JP2005354538A - Multiplexing apparatus and multiplexing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiplexing apparatus that can multi-process a 1 bit audio signal obtained by delta sigma processing to a variable bit rate image signal while maintaining a fixed rate without changing the picture quality of the image signal and an output time. <P>SOLUTION: ΔΣ modulation processing is applied to an analog audio signal inputted from an input terminal 2 at a ΔΣ modulator 3 and the 1 bit audio signal is obtained. An MPEG 2-TS signal including the 1 bit audio signal obtained by the ΔΣ modulation and a variable bit rate image signal inputted from an input terminal 4 are transferred to a MPEG 2-TS signal editing machine 5. The MPEG 2-TS editing machine 5 embeds the 1 bit audio signal obtained by the ΔΣ modulation into the MPEG 2-TS signal, and outputs it to an output terminal 6 as the MPEG 2-TS signal including the variable bit rate image signal and the 1 bit audio signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multiplexing apparatus and multiplexing method for multiplexing audio data and video data, and in particular, a 1-bit audio signal obtained by subjecting an analog audio signal to ΔΣ modulation processing can be changed while maintaining a fixed bit rate. The present invention relates to a multiplexing apparatus and a multiplexing method for multiplexing on a bit rate video signal.

  Delta-sigma-modulated 1-bit audio signals have a very high sampling frequency and short data compared to the data format used in conventional digital audio (for example, the sampling frequency is 44.1 KHz and the data word length is 16 bits). It is characterized by a word length (for example, sampling frequency is 64 times 44.1 KHz and data word length is 1 bit), and the transmittable frequency band is wide. Further, even with a 1-bit signal by ΔΣ modulation, a high dynamic range can be ensured in an audio band that is low with respect to an oversampling frequency of 64 times. Utilizing this feature, it can be applied to high-quality recorders and data transmission.

  The ΔΣ modulation circuit itself is not a new technology in particular, and its circuit configuration is suitable for IC integration, and AD conversion accuracy can be obtained relatively easily. Circuit.

  The ΔΣ-modulated signal can be converted back to an analog audio signal by passing it through a simple analog low-pass filter.

  In addition, there is an international standard called MPEG (Moving Picture Expert Group) for encoding video signals. In MPEG, video signals are compressed by removing redundancy in the spatial domain and the temporal domain. Discrete cosine transform is used to remove redundancy in the spatial domain. When an image is converted into data in the spatial frequency domain, the data is biased toward the low frequency side. As a result, by assigning a smaller number of bits to high-frequency data, an image can be encoded with a smaller number of bits than before conversion. Interframe prediction is used to remove redundancy in the time domain. A moving image is composed of images called a plurality of frames. In many cases, each image is similar between a frame and the immediately preceding frame, which is an image 1/30 second before. Therefore, if only the difference from the current frame is extracted and encoded based on the immediately preceding frame, the number of bits can be reduced. This is called interframe prediction. In MPEG encoding, by assigning more data to locations where the difference is large and using less data to locations where the difference is small, the overall data amount can be further reduced without degrading image quality. This indicates that the transmission path has a variable bit rate.

  Further, there is an international standard called MPEG2 TransportStream (hereinafter referred to as MPEG2-TS) as a multiplexing method of video signals, audio signals, and other additional digital signals. The MPEG2-TS digital signal is divided into 188-byte fixed-length packets (hereinafter referred to as TS packets) and transmitted. The TS packet includes items indicating a cyclic counter, a bit error display, and the like, and is assumed to be applied to an environment in which a data transmission error occurs, such as broadcasting or a communication network. MPEG2-TS is used in communication channels with a fixed transmission rate. Examples of practical use include SkyperfecTV, DirecTV, and BS digital broadcasting.

  MPEG2-TS can transmit a packet including time information (Program Clock Reference: hereinafter, PCR). The PCR includes time information referred to by the decoder, and is configured so that the time of the decoder can be set at the time intended on the encoder side. In MPEG2-TS, PCR is transmitted at regular intervals, and the interval is set to 0.1 seconds or less.

  In the multiplexing of digital signals, the multiplexing method of video signals and audio signals with a fixed bit rate is easy if the bit rate of each digital signal is used. What is necessary is just to multiplex so that the signal amount of each digital signal transmitted may become fixed in a certain time interval. This method is used in commercially available multiplexing software.

  Japanese Patent Laid-Open No. 08-172614 discloses a configuration in which a delta-sigma modulation circuit is used for analog / digital conversion of an audio signal in an audio / video multiplex transmission apparatus that multiplexes video signals and audio signals and performs digital transmission. Has been. A memory that reads and accumulates video signals with a predetermined amount of information and reads the video signal data at the timing specified by the transmission frame, and converts the analog audio signal into digital data at each clock cycle of a predetermined frequency by delta-sigma modulation. A delta-sigma modulator that converts and outputs the transmission frame in a predetermined cycle, and multiplexes video signal data output from the memory and audio signal data output from the delta-sigma modulator to generate a serial signal. And a multiplex circuit for outputting.

JP 08-172614 A

  By the way, in the above-mentioned Patent Document 1, the video signal has a predetermined rate, that is, a fixed rate, and a fixed-rate delta-sigma modulation signal is multiplexed on the fixed-rate video signal. As described above, in the multiplexing of digital signals, multiplexing of video signals and audio signals with a fixed bit rate is easy if the bit rate of each digital signal is used. What is necessary is just to multiplex so that the signal amount of each digital signal transmitted may become fixed in a certain time interval.

  On the other hand, the multiplexing of video signal and digital audio signal of variable bit rate is a multi-purpose such as data transmission using a digital versatile disk (DVD) or a network having a high-speed transmission path, which is reproduced by a personal computer. It will become indispensable in the field of media data transmission.

  However, at present, for example, the image quality and output time of a 1-bit audio signal obtained by delta-sigma modulation processing at a fixed rate with a variable bit rate video signal encoded by MPEG at a fixed rate. It was difficult to multiplex without changing the above. Since the amount of data of the 1-bit audio signal is large, if this audio signal and a data portion that requires a high bit rate of a video signal with a variable bit rate are multiplexed, a predetermined transmission rate may be exceeded. There will be a hindrance to transmission.

  The present invention has been made in view of the above circumstances, and the image signal quality and output time of a video signal of variable bit rate are set to a video signal of variable bit rate while the 1-bit audio signal obtained by the delta-sigma modulation processing is kept at a fixed rate. It is an object of the present invention to provide a multiplexing apparatus and a multiplexing method that can perform multiplexing processing without change.

  In order to solve the above problems, a multiplexing apparatus according to the present invention multiplexes a 1-bit audio signal obtained by subjecting an analog audio signal to ΔΣ modulation processing to a video signal having a variable bit rate while maintaining a fixed bit rate. Is a multiplexing device that extracts a reference clock arranged at a predetermined time interval in a plurality of continuous packets including a video signal of a variable bit rate, and detects the predetermined time interval between the extracted reference clocks Calculated by the time interval detecting means, unnecessary packet number calculating means for calculating the number of packets unnecessary for transmission in each predetermined time interval detected by the time interval detecting means, and the unnecessary packet number calculating means. Minimum unnecessary packet numerical value detecting means for calculating the minimum value of the number of unnecessary packets at all time intervals, and the minimum unnecessary packet number. If the number of packets including the 1-bit audio signal per predetermined time interval is less than the minimum number of unnecessary packets detected by the packet numerical value detecting means, the 1-bit audio signal per predetermined time interval is included in all time intervals. Embedding means for embedding a plurality of packets.

  In the multiplexing apparatus according to the present invention, the embedding unit calculates the number of packets including the 1-bit audio signal necessary per the predetermined time interval, compares the number with the minimum value of the number of unnecessary packets, and determines the number of unnecessary packets. If there are more, the same number of invalid data packets as the difference packet number are embedded in all time intervals, and then a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals.

  The multiplexing apparatus according to the present invention further includes invalid data packet replacing means for replacing unnecessary packets in the predetermined time intervals calculated by the unnecessary packet number calculating means with invalid data packets having the same number of packets, The minimum unnecessary packet numerical value detecting means detects the number of invalid data packets corresponding to the minimum value among the invalid data packets in all the time intervals replaced by the invalid data packet replacing means, and the embedding means includes: A plurality of packets including the 1-bit audio signal having a smaller number of packets than the invalid data packets having the minimum number of packets detected by the minimum unnecessary packet numerical value detecting means are embedded in the invalid data in all the time intervals. Also good.

  Further, the embedding means has the same number of packets as the difference when the number of packets including the 1-bit audio signal is larger than the number of invalid data packets with the minimum number of packets detected by the minimum unnecessary packet numerical value detection means. After invalid data packets are embedded in all time intervals, a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals.

  In order to solve the above problems, a multiplexing method according to the present invention multiplexes a 1-bit audio signal obtained by subjecting an analog audio signal to ΔΣ modulation processing to a video signal having a variable bit rate while maintaining a fixed bit rate. Is a multiplexing method for extracting a reference clock arranged at a predetermined time interval in a plurality of continuous packets including a video signal with a variable bit rate, and detecting the predetermined time interval between the extracted reference clocks Calculated by the time interval detecting step, the unnecessary packet number calculating step for calculating the number of packets unnecessary for transmission in each predetermined time interval detected by the time interval detecting step, and the unnecessary packet number calculating step. A minimum unnecessary packet value detection step for calculating a minimum value of the number of unnecessary packets at all time intervals, If the number of packets including the 1-bit audio signal per predetermined time interval is smaller than the minimum number of unnecessary packets detected by the packet numerical value detection step, the 1-bit audio signal per predetermined time interval is included in all time intervals. And an embedding step of embedding a plurality of packets.

  In the embedding step, the number of packets including the 1-bit audio signal necessary per the predetermined time interval is calculated, and compared with the minimum value of the number of unnecessary packets. The same number of invalid data packets are embedded in all time intervals, and then a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals.

  The multiplexing method according to the present invention further includes an invalid data packet replacing step of replacing unnecessary packets in the predetermined time intervals calculated by the unnecessary packet number calculating step with invalid data packets having the same number of packets. The minimum unnecessary packet numerical value detection step detects the number of invalid data packets corresponding to the minimum value among the invalid data packets in all the time intervals replaced by the invalid data packet replacement step, and the embedding step Embeds a plurality of packets including the 1-bit audio signal having a smaller number of packets than the invalid data packets having the minimum number of packets detected in the minimum unnecessary packet numerical value detection step in the invalid data in all the time intervals.

  In the embedding step, when there are more plural packets including the 1-bit audio signal than the number of invalid data packets with the minimum number of packets detected by the minimum unnecessary packet numerical value detection step, the number of invalid data is the same as the number of packets of the difference. After embedding packets in all time intervals, a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals.

  In the present invention, based on MPEG2-TS including a variable bit rate video signal, the minimum information necessary for MPEG2-TS transmission, a TS packet including video signal and time information (PCR) is left, and others The TS packet is converted into a TS packet including a 1-bit audio signal.

  Since the video signal has a variable bit rate, the ratio of the number of TS packets including the video signal is high at a certain time interval, and the transmission bit rate of the TS packet including the 1-bit audio signal cannot be kept fixed (overflow). The same number of TS packets are inserted between the PCRs adjacent to each other, and the TS packets containing the overflowing 1-bit audio signal are allocated to the inserted TS packets. . When it is not used as a TS packet including a 1-bit audio signal, an invalid data packet (hereinafter referred to as a NULL packet) is used.

  Finally, the TS packet information including the 1-bit audio signal is added to the TS packet including information necessary for MPEG2-TS transmission.

  According to the present invention, in MPEG2-TS including a video signal with a variable bit rate, the relationship between the PCR and the decoding / reproduction time of the video signal is kept consistent. Also, inserting the same number of TS packets between two adjacent PCRs means that the bit rate of the entire MPEG2-TS is increased. Even when the bit rate increases, the PCR value and video signal decoding / playback time value are not changed, so the video signal decoding system is the same as before TS packet insertion and the processing is the same. -Does not affect playback time.

  Also, by keeping the transmission bit rate of TS packets including 1-bit audio signals fixed, it is possible to reproduce audio signals without interruption.

  According to the multiplexing apparatus and the multiplexing method of the present invention, an analog audio signal is converted to a ΔΣ-modulated 1-bit audio signal and multiplexed with the video signal, and the video signal has a variable bit rate. At this time, the bit rate in the multiplexing is converted to enable multiplexing while keeping the 1-bit audio signal at a fixed rate. In other words, the 1-bit audio signal obtained by the delta-sigma modulation process is multiplexed at a fixed bit rate without changing the image quality and output time of the video signal.

  Multiplexing of a variable bit rate video signal and a digital signal is indispensable in the field of multimedia data transmission, and further development of the 1-bit audio signal in the MPEG standard is expected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is a multiplexing apparatus that multiplexes a stereo 2ch 1-bit audio signal and a high-definition quality video signal. In particular, the high-definition quality video signal is an MPEG2-TS signal including a variable bit rate video signal.

  FIG. 1 is a block diagram of a multiplexing apparatus 1 according to the present embodiment. The analog audio signal 22 input from the input terminal 2 is subjected to ΔΣ modulation processing by the ΔΣ modulator 3 to obtain a 1-bit audio signal 23. The MPEG2-TS signal 21 including the 1-bit audio signal 23 obtained by the ΔΣ modulation and the variable bit rate video signal input from the input terminal 4 is transmitted to the MPEG2-TS signal editor 5.

  The MPEG2-TS signal editor 5 embeds the 1-bit audio signal 23 obtained by the ΔΣ modulation in the MPEG2-TS signal 21 as an MPEG2-TS signal 24 including a variable bit rate video signal and a 1-bit audio signal. Output to the output terminal 6.

  An MPEG2-TS signal 21 including a video signal with a variable bit rate is generated by the MPEG2 multiplexer 10 having the configuration shown in FIG. In FIG. 2, video data 11, audio data 12, and other data 13 are converted into corresponding encoding devices, that is, an MPEG2 video encoding device 14, an MPEG2 audio AAC (Advanced Audio Coding) encoding device 15 and others. The encoded stream data (also referred to as elementary streams) 17, 18 and 19 are obtained.

  The MPEG2 video encoding device 14 compresses the video signal using a compression technique such as motion compensation prediction, discrete cosine transform DCT, quantization, or variable length encoding. Motion compensated prediction uses temporal redundancy to reduce the amount of information. Discrete cosine transform reduces the amount of information using spatial redundancy within the screen.

  The MPEG2 audio AAC encoding device 15 encodes audio data having a sampling frequency of 8 to 96 kHz. The number of channels and the bit rate can be arbitrarily selected. In the case of stereo 2ch, the bit rate is approximately within 200kbps.

  The multiplexing unit 20 multiplexes these elementary streams to generate a unified transport stream (also referred to as a multiplexed stream) 21. In particular, in the method defined in MPEG2, at the time of this multiplexing, synchronization information such as PCR described later with respect to the time axis of the image and the sound signal is also recorded in the transport stream.

  The other encoding device 13 encodes, for example, information PSI necessary for transmission and digital storage media information DSMI. Information necessary for transmission is also called program specification information (Program Specific Information: PSI), which is essential information for MPEG2-TS transmission. The digital storage media information DSMI is information required when receiving a digital broadcast and recording it on a medium, for example.

  In the multiplexing unit 20, the stream data 17 from the MPEG2 video encoding device 14, the stream data 18 from the MPEG2 audio AAC encoding device 15, and the stream data 19 from other encoding devices 16, regardless of the type, Register FIFO. The transmission channel is divided into packet lengths, and each packet packet is sent to the transmission channel according to FIFO registration every time a packet slot arrives. Even if a packet slot arrives, if the FIFO registration is empty, an invalid data (NULL) packet is inserted. In this way, the multiplexing unit 20 forms the transport stream TS.

  FIG. 3 is a diagram illustrating the structure of the transport stream TS multiplexed by the multiplexing unit 20. As shown in FIG. 3A, the transport stream TS is configured by multiplexing transport packets having a fixed length of 188 bytes (bytes). FIG. 3B is a diagram illustrating the structure of a TS packet. It consists of 4-byte header (Hader) information and 184-byte (bytes) TS payload. As shown in FIG. 3C, the 8-bit synchronization signal (SyncByte) in the header information indicates the TS start code, and is used to detect the beginning of the TS packet by the MPEG decoder on the receiving device side. Used. The error indication (1 bit) indicates the presence or absence of a bit error in this TS packet. The unit start display (1 bit) indicates whether the payload starts from the beginning of the data unit of video, audio, or PSI. The priority indication (TS packet priority, 1 bit) indicates the importance of this TS packet. PID (Packet Identification, 13 bits) is a packet identifier and stream identification information. Scramble control (2 bits) indicates whether or not the payload portion is scrambled. The adaptation field (AF) control (2 bits) indicates the presence / absence of an adaptation field to be described later. The structure shown in FIG. 3 has no adaptation field. The cyclic counter (4 bits) determines whether or not a part of the packets having the same PID is partially discarded based on the continuity of the count information. The cyclic counter is always 0x0 for null packets. The TS payload contains video data, audio data, and PSI data. In the case of a NULL packet, the payload area is filled with 0xFF.

  FIG. 4 shows a TS packet structure with an adaptation field. The adaptation field control of the header information indicates that there is an adaptation field (FIG. 4B). The first 8 bits of the adaptation field indicate the adaptation field length. In the discontinuous display, it is indicated that the system clock is reset and new contents are obtained in the next packet having the same PID. The random access display indicates the start of a video sequence header or audio frame, and the entry point at the time of random access can be detected by this random access display. The stream priority indication indicates that an important part of the individual stream is in the payload of this packet. A flag is provided after the stream priority display, and an optional field of conditional coding is set by this flag. After this optional field, a stuffing byte that is invalid data is provided as necessary.

  In the optional field, as shown in FIG. 4C, a PCR field (48 bits) in which a PCR value as time reference information is set, an OPCR (Original Program Clock Referene) as an original program reference time, and editable. A splice countdown indicating the number of transport packets with the same PID up to a point is placed. In the 48-bit PCR field, PCRBase (33 bits), res (6 bits), and PCRExtension (9 bits) are described as shown in FIG. PCR is 27 MHz.

  PSI (Program Specific Information) necessary for transmission of the TS packet is stored in the payload portion of the TS packet as shown in FIG. Types of PSI necessary for MPEG2-TS transmission include PAT (Program Association Table) and PMT (Program Map Table) having a hierarchical data structure. PAT represents the PID and program identification number of the program map table ProgramMapTable. PMT designates PID of elements (video, audio, etc.) constituting the program.

  FIG. 6 is a diagram illustrating an example of a hierarchical data structure. FIG. 6A shows a TS packet including PAT (PID: 0x00 fixed). PAT data specifying PMT PID (0x10) is included in the TS payload. FIG. 6B shows a TS packet including PMT (PID: 0x10). Contains PMT data that specifies the PID of each element. For example, PID (0x60) of a TS packet including video data, PID (0x70) of a TS packet including audio data, and the like. FIG. 6C shows a TS packet containing video (PID: 0x60), and FIG. 6D shows a TS packet containing audio (PID: 0x70).

  The MPEG2-TS signal editor 5 shown in FIG. 1 includes the TS packet including video data, the TS packet including audio data, the PSITS packet including PSI data, the NULL packet, and the digital data described above. A transport stream composed of packets composed of storage media information is input as an MPEG2-TS signal including the video signal of the variable bit rate.

  FIG. 7 is a specific example of the transport stream TS multiplexed by the multiplexing unit 20 and input to the MPEG2-TS signal editor 5. TS packets A1 including audio data follow TS packets V1 and V2 including video data, an invalid data (NULL) packet is inserted, and information necessary for transmission (program specific information: PSI) is included. TS packet P, TS packets V3 and V4 including video data, NULL packet, TS packets V5 and V6, and digital storage media information DSMI follow in the time axis t direction. Both are TS packets with a fixed length of 188 bytes.

  Here, the packet composed of the above-mentioned digital storage media information DSMI is necessary for, for example, BS digital broadcasting, as specifying recording on a medium such as a magneto-optical disk, a hard disk drive (HDD), a semiconductor memory, or a magnetic tape. However, it is unnecessary information from the viewpoint of simply transmitting and receiving MPEG2-TS packets and playing them back.

  In the present invention, the high-quality 2-channel 1-bit audio signal obtained by the ΔΣ modulator 3 in the MPEG2-TS signal editor 5 is converted into an MPEG2-TS signal including the video signal of the variable bit rate. Since multiplexing is performed, TS packets (by the MPEG2AAC audio encoder) that already include the audio data multiplexed by the multiplexing unit 20 shown in FIG. 2 are unnecessary.

  Therefore, the MPEG2-TS signal editor 5 uses the minimum information (PSI information), video data, and time information necessary for transmission with respect to the MPEG2-TS signal 21 including the original variable bit rate video signal. The TS packet including (PCR) is left, and the packet including the digital storage media information DSMI and the packet unnecessary for the system such as the audio TS packet are converted into the TS packet including the 2ch high-quality 1-bit audio signal. Replace.

  FIG. 8 shows the configuration of the ΔΣ modulator 3 that generates the high-quality 1-bit audio signal 23. This ΔΣ modulator 3 is configured by a combination of one integrator 32 and one 1-bit quantizer 33 and a feedback system of the quantized output thereof. Specifically, an adder 31 in which an input signal G is supplied to a positive input terminal and a feedback output to be described later is supplied to a negative input terminal, an integrator 32 that performs integration processing on the addition output of the adder 31, and the integration And a 1-bit quantizer 33 that quantizes the integrated output of the multiplier 32 into a 1-bit digital signal every sampling period. The quantized output H of the 1-bit quantizer 33 is fed back to the adder 31 as a negative sign, and added (subtracted as a result) to the input signal G. A 1-bit digital signal H is derived from the 1-bit quantizer 33 as a quantized output. The integrator 32 includes an adder 32a and a delay unit 32b.

  Here, as shown in FIG. 9, the 1-bit quantizer 33 performs a quantization process on the input signal X (n) with reference to a threshold value Th that is invariant with respect to time and is always 0. 1-bit output signal Y (n) is generated. That is, the 1-bit quantizer 33 determines a binary level between 0 and less than 0 with respect to the input signal X (n) as a boundary, and performs a quantization process.

  Further, FIG. 10 shows a configuration of a ΔΣ modulator 40 including a plurality of integrators. The ΔΣ modulator 40 shown in FIG. 10 is a fifth-order ΔΣ modulator including five integrators 43, 46, 49, 52 and 55. In addition, this ΔΣ modulator 40 includes adders 42, 45, 48, 51 and 54 for adding a multi-bit digital signal to each integrator before the five integrators 43, 46, 49, 52 and 55. And four attenuators 44, 47, 50 and 53 connected after the first to fourth integrators 43, 46, 49 and 52 of the five integrators, and the fifth integrator. The 1-bit quantizer 56 connected to the back of the generator 55 is the same as the 1-bit quantizer 33, and the bit length of the 1-bit digital signal from the 1-bit quantizer 56 is converted into multiple bits. A bit length converter 57 supplied to the adders 42, 45, 48, 42 and 54 so as to be input to the integrators 43, 46, 49, 52 and 55.

  The first integrator 43 integrates the input signal supplied via the input terminal 41 and the adder 42. Therefore, the output from the adder similar to the adder 32a shown in FIG. 8 is delayed by the delay device similar to the delay device 32b and returned to the adder. The same applies to the second to fifth integrators 46, 49, 52 and 55. The integration output from the fifth integrator 55 is supplied to the 1-bit quantizer 56.

The 1-bit quantizer 56 may set the threshold level Th referred to in the quantization process to a threshold value that is constant with respect to time and always 0, as shown in FIG. Then, Δq based on the amplitude obtained in the integrator in the final stage may be used. Specifically, a value SαD _end obtained by multiplying the maximum value D _end of the amplitude of the signal generated in the final stage integrator by a constant Sα is set as an optimum variable threshold level Δq. That is, Δq = SαD _end is calculated. If this calculation method is used, a result obtained by multiplying a constant uniquely determined by any ΔΣ modulation configuration can be set to an optimum variable threshold level.

In this way, when Δq is calculated based on the amplitude D _end of the signal inside the fifth integrator 55 which is the final stage, the 1-bit quantizer 56 applies the quantum applied to the integration output of the fifth integrator 55. In the conversion processing, the threshold level to be referenced is appropriately and randomly varied with respect to the time axis, so that distortion depending on the input signal is not generated. This 1-bit output signal is derived from the output terminal 58 and supplied to the bit length converter 57.

  The bit length converter 57 converts the bit length of the 1-bit signal from the 1-bit quantizer 56, adds a negative sign to the adders 42, 45, 48, 51 and 54 and feeds back. Accordingly, the adders 42, 45, 48, 51 and 54 are supplied from the signals supplied from the input terminal 41 and the previous integrators 43, 46, 49 and 52 through the attenuators 44, 47, 50 and 53, respectively. The output signal of the bit length converter 57 is subtracted.

  The attenuators 44, 47, 50, and 53 attenuate the integration outputs of the integrators 43, 46, 49, and 52 using the coefficients K1, K2, K3, and K4, and add them to the adders 45, 48, 51, and 54, respectively. Supply.

  As described above, when the threshold level referred to by the ΔΣ modulator 40 in the quantization process in the 1-bit quantizer 56 is appropriately and randomly variable with respect to the time axis, distortion depending on the input signal is generated. There is no.

  Next, an MPEG2-TS signal editor 5 for multiplexing the high-quality 1-bit audio signal obtained by the ΔΣ modulators 3 and 40 into an MPEG2-TS signal including the video signal of the variable bit rate is illustrated. 11 will be described. The MPEG2-TS signal editor 5 embeds the 1-bit audio signal 23 obtained by the ΔΣ modulation in the MPEG2-TS signal 21 and outputs it as an MPEG2-TS signal including a variable bit rate video signal and a 1-bit audio signal. Output to terminal 70.

  For this reason, the MPEG2-TS signal editor 5 constitutes the transport stream supplied from the multiplexing unit 20 shown in FIG. 2 and is arranged at a predetermined time interval INT among a plurality of continuous packets. A PCR interval INT detector 63 for detecting the predetermined time interval INT between clocks (PCR) is provided. Further, the MPEG2-TS signal editor 5 includes an unnecessary packet number calculation unit 64 that calculates the number of packets that are unnecessary for transmission in the predetermined time interval INT detected by the PCR interval INT detection unit 63, and an unnecessary packet. A minimum unnecessary packet numerical value detection unit (shown as minimum packet numerical value detection) 68 for calculating a minimum value of the number of unnecessary packets calculated by the packet number calculation unit 64; Also, the MPEG2-TS signal editor 5 determines that the total time is less if the number of packets including the 1-bit audio signal per the predetermined time interval is smaller than the minimum number of unnecessary packets calculated by the minimum unnecessary packet value detection unit 68. And an embedding unit 69 for embedding a plurality of packets including the 1-bit audio signal per predetermined time interval in the interval.

  The PCR interval INT detection unit 63 is a reference clock that is time information arranged in a predetermined time interval INT in a plurality of consecutive packets constituting the transport stream supplied from the transport stream multiplexing unit 20. (PCR) is first extracted, and a predetermined time interval INT in the extracted reference clock (PCR) is detected. As described above, MPEG2-TS can transmit a packet including time information PCR. The PCR includes time information referred to by the decoder, and is configured so that the time of the decoder can be set at the time intended on the encoder side. In MPEG2-TS, PCR is transmitted at regular intervals, and the interval is set to 0.1 seconds or less. For example, it is assumed that PCRs are arranged at intervals of 0.03 seconds in the multiplexing unit 20 in a plurality of continuous packets constituting the transport stream. The PCR interval INT detection unit 63 detects PCR from the adaptation field of the transport packet. Then, a time interval (interval INT) between adjacent PCRs is detected.

  The unnecessary packet number calculation unit 64 calculates the number of packets that can be transmitted at a predetermined time interval INT, and the video signal in the packet including the video signal at each predetermined time interval INT. A second packet number calculation unit 66 that calculates a total second packet number with essential information for packetization, and a first time at each predetermined time interval INT calculated by the first packet number calculation unit 65 And a packet number difference calculation unit 67 for calculating a packet number difference between the second packet number and the second packet number at each predetermined time interval calculated by the second packet number calculation unit 66.

  The minimum unnecessary packet numerical value detection unit 68 calculates the minimum value of the number of unnecessary packets calculated by the unnecessary packet number calculation unit 64.

  The data embedding unit 69 calculates the number of packets including the 1-bit audio signal necessary per predetermined time interval INT, compares the number with the minimum value of the number of unnecessary packets, and if less than the minimum value of the number of unnecessary packets, A plurality of packets including a 1-bit audio signal are embedded in a time interval.

  Next, the operation of the MPEG2-TS signal editor 5 will be described with reference to the flowcharts of FIGS. 12 to 14 and the conceptual diagrams of FIGS.

  First, the MPEG2-TS signal editor 5 sets i = 0 in the PCR interval INT detector 63 (step S1), and detects the PCR interval INTi (step S2). As shown in FIG. 15A, adjacent PCRn and PCRn + 1 are detected, and the predetermined interval INT0 is detected.

  In step S3, the number of unnecessary packets in the predetermined interval INT0 is calculated using the unnecessary packet number calculation unit 64. At this time, the unnecessary packet number calculation processing unit 64 processes a subroutine of steps S11 to S13 shown in FIG. In step S11, the first packet number calculator 65 calculates the number of packets that can be transmitted at a predetermined interval INT0 from the bit rate and INT0. In step S12, the second packet number calculator 66 calculates the number of packets of the video signal 80 and the packetization essential information 83 in the packet including the video signal at the predetermined interval INT0. In FIG. 15, the video signal 80 and MPEG2 audio data (AAC) 81 are included in the number of packets that can be transmitted at a predetermined interval INT0. The packetization essential information 83 is not included. In step S13, the packet number difference calculation unit 67 calculates the packet number difference between the first packet number (the number of transmittable packets) and the video signal 80 in the packet including the video signal. As a result, the number of unnecessary packets 84 in INT0 shown in FIG. 15B can be calculated.

  In step S4, i = i + 1 is set, and steps S2 to S4 are repeated until it is determined in step S5 that i = END. When it is determined in step S5 that i = END, as shown in FIG. 15B, the number of unnecessary packets 84 in each of INT0, INT1,. Note that in INT4 and INT7, the number of unnecessary packets 84 excluding the video signal 80 and the packetization essential information 83 is calculated.

  In step S6, the minimum unnecessary packet numerical value detection unit 68 is used to detect the minimum value dun of the number of unnecessary packets 84. In the case of FIG. 15, the number of unnecessary packets 84 of ITN2 is the unnecessary packet 85 having the minimum value dun.

  In step S7, if the TS packet 86 including the 1-bit audio signal necessary for the PCR predetermined interval INT is smaller than the unnecessary packet 85 having the minimum value dun using the data embedding unit 69, 1 is added to all INTs. Fill multiple TS packets containing bit audio signals. At this time, the data embedding unit 69 processes a subroutine of steps S21 to S23 shown in FIG. In step S21, the number of packets (dΣΔ) including the 1-bit audio signal necessary for the predetermined interval INTi is calculated. In step S22, the number dΣΔ of TS packets 86 (FIG. 15B) including 1-bit audio signals necessary for the PCR predetermined interval INT and the minimum number of unnecessary packets 85 (FIG. 15B). Compare with dun. If the number of TS packets dΣΔ is smaller than the minimum value dun (YES), the process proceeds to step S23, and TS packets 86 of the TS packet number dΣΔ including 1-bit audio signals are embedded in all INTs.

  For example, assume that the minimum value dun of the unnecessary TS packet 85 in FIG. 15B is 150 packets through the processing of the unnecessary packet number calculation unit 64 and the minimum unnecessary packet numerical value detection unit 68.

  A 1-bit audio signal has a frame of 75 Hz in accordance with DSD (Direct Stream Digital) regulations. 75 frames are 1 second (s), and one frame consists of 52 packets, so 3900 packets per s. In FIG. 15, when PCR is arranged at intervals of 0.03 seconds, since INT = 0.03 seconds, 3900 × 0.03 = 117 packets per PCR time interval INT. That is, it becomes a TS packet including 1-bit audio signal of 117 packets (dΣΔ) per INT.

  In step S22 of FIG. 14, the data embedding unit 69 compares dΣΔ (117 packets) with dun (150 packets). In this case, since the minimum value dun of the unnecessary TS packet 85 is large, it is determined YES and the process proceeds to step S23, where the data embedding unit 69 has the TS packet number dΣΔ including 1-bit audio signals in all INTs. The packet 86 is embedded.

  As a result, as shown in FIG. 15C, a TS packet 86 including a 1-bit audio signal can be multiplexed into a TS packet 80 including a video signal over all INTs without changing the A bit rate. . Further, the packetization essential information 83 is multiplexed in INT4 and INT7. Finally, TS packet information including a 1-bit audio signal is added to a TS packet including information necessary for MPEG2-TS transmission. Specifically, the description relating to the MPEG2 audio data AAC in the PSI information in the packetization essential information 83 is rewritten to a description relating to DSD obtained by ΣΔ modulation.

  In the MPEG2-TS signal editor 5, the data embedding unit 69 determines the difference when the number of packets including the 1-bit audio signal required per predetermined time interval INT is larger than the minimum number of unnecessary packets. The number of invalid null packets equal to the number of packets is embedded in the entire time interval, and then the TS packets 86 having the TS packet number dΣΔ are embedded in the entire time interval.

  Therefore, in the flowchart of FIG. 14, the data embedding unit 69 determines that the number of packets including NO, that is, a 1-bit audio signal, is greater than the minimum number of unnecessary packets in the branch of step S22. If so, the process proceeds to step S24. In step S24, the data embedding unit 69 embeds NULL data equal to or larger than (dΣΔ−dun) over all INTs. Thereafter, in step S23, TS packets including 1-bit audio signals are embedded in all INTs. Finally, TS packet information including a 1-bit audio signal is added to a TS packet including information necessary for MPEG2-TS transmission.

  A series of processes in which the MPEG2-TS signal editor 5 selects NO in the branch of step S22 and performs packet embedding in step S23 after the process of step S24 will be described using the conceptual diagram of FIG.

  Assume that the number of unnecessary packets 84 in each of INT0, INT1,... INT8. Note that in INT4 and INT7, the number of unnecessary packets 84 excluding the video signal 80 and the packetization essential information 83 is calculated.

  Next, the MPEG2-TS signal editor 5 detects the minimum value dun of the number of unnecessary packets 84 using the minimum unnecessary packet numerical value detecting unit 68 in step S6 of the flowchart of FIG. In the case of FIG. 16, the number of unnecessary packets 84 of ITN5 is the unnecessary packet 85 having the minimum value dun.

  Next, the MPEG2-TS signal editor 5 uses the data embedding unit 69 and the number of TS packets 86 including the 1-bit audio signal necessary for the PCR predetermined interval INT is not required to be the packet number minimum value dun. It is checked in step S22 (FIG. 14) of the subroutine of step S7 in FIG. As shown in FIG. 16B, the number of TS packets 86 including the 1-bit audio signal necessary for the PCR predetermined interval INT is larger than the unnecessary packets 85 having the packet number minimum value dun. For this reason, as in FIG. 15C, if the TS packet 86 including the 1-bit audio signal is multiplexed with the TS packet 80 including the video signal over the entire INT, 1 as shown in FIG. The TS packet 86 including the bit audio signal overflows from the A bit rate with INT0, INT5, and INT8. This makes it impossible to transmit a multiplexed transport stream.

  Therefore, the MPEG2-TS signal editor 5 embeds NULL data equal to or greater than (dΣΔ-un) over all INTs by the process of step S24 using the data embedding unit 69. Thereafter, in step S23, TS packets including 1-bit audio signals are embedded in all INTs. Finally, TS packet information including a 1-bit audio signal is added to a TS packet including information necessary for MPEG2-TS transmission. As a result, as shown in FIG. 16D, by inserting the same number (dΣΔ-dun) of TS packets between two adjacent INTs, the bit rate of the entire MPEG2-TS is changed to that shown in FIG. ), The B bit rate can be higher than the A bit rate.

  Note that the multiplexing apparatus 1 shown in FIG. 1 may use an MPEG2-TS signal editor 75 having the configuration shown in FIG. 17 instead of the MPEG2-TS signal editor 5. The MPEG2-TS signal editor 75 is different from the MPEG2-TS signal editor 5 in that unnecessary packets having the number of packets calculated by the unnecessary packet number calculation unit 64 are replaced with null data by the invalid data replacement unit 76. is there. The minimum number of packets is detected by the minimum packet number detection unit 68 for all null packets of the time interval INT that have been replaced with unnecessary packets by the invalid data replacement unit 76. The minimum value (B) of the NULL packet detected by the minimum packet number detection unit 68 is the number of TS packets including a 1-bit audio signal necessary for INT between PCRs in the data embedding unit 69 (A). Compared with

  The data embedding unit 69 compares the minimum value (B) of the null packet with the number (TS) of TS packets including the 1-bit audio signal. As a result, if (A−B)> 0 is not satisfied, If the minimum value (B) is larger than the number (A) of TS packets including a 1-bit audio signal, the NULL packet portion is replaced with a TS packet including a 1-bit audio signal. If (A−B)> 0, that is, if the minimum value (B) of the NULL packet is smaller than the number (A) of TS packets including a 1-bit audio signal, (A−B) Null packets are inserted into the entire MPEG2-TS signal for each INT, and the null packet portion is replaced with a TS packet including a 1-bit audio signal.

  The processing procedure of the MPEG2-TS signal editor 75 will be described with reference to the flowchart of FIG. First, the MPEG2-TS signal editor 75 uses the first packet number calculation unit 65, the second packet number calculation unit, and the packet number difference calculation unit 67 of the unnecessary packet number calculation unit 64 shown in FIG. Unnecessary packets are calculated and replaced with NULL data by the invalid data replacement unit 76 (step S31).

  Next, the MPEG2-TS signal editor 75 uses the data embedding unit 69 to determine the number of TS packets including the 1-bit audio signal necessary for the predetermined time interval INT in step S32 as in step S21 of FIG. (A) is calculated.

  At the same time or before, the MPEG2-TS signal editor 75 calculates the minimum value (B) of the number of null packets in all INTs by the minimum packet number detection unit 68 in step S33.

  Then, the MPEG2-TS signal editor 75 uses the data embedding unit 69 to compare the minimum value (B) of the NULL packet with the number (A) of TS packets including the 1-bit audio signal in step S34. As a result, if (A−B)> 0 is not satisfied (NO), the process proceeds to step S35, and the NULL packet portion is replaced with a TS packet including a 1-bit audio signal. Here, if there is a surplus of null packets, the null packet remains unchanged.

  If (A−B)> 0 in step S34, the process proceeds to step S36, and (A−B) NULL packets are inserted for each INT over the entire MPEG2-TS signal. Thereafter, the process proceeds to step S35, where the NULL packet portion is replaced with a TS packet including a 1-bit audio signal. Here, if there is a surplus of null packets, the null packet remains unchanged.

  Finally, in step S35, the MPEG2-TS signal editor 75 adds the information of the TS packet including the 1-bit audio signal to the TS packet including the information necessary for MPEG2-TS transmission by the data embedding unit 69. To do.

  19 and 20 are diagrams conceptually showing the relationship between the number of TS packets 90 and NULL packets 91 including a video signal and the bit rate. As shown in FIG. 19A, when an unnecessary TS packet except an TS packet 90 including a video signal in an MPEG2-TS stream of A bit rate is replaced with a NULL packet 91, a sufficient NULL packet 91 is obtained. If the NULL packet 91 portion is replaced with a TS packet 92 including a 1-bit audio signal as shown in FIG. 19B, the A bit rate does not change. There is no effect on MPEG2-TS transmission.

  However, as shown in FIG. 20 (a), when a sufficient NULL packet is not secured, even if an attempt is made to replace the NULL packet portion with a TS packet 92 including a 1-bit audio signal, the MPEG2-TS A bit rate is determined. It overflows. Therefore, the MPEG2-TS signal editor 75 increases the bit rate by inserting (AB) NULL packets between the PCRs, that is, all INTs over the entire MPEG2-TS signal in step S36 of FIG. Correspond with. The bit rate of the entire MPEG2-TS stream is set higher than the A bit rate like the B bit rate, and a sufficient NULL packet portion is secured. Thereafter, the secured NULL packet portion is replaced with a TS packet 92 including a 1-bit audio signal in step S35, so that the TS packet including the 1-bit audio signal does not overflow as shown in FIG. It can be transmitted as an MPEG2-TS signal. That is, multiplexing with a variable bit rate video signal has been completed. Finally, the information of the TS packet including the 1-bit audio signal is added to the TS packet including the information necessary for transmission of the MPEG2-TS signal, and the multiplexing is finished.

  In this embodiment, a 2-channel 1-bit audio signal is used. However, a multi-channel 1-bit audio signal can be used. In this case, the number (A) of TS packets including the 1-bit audio signal necessary for the predetermined time interval INT is larger than that in the case of 2ch.

  FIG. 21 shows the configuration of an MPEG2-TS reference decoder 100 that decodes MPEG2-TS multiplexed and transmitted by the multiplexer 1 of FIG. The MPEG2-TS supplied to the input terminal is a time-division multiplexed transport packet for each decoding device, and is switched by the changeover switch 101 according to the PID which is the content identification information of the header information. Are sent to the corresponding TS buffers 106, 112, and 115 of the decoder 103, the 1-bit audio signal decoder 104,.

  The TS buffer 106 of the video decoder unit 103, the TS buffer 112 of the audio decoder unit 104, and the TS buffer 115 of the other decoder units 105 each have a capacity of 512 bytes. Video data, DSD audio data, and other data buffered by the TS buffers 106, 112, and 115 with a capacity of 512 bytes each are main buffers 107, 113 that serve as system target decoder (STD) buffers. , And 116.

  The video data buffered in the main buffer 107 is sent to the video decoder 109 via the elementary stream ES buffer 108, and the data read from the audio main buffer 113 is sent to the audio decoder 114, and the other Data read from the main buffer 116 is sent to the system decoder 117.

  Decoded data related to system control from the system decoder 117 is sent to the video decoder 109 and the audio decoder 114.

  The video decoder 145 decodes the video data according to the decode data related to system control from the system decoder 117. At this time, if the decoded data is a so-called I picture (intra-frame encoded image) or P picture (forward prediction encoded image), the decoded data is sent to one selected terminal of the changeover switch 111 via the delay buffer 110. In the case of a B picture (bidirectional predictive encoded image), it is sent to the other selected terminal, and the output from the changeover switch 111 is taken out as a video output.

  The audio decoder 114 decodes the DSD data in accordance with the decode data related to system control from the system decoder 117, and derives it as an audio output.

It is a block diagram of the multiplexing apparatus of embodiment of this invention. 1 is a block diagram of an MPEG2 multiplexing device. It is a figure which shows the structure of a transport stream (TS). It is a figure which shows TS packet structure with an adaptation field. It is a figure which shows the payload part of TS packet in which PSI (Program Specification Information: Program Specific Information) enters. It is a figure which shows the example of a hierarchical data structure. It is a figure which shows the specific example of the transport stream (TS) multiplexed by the multiplexing part and input into an MPEG2-TS signal editing machine. It is a figure which shows the structure of a delta-sigma modulator. It is a figure for demonstrating the process of a 1 bit quantizer. FIG. 5 is a diagram illustrating a configuration of a fifth-order ΔΣ modulator. It is a figure which shows the structure of an MPEG2-TS signal editing machine. It is a flowchart which shows the process sequence of an MPEG2-TS signal editing machine. It is a flowchart which shows an unnecessary packet number calculation process. It is a flowchart which shows a packet embedding process. It is a conceptual diagram for demonstrating operation | movement of an MPEG2-TS signal editing machine. It is a conceptual diagram for demonstrating other operation | movement of an MPEG2-TS signal editing machine. It is a figure which shows the other structure of an MPEG2-TS signal editing machine. It is a flowchart which shows the process sequence of the other MPEG2-TS signal editing machine. It is a conceptual diagram for demonstrating operation | movement of the other MPEG2-TS signal editing machine. It is a conceptual diagram for demonstrating other operation | movement of other MPEG2-TS signal editing machines. It is a figure which shows the structure of an MPEG2-TS reference | standard decoder.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Multiplexer, 3 delta-sigma modulator, 5 MPEG2-TS signal editor, 63 PCR interval INT detection part, 64 Unnecessary packet number calculation part, 65 1st packet number calculation part, 66 2nd packet number calculation part , 67 packet number difference calculation unit, 68 minimum unnecessary packet numerical value detection unit, 69 data embedding unit

Claims (12)

A multiplexing device for multiplexing a 1-bit audio signal obtained by subjecting an analog audio signal to ΔΣ modulation processing to a video signal with a variable bit rate while maintaining a fixed bit rate,
Time interval detection means for extracting a reference clock arranged at a predetermined time interval in a plurality of continuous packets including a video signal of a variable bit rate, and detecting the predetermined time interval between the extracted reference clocks;
Unnecessary packet number calculating means for calculating the number of packets unnecessary for transmission in each predetermined time interval detected by the time interval detecting means;
Minimum unnecessary packet numerical value detecting means for calculating a minimum value in all time intervals of the number of unnecessary packets calculated by the unnecessary packet number calculating means;
If the number of packets including the 1-bit audio signal per predetermined time interval is smaller than the minimum unnecessary packet number detected by the minimum unnecessary packet numerical value detecting means, the 1-bit audio per predetermined time interval in all time intervals. A multiplexing apparatus comprising: an embedding unit that embeds a plurality of packets including a signal. The above unnecessary packet number calculating means
First packet number calculating means for calculating the number of transmittable packets in the predetermined time interval;
Second packet number for calculating the total second packet number of the video signal in the packet including the video signal and the essential information for packetization in each predetermined time interval detected by the time interval detection means A calculation means;
A first packet number at each of the predetermined time intervals calculated by the first packet number calculation means, and a second packet number at the predetermined time intervals calculated by the second packet number calculation means; The multiplexing apparatus according to claim 1, further comprising: a packet number difference calculating unit that calculates a difference in each packet number. The embedding means is
The number of packets including the 1-bit audio signal necessary per the predetermined time interval is calculated, and compared with the minimum value of the number of unnecessary packets. 2. The multiplexing apparatus according to claim 1, wherein a plurality of packets including the 1-bit audio signal are embedded.   The embedding means calculates the number of packets including a 1-bit audio signal necessary per the predetermined time interval, compares the number with the minimum value of the number of unnecessary packets, and if the number is larger than the number of unnecessary packets, the difference packet number 4. The multiplexing apparatus according to claim 3, wherein the same number of invalid data packets are embedded in all time intervals, and then a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals. Further comprising invalid data packet replacing means for replacing unnecessary packets in the predetermined time intervals calculated by the unnecessary packet number calculating means with invalid data packets having the same number of packets;
The minimum unnecessary packet numerical value detection means detects the number of invalid data packets corresponding to the minimum value among the invalid data packets in each time interval replaced by the invalid data packet replacement means,
The embedding unit includes a plurality of packets including the 1-bit audio signal having a smaller number of packets than the invalid data packet having the minimum number of packets detected by the minimum unnecessary packet numerical value detecting unit. The multiplexing apparatus according to claim 1, wherein the multiplexing apparatus is embedded in the apparatus.   When the number of packets including the 1-bit audio signal is larger than the number of invalid data packets with the minimum number of packets detected by the minimum unnecessary packet numerical value detection unit, the embedding unit has the same number of invalid data as the difference number of packets. 6. The multiplexing apparatus according to claim 5, wherein a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals after packets are embedded in all time intervals. A multiplexing method for multiplexing a 1-bit audio signal obtained by subjecting an analog audio signal to ΔΣ modulation processing to a video signal having a variable bit rate while maintaining a fixed bit rate,
A time interval detection step of extracting a reference clock arranged at a predetermined time interval in a plurality of continuous packets including a video signal having a variable bit rate, and detecting the predetermined time interval between the extracted reference clocks;
An unnecessary packet number calculating step of calculating the number of packets unnecessary for transmission in each predetermined time interval detected by the time interval detecting step;
A minimum unnecessary packet numerical value detecting step for calculating a minimum value in all time intervals of the number of unnecessary packets calculated by the unnecessary packet number calculating step;
If the number of packets including the 1-bit audio signal per predetermined time interval is smaller than the minimum unnecessary packet number detected by the minimum unnecessary packet numerical value detection step, the 1-bit audio per predetermined time interval in all time intervals An embedding step of embedding a plurality of packets including a signal. The unnecessary packet number calculating step
A first packet number calculating step of calculating the number of transmittable packets in the predetermined time interval;
The second packet number for calculating the total second packet number of the video signal in the packet including the video signal and the essential information for packetization in each predetermined time interval detected by the time interval detection step. A calculation process;
A first number of packets in each of the predetermined time intervals calculated by the first packet number calculation step, and a second number of packets in the predetermined time intervals calculated by the second packet number calculating means; The multiplexing method according to claim 7, further comprising: a packet number difference calculating step of calculating each packet number difference. The embedding step is
The number of packets including the 1-bit audio signal necessary per the predetermined time interval is calculated, and compared with the minimum value of the number of unnecessary packets. 8. The multiplexing method according to claim 7, wherein a plurality of packets including the 1-bit audio signal are embedded.   In the embedding step, the number of packets including the 1-bit audio signal necessary per the predetermined time interval is calculated, and compared with the minimum value of the number of unnecessary packets. 10. The multiplexing method according to claim 9, wherein the same number of invalid data packets are embedded in all time intervals, and then a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals. An invalid data packet replacement step of replacing unnecessary packets in the predetermined time intervals calculated by the unnecessary packet number calculation step with invalid data packets having the same number of packets;
The minimum unnecessary packet numerical value detection step detects the number of invalid data packets corresponding to the minimum value among the invalid data packets in all the time intervals replaced by the invalid data packet replacement step,
In the embedding step, invalid data in each of the time intervals is divided into a plurality of packets including the 1-bit audio signal having a smaller number of packets than the invalid data packet having the minimum number of packets detected in the minimum unnecessary packet numerical value detection step. The multiplexing method according to claim 7, wherein the multiplexing method is embedded in. In the embedding step, when there are more plural packets including the 1-bit audio signal than the invalid data packet having the minimum number of packets detected in the minimum unnecessary packet numerical value detecting step, the same number of invalid data as the number of packets of the difference is included. 12. The multiplexing method according to claim 11, wherein a plurality of packets including the 1-bit audio signal per predetermined time interval are embedded in all time intervals after packets are embedded in all time intervals.

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