio coding tools. It also supports a mechanism
representing synthesized sounds. Low-overhead MPEG-4 Audio Transport representing synthesized sounds. Low-overhead MPEG-4 Audio Transport
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bitstreams, therefore, are desirable to be directly mapped into the RTP bitstreams, therefore, are desirable to be directly mapped into the RTP
packets without using MPEG-4 Systems. packets without using MPEG-4 Systems.
Furthermore, if the payload of a packet is a single audio frame, a packet Furthermore, if the payload of a packet is a single audio frame, a packet
loss does not impair the decodability of adjacent packets. Therefore, a loss does not impair the decodability of adjacent packets. Therefore, a
payload specific header for MPEG-4 Audio is not required as same as one payload specific header for MPEG-4 Audio is not required as same as one
for the other audio coders. for the other audio coders.
1.4 MPEG-4 Audio/Visual upstream messaging on RTCP packets 1.4 MPEG-4 Audio/Visual upstream messaging on RTCP packets
In some cases, MPEG-4 Audio/Visual has upstream messaging Some particular tools of MPEG-4 Audio/Visual support upstream messaging
functionalities. These messages are extremely Audio/Visual specific, functionalities. These messages are extremely Audio/Visual specific,
since coders directly use these messages for controlling coding since coders directly use these messages for controlling coding
parameters. From the point of view of controlling parameters, these parameters. From the point of view of controlling parameters, these
messages should be transmitted without delay. Therefore these messages messages should be transmitted without delay. Therefore, these messages
are directly mapped onto some kind of low delay RTCP packets. are directly mapped onto some kind of low delay RTCP packets. The use of
this type of RTCP packets is limited to the case when the MPEG-4 upstream
functionalities in some particular profiles are used (e.g. MPEG-4 Visual
Advanced Real Time Simple Profile, NEWPRED tool).
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [7]. document are to be interpreted as described in RFC-2119 [7].
3. RTP Packetization of MPEG-4 Visual bitstream 3. RTP Packetization of MPEG-4 Visual bitstream
This section specifies the RTP packetization rule for MPEG-4 Visual This section specifies the RTP packetization rule for MPEG-4 Visual
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plus the cumulative number of whole seconds specified by module_time_base plus the cumulative number of whole seconds specified by module_time_base
and time_code of Group_of_VideoObjectPlane() if present. In the case of and time_code of Group_of_VideoObjectPlane() if present. In the case of
interlaced video, a VOP consists of lines from two fields and the interlaced video, a VOP consists of lines from two fields and the
timestamp indicates the composition time of the first field. If the RTP timestamp indicates the composition time of the first field. If the RTP
packet contains only configuration information and/or packet contains only configuration information and/or
Group_of_VideoObjectPlane(), the composition time of the subsequent VOP Group_of_VideoObjectPlane(), the composition time of the subsequent VOP
in the coding order is used. If the RTP packet contains only in the coding order is used. If the RTP packet contains only
visual_object_sequence_end_code, the composition time of the immediately visual_object_sequence_end_code, the composition time of the immediately
preceding VOP in the coding order is used. preceding VOP in the coding order is used.
Unless specified by an out-of-band means, the resolution of the timestamp Unless specified by an out-of-band means (e.g. SDP parameter or MIME
is set to its default (90KHz). parameter as defined in section 6), the resolution of the timestamp is
set to its default (90KHz).
SSRC, CC and CSRC fields are used as described in RFC 1889 [8]. SSRC, CC and CSRC fields are used as described in RFC 1889 [8].
3.2 Fragmentation of MPEG-4 Visual bitstream 3.2 Fragmentation of MPEG-4 Visual bitstream
A fragmented MPEG-4 Visual bitstream is mapped directly onto the RTP A fragmented MPEG-4 Visual bitstream is mapped directly onto the RTP
payload without any addition of extra header fields or removal of any payload without any addition of extra header fields or removal of any
Visual syntax elements. The Combined Configuration/Elementary streams Visual syntax elements. The Combined Configuration/Elementary streams
mode is used. The following rules apply for the fragmentation. mode is used. The following rules apply for the fragmentation.
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(3) A header SHALL NOT be split into a plurality of RTP packets. (3) A header SHALL NOT be split into a plurality of RTP packets.
(4) Two or more VOPs SHALL be fragmented into different RTP packets so (4) Two or more VOPs SHALL be fragmented into different RTP packets so
that one RTP packet consists of the data bytes associated with an unique that one RTP packet consists of the data bytes associated with an unique
presentation time (that indicated to the timestamp field in the RTP presentation time (that indicated to the timestamp field in the RTP
packet header). packet header).
(5) A single video packet SHOULD NOT be split into a plurality of RTP (5) A single video packet SHOULD NOT be split into a plurality of RTP
packets. The size of a video packet SHOULD be adjusted such that the packets. The size of a video packet SHOULD be adjusted such that the
resulting RTP packet is not larger than the path-MTU. resulting RTP packet is not larger than the path-MTU. A video packet MAY
be split into a plurality of RTP packets when the size of the video
packet is large.
Hear, header means: Here, header means:
- Configuration information (Visual Object Sequence Header, Visual Object - Configuration information (Visual Object Sequence Header, Visual Object
Header and Visual Object Layer Header) Header and Video Object Layer Header)
- visual_object_sequence_end_code - visual_object_sequence_end_code
- The header of the entry point function for an elementary stream - The header of the entry point function for an elementary stream
(Group_of_VideoObjectPlane() or the header of VideoObjectPlane(), (Group_of_VideoObjectPlane() or the header of VideoObjectPlane(),
video_plane_with_short_header(), MeshObject() or FaceObject()) video_plane_with_short_header(), MeshObject() or FaceObject())
- The video packet header (video_packet_header() excluding - The video packet header (video_packet_header() excluding
next_resync_marker()) next_resync_marker())
- The header of gob_layer() - The header of gob_layer()
See 6.2.1 "Start codes" of ISO/IEC 14496-2[2][9][4] for the definition of See 6.2.1 "Start codes" of ISO/IEC 14496-2[2][9][4] for the definition of
the configuration information and the entry point functions. the configuration information and the entry point functions.
The video packet starts with the VOP header or the video packet header, The video packet starts with the VOP header or the video packet header,
followed by motion_shape_texture(), and ends with next_resync_marker() or followed by motion_shape_texture(), and ends with next_resync_marker() or
next_start_code). next_start_code).
3.3 Examples of packetized MPEG-4 Visual bitstream 3.3 Examples of packetized MPEG-4 Visual bitstream
Considering that MPEG-4 Visual is used on a wide variety of networks from Considering that MPEG-4 Visual is used on a wide variety of networks from
several Kbps to many Mbps, from guarantied networks with almost error- several Kbps to many Mbps, from guaranteed networks which are almost
free to mobile networks with high error rate, it is not desired to apply error-free to mobile networks with high error rate, it is desirable not
too much restriction on the fragmentation like a single video packet to apply too much restriction to the fragmentation. On the other hand, a
shall always be mapped on a single RTP packet. On the other hand, a
careless media unaware fragmentation will cause degradation of the error careless media unaware fragmentation will cause degradation of the error
resiliency and the bandwidth efficiency. The fragmentation criteria resiliency and the bandwidth efficiency. The fragmentation criteria
described in 3.2 are flexible but to define the minimum rules to prevent described in 3.2 are flexible but to define the minimum rules to prevent
the meaningless fragmentation of e.g. splitting a header into packets. meaningless fragmentation.
For video coding media such as H.261 or MPEG-1/2, the additional media For video coding media such as H.261 or MPEG-1/2, the additional media
specific RTP header works effectively for recovering e.g. a picture specific RTP header works effectively for recovering, e.g., of a picture
header corrupt by packet losses. However, there is an error resilience header corrupted by packet losses. However, there is an error resilience
functionality inside MPEG-4 Visual to recover corrupt headers. This functionality inside MPEG-4 Visual to recover corrupt headers. This
functionality can commonly be used on RTP/IP network as well as other functionality can commonly be used on RTP/IP network as well as other
networks. (H.223/mobile, MPEG-2/TS, etc.) Therefore, there is no strong networks. (H.223/mobile, MPEG-2/TS, etc.) Therefore, there is no strong
reason to define MPEG-4 Visual specific extra RTP header fields. reason to define MPEG-4 Visual specific extra RTP header fields.
Figure 2 shows examples of RTP packets generated based on the criteria Figure 2 shows examples of RTP packets generated based on the criteria
described in 3.2 described in 3.2
(a) is an example of the first RTP packet or the random access point of (a) is an example of the first RTP packet or the random access point of
an MPEG-4 visual bitstream. This RTP packet contains the configuration an MPEG-4 visual bitstream. This RTP packet contains the configuration
information. According to the criterion (1), the Visual Object Sequence information. According to the criterion (1), the Visual Object Sequence
Header(VS header) is placed at the beginning of the RTP payload, and the Header(VS header) is placed at the beginning of the RTP payload, and the
Visual Object Header and the Visual Object Layer Header(VO header, VOL Visual Object Header and the Video Object Layer Header(VO header, VOL
header) follow it. Since the fragmentation rule defined in 3.2 guaranties header) follow it. Since the fragmentation rule defined in 3.2 guarantees
that the configuration information, starting with that the configuration information, starting with
visual_object_sequence_start_code, is always placed at the beginning of visual_object_sequence_start_code, is always placed at the beginning of
the RTP payload, RTP receivers can detect the random access point by the RTP payload, RTP receivers can detect the random access point by
checking if the first 32-bit field of the RTP payload is checking if the first 32-bit field of the RTP payload is
visual_object_sequence_start_code. visual_object_sequence_start_code.
(b) is an example the RTP packet that contains (b) is another example of the RTP packet containing the configuration
information. The difference from the example (a) is that this RTP packet
also contains a video packet in the VOP following the configuration
information. Since the length of the configuration information is
relatively short (typically several ten bytes), an RTP packet containing
only the configuration information may increase the overhead. Therefore,
the configuration information and the immediately following GOV and/or (a
part of) VOP can be packetized into a single RTP packet like this
example.
(c) is an example the RTP packet that contains
Group_of_VideoObjectPlane(GOV). Following the criterion (1), the GOV is Group_of_VideoObjectPlane(GOV). Following the criterion (1), the GOV is
placed at the beginning of the RTP payload. It is a waste of RTP/IP placed at the beginning of the RTP payload. It is a waste of RTP/IP
header overhead to generate a RTP packet containing only a GOV whose header overhead to generate a RTP packet containing only a GOV whose
length is 7 bytes. Therefore, (a part of) the following VOP can be placed length is 7 bytes. Therefore, (a part of) the following VOP can be placed
in the same RTP packet as shown in (b). in the same RTP packet as shown in (c).
(c) is an example that one video packet is packetized into one RTP (d) is an example of the case where one video packet is packetized into
packet. When the packet-loss rate of the underlying network is high, this one RTP packet. When the packet-loss rate of the underlying network is
kind of packetization is recommended. It is strongly recommended to set high, this kind of packetization is recommended. It is strongly
resync_marker_disable to 0 in the VOL header to enable adjustment of the recommended to set resync_marker_disable to 0 in the VOL header to enable
video packet size. Even when the RTP packet containing the VOP header is adjustment of the video packet size. Even when the RTP packet containing
discarded by a packet loss, the other RTP packets can be decoded by using the VOP header is discarded by a packet loss, the other RTP packets can
the HEC(Header Extension Code) information in the video packet header. No be decoded by using the HEC(Header Extension Code) information in the
extra RTP header field is necessary. video packet header. No extra RTP header field is necessary.
(d) is an example that more than one video packets are packetized into (e) is an example of the case where more than one video packets are
one RTP packet. This kind of packetization is effective to save the packetized into one RTP packet. This kind of packetization is effective
overhead of RTP/IP headers if the bit-rate of the underlying network is to save the overhead of RTP/IP headers if the bit-rate of the underlying
low. However, it will decrease the packet-loss resiliency because network is low. However, it will decrease the packet-loss resiliency
multiple video packets are discarded by a single RTP packet loss. The because multiple video packets are discarded by a single RTP packet loss.
adequate number of video packets in a RTP packet and the RTP packet The adequate number of video packets in a RTP packet and the RTP packet
length depend the packet-loss rate and the bit-rate of the underlying length depend the packet-loss rate and the bit-rate of the underlying
network. network.
Figure 3 shows examples of RTP packets prohibited by the criteria of 3.2. Figure 3 shows examples of RTP packets prohibited by the criteria of 3.2.
Fragmentation of a header into multiple RTP packets, like (a), will not Fragmentation of a header into multiple RTP packets, like (a), will not
only increase the overhead of RTP/IP headers but also decrease the error only increase the overhead of RTP/IP headers but also decrease the error
resiliency. Therefore, it is prohibited by the criterion (3). resiliency. Therefore, it is prohibited by the criterion (3).
When concatenating more than one video packets into a RTP packet, VOP When concatenating more than one video packets into an RTP packet, VOP
header or video_packet_header() shall not be placed in the middle of the header or video_packet_header() shall not be placed in the middle of the
RTP payload. The packetization like (b) is not allowed by the criterion RTP payload. The packetization like (b) is not allowed by the criterion
(2). This is because of the error resiliency. Comparing this example with (2). This is because of the error resiliency. Comparing this example with
Figure 2(c), two video packets are mapped onto two RTP packets in both Figure 2(c), two video packets are mapped onto two RTP packets in both
cases. However, there is a difference between the packet-loss resiliency. cases. However, there is a difference between the packet-loss resiliency.
When the second RTP packet is lost, both video packets 1 and 2 are lost When the second RTP packet is lost, both video packets 1 and 2 are lost
in the case of Figure 3(b) whereas only video packet 2 is lost in the in the case of Figure 3(b) whereas only video packet 2 is lost in the
case of Figure 2(c). case of Figure 2(c).
A RTP packet containing more than one VOPs, like (c), is not allowed. An RTP packet containing more than one VOPs, like (c), is not allowed.
+------+------+------+------+ +------+------+------+------+
(a) | RTP | VS | VO | VOL | (a) | RTP | VS | VO | VOL |
|header|header|header|header| |header|header|header|header|
+------+------+------+------+ +------+------+------+------+
+------+------+------+------+------------+
(b) | RTP | VS | VO | VOL |Video Packet|
|header|header|header|header| |
+------+------+------+------+------------+
+------+-----+------------------+ +------+-----+------------------+
(b) | RTP | GOV |Video Object Plane| (c) | RTP | GOV |Video Object Plane|
|header| | | |header| | |
+------+-----+------------------+ +------+-----+------------------+
+------+------+------------+ +------+------+------------+ +------+------+------------+ +------+------+------------+
(c) | RTP | VOP |Video Packet| | RTP | VP |Video Packet| (d) | RTP | VOP |Video Packet| | RTP | VP |Video Packet|
|header|header| (1) | |header|header| (2) | |header|header| (1) | |header|header| (2) |
+------+------+------------+ +------+------+------------+ +------+------+------------+ +------+------+------------+
+------+------+------------+------+------------+------+------------+ +------+------+------------+------+------------+------+------------+
(d) | RTP | VP |Video Packet| VP |Video Packet| VP |Video Packet| (e) | RTP | VP |Video Packet| VP |Video Packet| VP |Video Packet|
|header|header| (1) |header| (2) |header| (3) | |header|header| (1) |header| (2) |header| (3) |
+------+------+------------+------+------------+------+------------+ +------+------+------------+------+------------+------+------------+
Figure 2 - Examples of RTP packetized MPEG-4 Visual bitstream Figure 2 - Examples of RTP packetized MPEG-4 Visual bitstream
+------+-------------+ +------+------------+------------+ +------+-------------+ +------+------------+------------+
(a) | RTP |First half of| | RTP |Last half of|Video Packet| (a) | RTP |First half of| | RTP |Last half of|Video Packet|
|header| VP header | |header| VP header | | |header| VP header | |header| VP header | |
+------+-------------+ +------+------------+------------+ +------+-------------+ +------+------------+------------+
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payload elements. A payload element SHOULD NOT be fragmented. payload elements. A payload element SHOULD NOT be fragmented.
(2) If the audioMuxElement includes StreamMuxConfig, StreamMuxConfig (2) If the audioMuxElement includes StreamMuxConfig, StreamMuxConfig
SHALL be included into the RTP packet containing the first payload SHALL be included into the RTP packet containing the first payload
element. element.
5. RTCP Packetization of MPEG-4 upstream messages 5. RTCP Packetization of MPEG-4 upstream messages
This section specifies the usage of particular RTCP packets to carry the This section specifies the usage of particular RTCP packets to carry the
upstream messages generated using the MPEG-4 Audio/Visual upstream upstream messages generated using the MPEG-4 Audio/Visual upstream
messaging functionalities, e.g. NEWPRED[4]. RTCP packets specified in messaging functionalities. In the current specification, NEWPRED in the
this section SHALL ONLY be used when it is indicated by the profile and MPEG-4 Visual Advance Real Time Simple (ARTS) Profile[4] is only the tool
level indication of MPEG-4 the codecs have such functionalities. (e.g. which uses this RTCP payload specification. This particular RTCP packet
Advanced Real Time Simple Visual Profile[4]) SHALL ONLY be used when it is indicated by some out of band means that
the corresponding MPEG-4 Visual codec is compliant with the ARTS profile
and it is indicated in the configuration information of the MPEG-4 visual
bitstream that the NEWPRED tool is enabled (newpred_enable is set to 1).
The MPEG-4 upstream messages are transmitted on particular RTCP packets, 5.1. Abstract of NEWPRED in the ARTS profile
like H.261 RTCP control packets [10]. NEWPRED in the ARTS profile is an error resilience tool using the
upstream messages from the decoder to the encoder. As the inter-frame
coding is used in the MPEG-4 Visual standard, the image degradation by
packet loss will be propagated to the after several frames. In order to
prevent the temporal error propagation, the reference frames of the
inter-frame coding are switched according to the upstream messages in the
NEWPRED. As the correct frames are used as the reference frame, the
error propagation is refreshed.
In the case that the RTP session uses a multicast address, the MPEG-4 As neither the re-transmission nor the intra refresh are used, the coding
upstream message packets are not transmitted to the normal RTCP efficiency can be kept high. And the NEWPRED can achieve the faster
destination transport address. Instead, these upstream message packets error recovery than the intra refresh.
are sent directly via unicast from the decoder to the coder. The
destination port number of these upstream message packets is always same
to the port number of the normal RTCP address.
As a consequence, these upstream message packets may only be used when no There are two types of upstream messages; acknowledged message (NP_ACK)
RTP mixers or translators intervene in the path from the coder to the and non-acknowledged message (NP_NACK). NP_ACK and/or NP_NACK messages
decoder. If such intermediate systems do intervene, the address of the are transmitted on the particular RTCP packets in the NEWPRED. The
coder would no longer be present as the network-level source address in selecting methods of reference frames are dependent on the kind of used
packets received by the decoder, and in fact, it might not be possible messages.
for the decoder to send packets directly to the coder.
Some reliable multicast protocols use similar NACK control packets 5.2. Particular RTCP packets keep low delay
transmitted over the normal multicast distribution channel, however they
typically use random delays to prevent a NACK implosion problem. The goal
of such protocols is to provide reliable multicast packet delivery at the
expense of delay, which is appropriate for applications such as a shared
whiteboard.
On the other hand, real-time Audio/Visual transmission is more sensitive The real-time Audio/Visual transmission is more sensitive to delay and
to delay and does not require full reliability. For Audio/Visual does not require full reliability. For Audio/Visual applications it is
applications it is more effective to send the MPEG-4 upstream message more effective to send the MPEG-4 upstream message packets as soon as
packets as soon as possible, i.e. as soon as a loss is detected, without possible, i.e. as soon as a loss is detected, without adding any random
adding any random delays. delays.
5.1. MPEG-4 Visual upstream message packets definition 5.3. Congestion control
In the cases of the demand type of intra refresh or the re-transmission,
the amount of bits during the congestion is larger than that in the error
free terms. Therefore they may cause some another congestion. While in
the NEWPRED, as the intra-frame coding is not used, the increased amount
of bits is much lower than that of the intra refresh or the re-
transmission even in the case of packet loss. Therefore NEWPRED causes
less additional burden for the congestion.
The amount of the upstream messages is dependent on the strategy of the
selecting methods of reference frames of the encoder and that of the
sending upstream messages of the decoder. In order to avoid congestion,
the amount of upstream message packets should be small. In the NEWPRED,
the decoder can control the amount of them by not sending some upstream
messages; For example, in the case that the NP_NACK messages are mainly
used to select the reference frames in the encoder, the decoder may not
send the NP_ACK messages even if it receives downstream data. On the
other hand, in the case that the NP_ACK messages are mainly used in the
encoder, the decoder may not send the NP_NACK messages. The amount of the
upstream messages is at most 5% (normally about 1%) of the visual
downstream data.
Especially the amount of NP_ACK messages is decreased in the case of
packet loss. Therefore the NP_ACK message has no additional burden for
the congestion. On the other hand, NP_NACK messages corresponding to the
lost packets are usually sent after the congestion, because the decoder
detects the packet loss after the next downstream packet reaches.
Therefore the NP_NACK message has less additional burden for the
congestion, too.
And to reduce the number of particular RTCP packets, multiple upstream
messages can be concatenated in the payload of one particular RTCP
packet. In this case, it is desirable to send these concatenated
messages as soon as possible.
The particular RTCP transmission interval is according to the interval of
the decoding the visual downstream data. Both the receiving interval of
the visual RTP packet and the decoding time for each packet data have
some jitter for themselves. Therefore the particular RTCP transmission
interval has some jitter for itself. It is effective for the congestion
control, and there is no need to add any random delays. This means that
the size of sending jitter is enough to avoid another congestion only in
case of the unicast.
5.4. Limiting to Unicast
The NEWPRED can work in multicast only in the case that the number of
decoders is small. However in order to avoid the additional congestion,
the NEWPRED over RTP/RTCP SHALL NOT be used in multicast.
5.5. Relations with SR and RR
The particular low delay RTCP packets for the MPEG-4 upstream messages
SHALL be treated as the completely different kind of packets from the
normal RTCP packets; such as SR, RR and so on.
For example, if the particular RTCP packets would be included in the
calculation of RTCP sending interval, the RR packets should be generated
in the timing of the particular low delay RTCP packets. In this case,
the interval of the RR packets would be smaller than 5 seconds, and the
number of the normal RTCP packets is much increased. It is bad for the
congestion.
Therefore all particular RTCP packets SHALL be ignored to analyze the
information in the sender and receiver reports (SR and RR), and only
normal RTCP packets are used.
Multiple particular RTCP packets can be concatenated without any
intervening separators to form a compound RTCP packet. The normal
compound RTCP packet SHOULD start with SR or RR packets. However in the
case of compound particular RTCP packet, other normal RTCP packets SHALL
NOT be included, and only particular RTCP packets SHALL be included in
one compound particular RTCP packet.
5.6. MPEG-4 Visual upstream message packets definition
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P| UMT | PT=RTCP_MP4UM | length | |V=2|P| UMT | PT=RTCP_MP4U | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC | | SSRC |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| MPEG-4 Upstream Messages Payload (byte aligned) | | MPEG-4 Upstream Messages Payload (byte aligned) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : padding | | : padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
version (V): 2 bits version (V): 2 bits
Identifies the version of RTP, which is the same in RTCP packets as Identifies the version of RTP, which is the same in RTCP packets as
skipping to change at page 12, line 8 skipping to change at page 14, line 31
If the padding bit is set, this RTCP packet contains some additional If the padding bit is set, this RTCP packet contains some additional
padding octets at the end which are not part of the control padding octets at the end which are not part of the control
information. The last octet of the padding is a count of how many information. The last octet of the padding is a count of how many
padding octets should be ignored. In the case several upstream padding octets should be ignored. In the case several upstream
messages are mapped onto one RTCP packet, padding should only be messages are mapped onto one RTCP packet, padding should only be
required on the last individual message. required on the last individual message.
upstream message type (UMT): 5 bits upstream message type (UMT): 5 bits
Identifies the type of the MPEG-4 upstream messages. Identifies the type of the MPEG-4 upstream messages.
0: forbidden 0: forbidden
1: MPEG-4 Visual NEWPRED 1: MPEG-4 Visual NEWPRED in the ARTS Profile
2-63: reserved 2-63: reserved
In this internet-draft, only NEWPRED is assigned as the candidate of In this internet-draft, only the NEWPRED in the ARTS profile is
the UMT for the moment. Some other MPEG-4 Audio/Visual applications assigned as the candidate of the UMT for the moment. Some other
using the upstream messages may be assigned in the future. MPEG-4 Audio/Visual applications using the upstream messages may be
assigned in the future.
packet type (PT): 8 bits packet type (PT): 8 bits
The value of the packet type (PT) identifier is the constant The value of the packet type (PT) identifier is the constant
RTCP_MP4UM (TBD). RTCP_MP4U (TBD).
SSRC: 32 bits SSRC: 32 bits
SSRC is the synchronization source identifier for the sender of this SSRC is the synchronization source identifier for the sender of this
packet. packet.
MPEG-4 Upstream Message Payload: variable MPEG-4 Upstream Message Payload: variable
The syntax and semantics of the MPEG-4 upstream messages are defined The syntax and semantics of the MPEG-4 upstream messages are defined
in the ISO/IEC 14496-2/3[4][5]. All messages are byte aligned. in the ISO/IEC 14496-2/3[4][5]. All messages are byte aligned.
Normally one message is mapped onto one RTCP packet, and several Normally one message is mapped onto one RTCP packet, and several
messages with same UMT could be continuously mapped onto one RTCP messages with same UMT could be continuously mapped onto one RTCP
packet. One message SHALL NOT be fragmented into different RTCP packet. One message SHALL NOT be fragmented into different RTCP
packets. packets.
6. Security Considerations 6. MIME type registration for MPEG-4 Audio/Visual streams
The following sections describe the MIME type registrations for the MPEG-
4 Audio/Visual streams. MIME type registration and SDP usage for the
MPEG-4 Visual stream are described in sections 6.1 and 6.2, respectively.
MIME type registration and SDP usage for the MPEG-4 Audio stream are
described in sections 6.3 and 6.4, respectively.
(In the following sections, the RFC number "XXXX" represents the RFC
number, which should be assigned for this Internet Draft.)
6.1 MIME type registration for MPEG-4 Visual
MIME media type name: video
MIME subtype name: MP4V
Required parameters: none
Optional parameters:
rate: This parameter is used only for RTP transport. It indicates the
resolution of the timestamp field in the RTP header. If this parameter
is not specified, the default value of 90000 (90KHz) is used.
profile-level-id: A decimal representation of MPEG-4 Visual Profile
Level indication value (profile_and_level_indication) defined in Table
G-1 of ISO/IEC 14496-2 [2][4].
mpeg4-newpred-upstream-message: A boolean number to indicate the
receiver capability of sending the upstream message of NEWPRED in
MPEG-4 video. The upstream messages are delivered on the particular
RTCP packets which are described in section 5. This optional exist
when and only when the "profile-level-id" is 145, 146, 147 or 148
(Advance Real Time Simple Profile/Level 1, 2, 3 or 4).
Example usages for these parameters are show bellow:
- MPEG-4 Visual Core Profile/Level 2:
Content-type: video/mp4v; profile-level-id=34
- MPEG-4 Visual Advanced Real Time Simple Profile/Level 1, upstream
message is used:
Content-type: video/mp4v; profile-level-id=145; mpeg4-newpred-
upstream-message=1
Published specification:
The specification of MPEG-4 Visual stream is presented in ISO/IEC
14469-2[2][4][9]. The RTP payload format is described in RFCXXXX.
Encoding considerations:
A video bitstream must be generated according to the MPEG-4 Visual
specification (ISO/IEC 14496-2). The video bitstream is binary data,
and must be encoded for non-binary transport; the Base64 encoding is
suitable for Email. This type is also defined for transfer via RTP.
The RTP packets must be packetized according to the MPEG-4 Visual RTP
payload format defined in RFCXXXX.
Security considerations:
See section 9 of RFCXXXX.
Interoperability considerations:
MPEG-4 Visual provides a large and rich set of tools for the coding of
visual objects. In order to allow effective implementations of the
standard, subsets of the MPEG-4 Visual tool sets have been identified,
that can be used for specific applications. These subsets, called
'Profiles', limit the tool set a decoder has to implement. For each of
these Profiles, one or more Levels have been set, restricting the
computational complexity. A Profile@Level combination allows:
o a codec builder to implement only the subset of the standard he
needs, while maintaining interworking with other MPEG-4 devices built
to the same combination, and
o checking whether MPEG-4 devices comply with the standard
('conformance testing').
The visual stream SHALL be compliant with the MPEG-4 Visual
Profile@Level specified by the parameter "profile-level-id". The
interoperability between a sender and a receiver may be achieved by
specifying the parameter "profile-level-id" in MIME content, or by
exchanging this parameter in the capability exchange procedure.
Applications which use this media type:
Audio and visual streaming and conferencing tools, Internet messaging
and e-mail applications.
Additional information: none
Person & email address to contact for further information:
The authors of RFCXXXX. (See section 9)
Intended usage: COMMON
Author/Change controller:
The authors of RFCXXXX. (See section 9)
6.2 SDP usage of MPEG-4 Visual
The MIME media type video/MP4V string is mapped to fields in the Session
Description Protocol (SDP), RFC 2327, as follows:
o The MIME type (video) goes in SDP "m=" as the media name.
o The MIME subtype (MP4V) goes in SDP "a=rtpmap" as the encoding name.
o The optional parameter "rate" goes in "a=rtpmap" as clock rate.
o The optional parameter "profile-level-id" MAY go in "a=fmtp" line. The
optional parameter "mpeg4-newpred-upstream-message" MAY go in "a=fmtp"
line, when and only when the "profile-level-id" is 145, 146, 147 or
148(Advance Real Time Simple Profile/Level 1, 2, 3 or 4). The format and
syntax of these parameters is the MIME media type string as a semicolon
separated list of parameter=value pairs.
The followings are some examples of the media representation in SDP:
Simple Profile/Level 1, rate=90000(90KHz), "profile-level-id" is present
in "a=fmtp" line:
m=video 49170/2 RTP/AVP 98
a=rtpmap:98 MP4V/90000
a=fmtp:98 profile-level-id=1
Advance Real Time Simple Profile/Level 1, rate=25(25Hz), "profile-level-
id" and " newpred- mpeg4- upstream-message" are present in "a=fmtp" line:
m=video 49170/2 RTP/AVP 98
a=rtpmap:98 MP4V/25
a=fmtp:98 profile-level-id=145; mpeg4-newpred-upstream-message=1
6.3 MIME type registration of MPEG-4 Audio
MIME media type name: audio
MIME subtype name: MP4A
Required parameters:
rate: the rate parameter indicates the RTP time stamp clock rate. The
default value is 90000. Other rates CAN be specified only if it would
be set to the same value with the audio sampling rate (number of
samples per second).
Optional parameters:
profile-level-id: a decimal representation of MPEG-4 Audio Profile
Level indication value defined in ISO/IEC 14496-1 [11]. This parameter
indicates the capability of subsets in MPEG-4 Audio tools.
object: a decimal representation of MPEG-4 Audio Object Type value
defined in ISO/IEC 14496-3 [5]. This parameter specifies the tool to
be used by the coder. It CAN be used to limit the capability within
the specified "profile-level-id".
bitrate: the data rate for the audio bit stream.
cpresent: this parameter indicates whether audio payload configuration
data is multiplexed into the RTP payload (See section 4.1 in this
document).
config: a hexadecimal representation of octet string indicating the
audio payload configuration data "StreamMuxConfig" defined in ISO/IEC
14496-3 [5]. The configuration data is mapped into the octet string in
an MSB-first basis. The first bit of the configuration data shall be
located at the MSB of the first octet. In the last octet, zero-padding
bits shall follow the configuration data, if necessary.
ptime: RECOMMENDED duration of each packet in milliseconds.
Published specification:
The payload format specification is described in this document. The
specification of encoding is provided in ISO/IEC 14496-3 [3][5].
Encoding considerations:
This type is only defined for transfer via RTP [RFC YYYY, draft-ietf-
avt-rtp-new].
Security considerations:
See section 9 of RFCXXXX.
Interoperability considerations:
MPEG-4 Audio provides a large and rich set of tools for the coding of
visual objects. In order to allow effective implementations of the
standard, subsets of the MPEG-4 Audio tool sets have been identified
similar to MPEG-4 Audio (See section 6.1).
The audio stream SHALL be compliant with the MPEG-4 Audio
Profile@Level specified by the parameter "profile-level-id". The
interoperability between a sender and a receiver may be achieved by
specifying the parameter "profile-level-id" in MIME content, or by
exchanging this parameter in the capability exchange procedure.
Furthermore, the "object" parameter can be used to limit the
capability within the specified Profile@Level in capability exchange.
Applications which use this media type:
Audio and video streaming and conferencing tools.
Additional information: none
Personal & email address to contact for further information:
See section 9 of RFCXXXX.
Intended usage: COMMON
Author/Change controller:
See section 9 of RFCXXXX.
6.4 SDP usage of MPEG-4 Audio
The MIME media type audio/MP4A string is mapped to fields in the Session
Description Protocol (SDP), RFC 2327, as follows:
o The MIME type (audio) goes in SDP "m=" as the media name.
o The MIME subtype (MP4A) goes in SDP "a=rtpmap" as the encoding name.
o The required parameter "rate" goes in "a=rtpmap" as clock rate.
o The optional parameter "ptime" goes in SDP "a=ptime" attribute.
o The optional parameter "profile-level-id" goes in "a=fmtp" line to
indicate the coder capability. The "object" parameter goes in "a=fmtp"
attribute. Any payload-format-specific parameters "bitrate", "cpresent"
and "config" go in "a=fmtp" line. The format and syntax of these
parameters is the MIME media type string as a semicolon separated list of
parameter=value pairs.
The followings are some examples of the media representation in SDP:
For 6 kb/s CELP bitstream (the audio sampling rate of 8 kHz),
m=audio 49230 RTP/AVP 96
a=rtpmap:96 MP4A/8000
a=fmtp:96 profile-level-id=9;object=8;cpresent=0;config=9128B1071070
a=ptime:20
For 64 kb/s AAC LC stereo bitstream (the audio sampling rate is 24 kHz),
m=audio 49230 RTP/AVP 96
a=rtpmap:96 MP4A/24000
a=fmtp:96 profile-level-id=1; bitrate=64000; cpresent=0;
config=9122620000
In the above two examples, the audio configuration data is not
multiplexed into the RTP payload and is described only in SDP.
Furthermore, the "clock rate" is set to the audio sampling rate. If it is
set to its default, the audio sampling rate can be obtained by parsing
the "config" parameter.
The following example shows that the audio configuration data appears in
the RTP payload. The value specified in "config" parameter is used as an
initial value to setup coding parameters.
m=audio 49230 RTP/AVP 96
a=rtpmap:96 MP4A/90000
a=fmtp:96 cpresent=1; config=9128B1071070
7. Security Considerations
RTP packets using the payload format defined in this specification are RTP packets using the payload format defined in this specification are
subject to the security considerations discussed in the RTP specification subject to the security considerations discussed in the RTP specification
[8]. This implies that confidentiality of the media streams is achieved [8]. This implies that confidentiality of the media streams is achieved
by encryption. Because the data compression used with this payload format by encryption. Because the data compression used with this payload format
is applied end-to-end, encryption may be performed on the compressed data is applied end-to-end, encryption may be performed on the compressed data
so there is no conflict between the two operations. so there is no conflict between the two operations.
This payload type does not exhibit any significant non-uniformity in the This payload type does not exhibit any significant non-uniformity in the
receiver side computational complexity for packet processing to cause a receiver side computational complexity for packet processing to cause a
potential denial-of-service threat. potential denial-of-service threat.
7. References 8. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, 1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9,
RFC 2026, October 1996. RFC 2026, October 1996.
2 ISO/IEC 14496-2:1999, "Information technology - Coding of audio-visual 2 ISO/IEC 14496-2:1999, "Information technology - Coding of audio-visual
objects - Part2: Visual", December 1999. objects - Part2: Visual", December 1999.
3 ISO/IEC 14496-3:1999, "Information technology - Coding of audio-visual 3 ISO/IEC 14496-3:1999, "Information technology - Coding of audio-visual
objects - Part3: Audio", December 1999. objects - Part3: Audio", December 1999.
skipping to change at page 13, line 25 skipping to change at page 20, line 47
6 ISO/IEC 14496-1:1999, "Information technology - Coding of audio-visual 6 ISO/IEC 14496-1:1999, "Information technology - Coding of audio-visual
objects - Part1: Systems", December 1999. objects - Part1: Systems", December 1999.
7 Bradner, S., "Key words for use in RFCs to Indicate Requirement 7 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997 Levels", BCP 14, RFC 2119, March 1997
8 H. Schulzrinne, S. Casner, R. Frederick, V. Jacobson "RTP: A Transport 8 H. Schulzrinne, S. Casner, R. Frederick, V. Jacobson "RTP: A Transport
Protocol for Real Time Applications", RFC 1889, Internet Engineering Protocol for Real Time Applications", RFC 1889, Internet Engineering
Task Force, January 1996. Task Force, January 1996.
9 ISO/IEC 14496-2/DCOR1, October 1999. 9 ISO/IEC 14496-2/COR1, "Information technology - Coding of audio-visual
objects - Part2: Visual, Technical corrigendum 1", March 2000.
10 T. Turletti, C. Hitema, "RTP Payload Format for H.261 Video Streams",
RFC 2032, Octover 1996.
8. Author's Addresses 9. Author's Addresses
Yoshihiro Kikuchi Yoshihiro Kikuchi
Toshiba corporation Toshiba corporation
1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan
Email: kiku@eel.rdc.toshiba.co.jp Email: yoshihiro.kikuchi@toshiba.co.jp
Yoshinori Matsui Yoshinori Matsui
Matsushita Electric Industrial Co., LTD. Matsushita Electric Industrial Co., LTD.
1006, Kadoma, Kadoma-shi, Osaka, Japan 1006, Kadoma, Kadoma-shi, Osaka, Japan
Email: matsui@drl.mei.co.jp Email: matsui@drl.mei.co.jp
Toshiyuki Nomura Toshiyuki Nomura
NEC Corporation NEC Corporation
4-1-1,Miyazaki,Miyamae-ku,Kawasaki,JAPAN 4-1-1,Miyazaki,Miyamae-ku,Kawasaki,JAPAN
Email: t-nomura@ccm.cl.nec.co.jp Email: t-nomura@ccm.cl.nec.co.jp
skipping to change at line 594 skipping to change at line 940
Email: fukunaga444@oki.co.jp Email: fukunaga444@oki.co.jp
Hideaki Kimata Hideaki Kimata
Nippon Telegraph and Telephone Corporation Nippon Telegraph and Telephone Corporation
1-1, Hikari-no-oka, Yokosuka-shi, Kanagawa, Japan 1-1, Hikari-no-oka, Yokosuka-shi, Kanagawa, Japan
Email: kimata@nttvdt.hil.ntt.co.jp Email: kimata@nttvdt.hil.ntt.co.jp
Full Copyright Statement Full Copyright Statement
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This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
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and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
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