We claim:
[Claim 1]
A method for transmitting in a digital broadcast network (715) a plurality of data streams generated from a transport stream (TS), the TS including a plurality of TS packets that each correspond to a fixed-length TS data packet containing digital broadcast data or a NULL packet, at least one of the plurality of the data streams including a plurality of header compressed TS packets, the plurality of TS packets before header compression each having a header (120) including a packet identifier (125) with a predefined length of a plurality of bits, the packet identifier relating to the TS data packet before header compression being any one of a plurality of packet identifiers, the packet identifier relating to the NULL packet before header compression being a predefined packet identifier that is different from the plurality of packet identifiers, the method comprising the steps of:
identifying a header (120) of each of the plurality of TS packets before header compression, characterized by
mapping, with respect to at least one of the plurality of packet identifiers relating to the TS data packets before header compression, a plurality of TS packets to a single physical layer pipe with header compression, said plurality of TS packets consisting of a plurality of TS data packets having the same packet identifier and one or more NULL packets,
generating header compressed TS packets by replacing the packet identifier (125) in each of the headers of the plurality of TS packets which are mapped to the physical layer pipe with header compression with a one-bit indicator (510) indicating whether said TS packet is a NULL packet, the one-bit indicator having a smaller number of bits than the packet identifier, and
transmitting a physical layer frame onto which the physical layer pipe with header compression is mapped, the physical layer frame including (i) the packet identifier relating to the plurality of TS data packets mapped to the physical layer pipe with header compression and a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression, or (ii) the packet identifier relating to the plurality of TS data packets mapped to the physical layer pipe with header compression, a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression, and one or more header compressed NULL packets corresponding to at least part of the one or more NULL packets mapped to the physical layer pipe with header compression. [Claim 2] The method as claimed in Claim 1, wherein
the header of each TS data packet further includes a four-bit length continuity counter that indicates a sequence number of the TS data packet, and
the method further comprises the step of replacing, to generate the header compressed TS data packet, said continuity counter in the header of said TS data packet with a one-bit duplicated packet indicator (520) indicating whether said TS data packet is a repetition of a previously processed packet.
[Claim 3]
The method as claimed in Claim 1, wherein
the header of the TS data packet further includes a transport error indicator for indicating whether the TS data packet has an error, and

the method farther comprises the step of deleting said transport error indicator from the header of said TS data packet to generate the header compressed TS data packet.
[Claim 4]
A method for receiving in a digital broadcast network (715) a plurality of data streams generated from a transport stream (TS), the TS including a plurality of TS packets that each correspond to a fixed-length TS data packet containing digital broadcast data or a NULL packet, at least one of the plurality of data streams including a plurality of header compressed TS packets,
the plurality of TS packets before header compression each having a header (120) including a packet identifier (125) with a predefined length of a plurality of bits, the packet identifier relating to the TS data packet before header compression being any one of a plurality of packet identifiers, the packet identifier relating to the NULL packet before header compression being a predefined packet identifier that is different from the plurality of packet identifiers, characterized by
with respect to at least one of the plurality of packet identifiers relating to the TS data packets before header compression, a plurality of TS packets are mapped to a single physical layer pipe with header compression, said plurality of TS packets consisting of a plurality of TS data packets having the same packet identifier and one or more NULL packets,
the method comprising the steps of:
receiving a physical layer frame onto which the physical layer pipe with header compression is mapped, the physical layer frame including the packet identifier relating to the TS data packets mapped to the physical layer pipe with header compression, and a plurality of header compressed TS packets that are each generated by replacing the packet identifier (125) in each of the headers of the plurality of TS packets with a one-bit indicator (510) indicating whether said TS packet is a NULL packet, the one-bit indicator having a smaller number of bits than the packet identifier, the plurality of header compressed TS packets including (i) a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression or (ii) a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression, and one or more header compressed NULL packets corresponding to at least part of the one or more NULL packets mapped to the physical layer pipe with header compression;
identifying each of compressed headers (500) of the plurality of header compressed TS packets received in the physical layer pipe with header compression; extracting from the physical layer frame onto which the physical layer pipe with header compression is mapped, the packet identifier and the one-bit indicator of each of the compressed headers of the plurality of header compressed TS packets; and specifying the packet identifier of each of the TS packets based on the extracted packet identifier and the one-bit indicator of the header compressed TS packet.
[Claim 5]
An apparatus for transmitting in a digital broadcast network (715) a plurality of data streams generated from a transport stream, TS, the TS including a plurality of TS packets that each correspond to a fixed-length TS data packet containing digital broadcast data or a NULL packet, at least one of the plurality of data streams including a plurality of header compressed TS packets, the plurality of TS packets before header compression each having a header (120)

including a packet identifier (125) with a predefined length of a plurality of bits, the packet
identifier relating to the TS data packet before header compression being any one of a plurality
of packet identifiers, the packet identifier relating to the NULL packet before header
compression being a predefined packet identifier that is different from the plurality of packet
identifiers,
the apparatus comprising
an identifying unit configured to identify the header (120) of each of the plurality of TS packets
before header compression,
characterized by
a mapping unit (630) configured to map, with respect to at least one of the plurality of packet
identifiers relating to the TS data packets before header compression, a plurality of TS packets
consisting of a plurality of TS data packets having the same packet identifier and one or more
NULL packets, to a single physical layer pipe with header compression,
a generating unit (620) configured to generate header compressed TS packets by replacing the
packet identifier (125) in each of the headers of the plurality of TS packets which are mapped
to the physical layer pipe with header compression with a one-bit indicator (510) indicating
whether said TS packet is a NULL packet, the one-bit indicator having a smaller number of
bits than the packet identifier, and
a transmitting unit (650) configured to transmit a physical layer frame onto which the physical
layer pipe with header compression is mapped, the physical layer frame including (i) the packet
identifier relating to the plurality of TS data packets mapped to the physical layer pipe with
header compression and a plurality of header compressed TS data packets corresponding to the
plurality of TS data packets mapped to the physical layers pipe with header compression, or
(ii) the packet identifier relating to the plurality of TS data packets mapped to the physical layer
pipe with header compression, a plurality of header compressed TS data packets corresponding
to the plurality of TS data packets mapped to the physical layer pipe with header compression,
and one or more header compressed NULL packets corresponding to at least part of the one or
more NULL packets mapped to the physical layer pipe with header compression.
[Claim 6]
An apparatus for receiving in a digital broadcast network (715) a plurality of data streams
generated from a transport stream (TS), the TS including a plurality of TS packets that each
correspond to a fixed-length TS data packet containing digital broadcast data or a NULL
packet, at least one of the plurality of data streams including a plurality of header compressed
TS packets, the plurality of TS packets before header compression each having a header (120)
including a packet identifier (125) with a predefined length of a plurality of bits, the packet
identifier relating to the TS data packet before header compression being any one of a plurality
of packet identifiers, the packet identifier relating to the NULL packet before header
compression being a predefined packet identifier that is different from the plurality of packet
identifiers,
characterized by
with respect to at least one of the plurality of packet identifiers relating to the TS data packets
before header compression, a plurality of TS packets are mapped to a single physical layer pipe
with header compression, said plurality of TS packets consisting of a plurality of TS data
packets having the same packet identifier and one or more NULL packets,
the apparatus (600b) comprising:
a receiving unit (660) configured to receive physical layer frame onto which the physical layer
pipe with header compression is mapped, the physical layer frame including the packet
identifier relating to the TS data packets mapped to the physical layer pipe with header
compression, and a plurality of header compressed TS packets that are each generated by

replacing the packet identifier (125) in each of the headers of the plurality of TS packets with a one-bit indicator (510) indicating whether said TS packet is a NULL packet, the one-bit indicator having a smaller number of bits than the packet identifier, the plurality of header compressed TS packets including (i) a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression or (ii) a plurality of header compressed TS data packets corresponding to the plurality of TS data packets mapped to the physical layer pipe with header compression, and one or more header compressed NULL packets corresponding to at least part of the one or more NULL packets mapped to the physical layer pipe with header compression: an identifying unit configured to identify each of compressed headers (500) of the plurality of header compressed TS packets received in the physical layer pipe with header compression; an extracting unit (680) configured to extract, from the physical layer frame onto which the physical layer pipe with header compression is mapped, the packet identifier and the one-bit indicator of each of the compressed headers of the plurality of header compressed TS packets; and
a header decompression unit (695) configured to specify the packet identifier of each of the TS packets based on the extracted packet identifier and the one-bit indicator of the header compressed TS packet.
[Claim 7]
A method for transmitting transport stream packets, TS packets, comprising:
identifying identifiers of the TS packets, the TS packets including headers storing the identifiers, respectively, the identifiers each having a first bit-length, the TS packets including first data packets each having a first identifier and digital broadcast data, second data packets each having a second identifier and digital broadcast data, and a NULL packet having a third identifier;
mapping the first data packets and the second data packets onto a first physical layer pipe and a second physical layer pipe, respectively;
mapping the NULL packet onto the first physical layer pipe and the second physical layer pipe;
replacing the first identifier, the second identifier, and the third identifier with an indicator in order to compress the headers, the indicator having a second bit-length smaller than the first bit-length, the indicator indicating whether a TS packet having the indicator is the NULL packet; and
generating a frame to be transmitted such that the frame includes the first physical layer pipe and the second physical layer pipe.
[Claim 8]
The method as claimed in claim 7, further comprising:
transmitting information to specify mapping of the first data packets and the second data packets.
[Claim 9]
The method as claimed in claim 8, wherein the information includes the identifiers.
[Claim 10]

A method for receiving transport stream packets, TS packets, comprising:
receiving a frame in which a first physical layer pipe and a second physical layer pipe are included, first data packets and second data packets being mapped onto the first physical layer pipe and the second physical layer pipe, respectively, a NULL packet being mapped onto the first physical layer pipe and the second physical layer pipe, the first data packets and the second data packets each including digital broadcast data;
referring to headers of the TS packets including the first data packets, the second data packets, and the NULL packet, the headers each storing an indicator of a second bit-length, the indicator indicating whether a TS packet having the indicator is the NULL packet;
replacing the indicator of each of the first data packets with a first identifier to decompress the header of the each of the first data packets, the first identifier being included in identifiers of the TS packets and identifying the each of the first data packets;
replacing the indicator of each of the second data packets with a second identifier to decompress the header of the each of the second data packets, the second identifier being included in the identifiers and identifying the each of the second data packets; and
replacing the indicator of the NULL packet with a third identifier to decompress the header of the NULL packet, the third identifier being included in the identifiers and identifying the NULL packet, wherein
the identifiers each have a first bit-length larger than the second bit-length.
[Clam 11]
The method as claimed in claim 10, further comprising:
receiving information to specify mapping of the first data packets and the second data packets.
[Claim 12]
The method as claimed in claim 11, wherein the information includes the identifiers.