JP2022133163A - Content generation device, reception device, and program - Google Patents

Abstract

To recognize a change of a generation parameter during streaming content reproduction.SOLUTION: A content generation device 2 comprises: a media segment generation section 23 which generates a media segment in accordance with a generation parameter to be used for generating a segment of a video content; an initialization segment generation section 24 which generates a new initialization segment including information required for decoding the media segment in accordance with the change of the generation parameter; a manifest generation section 25 which generates a manifest file including segment correspondence information indicating a corresponding initialization segment for each media segment; and a content transmission section 26 which transmits the media segment, the initialization segment and the manifest file.SELECTED DRAWING: Figure 2

Description

The present invention relates to a content generation device, a reception device, and a program.

In recent streaming video distribution on the Internet, a method of streaming distribution using the HTTP protocol by a general-purpose Web server has become mainstream. MPEG-DASH (ISO/IEC23009-1), which is an international standard, is an example of such a streaming delivery method (adaptive streaming) based on the HTTP protocol.

In MPEG-DASH, a Web server is provided with a manifest file that describes initialization segments, media segments, their URLs, and video content attributes. A media segment is a segment obtained by dividing a stream of video content encoded with one or more qualities (parameters such as screen size and bit rate) into files of several seconds to several tens of seconds each. The initialization segment contains metadata necessary to present the segment, such as generation parameters for encoding, encryption, and so on. From the manifest file, the receiving device takes into consideration the screen size of the receiving device and the state of the network bandwidth of the transmission path, selects the quality at the appropriate time, receives segments one after another, and joins them into a single video content for playback. (see, for example, Non-Patent Document 1).

In addition to the above-mentioned quality switching, as a method of providing a video streaming service, multi-view video/multilingual audio distribution, program distribution according to organization like broadcasting, and the like are conceivable. MPEG-DASH defines a manifest description method that enables such services.

FIG. 7 shows a conceptual diagram of a manifest file in MPD (Media Presentation Description) format of MPEG-DASH. The MPD format has a hierarchical structure in the order of Period, AdaptationSet, and Representation. A period indicates one section in which content is divided in the time direction, and the example in FIG. 7 indicates that periods each having a media duration of 300 seconds are connected. A Period consists of one or more AdaptationSets.

AdaptationSet indicates information of media components (video, audio, text, etc.), and can include a plurality of components with different expressions (video from another angle, audio in another language, etc.) in the same media format. In the example of FIG. 7, there are two videos (mimeType=video/mp4) and one audio (mimeType=audio/mp4). Information of each media component included in AdaptationSet is indicated by Representation.

Information of a segment (Initialization Segment, Media Segment), which is actual data constituting a media element, is described in Representation. Initialization Segment indicates an initialization segment, and Media Segment indicates a media segment. In the example of FIG. 7, the file name of the media segment is obtained by incrementing the sequence number ($Number$) for each segment length (duration=5s).

With such a manifest file, it is possible to sequentially receive the segments (initialization segment and media segment) forming the media component (AdaptationSet) selected in the Period, and to reselect the media component. allows switching to reception of segments forming another media component and displaying another video.

In addition, in Non-Patent Document 2, by preparing a common initialization segment that includes generation parameters for all Representations included in one AdaptationSet, only inserting a common initialization segment at the beginning in the AdaptationSet allows Representation A method is disclosed for realizing adaptive streaming without inserting an initialization segment every time switching is performed.

In addition, in Patent Document 1, by generating a distribution stream by replacing a part of a stream after switching with a stream generated as a reference image from pictures before and after switching to a stream with a different bit rate, A technique for suppressing changes in the image quality of the image is disclosed.

JP 2015-19329 A

“Next Generation Video Distribution Technology ``MPEG-DASH'' Technical Overview and Standardization/Related Technology Trends”, Journal of the Institute of Image Information and Television Engineers, Vol.67, No.2, 2013, p.109-115 "Digital Video Broadcasting (DVB); MPEG-DASH Profile for Transport of ISO BMFF Based DVB Services over IP Based Networks - DVB Document A168", [online], October 2019, [searched on February 22, 2021], Internet <URL: https://dvb.org/wp-content/uploads/2019/12/a168_dvb_mpeg-dash_oct_2019.pdf>

FIG. 8 is a diagram showing the concept of buffers in the receiving device. When switching to a stream (Representation) with a different generation parameter, the receiving device inserts the initialization segment of the switching destination Representation immediately before inserting media segments belonging to the switching destination Representation into the buffer, as shown in FIG. insert. As a result, it is possible to appropriately notify the subsequent decoder of the buffer of the generation parameters of the subsequent media segment, so that seamless adaptive streaming can be realized. In FIG. 8, each quality media segment is composed of three blocks, and one block corresponds to one Representation.

However, in the MPEG-DASH standard, as shown in FIG. 7, only one initialization segment information can be described in one Representation. Therefore, if the generation parameter of the initialization segment described in the Representation is changed while the receiving device is reproducing one Representation, the receiving device can recognize the content and change timing. could not.

Also, even if the technology described in Non-Patent Document 2 is used, the receiving device cannot recognize the change of the generation parameter during the reproduction of the Representation. Further, the technique described in Patent Document 1 is not necessarily applicable to changing generation parameters such as changing resolution and encryption key.

SUMMARY OF THE INVENTION An object of the present invention, which has been made in view of such circumstances, is to provide a content generation device capable of continuing stable streaming by enabling a reception device to recognize changes in generation parameters during playback of streaming content. It is to provide a device and a program.

In order to solve the above problems, a content generation device according to one embodiment is a content generation device that generates segments of video content and a manifest file, and according to generation parameters used to generate segments of video content, a media segment generation unit for generating media segments; an initialization segment generation unit for generating new initialization segments containing information necessary to decode the media segments according to the change in the generation parameters; and the media segments. a manifest generation unit that generates a manifest file including segment correspondence information indicating the initialization segment corresponding to each; and a content transmission unit that transmits the media segment, the initialization segment, and the manifest file.

Furthermore, in one embodiment, the segment correspondence information may be information for specifying the file name of the media segment and the file name of the initialization segment corresponding to the media segment.

Furthermore, in one embodiment, the manifest generation unit adds the segment correspondence information to a manifest file conforming to the MPD (Media Presentation Description) format, so that information of a plurality of initialization segments is included in one Representation. You may generate a described manifest file.

Further, in order to solve the above problems, a receiving device according to one embodiment is a receiving device that receives an initialization segment of video content, a media segment, and a manifest file, and receives an initialization segment corresponding to each media segment. a manifest acquisition unit that acquires a manifest file in which segment correspondence information is described, and generates a segment URL list that associates the playback time of the media segment with the URL of the initialization segment and the media segment; and playback of the media segment a buffer control unit for extracting the URL of the media segment and the URL of the initialization segment corresponding to the media segment, based on the segment URL list and the playback time updated together with the segment URL list; a segment obtaining unit for obtaining the media segment based on the URL of the initialization segment and obtaining the initialization segment based on the URL of the initialization segment.

Further, in order to solve the above problem, a program according to one embodiment causes a computer to function as the content generation device.

Moreover, in order to solve the above problem, a program according to one embodiment causes a computer to function as the above receiving device.

Advantageous Effects of Invention According to the present invention, it becomes possible for a receiving device to recognize a change in a generation parameter during reproduction of streaming content and continuously reproduce the content. Therefore, it is possible to dynamically change the generation parameters of the stream being distributed in accordance with network band fluctuations and operational requirements of service providers.

1 is a diagram showing an outline of a content distribution system including a receiving device and a content generation device according to one embodiment of the present invention; FIG. 1 is a block diagram showing a configuration example of a content generation device according to an embodiment of the present invention; FIG. FIG. 3 is a diagram showing an example of a manifest file in MPD format generated by the content generation device according to one embodiment of the present invention; 4 is a flow chart showing a content generation method of a content generation device according to an embodiment of the present invention; 1 is a block diagram showing a configuration example of a receiver according to an embodiment of the present invention; FIG. 4 is a flow chart showing a segment acquisition control method for a receiver according to an embodiment of the present invention; It is a figure which shows the concept of the conventional manifest file. FIG. 4 is a diagram showing the concept of a buffer in a conventional receiving device;

An embodiment of the present invention will be described in detail below with reference to the drawings. In the embodiment described below, as an example, the manifest file is in MPEG-DASH (ISO/IEC23009-1) MPD format.

FIG. 1 shows an outline of a content distribution system including a receiving device and a content generating device according to one embodiment of the present invention. A content distribution system is a system that distributes video content composed of a plurality of segments and a manifest file for each segment. Receiving device 1 and distribution server 3 are connected via the Internet. The content generation device 2 and the distribution server 3 may be connected by a dedicated local network, or may be connected via the Internet.

The receiving device 1 receives segments (initialization segments and media segments) of moving image content and manifest files from the distribution server 3, and performs streaming playback.

The content generation device 2 generates segments and manifest files of video content and supplies them to the distribution server 3 .

The distribution server 3 is a server that distributes the manifest file and segment of the URL specified by the receiving device 1 to the receiving device 1, and can be, for example, a general web server.

(content generation device)
Next, details of the content generation device 2 will be described. FIG. 2 is a block diagram showing a configuration example of the content generation device 2. As shown in FIG. The content generation device 2 shown in FIG. , and a communication I/F 27 .

The material video output unit 21 outputs the content to be generated to the media segment generation unit 23 from the material video input from the outside or the material video stored in advance.

The generation parameter changing unit 22 sets or changes the generation parameters, and outputs the generation parameters to the media segment generation unit 23 and the initialization segment generation unit 24 . Generation parameters are parameters used to generate segments of video content, such as media encoding parameters (resolution, bit rate, etc.), encryption parameters for content protection, and the like. Generation parameters may be set or changed by a user through an input interface. The generation parameter changing unit 22 also outputs a parameter change trigger indicating the timing of changing the generation parameter to the initialization segment generation unit 24 .

The media segment generator 23 generates media segments according to the generation parameters. The media segment generator 23 includes an encoder 231 and a segmenter 232 .

The encoding unit 231 encodes the material video signal input from the material video output unit 21 using an existing encoding method or encrypts the material video signal using an existing encryption method according to the generation parameters input from the generation parameter changing unit 22. . Existing coding schemes include, for example, H.264. 264|MPEG-4 AVC (Advanced Video Coding), H.264 | 265|MPEG-H HEVC (High Efficiency Video Coding). An existing encryption method is, for example, the AES (Advanced Encryption Standard) method. The encoding section 231 then outputs the encoded stream to the segmentation section 232 . Audio can also be processed in the same manner as video.

The segmentation unit 232 segments the encoded stream input from the encoding unit 231 in, for example, the ISO-BMFF (ISO-Base Media File Format) format to generate media segments containing media information. The segmentation unit 232 then outputs the generated media segments to the manifest generation unit 25 .

The initialization segment generation unit 24 receives generation parameters and parameter change triggers from the generation parameter change unit 22 . Then, the initialization segment generator 24 generates a new initialization segment including information necessary for decoding the media segment in accordance with the change of the generation parameter. For example, the initialization segment generator 24 segments in the ISO-BMFF (ISO-Base Media File Format) format to generate an initialization segment including generation parameters. The initialization segment generator 24 then outputs the generated initialization segment to the manifest generator 25 .

The manifest generation unit 25 receives media segments from the segmentation unit 232 and inputs initialization segments from the initialization segment generation unit 24 . Then, the manifest generation unit 25 generates a manifest file including segment correspondence information. The segment correspondence information is information indicating an initialization segment corresponding to each media segment. The manifest generation unit 25 adds segment correspondence information to, for example, a manifest file conforming to the MPD format of conventional MPEG-DASH. The manifest generator 25 then outputs the initialization segment, the media segment, and the manifest file to the content transmitter 26 . The manifest file may be generated by a method of sequentially updating each time a segment is input, or may be performed after inputting all segments.

The content transmission unit 26 transmits the initialization segment, the media segment, and the manifest file input from the manifest generation unit 25 to the distribution server 3 via the communication I/F 27 .

A specific example of content generated by the content generation device 2 will now be described with reference to FIG. FIG. 3 shows an example (excerpt) of an MPD format manifest file to which segment correspondence information has been added. Here, the segment correspondence information consists of the file name of a media segment and the initialization segment corresponding to the media segment. It is used as information for specifying the file name of the file.

FIG. 3 shows a manifest file when the content duration is 32 seconds, the segment length is 2 seconds, and the generation parameters are changed every 8 seconds from the start of encoding. In this example, there is one Period whose content duration information (duration) is 32 seconds, and one AdaptationSet whose media format is video (mimeType="video/mp4") exists in the Period. exists one.

Here, a method for identifying a media segment containing a certain playback time and a file name of an initialization segment corresponding to the media segment will be described.

The value of start on the second line in FIG. 3 indicates that the period start time is zero. The value of timescale on the fourth line in FIG. 3 indicates that the timescale (the number of graduations per second) of AdaptationSet is 1,000.

The value of media on the 13th line in FIG. 3 indicates that the reference value of the file name of the media segment is s1_$Time$.mp4, and the value obtained by replacing $Time$ with the time stamp value of the media segment is the file name. becomes. Also, the value of initialization indicates that the reference value of the file name of the initialization segment is s1_init_$Index$.mp4, and the value obtained by replacing $Index$ with the identifier of the initialization segment becomes the file name.

Also, SegmentTimeline shown in the 5th to 10th lines of FIG. 3 indicates the relationship between the playback start time of each segment, the segment length, and the identifier of the corresponding initialized segment. In S, t is the playback start time, d is the segment length, i is the identifier of the initialized segment, r is i, and d is the number of continuations of the same segment. That is, S on the 6th line indicates that the start time is 0 (t=0), the segment length is 2 seconds (d/timescale), the index of the initialization segment is 0, and the same i and d continue for 3 segments. showing. Therefore, the segment file names are s1_0.mp4, s1_2000.mp4, s1_4000.mp4, and s1_6000.mp4 for media segments with start times of 0, 2, 4, and 6 seconds, and the corresponding initialization segments file name is s1_init_0.mp4. Also, from the 7th line in FIG. 5 , the media segments with start times of 8 seconds, 10 seconds, 12 seconds, and 14 seconds are s1_8000.mp4, s1_10000.mp4, s1_12000.mp4, and s1_14000.mp4. You can see that the initialization segment is s1_init_1.mp4. In this way, it is possible to specify the file name of the media segment containing a certain playback time and the file name of the initialization segment corresponding to the media segment.

In the example of FIG. 3, the 5th to 10th and 13th lines are segment correspondence information. Here, i is an identifier that is not defined in the conventional standard, and $Index$ is a variable that is not defined in the conventional standard. In this way, the manifest generation unit 25 adds segment correspondence information to a manifest file conforming to the MPD format, thereby generating a manifest file in which information on a plurality of initialization segments is described within one Representation. becomes possible. In the example of FIG. 3, information of four initialization segments with i=0 to 3 is described for Representation with id=1.

(Content generation method)
Next, the content generation method of the present invention will be described with reference to the flowchart of FIG.

In step S001, the generation parameter changing unit 22 confirms whether or not the generation parameters have been initialized if before the start of encoding, and confirms whether or not the generation parameters have been changed if the encoding has started. . If the generation parameters are initialized or changed (step S001-YES), the process proceeds to step S002, and if the generation parameters are not initialized or changed (step S001-NO), the process proceeds to step S004. proceed.

In step S002, the generation parameter changing unit 22 sets the set or changed generation parameter as a new generation parameter.

In step S003, the initialization segment generator 24 generates an initialization segment based on newly generated parameters.

In step S004, the encoding unit 231 continues encoding using the previously set parameters.

In step S005, the segmentation unit 232 generates media segments segmented at predetermined intervals.

In step S006, the manifest generation unit 25 associates the initialization segment for each generation parameter with the media segment generated by each generation parameter.

In step S<b>007 , the manifest file is updated by the manifest generation unit 25 . And the initialization segment, the media segment, and the manifest file are transmitted by the content transmission part 26 and communication I/F27.

In step S008, it is checked whether the encoding has reached the end of the content or whether the end of encoding has been instructed. If the encoding reaches the end of the content, or if there is an encoding end instruction (step S008-YES), the process ends. If the encoding has not reached the end of the content and there is no encoding end instruction (step S008-NO), the process continues.

A computer can be preferably used to function as the content generation device 2 described above. , and the program can be read and executed by the processor of the computer. This program can be recorded on a computer-readable recording medium.

(receiving device)
Next, details of the receiving device 1 will be described. FIG. 5 is a block diagram showing a configuration example of the receiving device 1. As shown in FIG. The receiving device 1 shown in FIG. 5 includes a communication I/F 10, a manifest acquisition unit 11, a segment list storage unit 12, a segment acquisition unit 13, a buffer 14, a buffer control unit 15, a reproduction control unit 16, A playback control user I/F 17 , a playback unit 18 , and a display unit 19 are provided.

The manifest acquisition unit 11 receives the manifest file of the desired program from the distribution server 3 via the communication I/F 10 . Then, the manifest acquisition unit 11 analyzes the manifest file in which the segment correspondence relationship information is described, generates a segment URL list in which the playback time of the media segment is associated with the URL of the initialization segment and the media segment, A URL list is stored in the segment list storage unit 12 .

The segment acquisition unit 13 inputs the URL of the segment to be acquired from the buffer control unit 15 and requests the distribution server 3 via the communication I/F 10 to make a request including the input segment URL. As a response to the request, the segment acquisition unit 13 receives segments from the distribution server 3 via the communication I/F 10 and outputs the segments to the buffer control unit 15 .

The buffer 14 receives the segment from the buffer control unit 15 and stores the media segment in association with the initialization segment, the playback start time and the playback duration (segment length) of the media segment. Then, the buffer 14 outputs to the buffer control unit 15 the segment playback time and playback duration information of all media segments currently being stored. In addition, the buffer 14 sequentially outputs the segments of the playback times requested by the playback unit 18 to the playback unit 18 .

The reproduction control unit 16 outputs the current reproduction state (during reproduction, stopped) and the current reproduction time information input from the reproduction unit 18 to the reproduction control user I/F 17 . Further, when a reproduction start/stop command is input from the reproduction control user I/F 17, the reproduction control unit 16 instructs the reproduction unit 18 to start/stop reproduction.

The reproduction control user I/F 17 is a function for controlling reproduction by user's operation. Equipped with a playback start/stop button and a button that enables a seek operation to a desired playback time. You may display time graphically. For example, a horizontally long bar with the start time of the content on the left and the end time on the right is displayed at the bottom of the playback screen. By moving from the left end to the right end, it is possible to grasp at a glance which part of the entire reproduction time is currently being reproduced. Further, by changing the knob-like operation portion, a seek operation to a desired playback time may be performed.

When the playback command including the playback start time is input from the playback control unit 16, the playback unit 18 sequentially inputs media segments from the buffer 14 based on the playback start time, and converts the media segments into initialization segments corresponding to the media segments. is decoded using the parameters indicated by , and output to the display unit 19 . The reproducing unit 18 also outputs to the reproduction control unit 16 reproduction time information, which is reproduction time information updated along with the reproduction of the media segment. Further, when a stop command is input from the reproduction control unit 16, the reproduction unit 18 stops reproduction.

The display unit 19 displays the decoded media data input from the playback unit 18 according to the media format.

The buffer control unit 15 determines (extracts) the URL of the segment to be acquired from the playback time information and the segment URL list input from the playback control unit 16 , and outputs it to the segment acquisition unit 13 . The buffer control unit 15 also outputs the segment input from the segment acquisition unit 13 to the buffer 14 .

(Segment Acquisition Control Method)
Next, the segment acquisition control method of the receiver 1 will be described with reference to the flowchart of FIG. In the flowchart shown in FIG. 6, it is assumed that the manifest acquisition unit 11 has already acquired the manifest file from the distribution server 3 and the segment URL list is already created. It is also assumed that the buffer 14 has a range from the start time to the end time of the Period described in the MPD, and stores the segments in association with information on the reproduction start time and the reproduction continuation time. Also, the range in which content segments are inserted into the buffer 14 is called a buffered segment range.

In step S101, when any playback is started in the playback control user I/F 17, the playback control unit 16 outputs the playback start time to the buffer control unit 15 as the current playback time.

In step S102, the buffer control unit 15 determines whether or not the current playback time is within the buffered segment range. If it is within the buffered segment range (step S102-YES), the process proceeds to step S103, and if not within the buffered segment range (step S102-NO), the process proceeds to step S104.

In step S103, the buffer control unit 15 extracts the URL of the media segment following the buffered segment range and the URL of the initialization segment corresponding to the media segment from the segment URL list.

In step S104, the buffer control unit 15 extracts the URL of the media segment including the current start time and the URL of the initialization segment corresponding to the media segment from the segment URL list.

In step S105, the buffer control unit 15 determines whether or not the URL of the extracted initialization segment is different from the URL of the previously obtained media segment. If different (step S105-YES), the process proceeds to step S106, and if they match (step S105-NO), the process proceeds to step S108.

In step S106, the segment acquisition unit 13 transmits a segment request including the URL of the extracted initialization segment to the distribution server 3, and receives the initialization segment corresponding to the request.

In step S<b>107 , the received initialization segment is inserted into the buffer 14 by the buffer control unit 15 .

In step S108, the segment acquisition unit 13 transmits a segment request including the URL of the media segment extracted in step S103 or step S104 to the distribution server 3, and receives the media segment corresponding to the request.

In step S<b>109 , the received media segment is inserted into the buffer 14 by the buffer control unit 15 .

In step S110, it is checked whether the end of the segment URL list has been reached or the stop button has been pressed. When the end of the segment URL list is reached or the stop button is pressed (step S110-YES), the process ends. If the end of the segment URL list has not been reached and the stop button has not been pressed (step S110-NO), the process proceeds to step S1111.

In step S111, the reproduction unit 18 continues reproduction, updates the current reproduction time, and returns the process to step S102.

A computer can be preferably used to function as the receiving device 1 described above, and such a computer stores a program describing processing details for realizing each function of the receiving device 1 in a storage unit of the computer. It can be realized by reading out and executing this program by the processor of the computer. This program can be recorded on a computer-readable recording medium.

As described above, the content generation device 2 or a program for functioning as the content generation device 2 generates new initialization segments according to changes in generation parameters, and generates a manifest file containing segment correspondence information. Then, the receiving device 1 or a program for functioning as the receiving device 1 can recognize changes in generation parameters during streaming content playback by acquiring a manifest file in which segment correspondence information is described, and can stably You will be able to continue streaming.

Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many modifications and substitutions may be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as limited by the embodiments described above, and various modifications and changes are possible without departing from the scope of the appended claims. For example, a plurality of constituent blocks or processing steps described in the embodiments may be combined into one or one may be divided into a plurality.

1 Receiving Device 2 Content Generating Device 3 Distribution Server 10 Communication I/F
REFERENCE SIGNS LIST 11 manifest acquisition unit 12 segment list storage unit 13 segment acquisition unit 14 buffer 15 buffer control unit 16 playback control unit 17 playback control user I/F
18 reproduction unit 19 display unit 21 material video output unit 22 generation parameter change unit 23 media segment generation unit 24 initialization segment generation unit 25 manifest generation unit 26 content transmission unit 27 communication I/F
231 encoding unit 232 segmenting unit

Claims (6)

A content generation device that generates video content segments and manifest files,
a media segment generator for generating media segments according to generation parameters used to generate segments of video content;
an initialization segment generation unit that generates a new initialization segment containing information necessary to decode the media segment in accordance with the change in the generation parameter;
a manifest generation unit that generates a manifest file including segment correspondence information indicating the initialization segment corresponding to each media segment;
a content transmission unit that transmits the media segment, the initialization segment, and the manifest file;
A content generation device comprising: 2. The content generation device according to claim 1, wherein said segment correspondence information is information for specifying a file name of a media segment and a file name of an initialization segment corresponding to said media segment. The manifest generation unit adds the segment correspondence information to a manifest file conforming to the MPD (Media Presentation Description) format, thereby generating a manifest file in which information on a plurality of initialization segments is described within one Representation. 3. The content generation device according to claim 1 or 2, wherein: A receiving device that receives initialization segments, media segments, and manifest files of video content,
Acquire a manifest file that describes segment correspondence information indicating the initialization segment corresponding to each media segment, and generate a segment URL list that associates the playback time of the media segment with the URL of the initialization segment and the media segment. a manifest acquisition unit that
a buffer control unit that extracts the URL of the media segment and the URL of the initialization segment corresponding to the media segment based on the segment URL list and the playback time updated along with the playback of the media segment;
a segment acquisition unit that acquires the media segment based on the URL of the media segment and acquires the initialization segment based on the URL of the initialization segment;
A receiver, comprising: A program for causing a computer to function as the content generation device according to any one of claims 1 to 3. A program for causing a computer to function as the receiving device according to claim 4.

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