JP5030986B2 - Video transmission apparatus and video transmission system - Google Patents

Description

  The present invention compresses and encodes one frame of an input video in a predetermined encoding unit (for example, a slice unit) to generate a plurality of encoded video data, packetizes the plurality of encoded video data, and transmits the packetized data to a network. The present invention relates to a video transmission device and a video transmission system to which the video transmission device is applied.

In recent years, with the increase in network speed, the demand for digital video transmission over the network has increased, and a plurality of transmission methods have been proposed.
As a transmission method for transmitting a compressed video stream to a network, a transmission method defined by RFC (Request For Comment) of IETF (Internet Engineering Task Force) is well known.
For example, ITU-T H.I. There is RFC1889 (Non-Patent Document 1) that defines RTP (Real Time Transport Protocol) for IP transmission of video streams conforming to H.264.
RTP defines a transmission protocol suitable for transmitting real-time data such as audio and video over a network.

FIG. 6 is an explanatory diagram showing the data format of the header of the RTP packet.
In FIG. 6, “timestamp” expresses time information of a payload of the RTP packet (data itself to be transmitted by the RTP packet).
In the case of RFC that transmits video encoded data such as MPEG or H264, time information indicating the time (90 KHz unit time) at which the payload is displayed is stored in “timestamp”.
On the receiving side of the RTP packet, the video obtained by the decoding process is displayed at the correct time by referring to “timestamp” included in the header of the RTP packet.

Therefore, if the video transmission apparatus uses the RTP packet, the display time of the video data transmitted by the RTP packet can be expressed with an accuracy of 90 KHz.
However, since the initial value of “timestamp” included in the header of the RTP packet is given a random value, the absolute time cannot be expressed.
That is, if “timestamp” is used, it is possible to express the relative display time of the next video frame with an accuracy of 90 KHz from the display time of the previous video frame. The absolute time indicating year, month, day, hour, minute and second cannot be expressed.

“RFC1889-RTP: A Transport Protocol for Real-Time Applications”, [online], [searched February 17, 2009], Internet <http://www.faqs.org/rfcs/rfc1889.html>

Since the conventional video transmission apparatus is configured as described above, if the RTP packet is used, the display time of the video data transmitted by the RTP packet can be expressed with an accuracy of 90 KHz, but the absolute time is expressed. I can't.
For this reason, for example, when video images transmitted from a large number of cameras are displayed at the same time and video monitoring is performed, there is a problem that a plurality of videos cannot be synchronized in a strict sense.
In addition, when one camera uses multicast communication or the like to transmit video to many receivers, different time information is associated with the same frame, which may cause inconvenience. was there.

  The present invention has been made to solve the above-described problems, and is a video transmission apparatus capable of transmitting time information indicating an absolute time in accordance with the RTP transmission method without increasing the amount of information in the header. And to obtain a video transmission system.

  The video transmission apparatus according to the present invention provides encoding means for a header of video encoded data other than the last video encoded data of one frame among a plurality of video encoded data generated by the encoding means. The time information in small time units is inserted in the time information generated by, and the time information in large time units is inserted in the time information for the header of the last video encoded data of one frame. It is what I did.

  According to the present invention, among the plurality of video encoded data generated by the encoding means, the header of the video encoded data other than the last video encoded data of one frame is generated by the encoding means. The time information in the small time unit is inserted in the time information, and the time information in the large time unit is inserted in the time information in the header of the last encoded video data of one frame. Therefore, there is an effect that time information indicating the absolute time can be transmitted in accordance with the RTP transmission method without increasing the amount of information in the header.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the video transmission system by Embodiment 1 of this invention. It is explanatory drawing which shows the encoding process of the video encoding part. It is explanatory drawing which shows the packetization process of the packet transmission part. It is a block diagram which shows the video transmission system by Embodiment 2 of this invention. It is explanatory drawing which shows the packetization process of the packet transmission part. It is explanatory drawing which shows the data format of the header of a RTP packet.

Embodiment 1 FIG.
1 is a block diagram showing a video transmission system according to Embodiment 1 of the present invention.
In FIG. 1, each time a video frame 1 is input, the video transmission device 1 compresses and encodes the frame in a predetermined coding unit (for example, a slice unit) to generate a plurality of video coded data. A process of packetizing the video encoded data and transmitting it to the network 2 is performed.
The network 2 is a transmission line connecting the video transmission device 1 and the video reception device 3, and transmits the video packet transmitted from the video transmission device 1 to the video reception device 3.
When receiving the video packet transmitted by the network 2, the video receiver 3 separates a plurality of encoded video data and time information from the video packet, decodes the video from the encoded video data, and outputs the time information. The process of outputting the video at the timing corresponding to.

The clock generation unit 11 of the video transmission apparatus 1 performs processing for generating a clock.
The video encoding unit 12 uses the clock generated by the clock generation unit 11 to compress and encode one frame of the input video in a predetermined encoding unit (for example, a slice unit in MPEG encoding). The video encoded data is generated, and the time information t indicating the absolute time for displaying the video encoded data is generated. Note that the video encoding unit 12 constitutes encoding means.

The packet transmission unit 13 generates a video packet by adding a header including the time information t generated by the video encoding unit 12 to a plurality of video encoded data, and transmits the video packet to the network 2. carry out.
That is, the packet sending unit 13 performs video coding on the header of video encoded data other than the last video encoded data of one frame among the plurality of video encoded data generated by the video encoding unit 12. The time information in a small time unit (for example, in milliseconds) is inserted into the time information t generated by the unit 12, and for the header of the last video encoded data of one frame, the time information t Among them, processing for inserting time information in a large time unit (for example, in seconds) is performed.
The packet sending unit 13 constitutes a video packet sending unit.

The clock generation unit 31 of the video reception device 3 performs processing for generating a clock.
The packet receiving unit 32 receives the video packet transmitted from the video transmission apparatus 1 and performs a process of separating a plurality of encoded video data and time information t from the video packet. The packet receiver 32 constitutes a video packet receiver.
The video decoding unit 33 decodes video from the plurality of video encoded data separated by the packet receiving unit 32, refers to the clock generated by the clock generation unit 31, and displays the video at a timing corresponding to the time information t. Perform the output process. Note that the video decoding unit 33 constitutes decoding means.

Next, the operation will be described.
The clock generation unit 11 of the video transmission device 1 performs processing for generating a clock.
When one frame of video is input, the video encoding unit 12 uses the clock generated by the clock generation unit 11 to convert the one frame into a predetermined encoding unit (for example, a slice unit in MPEG encoding). In addition to generating a plurality of encoded video data, time information t indicating the absolute time for displaying the encoded video data is generated.

Here, FIG. 2 is an explanatory diagram showing the encoding process of the video encoder 12.
Hereinafter, the encoding process of the video encoding unit 12 will be described in detail with reference to FIG.
FIG. 2 shows an example in which video frames are input at times t0, t1, t2, and t3.
In the video encoding unit 12, for example, when one video frame 50 is input at time t 0, for example, by performing compression encoding processing that is independent in units of slices, A plurality of encoded video data 51 to 54 is generated.
When the video encoding unit 12 generates a plurality of video encoded data 51 to 54, the video encoding unit 51 refers to the clock generated by the clock generation unit 11 and displays the absolute time (year / month / day / day) for displaying the video encoded data 51 to 54 The time information t indicating the minute and second) is generated. However, since the video encoded data 51 to 54 constitute video of the same frame, the display times of the video encoded data 51 to 54 are the same time.

  When the video encoding unit 12 generates the video encoded data 51 to 54 and the time information t indicating the absolute time for displaying the video encoded data 51 to 54, the packet transmission unit 13 generates a header including the time information t. A video packet is generated by adding to the encoded video data 51 to 54, and the video packet is transmitted to the network 2.

Here, FIG. 3 is an explanatory diagram showing packetization processing of the packet transmission unit 13.
Hereinafter, the packetization process of the packet transmission unit 13 will be described in detail with reference to FIG.
First, the RTP header of FIG. 6 is assumed as a header added to the video encoded data 51 to 54.
The RTP header has a 32-bit data field for storing the above “timestamp”.
In the case of RTP, “1” is stored in the M bit (see FIG. 6) in the RTP header of the video encoded data 54 which is the last video encoded data of one frame, and the last video encoded data. It is stipulated that “0” is stored in the M bit in the RTP header of the video encoded data 51 to 53 that is not.

  Therefore, the packet transmission unit 13 stores “0” in the M bits in the RTP header added to the video encoded data 51 to 53, and includes the small time unit in the time information t generated by the video encoding unit 12. By storing the time information (for example, in milliseconds), that is, the lower 32 bits of the time information t generated by the video encoding unit 12 in the “timestamp” data field of the RTP header, an RTP header is added. Video encoded data 55 to 57 are generated.

  Further, the packet transmission unit 13 stores “1” in the M bit in the RTP header added to the video encoded data 54 which is the last video encoded data, and the time information t generated by the video encoding unit 12. In the time information in the large time unit (for example, second unit), that is, the bit higher than the lower 32 bits in the time information t generated by the video encoding unit 12 (for example, if the time information is 64-bit information). For example, the upper 32 bits and the upper 16 bits if the time information is 48 bits) are stored in the “timestamp” data field of the RTP header, thereby generating video encoded data 58 with an RTP header.

Information other than “timestamp” in the RTP header is the same as the information defined in RTP (see FIG. 6).
As described above, the packet transmission unit 13 generates a video packet (video encoded data 55 to 58 with an RTP header), and transmits the video packet to the network 2.

When receiving the video packet transmitted from the video transmission device 1, the packet receiving unit 32 of the video receiving device 3 separates the encoded video data 51 to 54 and the RTP header including time information from the video packet.
If the M bit in the RTP header is “1”, the packet receiver 32 indicates that the bit stored in the “timestamp” data field of the RTP header is the upper bit of the time information t, If the M bit is “0”, it is determined that the bit stored in the “timestamp” data field of the RTP header is the lower bit of the time information t, and the higher bit and the lower bit are combined. Thus, the time information t is restored.
t = upper bit + lower bit When the packet receiving unit 32 restores the time information t, the packet receiving unit 32 outputs the time information t and the encoded video data 51 to 54 to the video decoding unit 33.

When receiving the time information t and the encoded video data 51 to 54 from the packet receiver 32, the video decoding unit 33 decodes the video from the encoded video data 51 to 54.
When the video decoding unit 33 decodes the video from the video encoded data 51 to 54, the video decoding unit 33 refers to the clock generated by the clock generation unit 31 and outputs the decoded video at a timing corresponding to the time information t. Display the decoded video at the correct time.

  As is apparent from the above, according to the first embodiment, video encoded data other than the last video encoded data of one frame among the video encoded data 51 to 54 generated by the video encoding unit 12. For the RTP headers 51 to 53, the time information in small time units is inserted in the time information t generated by the video encoding unit 12, and the video encoding which is the last video encoded data of one frame is inserted. For the RTP header of the data 54, the time information in the large time unit is inserted in the time information t. Therefore, the RTP header conforms to the RTP transmission method without increasing the information amount of the RTP header. There is an effect that the time information indicating the absolute time can be transmitted.

Embodiment 2. FIG.
4 is a block diagram showing a video transmission system according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
The packet sending unit 14 generates a video packet by adding a header including the time information t generated by the video encoding unit 12 to a plurality of video encoded data, and transmits the video packet to the network 2. carry out.
That is, the packet transmission unit 14 deletes the time information in the small time unit (for example, in milliseconds) from the time information t generated by the video encoding unit 12 and deletes the lower time information, and then outputs a plurality of video codes. Is inserted into the header of the encoded data, the time information in large time units is divided, and the divided time information is inserted into the headers of the separate video encoded data.
The packet sending unit 14 constitutes a video packet sending unit.

  The packet receiving unit 34 of the video receiving device 3 receives the video packet transmitted from the video transmission device 1, and performs a process of separating a plurality of encoded video data and time information t from the video packet. The packet receiver 34 constitutes a video packet receiver.

Next, the operation will be described.
When the minimum unit of “timestamp” is extremely small and is expressed in a unit that is regarded as an error as time information on the video reception device 3 side, the time information t generated by the video encoding unit 12 is small. For time information in time units (for example, in milliseconds), lower time information may be deleted.

That is, when the minimum unit of time information t is 90 KHz unit as defined by RTP, the minimum unit of time information t is extremely small, and in the case of 8-bit data, the maximum error is 256/90000 seconds (about 2 msec). Error).
This level of error is in a range that can be generally ignored in consideration of the frame rate of the video (1/30 seconds). For this reason, for example, even if the lower 8 bits of the time information t are deleted, the deterioration due to the time information error does not occur.

Therefore, in the second embodiment, a mode in which the lower 8 bits of the time information t are deleted and transmitted will be described.
When the video encoding unit 12 of the video transmission apparatus 1 receives one frame of video as in the first embodiment, the video encoding unit 12 uses the clock generated by the clock generation unit 11 to perform predetermined encoding on the one frame. Time-coded information t indicating the absolute time at which the video encoded data 51 to 54 is displayed while the video encoded data 51 to 54 is generated by compression encoding in units (for example, in slice units in MPEG encoding). Is generated.

  When the video encoding unit 12 generates the video encoded data 51 to 54 and the time information t indicating the absolute time for displaying the video encoded data 51 to 54, the packet transmission unit 14 generates an RTP header including the time information t. Is added to the encoded video data 51 to 54 to generate a video packet, and the video packet is transmitted to the network 2.

Here, FIG. 5 is an explanatory diagram showing packetization processing of the packet transmission unit 14.
Hereinafter, the packetization process of the packet transmission unit 14 will be described in detail with reference to FIG.
Also in the second embodiment, the RTP header of FIG. 6 is assumed as a header added to the encoded video data 51-54.

First, the packet sending unit 14 extracts the lower 32 bits that are time information in small time units (for example, milliseconds) from the time information t generated by the video encoding unit 12, and deletes the lower 8 bits of the time information. To do.
The packet sending unit 14 describes the 24-bit time information remaining by deleting the lower 8 bits as the “timestamp” data field of the RTP header in the video encoded data 51 to 54 (in FIG. 5, “ts”). Field).

Next, the packet sending unit 14 has bits higher than the lower 32 bits in the time information t generated by the video encoding unit 12 (for example, if the time information is 64-bit information, the upper 32 bits and the time information is 48 bits). If it is information, the upper 16 bits are divided into four.
For example, if the upper bit is 32 bits, 8 bits of divided data n0, n1, n2, and n3 are generated by dividing into 4 parts.
When the packet sending unit 14 generates the 8-bit divided data n0, n1, n2, and n3, as shown in FIG. 5, the divided data n0, n1, n2, and n3 are converted into “RTP header“ Store in the remaining data fields of timestamp.

  In order to ensure the continuity of data packets, a 4-bit sequence number is inserted in the RTP header, and the divided data n0 is stored in the RTP header having the smallest value of the sequence number. The divided data n1 is stored in the RTP header having a small number value. Further, the divided data n2 is stored in the RTP header having the next smallest sequence number value, and the divided data n3 is stored in the RTP header having the largest sequence number value.

Information other than “timestamp” in the RTP header is the same as the information defined in RTP (see FIG. 6).
As described above, the packet transmission unit 14 adds the RTP header including the time information t ′ corresponding to the time information t (time information from which the lower 8 bits are deleted) to the video encoded data 51 to 54. When a video packet (video encoded data 61 to 64 with an RTP header) is generated, the video packet is transmitted to the network 2.

When receiving the video packet transmitted from the video transmission device 1, the packet receiving unit 34 of the video receiving device 3 separates the RTP header including the encoded video data 51 to 54 and the time information t ′ from the video packet.
The packet receiving unit 34 obtains 24-bit time information from the TS field of “timestamp” from the RTP header added to the video encoded data 61 to 64, and the divided data n0, Time information t ′ corresponding to time information t is restored by acquiring n1, n2, and n3 and synthesizing the 24-bit time information that is the lower bits and the divided data n0, n1, n2, and n3.
t≈t ′ = n0 + n1 + n2 + n3 + lower 24 bits
When the packet reception unit 34 restores the time information t ′, the packet reception unit 34 outputs the time information t ′ and the encoded video data 51 to 54 to the video decoding unit 33.

When receiving the time information t ′ and the encoded video data 51 to 54 from the packet receiver 34, the video decoding unit 33 decodes the video from the encoded video data 51 to 54 as in the first embodiment.
When the video decoding unit 33 decodes the video from the video encoded data 51 to 54, the video decoding unit 33 refers to the clock generated by the clock generation unit 31 and outputs the decoded video at a timing corresponding to the time information t ′. Display the decoded video at the correct time.

  As apparent from the above, according to the second embodiment, the time information in the small time unit (for example, millisecond unit) among the time information t generated by the video encoding unit 12 is the lower time information. Is inserted into the RTP header of the encoded video data 51 to 54, the time information in large time units is divided, and the divided data n0, n1, n2, and n3 are RTP of the encoded video data 51 to 54. Since each header is inserted, the time information indicating the absolute time can be transmitted in accordance with the RTP transmission method without increasing the information amount of the RTP header as in the first embodiment. There is an effect.

Embodiment 3 FIG.
In the first and second embodiments, the video encoding unit 12 generates the time information t indicating the absolute time for displaying the video encoded data 51 to 54. For example, UNIX (trademark registration: described below) Time information t indicating a time based on “January 1, 1970 00: 00: 0” that can be easily acquired by a Linux (trademark registration: description omitted below) system. You may do it.

Specifically, for example, the video encoding unit 12 sets the upper 32 bits of the time information t as the time based on “January 1, 1970 0: 0: 0”, and sets the lower 32 bits of the time information t as UNIX. Or a time in milliseconds from the start-up time that can be easily acquired by the Linux system.
As a result, it is possible to obtain time information t that is highly consistent with the UNIX or Linux system.

Embodiment 4 FIG.
In the third embodiment, the video encoding unit 12 shows the case where the lower 32 bits of the time information t are set to the time in milliseconds after the system is started, but the value of the lower 32 bits of the time information t is a predetermined time ( For example, when 1 hour) is counted, the lower 32 bits of the time information t may be reset to zero.
Thereby, the association with “year / month / day / hour / minute / second” indicated by the upper 32 bits of the time information t can be easily performed.

  1 video transmission device, 2 network, 3 video reception device, 11 clock generation unit, 12 video encoding unit (encoding unit), 13, 14 packet transmission unit (video packet transmission unit), 31 clock generation unit, 32, 34 Packet receiver (video packet receiver), 33 video decoder (decoder), 50 video frames, 51-54 video encoded data, 55-58 video encoded data with RTP header, 61-64 RTP header Video encoded data.

Claims (8)

  Encoding means for compressing and encoding one frame of an input video in a predetermined encoding unit to generate a plurality of video encoded data, and generating time information indicating a time for displaying the video encoded data; A video transmission apparatus comprising: a video packet transmitting unit configured to generate a video packet by adding a header including time information generated by the encoding unit to the plurality of encoded video data, and to transmit the video packet. The video packet transmitting means is configured to encode the header of video encoded data other than the last video encoded data of one frame among the plurality of video encoded data generated by the encoding means. The time information in a small time unit is inserted in the time information generated by the means, and for the header of the last video encoded data of one frame, the above time Video transmission apparatus characterized by inserting the time information of the large units of time in the broadcast.   Encoding means for compressing and encoding one frame of an input video in a predetermined encoding unit to generate a plurality of video encoded data, and generating time information indicating a time for displaying the video encoded data; A video transmission apparatus comprising: a video packet transmitting unit configured to generate a video packet by adding a header including time information generated by the encoding unit to the plurality of encoded video data, and to transmit the video packet. The video packet transmission means deletes the lower time information for the time information in small time units from the time information generated by the encoding means, and inserts it into the headers of the plurality of video encoded data. The video transmission apparatus is characterized in that the time information in large time units is divided and each piece of time information after division is inserted into a header of separate video encoded data. .   The encoding means generates time information indicating absolute time or time information indicating time based on a predetermined time as time information indicating time for displaying video encoded data. The video transmission apparatus according to claim 1 or 2.   The encoding means, when generating time information indicating a time with a predetermined time as a base point, zero-resets the time information in a small time unit in the time information every fixed time. The video transmission apparatus described.   The header added to the plurality of encoded video data by the video packet transmitting means is an RTP header, and different types of time information are inserted into the time stamp field of the RTP header. 4. The video transmission device according to claim 1.   The time information in the large time unit is the time information in the second unit, and the time information in the small time unit is the time information in the millisecond unit among the time information generated by the encoding means. The video transmission device according to claim 1.   Encoding means for compressing and encoding one frame of an input video in a predetermined encoding unit to generate a plurality of video encoded data, and generating time information indicating a time for displaying the video encoded data; and A video transmission apparatus including a video packet transmitting unit configured to generate a video packet by adding a header including time information generated by the encoding unit to the plurality of encoded video data, and to transmit the video packet; Video packet receiving means for receiving a video packet transmitted from a video transmission apparatus and separating a plurality of video encoded data and time information from the video packet, and a plurality of video encoded data separated by the video packet receiving means And a video receiving device having decoding means for decoding the video and outputting the video at a timing corresponding to the time information. In the video transmission system, the video packet transmission means of the video transmission apparatus includes video encoded data other than the last video encoded data of one frame among the plurality of video encoded data generated by the encoding means. For the header, time information in small time units is inserted in the time information generated by the encoding means, and for the header of the last video encoded data of one frame, A video transmission system in which time information in large time units is inserted.   Encoding means for compressing and encoding one frame of an input video in a predetermined encoding unit to generate a plurality of video encoded data, and generating time information indicating a time for displaying the video encoded data; and A video transmission apparatus including a video packet transmitting unit configured to generate a video packet by adding a header including time information generated by the encoding unit to the plurality of encoded video data, and to transmit the video packet; Video packet receiving means for receiving a video packet transmitted from a video transmission apparatus and separating a plurality of video encoded data and time information from the video packet, and a plurality of video encoded data separated by the video packet receiving means And a video receiving device having decoding means for decoding the video and outputting the video at a timing corresponding to the time information. In the video transmission system, the video packet transmission means of the video transmission apparatus deletes the time information in the small time unit from the time information generated by the encoding means, and deletes the plurality of time information. A video transmission system, characterized by being inserted into a header of encoded video data, dividing time information in units of large time units, and inserting each piece of time information after division into a header of separate encoded video data.

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