JP2012114612A - Image delivery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional image delivery system in which a delivery bit rate to a reception terminal is largely changed by receiving the influence of a change in an image data amount with encoding.SOLUTION: An image delivery system includes a real-time encoder 10 and an image delivery server 20. The real-time encoder 10 encodes image data, packetizes the data, and outputs the packet by a set fixed bit rate. The image delivery server 20 delivers the packet to be output from the real-time encoder 10 to a reception terminal 30.

Description

  The present invention relates to a video distribution system, and more particularly to a video distribution system that encodes video data and distributes it to a distribution destination.

  An example of a system for distributing video is described in Patent Document 1. The video distribution system described in Patent Document 1 includes a plurality of video / audio encoders, a data packet variable transmission device, a multiplexing device, and a modulator.

  Each video / audio encoder generates a packet stream from a plurality of video / audio inputs using an MPEG2 digital signal compression technique, and transmits the packet stream to a multiplexing device. The data packet variable transmission device generates an MPEG2 data packet from content data such as image data and program data, and transmits it to the multiplexing device. The multiplexing device multiplexes a plurality of packet streams and data packets received from the plurality of video / audio encoders and the data packet variable transmission device, and transmits the multiplexed data to the modulator. The modulator modulates the output of the multiplexing device and sends it to the satellite for satellite broadcasting and to the broadcasting station for terrestrial broadcasting.

  Also, the data packet variable transmission device includes a packetizing processor that converts a plurality of content data into MPEG2 transport packet of MPEG2 to create a plurality of packet files, and multiplexes a plurality of packets from the plurality of packet files. A packet transmission processor that adds and multiplexes NULL packets as necessary to achieve the specified bit rate input from the encoding device, and transmits MPEG2 transport packets multiplexed by this packet transmission processor at a set rate A packet transmission board.

  The multiplexing device changes the bit rate designated to the data packet variable transmission device when detecting a change in the video data amount. The data packet variable transmission device changes the multiplexing amount of content data packet transmission based on a specified bit rate. As a result, the video distribution system can efficiently transmit content data following changes in the video data amount.

JP 2001-211202 A

  In general, when an image is encoded, the amount of data is compressed. At this time, the amount of data after compression varies greatly depending on the situation of the video. For example, a high-definition video with a large amount of motion has a large amount of data, and a video without motion has a small amount of data after compression. Therefore, when a packet stream generated by encoding video is distributed, the distribution bit rate fluctuates drastically. Patent Document 1 describes that the amount of content data such as image data and program data is controlled to be a constant bit rate, but the amount of video data is controlled to be a constant bit rate. It is not described to do.

  In general, a receiving terminal in a video distribution system temporarily stores received data in a buffer, reads the data from the buffer, and plays back video at a desired video playback bit rate. Since there is a buffer, a certain amount of fluctuation in the distribution bit rate can be absorbed. However, if the distribution bit rate fluctuates beyond the allowable limit, the desired video playback bit rate cannot be maintained, and the video is crumpled. Depending on the timing, the buffer overflows and video information is lost, which causes block noise in the reproduced video.

  An object of the present invention is to provide a video distribution system that solves the problem that the distribution bit rate fluctuates greatly under the influence of a change in the amount of video data accompanying encoding.

A video distribution system according to an aspect of the present invention includes:
An encoder that encodes video data, packetizes it, and outputs it at a fixed bit rate,
A configuration is adopted in which a distribution device that distributes a packet output from the encoder to a distribution destination is provided.

  Since the present invention has the above-described configuration, it is possible to perform distribution at a constant bit rate even if the amount of encoded video data varies greatly.

It is a block diagram of a 1st embodiment of the present invention. It is explanatory drawing of schematic operation | movement of the 1st Embodiment of this invention. It is an operation | movement sequence diagram of the 1st Embodiment of this invention. It is a figure which shows the detail of the bit rate smoothing process in the 1st Embodiment of this invention. It is a block diagram of other embodiments of the present invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an embodiment using MPEG2 will be described. However, the video codec is not limited to MPEG2, and the present invention can use any video codec.
[First embodiment]
Referring to FIG. 1, the video distribution system according to the first embodiment of the present invention includes a real-time encoder 10, a video distribution server 20, and a receiving terminal 30. The real-time encoder 10, the video distribution server 20, and the receiving terminal 30 are connected to be able to communicate with each other through a network 100 such as the Internet.

  The real-time encoder 10 has a function of inputting and encoding video data output from the camera 11, packetizing it, and outputting it at a set fixed bit rate. The real-time encoder 10 includes an encoding unit 12, a bit rate smoothing unit 13, and a TS packetizing unit 14. Each of these means 12 to 14 can be realized by a computer and a program, for example. The program is provided by being recorded on a recording medium such as a magnetic disk. The computer reads the program recorded on the recording medium and executes the program, thereby realizing each of the above means 12 to 14 on the computer.

  The encoding unit 12 has a function of encoding video data output from the camera 11. The encoding method is arbitrary. For example, an MPEG2 digital signal compression technique can be used. The encoding unit 12 outputs the encoded data (encoded data) to the bit rate smoothing unit 13.

  The bit rate smoothing means 13 has a function of smoothing the video bit rate of the real-time encoder 10 so as to substantially match the set fixed bit rate. The set fixed bit rate is set to a value larger than the maximum value of the output bit rate of the encoding means 12 by a predetermined amount (for example, a preset margin). The bit rate smoothing unit 13 compares the data amount per unit time of the encoded data output from the encoding unit 12 with the reference data amount determined according to the fixed bit rate for each set unit time, Calculate the amount of missing data. Then, NULL data corresponding to the calculated data amount is output as data for padding into encoded data. The unit time is arbitrary, and may be, for example, 1 second, a time shorter than 1 second, or a time longer than 1 second.

  The TS packetizing unit 14 receives the encoded data output from the encoding unit 12 and the NULL data output from the bit rate smoothing unit 13, packetizes these data, and outputs them as TS packets. The TS packetizing unit 14 may receive the encoded data and the NULL data directly from the encoding unit 12 and the bit rate smoothing unit 13 or may receive the encoded data and the NULL rate via some storage device (for example, a FIFO buffer).

  The video distribution server 20 has a function of receiving TS packets output from the real-time encoder 10 through the network 100 and distributing them to the receiving terminals 30 that are distribution destinations through the network 100. The delivery bit rate of the video delivery server 20 is fixed. The video distribution server 20 sets the average bit rate of the real-time encoder 10 in the past predetermined period (for example, 5 seconds) as the distribution bit rate. In this embodiment, since the transmission bit rate of the real-time encoder 10 is substantially fixed, the distribution bit rate of the video distribution server 20 is also substantially fixed.

  The receiving terminal 30 is a device that receives and reproduces data distributed from the video distribution server 20 via the network 100. The receiving terminal 30 is configured by a personal computer, a portable terminal, or the like.

  Next, the outline of the operation of the present embodiment will be described with reference to FIG.

  The real-time encoder 10 encodes the video data of the camera 11, packetizes it, and transmits it to the video distribution server 20 through the network 100 at a fixed bit rate. At this time, as schematically shown by the balloon F1 in FIG. 2, the real-time encoder 10 inserts NULL data as appropriate by the bit rate smoothing unit 13 even if the output data amount of the encoding unit 12 fluctuates drastically. The data amount of the TS packet generated by the TS packetizing means 14 (video bit rate of the real-time encoder 10) is constant.

  The video distribution server 20 sets the average bit rate of the past certain period received from the real-time encoder 10 as the distribution bit rate. As a result, the distribution bit rate of the video distribution server 20 is constant as schematically shown by the balloon F2 in FIG.

  The video distribution server 200 distributes the video received from the real-time encoder 10 to the receiving terminal 30 at the above-described constant distribution bit rate (F3 in FIG. 2). As a result, the reception buffer amount of the reception terminal 30 becomes uniform, and stable reproduction is performed (F4 in FIG. 2).

  Next, the operation of this embodiment will be described in more detail with reference to FIG.

  When video data is output from the camera 11, the encoding means 12 of the real-time encoder 10 encodes the video data (A11). Next, the bit rate smoothing means 13 performs a bit rate smoothing process on the encoded data (A12). Next, the TS packetizing means 14 packetizes the data after the bit rate smoothing process and sends it to the video distribution server 20 (A13).

  The video distribution server 20 receives the data and accumulates it in a storage device (not shown) (A20).

On the other hand, when the receiving terminal 30 is activated (A30), after being in a video distribution reception waiting state,
A video distribution request is made to the video distribution server 20 (A31).

  In response to the request from the receiving terminal 30, the video distribution server 20 starts video distribution at a video bit rate calculated from the video data (an average bit rate for 5 seconds in one example) (A21). The receiving terminal 30 receives the distribution video and performs playback processing (A32).

  Next, the details of the video bit rate smoothing process in the real-time encoder 10 will be described with reference to FIG.

  A fixed bit rate and a sampling interval are set in advance in the bit rate smoothing means 13 of the real-time encoder 10 (A130 in FIG. 4).

  The fixed bit rate may be input to the real-time encoder 10 from the outside and stored, or the real-time encoder 10 may automatically calculate and store the fixed bit rate. For example, the bit rate smoothing unit 13 may calculate and store a fixed bit rate based on the encoded data output from the encoding unit 12. At that time, the bit rate smoothing means 13 calculates an average bit rate per unit time of the encoded data output from the encoding means 12, and a value obtained by adding a predetermined margin to the calculated average bit rate is a fixed bit. It may be calculated as a rate. The calculation of the fixed bit rate may be performed only once or may be periodically reviewed.

  The sampling interval may be input to the real-time encoder 10 from outside and stored, or the real-time encoder 10 may automatically calculate and store the sampling interval.

  The bit rate smoothing means 13 compares the actual data capacity with the expected data capacity at that time at the set sampling interval (A131 in FIG. 4). The actual data capacity refers to the capacity of encoded data output from the encoder 12. The expected data capacity is the capacity of the encoded data when it is assumed that the encoded data is output from the encoder 12 at the fixed bit rate.

  The bit rate smoothing means 13 calculates the remaining capacity obtained by subtracting the actual data capacity from the expected data capacity as an insufficient capacity, and generates (inserts) NULL data corresponding to the insufficient capacity (A132 in FIG. 4). For example, the bit rate smoothing means 13 resets the internal counter to 0 at the start of the sampling period, and counts up the counter by m each time m bytes of encoded data is output from the encoding means 12. Then, the bit rate smoothing means 13 uses the counter value at the end of the sampling period as the actual data capacity, and subtracts it from the expected data capacity to calculate the insufficient capacity.

  The bit rate smoothing means 13 repeatedly executes the above processes A131 and A132 (A133 in FIG. 4).

  Thus, according to this embodiment, the video distribution server 20 can distribute video data at a constant bit rate. This is because the transmission video bit rate on the real-time encoder 10 side is constant.

  Further, according to the present embodiment, since the distribution bit rate of the video distribution server 20 is made constant, the playback buffer on the receiving terminal 30 side does not fluctuate and smooth video playback is possible.

  In addition, according to the present embodiment, the real-time encoder 10 adds NULL data to the encoded data before packetization, so that the processing after packetization can be simplified.

  In the above embodiment, the data to be distributed is video data captured by the camera 11. However, the distribution data in the present invention is not limited thereto. In addition to the video data captured by the camera 11, audio data recorded by the camera 11 may be used as distribution data. Further, video data and audio data captured by means other than the camera 11 may be used as distribution data.

  In the above embodiment, the video distribution server 20 distributes video data received from one real-time encoder 10 to the receiving terminal 30. However, the present invention is not limited to such a configuration. For example, as shown in FIG. 5, the video distribution server 20 may distribute video data received from a plurality of real-time encoders 10 to the receiving terminal 30.

DESCRIPTION OF SYMBOLS 10 ... Real time encoder 11 ... Camera 12 ... Encoding means 13 ... Bit rate smoothing means 14 ... TS packetization means 20 ... Video distribution server 30 ... Receiving terminal 100 ... Network

Claims (8)

An encoder that encodes video data, packetizes it, and outputs it at a fixed bit rate,
A video distribution system comprising: a distribution device that distributes a packet output from the encoder to a distribution destination. The encoder is
An encoding means for encoding the video data;
For each set unit time, the data amount per unit time of the encoded data output from the encoding means is calculated to be insufficient compared to the reference data amount determined according to the fixed bit rate. Bit rate smoothing means for outputting NULL data of a data amount;
The video distribution system according to claim 1, further comprising: packetizing means for packetizing and outputting encoded data output from the encoding means and NULL data output from the bit rate smoothing means. 3. The video distribution system according to claim 2, wherein the fixed bit rate is set to a value larger by a predetermined amount than the maximum value of the output bit rate of the encoding means. 4. The video distribution system according to claim 1, wherein the video data is data output from a camera. The video distribution system according to claim 1, comprising a plurality of the encoders. A video distribution method in a video distribution system comprising an encoder and a distribution device,
The encoder encodes video data, packetizes it, and outputs it at a set fixed bit rate,
The video distribution system, wherein the distribution device distributes a packet output from the encoder to a distribution destination. Encoding means for encoding video data;
For each set unit time, the data amount per unit time of the encoded data output from the encoding means is calculated to be insufficient compared to a reference data amount determined according to a fixed bit rate, and the calculated data Bit rate smoothing means for outputting a quantity of NULL data;
An encoder comprising: encoding data output from the encoding means; and packetizing means for packetizing and outputting NULL data output from the bit rate smoothing means. Computer
Encoding means for encoding video data;
For each set unit time, the data amount per unit time of the encoded data output from the encoding means is calculated to be insufficient compared to a reference data amount determined according to a fixed bit rate, and the calculated data Bit rate smoothing means for outputting a quantity of NULL data;
A program for functioning as packetizing means for packetizing and outputting encoded data output from the encoding means and NULL data output from the bit rate smoothing means.

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