(12) United States Patent
`Imai et al.
`
`USOO6507611B1
`US 6,507,611 B1
`(10) Patent No.:
`Jan. 14, 2003
`(45) Date of Patent:
`
`(54) TRANSMITTING APPARATUS AND
`METHOD, RECEIVING APPARATUS AND
`METHOD, AND PROVIDING MEDIUM
`(75) Inventors: Kenichi Imai, Tokyo (JP); Minoru
`Tsuji, Chiba (JP); Takashi Koike,
`Kanagawa (JP)
`(73) Assignee: Sony Corporation, Tokyo (JP)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/299,509
`(22) Filed:
`Apr. 26, 1999
`(30)
`Foreign Application Priority Data
`May 8, 1998
`(JP) ........................................... 10-125633
`(51) Int. Cl." .............................. H04B 1/38; H04L 5/16
`(52) U.S. Cl. ................
`375/222; 375/220; 375/219
`(58) Field of Search ................................. 375/219, 220,
`375/221, 222, 257; 370/537, 469,453
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,931,250 A * 6/1990 Greszczuk .................. 375/222
`5,687,157 A 11/1997 Imai et al. ........
`... 369/124
`5,848,384 A 12/1998 Hollier et al. .............. 704/831
`
`5.960,035 A * 9/1999 Sridhar et al. .............. 375/219
`6,021,158 A
`2/2000 Schurr et al. ............... 375/211
`6,236,676 B1 * 5/2001 Shaffer et al. .............. 375/222
`
`FOREIGN PATENT DOCUMENTS
`
`5/1997 ............. G1OL/9/14
`
`JP
`9-127989
`* cited by examiner
`Primary Examiner Phuong Phu.
`(74) Attorney, Agent, or Firm-Sonnenschein, Nath &
`Rosenthal
`ABSTRACT
`(57)
`The invention intends to decode and reproduce digital audio
`Signals in real time. A transmission rate of a transmission
`line is detected, and a Selection instructing unit instructs, to
`an encoding Selecting circuit, a coding method which can
`provide coded data having a bit rate corresponding to the
`detected transmission rate. In response to the instruction
`from the Selection instructing unit, the encoding Selecting
`circuit controls a Switch So as to Select one of a plurality of
`encoderS for encoding an audio signal with different coding
`methods. Each frame of the audio signal cut out by a frame
`cutting circuit is Supplied to the encoder Selected by the
`Switch for encoding thereof. Resulting coded data is output
`ted after an ID representing the instructed coding method
`has been added to the coded data in a header inserting
`circuit.
`
`48 Claims, 17 Drawing Sheets
`
`
`
`
`
`
`
`AUDIO
`DATA
`
`FRAME
`CUTTING
`CIRCUIT
`
`SELECTION
`INSTRUCTING
`UNIT
`
`55
`
`
`
`
`
`ENCODING
`SELECTING
`CIRCUIT
`
`53
`
`54
`
`ENCODER
`
`ENCODER
`
`
`
`ENCODER
`
`HEADER
`INSERTING
`CIRCUIT
`
`TO MULTIPLIER 42
`
`Comcast - Exhibit 1006, page 1
`
`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 1 of 17
`
`US 6,507,611 B1
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`
`
`
`
`
`
`SERVER
`
`CLIENT
`TERMINAL
`
`CLIENT
`TERMINA
`
`Comcast - Exhibit 1006, page 2
`
`

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`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 2 of 17
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`US 6,507,611 B1
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`Z XHOM LEN OL
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`
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`TWNHEIXE
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`9 |
`
`9 |7 |
`
`
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`8 |Z |
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`Comcast - Exhibit 1006, page 3
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`

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`U.S. Patent
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`Jan. 14, 2003
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`Sheet 3 of 17
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`US 6,507,611 B1
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`N
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`Comcast - Exhibit 1006, page 4
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`

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`U.S. Patent
`
`Jan. 14, 2003
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`Sheet 4 of 17
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`US 6,507,611 B1
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`Z XHONALEN O 1
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`HEXETCH
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`Z9
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`Comcast - Exhibit 1006, page 5
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`U.S. Patent
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`Jan. 14, 2003
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`Sheet 5 of 17
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`US 6,507,611 B1
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`79
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`9
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`Comcast - Exhibit 1006, page 6
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`U.S. Patent
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`Jan. 14, 2003
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`Sheet 6 of 17
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`US 6,507,611 B1
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`F.G. 6
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`
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`CODED DATA OUTPUTTED
`FROM ENCODER 53m
`
`Comcast - Exhibit 1006, page 7
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`

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`U.S. Patent
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`Jan. 14, 2003
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`Sheet 7 of 17
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`US 6,507,611 B1
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`BOL
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`Z XHOM LEN
`WOH-]
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`cy
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`Comcast - Exhibit 1006, page 8
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`

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`U.S. Patent
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`Jan. 14, 2003
`
`Sheet 8 of 17
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`US 6,507,611 B1
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`
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`'98
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`„N99
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`399
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`HEOOOEC]C
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`18
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`Z8
`
`HECIWEH
`
`WWE HIS 118
`
`(TEOOO
`
`Comcast - Exhibit 1006, page 9
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`

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`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 9 of 17
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`US 6,507,611 B1
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`FIG. 9
`
`AUDIO DATA TRANSMITTING
`PROCESS BY SERVER
`
`S1
`CONNECTING PROCESS
`
`S2
`DETERMINE ABILITY OF
`CLIENT TERMINAL 3
`
`S3
`SET ENCODING SCHEDULE
`
`S4
`UPDATE OF DECODER
`REGUIRED?
`
`M
`
`
`
`S9
`CHANGE
`ENCODING
`SCHEDULE
`
`
`
`TRANSMIT UPDATE
`CONFIRMATION MESSAGE
`
`N
`
`UPDATE APPROVED?
`
`
`
`
`
`DECODER UPDATING
`PROCESS
`
`S8
`TRANSMIT AUDIO DATA
`
`Comcast - Exhibit 1006, page 10
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`

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`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 10 Of 17
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`US 6,507,611 B1
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`FIG 10A
`
`SERVER 1
`
`CLIENT TERMINAL 3
`
`ASSEF
`YSTEM
`NSMT
`INFORMATION
`INFORMATION--
`
`CLIENT PROCESSING
`ABILITY
`
`FIG 10B
`
`SERVER 1
`TRANSMISSION
`OF "SYSTEM
`NFORMATION
`REQUEST"
`
`CLIENT TERMINAL 3
`
`REOUEST
`SYSTEM
`INFORMATION
`- C -
`ACOUIRE
`SYSTEM
`INFORMATION
`
`TRANSMIT
`SYSTEM
`INFORMATION
`
`O
`CLIENT PROCESSING
`ABILITY
`
`O
`
`FIG. OC
`
`SERVER 1
`TRANSMISSION
`OF DUMMY
`DATA
`
`CLIENT TERMINAL 3
`
`TRANSMIT
`DUMMY DATA re
`
`
`
`
`
`
`
`TRANSMIT
`
`DECODING TIME reu
`
`CLIENT PROCESSING
`ABILITY
`
`Comcast - Exhibit 1006, page 11
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`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`( W)
`
`US 6,507,611 B1
`
`
`
`Sheet 11 Of 17
`
`|||||||ET[nO]EHOS
`8Z78Z|-0N|GJOONE
`
`Comcast - Exhibit 1006, page 12
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`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 12 Of 17
`
`US 6,507,611 B1
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`FIG. 12
`
`AUDIO DATA RECEIVING
`PROCESS BY CLIENT TERMINAL
`
`S11
`RECQUEST CONNECTION
`
`S12
`
`NOT
`UPDATE
`
`
`
`S18
`
`TRANSMIT
`DSAPPROVAL
`OF UPDATE
`
`
`
`N
`
`S13
`UPDATE CONFIRMATION
`MESSAGE TRANSMITTED?
`Y
`
`S14
`DETERMINE APPROVAL /
`DSAPPROVAL OF UPDATE
`UPDATE
`
`S15
`
`TRANSMIT UPDATE RECQUEST
`
`UPDATING PROCESS
`
`S16
`
`S17
`RECEIVE AND DECODE
`AUDIO DATA
`
`Comcast - Exhibit 1006, page 13
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`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 13 Of 17
`
`US 6,507,611 B1
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`FIG. 13
`
`SERVER 1
`
`CLIENT
`TERMINAL 3
`
`REQUEST
`FROM
`CLIENT
`
`RECEPTION TIME t
`TRANSMITTED
`BACKET LENGTH n1
`
`REPLY FROM
`SERVER
`
`RECQUEST
`FROM
`CLIENT
`
`RECEPTION TIME t2
`RECEIVED
`BACKET LENGTH n2
`
`COMMUNICATION BAND B
`= (n1+n2)/(t2-t1) (bps)
`
`Comcast - Exhibit 1006, page 14
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`

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`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 14 Of 17
`
`US 6,507,611 B1
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`F.G. 14
`
`
`
`TIMING TO REASSESS
`COMMUNICATION STATUS
`
`TRANSMISSION
`START TIME OF
`AUDIO SIGNAL
`
`Comcast - Exhibit 1006, page 15
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`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 15 Of 17
`
`US 6,507,611 B1
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`FIG. 15
`
`CLIENT
`TERMINAL 3
`
`SERVER 1
`
`Ngata
`
`ACK
`
`REPEATED
`S TIMES
`
`ACK
`
`Ngata
`
`ACK
`
`
`
`REARRANGE
`ENCODING
`SCHEDULE
`
`ACK
`
`Comcast - Exhibit 1006, page 16
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`

`

`US. Patent
`
`Jan. 14, 2003
`
`Sheet 16 0f 17
`
`US 6,507,611 B1
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`Comcast - Exhibit 1006, page 17
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`Comcast - Exhibit 1006, page 17
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`
`
`
`
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`

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`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 17 of 17
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`US 6,507,611 B1
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`F.G. 17
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`CODED J H H
`DATA
`
`-> TIME
`
`Comcast - Exhibit 1006, page 18
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`

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`US 6,507,611 B1
`
`1
`TRANSMITTING APPARATUS AND
`METHOD, RECEIVINGAPPARATUS AND
`METHOD, AND PROVIDING MEDIUM
`
`2
`According to a first aspect of the present invention, in a
`transmitting apparatus for outputting coded data resulted
`from encoding a time-Series digital Signal, the transmitting
`apparatus comprises a plurality of coding means for encod
`ing the digital Signal with a plurality of coding methods and
`outputting the coded data, instructing means for instructing,
`from among the plurality of coding methods, one for encod
`ing a part or the whole of the digital signal, Selecting means
`for Selecting the coded data obtained with the coding method
`instructed from the instructing means, adding means for
`adding, to the coded data Selected by the Selecting means,
`coding method information indicating the coding method
`used for obtaining the Selected coded data, and outputting
`means for outputting the Selected coded data added with the
`coding method information.
`According to a Second aspect of the present invention, in
`a transmitting method for use in a transmitting apparatus for
`outputting coded data resulted from encoding a time-Series
`digital Signal, the transmitting apparatus comprises a plu
`rality of coding means for encoding the digital Signal with a
`plurality of coding methods and outputting the coded data,
`and the transmitting method comprises an instructing Step of
`instructing, from among the plurality of coding methods,
`one for encoding a part or the whole of the digital Signal, a
`Selecting Step of Selecting the coded data obtained with the
`coding method instructed in the instructing Step, an adding
`Step of adding, to the coded data Selected in the Selecting
`Step, coding method information indicating the coding
`method used for obtaining the Selected coded data, and an
`outputting Step of outputting the Selected coded data added
`with the coding method information.
`According to a third aspect of the present invention, in a
`providing medium for providing a computer program for
`rendering a computer to execute processing to output coded
`data resulted from encoding a time-Series digital Signal, the
`computer comprises a plurality of coding means for encod
`ing the digital Signal with a plurality of coding methods and
`outputting the coded data, and the computer program
`includes an instructing Step of instructing, from among the
`plurality of coding methods, one for encoding a part or the
`whole of the digital signal, a Selecting Step of Selecting the
`coded data obtained with the coding method instructed in the
`instructing Step, an adding Step of adding, to the coded data
`Selected in the Selecting Step, coding method information
`indicating the coding method used for obtaining the Selected
`coded data, and an outputting Step of outputting the Selected
`coded data added with the coding method information.
`According to a fourth aspect of the present invention, in
`a receiving apparatus for receiving and processing coded
`data resulted from encoding a part or the whole of a
`time-Series digital Signal with one of a plurality of coding
`methods, the receiving apparatus comprises extracting
`means for extracting coding method information added to
`the coded data and indicating the coding method used for
`obtaining the coded data, recognizing means for recognizing
`a decoding method for decoding the coded databased on the
`coding method information, and decoding means for decod
`ing the coded data with the decoding method recognized by
`the recognizing means.
`According to a fifth aspect of the present invention, in a
`receiving method for receiving and processing coded data
`resulted from encoding a part or the whole of a time-Series
`digital Signal with one of a plurality of coding methods, the
`receiving method comprises an extracting Step of extracting
`coding method information added to the coded data and
`indicating the coding method used for obtaining the coded
`data, a recognizing Step of recognizing a decoding method
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to a transmitting apparatus
`and method, a receiving apparatus and method, and a
`providing medium. More particularly, the present invention
`relates to a transmitting apparatus and method, a receiving
`apparatus and method, and a providing medium which are
`Suitably used, for example, in the case of encoding and
`transmitting time-Series digital Signals. Such as audio signals,
`and receiving and decoding the digital signals to reproduce
`them in real time on the receiving Side.
`2. Description of the Related Art
`For example, when digital signals. Such as digital audio
`Signals are transmitted from the transmitting Side to the
`receiving Side via a network, e.g., Internet, it is customary
`that the digital Signals are transmitted after being com
`pressed and encoded into coded data on the transmitting
`Side, and the coded data is decoded on the receiving Side,
`because the data rate of the digital Signals is higher than the
`transmission band (i.e., the transmission rate) of the net
`work. Such transmission and reception of digital Signals is
`performed on the premise that the receiving Side includes a
`decoder corresponding to an encoder provided on the trans
`mitting Side.
`Coded data resulted from encoding made by an encoder
`on the transmitting Side is transmitted to the receiving side
`via a network as mentioned above, but the transmission rate
`of the coded data in the network generally varies due to the
`amount of traffic, etc. Apart from the case where the coded
`data is all downloaded and then decoded on the receiving
`Side, therefore, it may occur in the case of decoding the
`coded data while receiving the same that the transmission of
`the coded data becomes too late to decode and reproduce the
`audio signals in real time if the transmission rate of the
`network lowers below the data rate of the coded data.
`Also, although a System of Internet or any other network
`is designed So as to avoid the transmission of the coded data
`from becoming too late as far as possible, it is nevertheless
`Sometimes difficult to decode and reproduce audio signals in
`real time due to, e.g., the ability of hardware and the
`decoding method of a decoder on the receiving Side.
`More specifically, for example, when the coding method
`of an encoder on the transmitting Side is complex, the
`decoding method of a decoder for decoding the coded data,
`which has been encoded by the encoder, is also usually
`complex. In Such a case, if hardware on the receiving side
`has not a processing ability capable of coping with the
`complex decoding method, decoding of audio signals would
`be too late for the start of reproduction thereof. Further, the
`processing time required for the decoder to decode the coded
`data is greatly affected by the processing ability of hardware
`on the receiving Side. Accordingly, if the processing ability
`of hardware on the receiving Side is lower than expected by
`the transmitting Side, the time taken for decoding the coded
`data would be longer than expected by the transmitting Side,
`thus resulting in a difficulty in decoding and reproducing the
`audio signals in real time.
`SUMMARY OF THE INVENTION
`The present invention has been made in view of the state
`of art Set forth above, and intends to decode and reproduce
`digital signals in real time.
`
`15
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`Comcast - Exhibit 1006, page 19
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`3
`for decoding the coded data based on the coding method
`information, and a decoding Step for decoding the coded
`data with the decoding method recognized in the recogniz
`ing step.
`According to a Sixth aspect of the present invention, in a
`providing medium for providing a computer program for
`rendering a computer to process coded data resulted from
`encoding a part or the whole of a time-Series digital Signal
`with one of a plurality of coding methods, the computer
`program includes an extracting Step of extracting coding
`method information added to the coded data and indicating
`the coding method used for obtaining the coded data, a
`recognizing Step of recognizing a decoding method for
`decoding the coded data based on the coding method
`information, and a decoding Step for decoding the coded
`data with the decoding method recognized in the recogniz
`ing step.
`According to a Seventh aspect of the present invention, in
`a providing medium for providing coded data resulted from
`encoding a time-Series digital Signal, the providing medium
`provides coded data and coding method information that are
`obtained by instructing, from among a plurality of coding
`methods, one for encoding a part or the whole of the digital
`Signal, Selecting the coded data resulted from encoding the
`digital Signal with the instructed coding method, and adding,
`to the Selected coded data, coding method information
`indicating the coding method used for obtaining the Selected
`coded data.
`According to an eighth aspect of the present invention, in
`a transmitting apparatus for transmitting coded data resulted
`from encoding a digital Signal via a predetermined trans
`mission line, the transmitting apparatus comprises a plural
`ity of coding means for encoding the digital Signal with a
`plurality of coding methods and outputting the coded data,
`detecting means for detecting a transmission rate of the
`transmission line, Selecting means for Selecting one of the
`plurality of coding methods which is able to provide coded
`data having a bit rate corresponding to the transmission rate
`of the transmission line, and transmitting means for trans
`mitting the coded data obtained with the coding method
`Selected by Selecting means.
`According to a ninth aspect of the present invention, in a
`transmitting method for use in a transmitting apparatus for
`transmitting coded data resulted from encoding a digital
`Signal via a predetermined transmission line, the transmit
`ting apparatus comprises a plurality of coding means for
`encoding the digital Signal with a plurality of coding meth
`ods and outputting the coded data, and the transmitting
`method comprises a detecting Step of detecting a transmis
`Sion rate of the transmission line, a Selecting Step of Select
`ing one of the plurality of coding methods which is able to
`provide coded data having a bit rate corresponding to the
`transmission rate of the transmission line, and a transmitting
`Step of transmitting the coded data obtained with the coding
`method Selected in the Selecting Step.
`According to a tenth aspect of the present invention, in a
`providing medium for providing a computer program for
`rendering a computer to execute processing to transmit
`coded data resulted from encoding a digital Signal via a
`predetermined transmission line, the computer comprises a
`plurality of coding means for encoding the digital Signal
`with a plurality of coding methods and outputting the coded
`data, and the computer program includes a detecting Step of
`detecting a transmission rate of the transmission line, a
`Selecting Step of Selecting one of the plurality of coding
`methods which is able to provide coded data having a bit rate
`
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`US 6,507,611 B1
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`4
`corresponding to the transmission rate of the transmission
`line, and a transmitting Step of transmitting the coded data
`obtained with the coding method Selected in the Selecting
`Step.
`According to an eleventh aspect of the present invention,
`in a receiving apparatus for receiving coded data resulted
`from encoding a digital Signal via a predetermined trans
`mission line, the receiving apparatus compriseS receiving
`means for receiving the coded data encoded by a coding
`method capable of providing data having a bit rate corre
`sponding to a transmission rate of the transmission line, and
`decoding means for decoding the coded data.
`According to a twelfth aspect of the present invention, in
`a receiving method for receiving coded data resulted from
`encoding a digital Signal via a predetermined transmission
`line, the receiving method comprises a receiving Step of
`receiving the coded data encoded by a coding method
`capable of providing data having a bit rate corresponding to
`a transmission rate of the transmission line, and a decoding
`Step of decoding the coded data.
`According to a thirteenth aspect of the present invention,
`in a providing medium for providing a computer program
`for rendering a computer to execute processing to receive
`coded data resulted from encoding a digital Signal via a
`predetermined transmission line, the computer program
`includes a receiving Step of receiving the coded data
`encoded by a coding method capable of providing data
`having a bit rate corresponding to a transmission rate of the
`transmission line, and a decoding Step of decoding the coded
`data.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a diagram showing an exemplified construction
`of one embodiment of a transmission System to which the
`present invention is applied.
`FIG. 2 is a block diagram showing an exemplified con
`struction of hardware of a server 1 in FIG. 1.
`FIG. 3 is a block diagram showing an exemplified con
`struction of hardware of a client terminal 3 in FIG. 1.
`FIG. 4 is a block diagram showing an exemplified func
`tional construction of the server 1 in FIG. 2.
`FIG. 5 is a block diagram showing an exemplified con
`Struction of a coding unit 41, in FIG. 4.
`FIG. 6 is a diagram Showing a format of data outputted
`from a header inserting circuit 54 in FIG. 5.
`FIG. 7 is a block diagram showing an exemplified func
`tional construction of the client terminal 3 in FIG. 3.
`FIG. 8 is a block diagram showing an exemplified con
`struction of a decoding unit 72 in FIG. 7.
`FIG. 9 is a flowchart for explaining a transmitting process
`executed by the server 1.
`FIGS. 10A to 10C are diagrams each for explaining a
`process executed in step S2 of FIG. 9.
`FIGS. 11A to 11C are charts for explaining change of an
`encoding Schedule.
`FIG. 12 is a flowchart for explaining a receiving process
`executed by the client terminal 3.
`FIG. 13 is a diagram for explaining a manner of deter
`mining the transmission rate of a network 2.
`FIG. 14 is a chart for explaining the timing to change the
`encoding Schedule.
`FIG. 15 is a chart for explaining the timing to change the
`encoding Schedule.
`FIG. 16 is a block diagram showing another exemplified
`construction of the coding unit 41, in FIG. 4.
`
`Comcast - Exhibit 1006, page 20
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`

`S
`FIG. 17 is a chart for explaining a method of transmitting
`coded data to the client terminal.
`
`US 6,507,611 B1
`
`6
`FIG. 4 shows an exemplified functional construction of
`the server 1 in FIG. 2. The illustrated construction is
`basically realized upon the CPU 12 executing the applica
`tion programs Stored in the external Storage 16.
`Audio signals to be provided to the client terminal 3 are
`Supplied to an audio signal input circuit 31. In the audio
`Signal input circuit 31, analog audio Signals are A/D-
`converted into digital audio signals. Then, the audio signal
`input circuit 31 Separates the digital audio signals for each
`of channels, for example, and Supplies them to a coding
`circuit 32.
`More specifically, audio signals of a piece of music, for
`example, are separated for each of respective parts of guitar,
`piano, drum, Song (words), etc. that constitute the piece of
`music together, and are inputted to the audio signal input
`circuit 31 in a Synchronous relation. The audio Signal input
`circuit 31 outputs the audio signals of individual parts
`respectively as the audio signals of individual channels.
`Note that audio signals of two or more parts may be
`inputted to the audio signal input circuit 31 in a mixed
`condition. In this case, the audio Signal input circuit 31
`outputs the audio Signals in the mixed condition.
`Also, audio signals inputted to the audio signal input
`circuit 31 may be in the form of, e.g., MIDI (Musical
`Instrument Digital Interface) data (i.e., data for controlling
`a MIDI Sound Source) rather than the actual audio signals.
`The coding circuit 32 encodes the audio signals from the
`audio signal input circuit 31 at high efficiency.
`More specifically, in the embodiment shown in FIG.4, the
`coding circuit 32 comprises a number M of coding units 41
`to 41 and a multiplexer 42. The coding unit 41 (m=1,
`2, . . . , M) is Supplied with the audio signal of each
`corresponding channel from the audio signal input circuit
`31. The coding unit 41 encodes the audio Signal from the
`audio signal input circuit 31, and Supplies resulting coded
`data to the multiplexer 42. The multiplexer 42 multiplexes a
`number M of coded data outputted from the coding units 41
`to 41 respectively into one line, and Supplies them as
`multiplexed data to a transmitting circuit 33.
`The transmitting circuit 33 converts the multiplexed data
`into a format corresponding to the communication protocol
`adapted for transmitting it via the network 2, and transmits
`resulting data to the client terminal 3 via the network 2.
`FIG. 5 shows an exemplified construction of the coding
`unit 41 in FIG. 4.
`A frame cutting circuit 51 cuts the audio signal (audio
`data) from the audio signal input circuit 31 in units of frame
`having a predetermined length (e.g., a length Suitable for
`coding made by encoders 53 to 53, or a length Suitable for
`packet (network packet) transmission via the network 2),
`and then supplies resulting frames to a Switch 52. The Switch
`52 selects one of the encoders 53 to 53 under control of
`an encoding Selecting circuit 56. Accordingly, each frame
`outputted from the frame cutting circuit 51 is Supplied to one
`of the encoders 53 to 53 through the Switch 52.
`The encoders 53 to 53 (N is two or more) are con
`Structed to encode the audio Signal with different coding
`methods from each other (for example, linear PCM (Pulse
`Code Modulation), ADPCM (Adaptive Differential PCM),
`layers 1, 2, 3 of MPEG (Moving Picture Experts Group),
`ATRAC (Adaptive Transform Acoustic Coding), ATRAC 2,
`and HVXC (Harmonic Vector Excitation Coding)). Stated
`otherwise, in the embodiment, the encoders 53 to 53 are
`prepared by using encoders which perform encoding of the
`audio Signal with various coding methods, including a
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`Embodiments of the present invention will be described
`below.
`FIG. 1 shows an exemplified construction of one embodi
`ment of a transmission System (the term "system” means a
`plurality of devices assembled together in a logical corre
`lation regardless of whether the devices having their own
`constructions are all positioned in the same housing or not)
`to which the present invention is applied.
`In the transmission System, when a request for time-Series
`digital signals, e.g., digital audio signals, is issued from a
`client terminal 3 to a server 1 via a network 2 Such as
`Internet, ISDN (Integrated Service Digital Network) or
`PSTN (Public Switched Telephone Network), the server 1
`encodes the requested audio Signals with a predetermined
`coding method, and resulting coded data is transmitted to the
`client terminal 3 via the network 2. After receiving the coded
`data from the server 1, the client terminal 3 decodes the
`coded data and reproduces the original audio signals in real
`time, for example, (so-called streaming reproduction).
`FIG. 2 shows an exemplified construction of hardware of
`the server 1 in FIG. 1.
`A ROM (Read Only Memory) 11 stores, for example, an
`IPL (Initial Program Loading) program and so on. A CPU
`(Central Processing Unit) 12 executes an OS (Operating
`System), which is stored (recorded) in an external Storage
`16, in accordance with the IPL program stored in the ROM
`11, and also executes various application programs, which
`are stored in the external storage 16, under control of the OS,
`thereby carrying out a coding process of audio signals, a
`transmitting process of coded data resulted from the coding
`process to the client terminal 3, etc. A RAM (Random
`Access Memory) 13 Stores programs, data and So on which
`are necessary for operation of the CPU 12. An input device
`14 is constructed of, e.g., a keyboard, a mouse, a microphone
`or an external interface, and is operated when necessary data
`or command is inputted. The input device 14 is also con
`Structed to function as an interface for accepting input of
`digital audio signals externally applied to the client terminal
`3. An output device 15 is constructed of, e.g., a display, a
`Speaker or a printer, and displayS or outputs necessary
`information. The external Storage 16 comprises a hard disk,
`for example, and Stores the OS and the application programs
`mentioned above. Program modules provided to the client
`terminal 3 and Serving as decoders, described above, are also
`Stored in the external Storage 16. In addition, the external
`Storage 16 Stores other data including data necessary for
`operation of the CPU 22, etc. A communicating apparatuS 17
`carries out control required for communication via the
`network 2.
`FIG.3 shows an exemplified construction of hardware of
`the client terminal 3 in FIG. 1.
`The client terminal 3 is made up of illustrated components
`21-27, i.e., a ROM 21 to a communicating apparatus 27, and
`has a construction basically similarly to that of the Server 1
`made up of the ROM 11 to the communicating apparatus 17.
`Unlike the Server 1, an external Storage 26 Stores, as
`application programs, a program for decoding the coded
`data transmitted from the Server 1, programs for executing
`later-described processing, and So on. A CPU 22 executes
`those application programs to, for example, perform a
`decoding process of the coded data.
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`method which provides a relatively large (high) bit rate of
`the resulting coded data, but can reproduce an audio signal
`with relatively good reproducibility, a method which can
`provides a relatively small (low) bit rate of the resulting
`coded data, but reproduces an audio Signal with relatively
`poor reproducibility, a method which requires a larger
`amount of computation for decoding (Such a method usually
`also requires a larger amount of computation for coding), a
`method which requires a not So large amount of computation
`for decoding, and a method particularly Suitable for coding
`a voice (human Voice).
`One example of the coding method, which provides a
`relatively many bit rate of the resulting coded data, is the
`linear PCM (the coded data resulted with this coding method
`is the same as that obtained by outputting a digital audio
`Signal after A/D conversion as it is). Example of the coding
`method, which provides a relatively less bit rate of the
`resulting coded data (i.e., which provides a high compres
`sion rate), are MPEG layer 3 and ATRAC 2. One example
`of the coding method, which requires a not So large amount
`of computation for decoding, is ATRAC. Further, examples
`of the coding method suitable for a voice are HVXC and a
`method utilizing a linear estimation factor. Incidentally,
`HVXC is one of the methods previously proposed by the
`assignee of this application, and is disclosed in detail in, e.g.,
`Japanese Unexamined Patent Publication No. 9-127989
`(corresponding to U.S. Pat. No. 5,848,387).
`It is here assumed that even in the case of the encoderS all
`employing, e.g., ATRAC 2 only, if bit rates are different from
`each other, this means the use of “different coding methods”.
`In one example, therefore, all the encoders 53 to 53
`perform encoding with ATRAC 2, while data rates of coded
`data outputted from the encoders are 64 Kbps, 32. Kbps, 24
`Kbps, . . . , respectively.
`A Selection instructing unit 55 decides appropriate one
`from a plurality of coding methods corresponding to the
`encoders 53 to 53, as described later, and then instructs the
`encoding Selecting circuit 56 to Select the decided coding
`method. In response to the instruction, the encoding Select
`ing circuit 56 controls the Switch 52 so as to select the
`encoder which performs encoding with the instructed coding
`method. Accordingly, the frame outputted from the frame
`cutting circuit 51 is Supplied to Selected one of the encoders
`53 to 53 (referred to as the selected encoder hereinafter)
`through the Switch 52.
`In the selected one of the encoders 53 to 53, the frame
`Supplied thereto is encoded with the predetermined coding
`method (referred to as the Selected coding method herein
`after because it is executed in the Selected encoder). Coded
`data resulted from encoding made in the Selected encoder is
`supplied to the header inserting circuit 54 where an ID
`(Identification, i.e., coding method information) represent
`ing the Selected coding method is added to the coded data.
`Thus, in the illustrated embodiment, the audio signal is
`encoded with one of a number N of coding methods. Also,
`as described later, the Switch 52 may be changed over
`midway a Sequence of continued encoding of the audio
`Signal. In this case, one portion of the audio Signal is
`encoded with one coding method and the other part of the
`audio signal is encoded with another coding method. Taking
`into account Such a case, the header inserting circuit 54 adds,
`to the coded data of each frame, an ID indicating the coding
`method Selected to encode the frame, i.e., information
`indicating with which one of the coding methods each frame
`of the audio signal has been encoded.
`For example, the ID can be given by assigning unique
`numerals to the encoderS 53 to 53, respectively, and
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`expressing t