KR100529304B1 - Transport stream encoder of MPEG-2 - Google Patents

Abstract

The present invention relates to a TS encoder encoded in frame units.

The TS encoder according to the present invention includes a PES header generator for generating a PES header on a frame basis of an element stream; A control signal generator for generating a PES header valid section signal indicating a valid section of the PES header; A memory for recording / reading the PES header and the element stream generated in the PES header generator; A memory controller configured to control a write operation of the memory in synchronization with a PES header valid interval signal generated by the control signal generator and to generate a TS header interval signal indicating a section in which a TS header is to be written; A flag generator configured to control a read operation of the memory in synchronization with a TS header period signal generated by the memory controller and to generate a TS header flag indicating a timing at which a TS header is to be written; And a TS generator for adding a TS header to data read from the memory in synchronization with the TS header flag to output a TS packet.

Description

MPEG-2 transport stream encoder

The present invention relates to an MPEG-2 system encoder, and more particularly, to a TS encoder for encoding on a frame basis.

The MPEG-2 system defines the syntax of streams for MPEG audio and MPEG video. There are two types of such MPEG systems, one called a program stream (PS), which constitutes one program, and the other is a plurality of programs in a transport stream (TS). It can be configured.

The MPEG system employs a packet multiplexing scheme. Packet multiplexing is to divide a video / audio element stream (ES) into a string of bits of an appropriate length called a packet, and multiplex by attaching additional information such as a header. The header contains information for distinguishing video and audio packets. In MPEG, the length of a packet is up to 2 ¹⁶ (64 KB) to be suitable for various applications. In order to have flexibility, either a fixed length or a variable length can be taken for each packet. The length information of the packet is included in the header.

In the PS method, a plurality of packets (hereinafter referred to as Packetized Elementary Stream in MPEG-2) are grouped to form a pack, whereas in the TS method, a plurality of transport streams having a relatively short length are re-divided into one PES. ) Configure the packet. The length of a TS packet is 188 bytes and can be transmitted divided into four ATM cells.

There is a 4-byte header in the TS packet, and there is a PID (Packet ID) indicating which packet is contained in the header. The PID is described in a Program Management Table (PMT) of Program Specific Information (PSI). have. TS packets with a PID of "0" are used to transmit PSI.

Since the transport stream transmits a plurality of programs, information about which program each TS packet belongs to is required. This information is collectively called PSI and is transmitted by TS packet with designated ID or packet indicated by primary PSI. This PSI packet is composed of PAT, PMT, NIT, CAT and the like. PSI information is to be transmitted once within at least 0.7 seconds.

The PAT contains program information and contains the PID of the packet including the PMT.

The header also contains a traversal counter for checking the continuity of packets with the same PID.

The TS encoder plays a role of reconfiguring a PES packet (Packetized Elementary Stream) into TS packets. The length of the PES is not fixed and only has 16 bits of header information to indicate the length of the PES packet in the PES header. If the value of the packet length information is "0", it indicates that one PES packet is configured in one frame unit.

Existing technology allows multiple PS streams to be multiplexed in the construction of TS packets. Thus, H / W is complicated when multiplexing one PS stream. In addition, when the TS packet is configured in units of one frame, desired editing cannot be performed when the TS packet is edited or reconstructed. The reason is that since the PSI information exists once every 0.7 seconds, it is difficult to reconstruct information of a desired frame.

An object of the present invention is to provide a system encoder for generating a TS packet by configuring one PES packet into one frame.

A TS encoder according to the present invention for achieving the above object is a TS encoder for outputting a transport stream by inputting an MPEG elementary stream to generate a PES header in units of frames of the element stream. PES header generator; A control signal generator for generating a PES header valid section signal indicating a valid section of the PES header; A memory for recording / reading the PES header and the element stream generated in the PES header generator; A memory controller configured to control a write operation of the memory in synchronization with a PES header valid interval signal generated by the control signal generator and to generate a TS header interval signal indicating a section in which a TS header is to be written; A flag generator configured to control a read operation of the memory in synchronization with a TS header period signal generated by the memory controller and to generate a TS header flag indicating a timing at which a TS header is to be written; And a TS generator for adding a TS header to data read from the memory in synchronization with the TS header flag to output a TS packet. Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating the configuration of a PES packet and a TS packet of MPEG-2. In FIG. 1, (a) shows the structure of a PS packet, and (b) shows the structure of a TS packet. The PES packet and TS packet shown in FIG. 1 are specified in ISO / IEC 13818-1, a specification related to the MPEG2 system.

PES packets consist of a header and a payload, the length of which is variable. The length information of the PES packet is included in the header.

The TS packet consists of a header of 4 bytes, an adaptation field of n bytes, and a payload of 184-n, which is 188 bytes in length.

FIG. 2 shows a detailed configuration of the PES packet shown in FIG. 1.

In the PES packet shown in FIG. 2, each item is as follows.

pes start prefix: Start start code

stream_id; Stream id

pes_packet_length: Packet length

pes_scrambling_control: Scramble control

pes_priority: PES priority

data_alignment_indicator: data alignment indicator

copy_right: copyright

PTS_DTS_flag: Original / Copy

ESCR_FLAG: Erenentary Stream Clock Reference (ESCR) flag

ES_rate_flay: ES rate flag

DSM_trick_mode_flay: Digital Storage Midea trick mode flag

additional_copy_info_flag: bookkeeping copy information flag

PES_CRC_frag: PES CRC Flag

RES_extension_flag: PES extension flag

PES_header_data_length:

PTS: Program Time Stamp

FIG. 3 shows a detailed configuration of the TS packet shown in FIG. 1.

Each item in the TS packet shown in FIG. 3 is as follows.

syncbyte: sync byte "0x47"

transport_error_iondicator: error indication

payload_unit_start_indicator: Unit start indication

transport_priority: transport packet priority

PID: Packet ID

transport_scrambling_control: Scramble control

adaptation_field_control: adaptation

contnuity_counter: Traversal counter

4 shows a detailed configuration of a PAT packet. Each item shown in FIG. 4 is as follows. The PAT packet is special information transmitted by PID = "0". Each program number (16 bits) is a transport packet that transmits a table (Program Map Table) describing the components of the program.

table_id: Table ID

section syntax_indicator:

"One";

reserved:

section_length: Section length

transport_stream_id: ID of TS packet

reserved:

version_number: version number

current_next_indicator: presence of next section

section_number: Section number

program_number: The program number that you specify

reserved:

program_map_PID: External input PMT_PID

5 shows a detailed configuration of a PMT packet. The PMT describes the program identification number and the PID list of the transport packet in which the individual bit strings such as video and audio constituting the program are transmitted and the attached information.

Each component shown in FIG. 5 is as follows.

table_id: Table ID

section_syntax_indicator:

"0"

reserved:

section_length: Section length

program_number: Program number, can be redefined by the user.

transport_stream_id: ID of TS packet

reserved:

version_number: version number

current_next_indicator: presence or absence of the next section

section_number: section number

last_section_number: final section number

reserved:

PCR_PID:

reserved:

program_info_length:

stream_type: Specify stream type according to MPEG table 2-36

reserved:

elementary_PID: External input VTS_PID

reserved:

6 shows the configuration of a null packet. The TS encoder can basically multiplex a plurality of programs. Normally, the video is 9Mbps and the audio is 384Kbps. For example, if the TS encoder's transmission rate is 60Mbps, a null packet is transmitted while not transmitting video and audio.

7 is a block diagram showing a detailed configuration of a TS encoder according to the present invention. The apparatus shown in FIG. 7 includes a PES packet generator 10, a control signal generator 12, a memory controller 14, a video memory 16, an audio memory 18, a PCR generator 20, a flag generator 22. , A PSI generator 24, a CRC generator 26, and a TS packet generator 28.

The PES packet generator 10 is a block for generating PES on a frame basis. The PES packet generator generator 10 may know that the start of a frame in the elementary stream is performed by the frame reset signal (frame_rst) and the PES header as shown in FIG. 2 for each frame after N clocks from the frame reset signal. Occurs. PES headers are generated separately for video and audio.

The PES packet generator 10 inserts an elementary stream into the PES header to generate a PES packet.

The control signal generator 12 generates valid period signals vpes_vld and apes_vld indicating the valid period of the PES header generated by the PES packet generator 10. Since the PES header is generated after N clocks from the frame reset signal frame_rst, a valid section of audio and video is represented for each frame. In addition, since a PSI packet is inserted every frame, a PSI_st signal indicating a section for inserting PSI information is generated.

The memory controller 14 generates control signals for writing data to the audio and video memories 16 and 18 and control signals for generating TS packets. First, the address (vwr_address, awr_address) and enable (vwr_ena, awr_ena) signals are generated to record audio and video data in the respective memories 16 and 18.

Audio and video must be generated in different TS packets because each PID is present.

The first packet of each frame adds PCR. An adaptation field exists to insert the PCR, and the memory controller 14 generates vts_st and ats_st for inserting the PCR.

The seq_end signal is used to indicate the last packet of a frame.

When writing to the memories 16 and 18, seq_end is detected and the number of data is counted at that time and added to the data generator input. At this time, a valid address (val_addr) actually recorded is transmitted.

In this case, since stuffing data exists in the adaptation feed, it is necessary to generate a TS packet in which the adaptation exists.

The PCR generator 20 generates a signal pcr_st for generating PCR by the frame reset signal frame_rst. PCR generates a 27MHz clock as a signal for maintaining the same time condition in the encoder and the decoder.

The flag generator 22 generates a signal for reading the memories 16 and 18. The read address is generated by referring to vts_st, ats_st, pcr_st, seq_end, datnum, and valid_addr. However, using the counter 1-188 internally, the audio packet is not generated while the video packet is generated, and conversely, the video packet is not generated while the audio packet is generated. At this time, the timing for generating PSI data is secured to generate pat_flay and pmt_flag. These signals are input to the PSI generator 24 to generate actual PSI data.

Eight flags, five runs, and ts_cnt generated by the flag generator 22 are input to the TS generator 28.

PSI generator 24 generates a PSI packet. At this time, the PSI packet is composed of a PAT packet and a PMT packet. These PSI packets are generated by receiving a program number and signals of PCR_PID, PMT_PID, VTS_PID, and ATS_PID. program_number and PMT_PID are used in the PAT packet.

The CRC generator 26 adds a 32 bit CRC to the PSI packets generated by the PSI generator 24. The polynomial used here is (X ³² + X ²⁶ + X ²³ + X ²² + X ¹⁶ + X ¹² + X ¹¹ + X ¹⁰ + X ⁸ + X ⁷ + X ⁵ + X ⁴ + X ² + X + 1) .

The CRC generator 26 adds a 32-bit CRC to the PSI packet generated by the PSI generator 24 and outputs it as p-data.

The TS generator 28 generates an actual TS packet. The TS generator 28 receives 8 flags and generates them, and each flag is an important signal for generating a TS. Each flag is as follows.

pcr_flag: A signal indicating the timing at which pcr should be inserted when generating a TS packet. When this signal is present, the TS packet will have an adaptation feed.

pts_flag: A value indicating the time to be actually displayed in the PES packet, that is, when the PTS is inserted, the PCR value + N is added to the time when the TS packet is generated. pte_flag is a flag indicating timing at this time.

vpes_flag: The payload_unit_start_indicator of the vedeo TS packet is a signal indicating the timing at that time since it should be set to "1" for the TS packet at which every PES packet starts.

apes_flag: The payload_unit_start_indicator of the audio TS packet is a signal indicating the timing at that time since it should be set to "1" for the TS packet at which every PES packet starts.

pat_flag: A flag indicating timing of generating a PAT packet as shown in FIG. 4. The payload_unit_start_indicator of this PMT packet should be set to "1".

pmt_flag: A flag indicating timing of generating a PMT packet as shown in FIG. The payload_unit_start_indicator of this PMT packet should be set to "1".

ats_flag: A flag that indicates the timing at which the audio packet is generated.

vts_flag: A flag indicating the timing at which the vidio packet is generated.

Five runs are used to control each packet, ie PAT, PMT, video and audio packets, to not be created at the same time. A NULL packet as shown in FIG. 6 is generated except for a section in which TS packets are generated by vts_st, ats_st, and psi_st.

As described above, the TS encoder according to the present invention generates a TS packet in which one PES packet consists of one frame. Accordingly, there is an effect that the unit of one PES packet is not constant, and a much smaller H / W can be configured for a bitstream having a size in which the length of the PES packet cannot be represented by 16 bits.

In addition, since PCR is inserted in units of one frame, timing can be solved as a frame reset signal.

When the PES packet is configured in one frame unit, the TS packet may be edited and multiplexed in one frame unit by a Payload Unit Start Indicator (PUSI) of the TS packet.

If the last data of one frame is not composed of 1TS packet, stuffing data should be inserted into the adaptation feed. If the squence end code is detected and used, for example, 512 bytes without using one frame of memory There is an advantage that the insertion of the adaptation feed can be easily solved as a memory of the memory.

1 is a diagram illustrating the configuration of a PES packet and a TS packet of MPEG-2.

FIG. 2 shows a detailed configuration of the PES packet shown in FIG. 1.

FIG. 3 shows a detailed configuration of the TS packet shown in FIG. 1.

4 shows a detailed configuration of a PAT packet.

5 shows a detailed configuration of a PMT packet.

6 shows the configuration of a null packet.

7 is a block diagram showing a detailed configuration of a TS encoder according to the present invention.

Claims (7)

A TS encoder for outputting a transport stream by inputting an MPEG elementary stream, A PES header generator generating a PES header on a frame basis of an element stream; A control signal generator for generating a PES header valid section signal indicating a valid section of the PES header; A memory for recording / reading the PES header and the element stream generated in the PES header generator; A memory controller configured to control a write operation of the memory in synchronization with a PES header valid interval signal generated by the control signal generator and to generate a TS header interval signal indicating a section in which a TS header is to be written; A flag generator configured to control a read operation of the memory in synchronization with a TS header period signal generated by the memory controller and to generate a TS header flag indicating a timing at which a TS header is to be written; And a TS generator for adding a TS header to data read from a memory in synchronization with the TS header flag to output a TS packet. The TS encoder according to claim 1, wherein the PES header generator and the control signal generator operate in synchronization with a frame reset signal indicating a head of a frame. The method of claim 1, The control signal generator generates a sequence end signal indicating whether or not the last data in the element stream of the frame unit, the number of data of the last data, And the flag generator controls the memory with reference to the sequence end signal and the number of last data. The method of claim 3, The control signal generator generates a final address signal indicating the address of the last data in the element stream on a frame basis, And the flag generator controls the memory with reference to the last address signal. The TS encoder of claim 1, wherein the TS generator generates a null packet in a section in which a TS packet is not made. The apparatus of claim 1, further comprising: a PCR generator configured to generate PCR (Program Clock Reference) data and a PCR interval signal indicating a section in which PCR is to be recorded in units of frames of an element stream, The flag generator generates a PCR flag indicating a timing at which PCR is to be recorded in synchronization with a PCR section signal, The TS generator TS encoder, characterized in that for inserting the PCR data provided from the PCR generator according to the PCR flag. The apparatus of claim 6, further comprising: a PSI generator for generating PSI (Program Specification Information) data in units of frames of an element stream; Further comprising a CRC generator for adding an error correction code to the PSI data provided by the PSI generation unit, The flag generator generates a PSI flag indicating a timing at which PSI data is to be written, And the TS generator generates a PSI packet to which an error correction code provided from the CRC generator is added according to a PSI flag.