JP7847007B2 - Broadcast transmission equipment and broadcast reception equipment - Google Patents

Description

This invention relates to a broadcast transmission device and a broadcast reception device for a digital broadcasting system.

Conventional digital broadcasting employs a limited access system for pay-per-view broadcasts, restricting reception to subscribers only, and content protection systems for free broadcasts. In particular, access control systems for digital broadcasting using MMT (MPEG Media Transport, ISO/IEC 23008-1) as the multiplexing method scramble the data portion of the MMTP payload within the MMTP packets transmitting broadcast content (see Non-Patent Literature 1).

By the way, in video compression methods such as H.264/AVC and H.265/HEVC used in broadcast and communication content, the video stream is in NAL (Network Abstraction Layer) unit format. The first 32 bits describe the NAL unit length, and the next byte describes the NAL unit type. NAL unit types include non-VCL (Video Coding Layer) NAL units such as VPS, SPS, PPS, and SEI, as well as VCL units containing video data. VPS, SPS, PPS, and SEI are necessary information for decoding the video stream. The receiving video playback application obtains information from the slice header of these non-VCL NAL units and VCL NAL units to manage the operation of the video decoder, such as video size, frame rate, and buffer size.

Therefore, CENC (MPEG Common Encryption: ISO/IEC 23001-7), used for scrambling communication content, specifies that only non-VCL NAL units and VCL NAL unit slice header information should be transmitted without scrambling, allowing video playback applications to access this information even before scrambling and decoding the scrambled content (see Non-Patent Document 2).

ARIB STD-B61 "Access Control Method (Second Generation) and CAS Program Download Method in Digital Broadcasting" Part 1 "Access Control Method (Second Generation)" ISO/IEC 23001-07 “Information technology-MPEG systems technologies-Part 7: Common encryption in ISO base media file format files”

In digital broadcasting using MMT, as mentioned above, the entire video stream stored in the payload is scrambled during MMTP packetization. Therefore, it was not possible to include both the unscrambled and scrambled portions in a single payload.

It is possible to transmit the unscrambled and scrambled portions of a VCL NAL unit as separate MMTP packets. For example, the unscrambled slice header could be transmitted in an unscrambled MMTP packet, while the remaining slice data is transmitted in a scrambled MMTP packet. However, due to the small number of bytes in the slice header, the multiplexing efficiency may decrease.

Therefore, the present invention aims to provide a broadcast transmission device and a broadcast reception device that enable efficient transmission of partially scrambled content in a digital broadcasting system using MMT.

The broadcast transmission device according to the first embodiment is a broadcast transmission device for a digital broadcasting system using MMT as a multiplexing method, and comprises: scrambling means for scrambling a scrambled portion when a subsample extracted from a stream of video or audio broadcast content includes a scrambled portion that is subject to scrambling; and multiplexing means for placing scrambled range information, including length information of each division range of the scrambled portion and the unscrambled portion stored in the payload of the MMTP packet, in the header portion of the MMTP packet when the subsample, which includes the scrambled portion and the unscrambled portion, is stored in the payload of the MMTP packet.

The second embodiment of the broadcast receiving device is a broadcast receiving device for a digital broadcasting system using MMT as a multiplexing method, and comprises: a separation means that, upon receiving an MMTP packet in which scramble range information is placed in the header, uses the length information contained in the scramble range information to obtain from the payload of the MMTP packet a scrambled portion and an unscrambled portion of the division range stored in the payload of the MMTP packet in a subsample from the payload of the MMTP packet; a scramble decoding means that performs scramble decoding on the scrambled portion; and a playback means that compresses and decodes the broadcast content contained in the unscrambled portion and the scrambled portion after scramble decoding to reproduce it.

According to the present invention, it is possible to provide a broadcast transmission device and a broadcast reception device that can efficiently transmit partially scrambled content in a digital broadcasting system using MMT.

This diagram shows the configuration of a digital broadcasting system according to an embodiment. This diagram shows the configuration of a broadcast transmission device according to an embodiment. This is a diagram illustrating the operation of a broadcast transmission device according to an embodiment. This diagram shows the configuration of an MMTP packet carrying the scrambled portion according to the embodiment. This figure shows a specific example of the scrambling-related information multi-type header extension according to the embodiment. This figure shows a specific example of the scrambled range information multi-type header extension according to the embodiment. This is a diagram showing the configuration of a broadcast receiving device according to an embodiment. This is a flowchart (part 1) showing the multiplexing method according to the embodiment. This is a flowchart (part 2) showing the multiplexing method according to the embodiment. This is a diagram showing a modified example of the digital broadcasting system according to the embodiment. This is a diagram illustrating the multiplexing method in a digital broadcasting system related to the modified example.

The embodiments will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals.

(Digital broadcasting system)
First, the digital broadcasting system according to this embodiment will be described. Figure 1 is a diagram showing the configuration of the digital broadcasting system 1 according to this embodiment.

As shown in Figure 1, the digital broadcasting system 1 according to this embodiment is a broadcasting system based on the ARIB standard and includes a broadcast transmission device 100 and a broadcast receiving device 200.

The broadcast transmission device 100 is a device that transmits partially scrambled broadcast content. Broadcast content consists of media data such as video and audio. The broadcast transmission device 100 is installed, for example, in a broadcasting station. In this embodiment, the broadcast transmission device 100 transmits the partially scrambled broadcast content as an MMTP-processed stream based on the ARIB STD-B60 standard.

The broadcast receiving device 200 is a device that receives broadcast content via the broadcast transmission line 10. The broadcast transmission line 10 may be any type of broadcast transmission line, such as terrestrial broadcasting, satellite broadcasting, or cable broadcasting. The broadcast receiving device 200 is equipped with broadcast receiving functions such as a tuner, and performs scrambling and decoding of the received content based on the ARIB STD-B60 standard, and then plays back the broadcast content.

(Broadcast transmission equipment)
Next, the broadcast transmission device 100 according to this embodiment will be described. Figure 2 is a diagram showing the configuration of the broadcast transmission device 100 according to this embodiment. Figure 3 is a diagram illustrating the operation of the broadcast transmission device 100 according to this embodiment.

As shown in Figure 2, the broadcast transmission device 100 according to this embodiment includes a sampling means 110, a sub-sampling means 120, a unitization means 130, a scrambling means 140, and a multiplexing means 150.

The sampling means 110 divides a stream of video or audio broadcast content into samples, for example, one frame at a time, as shown in Figures 3(a) and (b). The broadcast content includes, for example, a video stream with a Network Abstraction Layer (NAL) structure compressed and encoded using video encoding schemes such as H.264|MPEG-4 AVC (Advanced Video Coding) or H.265|MPEG-H HEVC (High Efficiency Video Coding), and an audio stream such as MPEG-4 AAC (Advanced Audio Coding).

The subsampling means 120 divides a sample into multiple subsamples, as shown in Figures 3(c) and (d), consisting of a combination of a pair of unscrambled and scrambled sections, or either one or the other. In this case, the subsampling means 120 can, for example, in a video frame with an NAL structure, designate the portion containing information up to the VCL (Video Coding Layer) NAL unit slice header, including multiple non-VCL NAL units placed before the VCL NAL unit, as the unscrambled section, and the slice data of the VCL NAL unit as the scrambled section. Figure 3 shows an example where each sample is divided into three subsamples, but the number of subsample divisions may be one, two, or four or more (a portion of the subsamples divided to fit within a unit is called the "division range").

However, the sub-sampling means 120 may classify any position into non-scrambled and scrambled sections, or it may treat non-VCL units and VCL units as separate subsamples. Figure 3(d) shows an example where each subsample includes a set of non-scrambled and scrambled sections, but subsamples consisting only of non-scrambled sections or only of scrambled sections may also exist.

The unitization means 130, as shown in Figure 3(e), unitizes each subsample by dividing it so as not to exceed a pre-set MMTP packet size (e.g., 1400 bytes), or by combining multiple consecutive subsamples smaller than the MMTP packet size so as not to exceed the MMTP packet size. Figure 3(e) shows an example of dividing one subsample into two units and an example of combining two subsamples into one unit.

The scrambling means 140 sequentially scrambles the scrambled portion of each unit using a separately configured encryption key, for example, in AES 128-bit CTR mode. For scrambling, the scrambled portion is divided into 16-byte blocks sequentially from the beginning of the unit (the last block of a unit or subsample may be less than 16 bytes), and scrambling is performed on each block using the encryption key and a value obtained by adding a counter value to the initial MMT scramble value. The counter value is 0 for the first block of a unit and is continuously incremented by 1 for each block until all blocks within the unit have been scrambled.

The multiplexing means 150 performs multiplexing based on MMT. As shown in Figures 3(e) and (f), the multiplexing means 150 sequentially generates MMTP packets, each containing one unit in its payload, and multiplexes these MMTP packets into a single stream for transmission. As shown in Figure 3(f), the header portion of the MMTP packet can include an extended header area based on the MMT header extension method. In particular, the ARIB standard specifies multi-type header extension as an ARIB-specific specification for header extension.

Figure 4 shows the configuration of an MMTP packet carrying the scrambled portion according to this embodiment. Figure 4(a) shows a scrambled MMTP packet in which the unit stored in the payload consists only of the scrambled portion, and Figure 4(b) shows a partially scrambled MMTP packet in which the unit stored in the payload consists of both an unscrambled portion and a scrambled portion.

As shown in Figures 4(a) and 4(b), the multiplexing means 150 places a scramble-related information multitype header extension containing information about scrambling in the header portion of MMTP packets carrying the scrambled portion. The multiplexing means 150 does not need to place the scramble-related information multitype header extension in the header portion of MMTP packets that do not carry the scrambled portion (unscrambled MMTP packets).

As shown in Figure 4(b), when the multiplexing means 150 stores a subsample or its division range, including a scrambled portion and an unscrambled portion, in the payload of an MMTP packet, it places scrambled range information, including the length information of the scrambled portion and the unscrambled portion, in the header portion of the MMTP packet. In this embodiment, the multiplexing means 150 places the scrambled range information in the extended area (extended header area) of the header portion using a multi-type header extension. Such a multi-type header extension will be referred to as a "scrambled range information multi-type header extension."

In the example shown in Figure 4(b), the length of the unscrambled portion is 'a' bytes, and the length of the scrambled portion is 'b' bytes. In this case, the multiplexing means 150 includes length information indicating that the length of the unscrambled portion is 'a' bytes and the length of the scrambled portion is 'b' bytes in the scrambled range information multitype header extension. If the payload of a single MMTP packet contains multiple subsamples, and any of the subsamples contains an unscrambled portion and any of the subsamples contains a scrambled portion, the multiplexing means 150 provides the same number of scrambled range information multitype header extensions as the number of subsamples in the header portion of the MMTP packet. Specific examples of scrambled range information multitype header extensions will be described later.

Figure 5 shows a specific example of the scrambling-related information multi-type header extension according to this embodiment. Note that a portion of Figure 5 is referenced from Figure 3-1 of Part 1, Section 1 of ARIB STD-B61 2.3.

As shown in Figure 5, the multi-extension header type is set to 0x0001 based on ARIB B61. If the unit consists only of a subsample or the unscrambled portion of its divided range, the multiplexing means 150 indicates that the MMTP packet is not scrambled by setting the MMTP scramble control bit of the multi-type header extension to 0x00 or by not using the multi-type header extension.

On the other hand, if the unit consists of one or more subsamples including a scrambled section, the multiplexing means 150 indicates that scrambling has been applied by setting the MMTP scramble control bit of the multi-type header extension to 0x10 (scrambled, even key) or 0x11 (scrambled, odd key).

Furthermore, the multiplexing means 150 may determine the MMT scramble initial value, which is the initial value information for scrambling, by setting the MMT scramble initial value control bit to 0x00 and using the initial counter value generation method described in Section 4.5 of Chapter 4, Part 5 of ARIB TR-B39. Alternatively, the multiplexing means 150 may set the MMT scramble initial value control bit to 0x01 and describe the separately determined scramble initial value data for the unit as the MMT scramble initial value information. Note that whether the currently used encryption key is an odd-numbered key or an even-numbered key shall be identified separately by ECM (Entitlement Control Message), etc. Details regarding ECM can be found in ARIB STD-B61.

Figure 6 shows a specific example of the scrambled range information multitype header extension according to this embodiment. The scrambled range information multitype header extension describes the number of bytes in each subsample or its divided range, specifically the unscrambled and scrambled portions. As an example, the multitype header extension described in ARIB STD-B60 can be used for the scrambled range information multitype header extension. Figure 6 shows an example of the data structure of the scrambled range information multitype header extension, which includes information on the combination of the unscrambled and scrambled portions of one subsample or its divided range.

As shown in Figure 6, the scramble range information multitype header extension (Header_extension_byte_for_scramble_range_information) includes hdr_ext_end_flag, hdr_ext_type, hdr_ext_length, bytes_of_clear_data, and bytes_of_protected_data.

The `hdr_ext_end_flag` flag indicates whether or not other multitype header extensions following this one exist within the MMTP packet. For example, it should be 1 if a subsequent multitype header extension exists, and 0 otherwise.

`hdr_ext_type` is a value indicating the type of the multi-type header extension. The value indicating the type of the subsample-related information multi-type header extension is defined, for example, as 0x0004.

`hdr_ext_length` indicates the length of the data following this field in this multi-type header extension.

`bytes_of_clear_data` indicates the number of bytes in the unscrambled portion of the subsample or its division range, while `bytes_of_protected_data` indicates the number of bytes in the scrambled portion of the subsample or its division range.

If multiple subsamples exist, this can be described by setting `hdr_ext_end_flag` to 0 (indicating the existence of other multitype headers) and sequentially adding the scramble range information multitype header extension for each subsample.

(Broadcast receiving equipment)
Next, the broadcast receiving device 200 according to this embodiment will be described. Figure 7 is a diagram showing the configuration of the broadcast receiving device 200 according to this embodiment.

As shown in Figure 7, the broadcast receiving device 200 includes a separation means 210, a scrambling and decoding means 220, and a regeneration means 230.

The separation means 210 performs multiplex separation based on MMT. It extracts scrambled content from the received stream. When the separation means 210 receives an MMTP packet with scramble range information in the header, it uses the length information contained in the scramble range information to obtain from the MMTP packet payload the scrambled portion and the unscrambled portion of the subsample or its division range contained within the unit. Furthermore, when the separation means 210 receives an MMTP packet with multiple scramble range information entries in the header, it uses the length information contained in each of the multiple scramble range information entries to obtain multiple sets of scrambled and unscrambled portions from the payload.

The scramble decoding means 220 performs scramble decoding on the acquired scrambled portion. Specifically, the scramble decoding means 220 performs scramble decoding according to the information in the scramble-related information multi-type header extension and the scramble range information multi-type header extension.

The playback means 230 plays back the broadcast content by compressing and decoding the unscrambled portion and the scrambled portion that have been scrambled and decoded. The broadcast content may be compressed and encoded video data, and the playback means 230 may include a video decoder.

(Multiplexing method)
Next, the multiplexing method according to this embodiment will be described. Figures 8 and 9 are flowcharts illustrating the multiplexing method according to this embodiment. These flowcharts show the multiplexing of one unit in one sample. The encryption key is set separately, and in these flowcharts, it is assumed to be an even-numbered key.

In step S1, the sampling means 110 separates the samples from the input stream.

In step S2, the sub-sampling means 120 divides the sample into multiple sub-samples, each containing a non-scrambled portion (the portion not scrambled) and a scrambled portion (the portion that follows scrambled), or either one of these.

In step S3, the unitization means 130 divides the subsample so that it is no larger than a predetermined size (e.g., 1400 bytes), or combines multiple consecutive subsamples of a predetermined size or smaller to generate a unit of a predetermined size or smaller.

In step S4, the multiplexing means 150 determines whether the unit consists only of a subsample of the unscrambled portion. If the unit consists only of the unscrambled portion (step S4: YES), in step S5, the multiplexing means 150 sends it as an unscrambled MMTP packet and terminates processing for that unit.

On the other hand, if the unit includes parts other than the non-scrambled section (step S4: NO), in step S6, the scrambling means 140 determines the MMT scramble initial value IV, which is the initial information for scrambling the unit, and sets counter C to 0.

In step S7, the multiplexing means 150 determines whether the unit consists only of a subsample of the scrambled section. If the unit consists only of a subsample of the scrambled section (step S7: YES), in step S8, the multiplexing means 150 sets the multi-type header extension completion flag to 1 and generates the scramble-related information multi-type header extension. Then, in step S9, the multiplexing means 150 sets the number of subsamples N to 1 and proceeds to the processing in step S17.

On the other hand, if the unit includes parts other than the scrambling section (step S7: NO), in step S10, the multiplexing means 150 sets the multi-type header extension completion flag to 0 (indicating that there is a subsequent multi-type extension header) and generates the scramble range information multi-type header extension. Then, in step S11, the multiplexing means 150 sets the loop counter i to 0 and the number of subsamples to N, and starts the loop processing (steps S12 to S16).

In step S12, the multiplexing means 150 determines whether the subsample (i) is the last subsample (i = N-1) of the unit.

If it is not the last subsample (step S12: NO), in step S13, the multiplexing means 150 sets the multitype header extension completion flag to 0 and generates a scrambled range information multitype header extension including the number of bytes in the unscrambled portion and the number of bytes in the scrambled portion of subsample (i).

On the other hand, if it is the last subsample (step S12: YES), in step S14, the multiplexing means 150 sets the multi-type header extension completion flag to 1 and generates a scrambled range information multi-type header extension including the number of bytes in the unscrambled portion and the number of bytes in the scrambled portion of subsample (i).

In step S15, the multiplexing means 150 increments the loop counter i.

In step S16, the multiplexing means 150 determines whether the loop counter i is less than N. If the loop counter i is less than N (step S16: YES), the process returns to S12 and continues the loop processing.

On the other hand, if all subsamples have been processed (i = N) (step S16: NO), in step S17, the multiplexing means 150 resets the loop counter i to 0 and proceeds to the subsample scrambling process.

In step S18, the scrambling means 140 divides the scrambled portion of subsample (i) into blocks of 16 bytes each (the last block of the subsample may be less than 16 bytes).

In step S19, the scrambling means 140 sets the block's loop counter k to 0 and the number of blocks to M, and starts loop processing (steps S20 to S22) for the block.

In step S20, the scrambling means 140 scrambles the block (k) using AES 128 bits, with the encryption key and the value obtained by adding the MMT scrambling initial value IV and counter C.

In step S21, the scrambling means 140 increments both counter C and loop counter k.

In step S22, the scrambling means 140 determines whether the loop counter k is less than M. If the loop counter k is less than M (step S22: YES), the process returns to S20 and proceeds to the next block.

If all blocks have been processed (k = M) (step S22: NO), in step S23, the multiplexing means 150 increments the loop counter i.

In step S24, the multiplexing means 150 determines whether the loop counter i is less than N. If the loop counter i is less than N (step S24: YES), the process returns to step S18 and proceeds to the processing of the next subsample.

On the other hand, if all subsamples have been processed (i = N) (step S24: NO), in step S25, the multiplexing means 150 sends out scrambled MMT packets containing these subsamples and terminates processing.

(Summary of the embodiments)
As described above, the broadcast transmission device 100 for the digital broadcasting system 1 using MMT as a multiplexing method includes: a scrambling means 140 that scrambles a scrambled portion when a subsample extracted from a stream of video or audio broadcast content includes a scrambled portion that is subject to scrambling; and a multiplexing means 150 that, when storing a subsample including a scrambled portion and an unscrambled portion in the payload of an MMTP packet, places scrambled range information, including length information of each of the division ranges stored in the payload of the MMTP packet from the scrambled portion and the unscrambled portion, in the header portion of the MMTP packet.

Furthermore, the broadcast receiving device 200, upon receiving an MMTP packet in which scramble range information is placed in the header, includes a separation means 210 that uses the length information contained in the scramble range information to obtain from the payload of the MMTP packet the scrambled portion and the unscrambled portion of the division range stored in the payload of the MMTP packet in the subsample. It also includes a scramble decoding means 220 that performs scramble decoding on the scrambled portion, and a playback means 230 that compresses and decodes the broadcast content contained in the unscrambled portion and the scrambled portion after scramble decoding to reproduce it.

This allows the broadcast receiving device 200 to identify both the unscrambled and scrambled portions within the MMTP packet payload, even when subsamples stored in the MMTP packet payload are partially scrambled. Therefore, it is possible to include both the unscrambled and scrambled portions in a single MMTP packet payload. Thus, in a digital broadcasting system 1 using MMT, partially scrambled content can be transmitted efficiently.

In particular, by making the non-scrambled section the information for managing the operation of the video decoder, such as the non-VCL NAL unit and the slice header of the VCL NAL unit, the playback means 230 (including the video decoder) of the broadcast receiving device 200 can obtain the information for managing the operation of the video decoder before performing scrambling and decoding, thus enabling rapid video playback.

Furthermore, when a subsample consisting only of the scrambled portion is stored in the payload of an MMTP packet, the multiplexing means 150 generates a scrambled MMTP packet containing the subsample in the payload without placing the scramble range information in the header of the MMTP packet. When a subsample consisting only of the unscrambled portion is stored in the payload, the multiplexing means 150 generates an unscrambled MMTP packet containing the subsample in the payload without placing the scramble range information in the header of the MMTP packet. This allows the scramble range information to be placed only when necessary, thereby suppressing an increase in overhead.

In this embodiment, the multiplexing means 150 of the broadcast transmission device 100 places the scramble range information in the extended area of the header using the MMT method's multi-type header extension. This makes it possible to transmit the scramble range information in MMTP packet units without significantly altering the existing ARIB standard.

In this embodiment, when the broadcast transmission device 100's multiplexing means 150 stores multiple subsamples in the payload, and any of the subsamples include a scrambled portion and any of them include an unscrambled portion, it places multiple scrambled range information corresponding to the subsamples in the header portion. This allows multiple subsamples, including scrambled and unscrambled portions, to be efficiently transmitted together in a single MMTP packet.

(A variation of the digital broadcasting system)
Next, a modified example of the digital broadcasting system 1 described above will be explained. Figure 10 is a diagram showing a modified example of the digital broadcasting system 1.

As shown in Figure 10, the digital broadcasting system 1 according to this modified example further includes a relay device 300 and a communication terminal 400.

The relay device 300 receives scrambled content via the broadcast transmission path 10. The relay device 300 is a relay device equipped with broadcast reception functions such as a tuner. It receives scrambled content transmitted via digital broadcasting and relays the scrambled content to the communication terminal 400 via the communication network 20 without performing scrambling or decoding. The communication network 20 is, for example, a LAN (Local Area Network) installed in a home. The LAN may also be a wireless LAN.

The communication terminal 400 is a terminal that does not have a broadcast reception function. The communication terminal 400 is, for example, a PC (Personal Computer), a smartphone, or a tablet device. The communication terminal 400 receives scrambled content relayed by the relay device 300 via the communication network 20, performs scrambling and decoding on the received scrambled content, and plays the broadcast content. The communication terminal 400 performs scrambling and decoding according to the CENC method, which is a scrambling method for communication content.

Furthermore, the broadcast receiving device 200 performs scrambling and decoding (hereinafter referred to as "broadcast scrambling and decoding") in accordance with the digital broadcasting access control method specified in ARIB STD-B61 (hereinafter referred to as the "ARIB method").

In this way, by relaying the scrambled content to the communication terminal 400 via the relay device 300, even the communication terminal 400, which does not have a broadcast reception function, can play the broadcast content. Here, since the content is transmitted in a scrambled state over the communication network 20, content protection is also ensured. However, regarding the scrambling method, the ARIB method is incompatible with the CENC method, making it difficult for the communication terminal 400 to perform communication scrambling and decoding of broadcast content scrambled using the ARIB method.

Therefore, in this modified example, the broadcast transmission device 100 scrambles and multiplexes the broadcast content in a manner compatible with the CENC system while conforming to the ARIB system, thereby transmitting the scrambled content, enabling the communication terminal 400 to perform communication scrambling and decoding on the scrambled content.

Figure 11 is a diagram illustrating the multiplexing method in the digital broadcasting system 1 according to this modified example. Figure 11(a) shows a comparison of the ARIB method and the CENC method, and Figure 11(b) shows the multiplexing method according to this modified example.

As shown in Figure 11(a), the ARIB method scrambles the data portion of the MMTP payload within each MMTP packet, using the data portion as the scrambling range. The initial scrambling value (IV: Initialization Vector) used for scrambling is set on a per-MMTP packet basis.

On the other hand, the CENC Subsample Encryption method scrambles the sample (e.g., one frame of video or audio) by dividing it into subsample units. However, it scrambles only the scrambled portion, leaving the content header information (unscrambled portion) untouched. The initial scramble value (IV) used for scrambling is set on a sample-by-sample basis.

As shown in Figure 11(b), the multiplexing method in this modified example, when a sample consists of multiple subsamples, sets the length of the scrambled portion of all subsamples except the last one to 0 or an integer multiple of the length of the encryption key used for scrambling. When the subsamples are unitized to a size that fits within an MMTP packet, if the unit includes the scrambled portion and the division range does not include the last byte of the last subsample of the sample, the subsamples and units are subsampled and unitized such that the length of the scrambled portion of the unit is an integer multiple of the length of the encryption key. This completes the scrambling at the MMTP packet level. This satisfies the constraints regarding the scrambling unit in both the ARIB and CENC methods.

Furthermore, the multiplexing method in this modified example defines a new multi-type header extension for scramble range information indicating the unscrambled and scrambled portions, as described above, and designates only the scrambled portion of the payload as the scrambled range. This multi-type header extension allows for partial scrambling while satisfying the constraints regarding the scramble range for both the ARIB and CENC methods.

Furthermore, in this modified multiplexing method, the IV of the unit containing the scrambled portion at the beginning of a subsample, which includes the scrambled portion at the beginning of the sample, is the same as the sample's IV. The IV for each subsequent unit is set unit by unit (i.e., per MMTP packet) based on the IV of the immediately preceding unit. This satisfies the constraints regarding the initial scramble value for both the ARIB and CENC methods.

Furthermore, the multiplexing method in this modified example employs an encryption algorithm usable with both the ARIB and CENC methods for scrambling. This encryption algorithm is in AES CTR mode.

By using this multiplexing method, it is possible to scramble and multiplex broadcast content in a manner that conforms to the ARIB system while remaining compatible with the CENC system. Therefore, both the broadcast receiving device 200 and the communication terminal 400 can perform scrambling and decoding on the same scrambled content. Thus, scrambled content transmitted via digital broadcasting can be played back on a variety of terminals.

While an example of using AES CTR mode as an encryption algorithm has been described, any encryption algorithm common to both the ARIB and CENC schemes is acceptable. If a new common encryption algorithm is introduced, it may be adopted instead of AES CTR mode.

(Other embodiments)
A program may be provided that causes a computer to execute each of the processes performed by the above-mentioned devices (broadcast transmission device 100, broadcast reception device 200, relay device 300, communication terminal 400). The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. Alternatively, the circuits that execute each of the processes performed by the above-mentioned devices (broadcast transmission device 100, broadcast reception device 200, relay device 300, communication terminal 400) may be integrated, and the device may be configured using a semiconductor integrated circuit (chipset, SoC).

The embodiments have been described in detail above with reference to the drawings, but the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the concept.

1: Digital broadcasting system 10: Broadcast transmission line 20: Communication network 100: Broadcast transmission device 110: Sampling means 120: Subsampling means 130: Unitization means 140: Scrambling means 150: Multiplexing means 200: Broadcast receiving device 210: Separation means 220: Scramble decoding means 230: Regeneration means 300: Relay device 400: Communication terminal

Claims (10)

A broadcast transmission device for a digital broadcasting system that uses MMT as a multiplexing method,
If a subsample extracted from a stream of video or audio broadcast content includes a scrambling section that is subject to scrambling, the system includes a scrambling means for scrambling the scrambling section,
When storing the subsample, which includes the scrambled portion and the unscrambled portion, in the payload of an MMTP packet, the multiplexing means includes placing scrambled range information, which includes length information for each of the division ranges stored in the payload of the MMTP packet, in the header portion of the MMTP packet, among the scrambled portion and the unscrambled portion.
A broadcast transmission device characterized by comprising the following: The broadcast transmission device according to claim 1, characterized in that the multiplexing means arranges the scramble range information in the extended area of the header using the MMT method header extension. When storing a segmented range consisting only of the scrambled portion of the subsample in the payload, the multiplexing means generates a scrambled MMTP packet that includes the segmented range in the payload without placing the scrambled range information in the header.
The broadcast transmission device according to claim 1 or 2, characterized in that, when a segmented range consisting only of the unscrambled portion of the subsample is stored in the payload, the multiplexing means generates an unscrambled MMTP packet that includes the segmented range in the payload without placing the scrambled range information in the header portion. The broadcast transmission device according to any one of claims 1 to 3, wherein, when a plurality of the subsamples are stored in the payload, and any one of the plurality of subsamples includes the scrambled portion and any one of the plurality of subsamples includes the unscrambled portion, the multiplexing means arranges a plurality of scrambled range information corresponding to the plurality of subsamples in the header portion. The aforementioned broadcast content includes compressed and encoded video data,
The broadcast transmission device according to any one of claims 1 to 4, characterized in that the unscrambled portion includes information contained in the compressed encoded video data, which is used to manage the operation of the video decoder on the receiving side. The broadcast transmission device according to any one of claims 1 to 4, characterized in that, if the sample extracted from the stream of broadcast content consists of multiple subsamples, the length of the scrambled portion of the subsamples, excluding the last one, is set to 0 or an integer multiple of the length of the encryption key used for scrambling, and if the division range stored in the payload of the MMTP packet of the subsample includes the scrambled portion and the division range does not include the last byte of the last subsample of the sample, the length of the scrambled portion is an integer multiple of the length of the encryption key. A broadcast receiving device for a digital broadcasting system that uses MMT as a multiplexing method,
When an MMTP packet is received in which scramble range information is placed in the header, separation means obtain from the payload of the MMTP packet the scrambled portion and the unscrambled portion of the division range stored in the payload of the MMTP packet in a subsample, using the length information contained in the scramble range information.
Scramble decoding means for performing scramble decoding on the scrambled section,
A playback means that plays back broadcast content by compressing and decoding the unscrambled section and the scrambled section that has undergone scrambled decoding,
A broadcast receiving device characterized by being equipped with the following features. The broadcast receiving device according to claim 7, characterized in that the scrambling range information is arranged in the extended area of the header using the MMT method header extension. The broadcast receiving device according to claim 7 or 8, wherein, when the separation means receives the MMTP packet in which a plurality of scramble range information is arranged in the header portion, it obtains a plurality of sets of the scrambled portion and the unscrambled portion from the payload using the length information contained in each of the plurality of scramble range information. The aforementioned broadcast content is compressed and encoded video data.
The playback means includes a video decoder,
The broadcast receiving device according to any one of claims 7 to 9, characterized in that the unscrambled section includes information for managing the operation of the video decoder.