KR100363733B1 - Multi-chennel image encoding system using synch priority detection - Google Patents

Abstract

A multichannel video encoding system for encoding a multichannel video signal whose input order and time of an input channel is determined by a synchronization signal includes means for separating a synchronization signal from a video signal of each channel, and a phase of the synchronization signal of the input channels. And means for determining the priority of the input channel according to the first priority, means for sequentially providing the multi-channel input signal by one channel according to the detected priority, and means for encoding the provided input signal. The multichannel video encoding system can obtain a stable encoding frame rate. In the related art, although the encoding frame rate is changed according to a change in time and a change in the number of input channels, in the present invention, the input channels are aligned using the phase of the synchronization signal between input channels, and thus the relationship between the change in time and the number of input channels is related. A constant image frame rate can be obtained without.

Description

MULTI-CHENNEL IMAGE ENCODING SYSTEM USING SYNCH PRIORITY DETECTION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel video encoding system, and more particularly, to a video encoding system capable of obtaining a stable frame rate through priority detection using phases between synchronization signals of an input channel.

The use of digital video systems with multiple signal sources, such as digital surveillance systems, remote video conferencing systems, multi-channel remote mechanization systems, remote monitoring systems, is increasing and their applications are expanding. For example, a bank's surveillance system receives video signals from cameras installed at bank entrances, interiors, safes, and atm machines.

In general, in an image encoding system for encoding an image input from a multi-channel signal source into one stream, the synchronization signal of the input digital video signal is determined by the synchronization signal generated by the analog video signal source. Synchronization signals generated by analog video signal sources do not have accurate periods. For example, in the case of a multi-channel surveillance system, even when using the surveillance cameras of the same product, the synchronization signal output from each camera is slightly different. Therefore, the phase difference of the synchronization signal of the input channel changes little by time, and thereby the encoded frame rate also changes little by little. In addition, even when image encoding is performed at a specific time, the encoded frame rate may vary depending on which channel's phase is referenced.

The problem of changing the frame rate described above becomes worse as the number of input channels increases. As the number of input channels increases, the change in phase of each input channel increases, and thus the change in frame rate is intensified.

Therefore, in a video encoding system having a multi-channel input, a method of obtaining a stable frame rate, that is, a method of obtaining a constant frame rate regardless of increase or decrease of the number of input channels and change of time is required.

An object of the present invention is to solve the problem of changing the frame rate of the multi-channel video encoding system described above, and to provide a video encoding system having a constant frame rate regardless of the number and time of input channels.

In order to achieve the object of the present invention, the input data is aligned based on the synchronization signal of one input channel, and the image encoding is performed using the aligned channel data sequentially. By such a method, a stable frame rate can be obtained.

1 is a block diagram of one embodiment of a multichannel video encoding system according to the present invention;

2 is a diagram showing phases between synchronization signals of four channels that are not aligned.

FIG. 3 is a diagram showing phases between four channels of synchronization signals when the synchronization signals of the four channels shown in FIG. 2 are aligned in accordance with the present invention. FIG.

4 is a flow chart illustrating a channel alignment method in accordance with the present invention.

<Code Description of Main Parts of Drawing>

13: priority detection and channel switcher

15: MPEG encoder

17: memory block switch

19: user code inserter

23: register

The multi-channel video encoding system for encoding a multi-channel video signal in which the input order and time of the input channel is determined by the synchronization signal according to the present invention,

Means for separating a synchronization signal from the video signal of each channel;

Means for determining the priority of the input channel according to the phase of the synchronization signal of the input channels;

Means for providing a multi-channel input signal one channel at a time in accordance with the detected priority.

Means for encoding the provided input signal

It includes.

As described above, the multi-channel video encoding system has a problem in that the frame rate changes according to the change in the number and time of input channels. In order to solve these problems, the present invention can detect a sequence of the synchronization signal of the input channel, and perform encoding according to the sequence of the detected synchronization signal to obtain a stable frame rate.

Hereinafter, a multi-channel MPEG encoding system using synchronization signal priority detection will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of an embodiment of a video encoding system according to the present invention. In an embodiment, a video signal is received from sixteen channels. In FIG. 1, an MPEG image compression system, which is a representative image compression technology characterized by multiple bit rates, versatility, various specifications, and scalability, is illustrated as an example of the present invention.

The input channels pass through a channel selector, i.e., a multiplexer 1, a video decoder 3, and a video data multiplexer 9. In this process, one channel to be encoded in the encoder 15 is selected.

The multiplexer 1 selects some of the analog signals input through a plurality of channels. In the multiplexer 1, four input channels of the sixteen input channels are selected. The signal primarily selected by the multiplexer 1 is input to the video decoder 3.

The video decoder 3 selects one of four input analog video signals and outputs a Y-U-V type digital video signal. The video decoder 3 can interpret NTSC and PAL data and outputs CCIR601 16-bit MPEG syntax. In the embodiment of the present invention, the video decoder 3 receives a composite NTSC signal. The CCIR601 syntax includes synchronization signals for frames, lines, and fields, and includes information about brightness (Y) and color difference (UV). Some have a scaling function, depending on the video decoder 3 used.

In the embodiment of the present invention, two video decoders 3 are used. Using two video decoders 3 can increase the frame rate. This is because it is possible to monitor two incoming video signals and select a channel suitable for the current MPEG encoding. A channel suitable for current MPEG encoding is determined by comparing the phases of the synchronization signals of the input channels. A method of determining channel input and processing order will be described in detail with reference to FIG. 4.

The video data multiplexer 9 selects one of the digital video signals output from the two video decoders 3.

The multiplexer 1, the video decoder 3, and the video data multiplexer 9 participating in the channel selection process are controlled by the video decoder controller 21. The channel selection signal output by the video decoder controller 21 is determined based on the register 23 and the information on the input channel provided from the priority detection and channel switching unit 13.

The digital video signal of the selected channel is stored in the memory 27 in units of fields. The memory block switching method is used to store the digital video signal in the memory 27 and to perform MPEG encoding by outputting the stored video signal. By using a memory block switching scheme, efficient sharing of memory between channels is possible. An address specifying a memory block for memory block switching is generated by the memory block switch 17.

The MPEG encoder 15 reads the digital video signal stored in the memory 27 to perform MPEG encoding. In the preferred embodiment of the present invention, for example, the VICA 1000 ^™ of TIOSYS is used as the MPEG encoder 15. The digital video signal used for MPEG encoding has, for example, a size of 352 × 230 for MPEG1 and 352 × 480 for MPEG2.

The synchronization signal for the input data of the MPEG encoder 15 is generated by the generator 11 and input to the MPEG encoder 15. At this time, the synchronization signal for the input data may not be generated. In this case, MPEG encoding for the input data is not performed.

As described above, the MPEG encoder 15 switches video signals input from a plurality of channels and performs MPEG encoding. Therefore, the MPEG encoded frame output by the MPEG encoder 15 is mixed into several input channels. Therefore, in order to reproduce these MPEG encoded frames using a single channel video encoder, the encoded frames must be separated for each channel. To this end, the user code inserter 19 writes information about the current input channel into the input video data.

The CPU 25 serves to initialize the register 23. Then, an interrupt generated by the channel switching unit 13 and the user code inserter 19 is received and the necessary information is recorded in the register 23. Upon receiving the interrupt of the channel switcher 13, channel information to be encoded at this point, an encoding mode (for example, generation of a P-frame or an I-frame) and the like are recorded. Upon receiving the interrupt of the user code inserter 19, the channel information and synchronization information to be currently encoded are recorded.

As mentioned above, it is desirable for a multichannel MPEG encoding system to maintain a constant frame rate. To this end, the digital video signal output by the video decoder 3 is aligned in accordance with the priority of the synchronization signal. Determination of the priority of the input channel is performed by priority detection and the channel switch 13 and the synchronization signal separator 7.

The priority detector 13 observes the synchronization signal of each input channel output from the synchronization signal separator 7. The synchronization signal of each input channel can also be detected from the output signal of the video decoder 3. However, since the synchronization signal separator 7 separates the synchronization signal using the analog video signal directly, it is possible to obtain the synchronization signal before the synchronization signal is normally output from the video decoder 3.

Once the priority detector 13 determines the priority by observing the synchronization signal of the input channel, the channel switcher 13 sends the priority of the determined channel to the video data multiplexer 9 and the video decoder 3 by For example, the video input data for each channel are selected according to the determined priority and inputted to the MPEG encoder 15.

FIG. 2 shows the phases of the synchronization signals of the four channels which are not aligned when the priority detector 13 detects the priority of the synchronization signals of the four channels.

Referring to the synchronization signal of one input channel in FIG. 2, it can be seen that the flow of the synchronization signal includes the synchronization signal 201 in the odd field and the synchronization signal 203 in the even field. The portion indicated by the black diagonal lines between the synchronization signals represents the field data 205 which is input data. In fact, field data exists between all synchronization signals. In one embodiment of the present invention, since MPEG encoding is performed using only one type of field without using both odd and even fields constituting one frame, Only field data actually used by the MPEG encoder 15 is indicated by black diagonal lines. It should be noted that the MPEG encoder 15 should continuously receive only the same type of field as the field first input in one channel. That is, if the odd field is encoded first in one channel, the odd field should be encoded next. If the even and odd fields are encoded alternately, discontinuous defects may occur in the image. Referring to FIG. 2, in order to distinguish field data 205 actually used by the MPEG encoder 15, portions corresponding to odd fields of each input channel are indicated by black lines.

When MPEG encoding the input data having the synchronization signal shown in FIG. 2 in the order of the first channel to the fourth channel, it takes time corresponding to four frames to encode the field data from the four channels. First, after performing MPEG encoding on an odd field of a first channel, a synchronization signal for a second channel is found. The closest synchronization signal for the second channel is an odd field synchronization signal, and receives odd field data (indicated by black diagonal lines) to perform MPEG encoding. The process of finding the closest synchronization signal and encoding the MPEG for the third and fourth channels is repeated. After MPEG encoding for the fourth channel, the synchronization signal of the nearest field is likewise found to perform MPEG encoding for the first channel. In this case, since the first channel performs MPEG encoding using odd field data, the first channel finds a synchronization signal of the closest odd field. It can be seen that it takes time corresponding to all four frames (corresponding to eight field synchronization signals in FIG. 2) to receive odd field data of the first channel and receive next odd field data.

As a result, when MPEG encoding is performed while the input channels are not aligned, the MPEG encoding execution time is determined according to the phase between the synchronization signals of the input channels. Therefore, when the order of input channels for MPEG encoding is changed, the frame rate is changed. In addition, since the period of the synchronization signal of each channel is not exactly the same, the phase between each input channel changes over time, and as a result, the frame rate changes over time.

The above-mentioned change in frame rate becomes more serious as the number of input channels increases. This is because, as the number of input channels increases, the width of phase change between input channels also increases. If there are n input channels, the width of the time taken to perform MPEG encoding on the n input channels may vary by n / 2 frames. The problem of changing the frame rate described above can be solved by aligning the input channels according to the phase of the synchronization signal as described below.

3 illustrates phases of synchronization signals between channels when the input channels illustrated in FIG. 2 are aligned according to the present invention.

The arrangement of the input channels according to the present invention is as follows. Determines a particular channel as the first input channel that is the first input channel. If the channel having the closest phase to the first input channel is determined as the second input channel, and the same process is repeated for the unaligned input channels, the priority for all channels is determined.

The above-described input channel alignment method will be described with reference to FIG. 3. First, the first channel is determined as the first input channel (the determination of the first input channel is arbitrarily determined). Now, comparing the remaining three channels with the first channel, the channel having the phase of the synchronization signal closest to the synchronization signal of the first channel is searched. As a result of the search, the fourth channel is determined as the second input channel. Now, for the second input channel, search for the third input channel using the same method as for searching for the second input channel from the first input channel. By repeating the above process, the input order for all channels is a first channel, a fourth channel, a third channel, and a second channel. As shown in the figure, only the third channel uses an even field for MPEG encoding, and the remaining channels use an odd field for MPEG encoding. After the input of the second channel, the input of the first channel must be received again. Although the synchronization signal of the first channel closest to the end of the field used for MPEG encoding of the second channel is the synchronization signal 207 of the even field, since the first channel uses the odd field, the synchronization signal of the even field is To find the synchronization signal 209 of the odd field generated in the field to receive the field data.

In the case of MPEG encoding through the above-described process, it can be seen that the time corresponding to three frames (from sync signal 201 to just before sync signal 209) takes time to encode four input channels once. As a result, it takes less time by one frame than in MPEG encoding in the order of the unaligned input channels of FIG. 2.

Even if the input order of the channels is determined, the phase change occurs over time because the synchronization signals of the respective input channels have different periods. Therefore, the input order must be rearranged according to the phase change of the synchronization signal between channels.

In the embodiment of the present invention, the priority of the input channel is continuously detected during the operation time of the MPEG encoding system. However, the information on the priority of the input channel detected every time is not immediately used for the alignment of the channel input, but is first recorded in the priority detection table. In addition, the priority detection table does not need to be updated for each period in which input channels are input once. Since the rate of phase change of each input channel is relatively slower than the frame rate of each channel, the priority detection table may be updated for each period having a time longer than one period of the input channel. In the embodiment of the present invention, the priority detection table may be provided in the register 23 or the priority detection and channel switching unit 13. The video decoder controller 21 reads the priority information stored in the table and uses this to generate a signal for selecting a channel input to the MPEG encoder 15 to determine the order of the channels.

4 is a flowchart illustrating an embodiment of an input channel alignment method according to the present invention.

In the reference channel setting step 401, one input channel among the input channels is set as the reference channel. Depending on which channel is set as the reference channel, there will be a change in the initial frame rate, but will converge at a constant frame rate over time. In an embodiment of the present invention, the reference channel may be the one with the lowest channel number.

In the closest synchronization phase search step 402, a channel having a synchronization signal located closest to the point from which the input field of the reference channel is terminated is searched among the remaining input channels except for the channels that are already aligned. The channel having the closest synchronization phase becomes the second input channel.

In a channel alignment completion determination step 403, it is determined whether alignment has been performed for all input channels.

If the alignment for all input channels is not complete, return to the nearest synchronous phase search step 402 to continue alignment to the remaining input channels.

When the sorting for all input channels is completed, the sorting process of the input channels is terminated, and the priority table for recording the sorting order of the input channels is updated (step 404).

Then, in step 405 of determining whether the reference channel needs to be reset, if there is a problem with the current reference channel (for example, if there is an error in the camera input of the channel or the channel is excluded from encoding) If it is necessary to reset, the process returns to the reference channel setting step 401. On the other hand, if there is no need for resetting, the process returns to the nearest synchronous phase search step 402 and repeats the above-described steps.

As described above, the multi-channel video encoding system using the synchronization signal priority detection according to the present invention has been described, but the scope of the present invention is not limited to the above embodiments, and may include various forms of modification and modification. have.

The multichannel MPEG encoding system according to the present invention can obtain a stable MPEG encoding frame rate. In the related art, the MPEG encoding frame rate is changed according to the change of time and the number of input channels. However, in the present invention, the input channels are aligned using the phase of the synchronization signal between input channels, thereby changing the time and the number of input channels. Regardless, a constant MPEG frame rate can be obtained.

Claims (5)

A multichannel video encoding system for encoding a multichannel video signal in which an input order and a time of an input channel are determined by a synchronization signal, Means for separating a synchronization signal from the video signal of each channel; Means for determining the priority of the input channel according to the synchronization signal phase of each of the separated input channels; Means for sequentially providing a multi-channel input signal by one channel based on the priority detected by said priority determining means. Means for encoding an input signal provided from said providing means Multi-channel video encoding system comprising a. The method of claim 1, The priority determining means further comprises memory means for storing the determined priority, And the providing means sequentially provides the multichannel input signals one channel at a time according to the priority stored in the memory means. In the method of determining the priority of the input channel to encode in a multi-channel video encoding system, (a) determining one of the input channels as the first input channel; (b) determining, as a next input channel, a channel having a synchronization signal having a phase closest to that of the first input channel among the remaining input channels except for the channel whose input order is determined; (c) repeating step (b) until the order for all channels is determined Input channel priority determination method comprising a. The method of claim 3, wherein And storing the determined order of the input channels as a priority table. The method of claim 4, wherein And periodically updating the order of the input channels stored in the priority table.