JP4030015B2 - Frame synchronizer and frame synchronization method - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a frame synchronizer, and more particularly to a technique for preventing video skipping and reading twice in a frame synchronizer during television broadcasting.
[0002]
[Prior art]
Currently, a frame synchronizer (hereinafter referred to as FS) that synchronizes asynchronous video data with a reference clock has been put into practical use. This FS has a ring buffer memory for storing video data, and it is desired to synchronize asynchronous video data by independently performing an operation of writing and reading video data into the ring buffer memory. This is synchronized with the reference clock.
[0003]
For example, the frame of the video data of the other station is written to the ring buffer memory at a write timing in accordance with the operation speed (the other station clock) in the frame of the video data of the other station (frame 0 (F0) → frame 1 (F1) → Frame 2 (F2)) is performed, and video data is read from the ring buffer memory (F0 → F1 → F2) at the read timing (reference clock) of the local station.
[0004]
By the way, when the read timing is fast, for example, the delay time on the ring buffer memory gradually decreases, and finally the read timing catches up with the write timing, and the processing fails. In order to prevent such processing from occurring, in FS, for example, (1) the difference between the data to be read and the data to be written is less than or equal to a threshold value α, and (2) the data to be read is a frame or field of video. In this case, the data to be read is moved backward by one frame and the same data is read twice (F0 → F1 → F1 → F2). Note that the threshold value α is such that even when the difference between the data to be read and the data to be written is large, the write timing can catch up with the read timing before the read data reaches the boundary between the frames stored in the ring buffer memory. Take the minimum required value (for example, data for one line). In this way, the read timing does not catch up with the write timing.
[0005]
On the other hand, when the read timing is late, the delay time on the ring buffer memory gradually increases. Therefore, the FS is, for example, (1) a difference between the data to be read and the data to be written is a threshold value (data amount for one frame + β) or less, and (2) the data to be read is a video frame or In the case of field boundary data, the data to be read is skipped by one frame (F0 → F2). The data amount of β may be “0”, but it may be a data value for one line, for example, taking into consideration that the other station clock fluctuates.
[0006]
[Problems to be solved by the invention]
However, in the FS as described above, even when video data is used for television broadcasting, there is a possibility that one frame skipping or two readings may occur, and when one frame skipping or two readings occur, It gave the viewers a sense of incongruity.
[0007]
In addition, there is a possibility that the control signal (CM queue, subtitle, etc.) on the television broadcast superimposed in the video data synchronization period may be affected.
[0008]
Accordingly, the present invention has been invented in view of the above problems, and an object of the present invention is to provide a frame synchronizer technique that minimizes frame skipping and double reading during television broadcasting.
[0009]
[Means for Solving the Problems]
  A first invention for achieving the object of the present invention is a frame synchronizer for synchronizing asynchronous video data with a reference clock,
  Storage means for storing video data;
  A writing means for writing asynchronous video data into the storage means with a clock of the video data;
  Reading means for reading out video data stored in the storage means with a reference clock;
  The difference between the writing position of the video data by the writing means in the storage means and the reading position of the video data of the reading means in the storage means isWhen the video data read by the reading means is used for television broadcasting when the first threshold value or lower or the second threshold value or higher is reached, the video data is used for television broadcasting. Monitors the use of the video data for television broadcasting, and when the video data read by the reading means is no longer used for television broadcasting, the reading means reads twice for one frame, orControl means for causing the reading means to skip one frame and to perform reading;
It is characterized by having.
[0010]
According to a second aspect of the present invention for achieving the object of the present invention, in the first aspect, the control means includes the writing position and the reading position even if the video data read by the reading means is used for television broadcasting. If the difference is equal to or smaller than a third threshold value smaller than the first threshold value, the reading means reads twice for one frame, and the video data read by the reading means is used for television broadcasting. When the difference between the writing position and the reading position is equal to or larger than a fourth threshold value that is larger than a second threshold value, the reading means is configured to skip one frame and perform reading.
[0011]
According to a third invention for achieving the object of the present invention, in the first and second inventions, the control means satisfies the above condition and the video data read by the reading means is a boundary between frames or fields. In this case, the reading unit is configured to read twice for one frame, or the reading unit is configured to read by skipping one frame.
[0012]
  A fourth invention for achieving the object of the present invention is a frame synchronization method for synchronizing asynchronous video data with a reference clock,
  Writing asynchronous video data to the storage device with the clock of the video data;
  Reading video data from the storage device with a reference clock;
  The difference between the video data writing position and the reading position in the storage device,When the first threshold value or less or the second threshold value or more is determined, it is determined whether the video data read from the storage device is used for television broadcasting, and when the video data is used for television broadcasting, Monitoring the use of the video data for television broadcasting;
As a result of the monitoring, when video data read by the reading unit is no longer used for television broadcasting, the reading unit reads twice for one frame, or skips the reading unit for one frame and performs reading.
It is characterized by having.
[0013]
According to a fifth aspect of the invention for achieving the object of the present invention, in the fourth aspect of the present invention, even when the read video data is used for television broadcasting, the video data write position in the storage device When the difference from the reading position is equal to or smaller than a third threshold value smaller than the first threshold value, the method further comprises a step of reading the video data reading position by one frame and reading twice. To do.
[0014]
The sixth invention for achieving the object of the present invention is the writing of the video data in the storage device in the fourth and fifth inventions, even when the read video data is used for television broadcasting. When the difference between the position and the read position is equal to or greater than a fourth threshold value that is greater than the second threshold value, the method further includes the step of reading the video data by advancing the read position of the video data by one frame. It is characterized by that.
[0015]
According to a seventh aspect of the present invention that achieves the object of the present invention, in the fourth, fifth, and sixth aspects of the invention, the timing at which the reading position of the video data is read back twice by one frame or the reading position of the video data is 1 The timing of reading the video data by moving the frame forward is performed at the timing when the reading position of the video data becomes the boundary of the frame or field.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described.
[0017]
In the first embodiment, a transmission method for transmitting 60 frames of video data per second, for example, a transmission method such as 525p will be described. One frame is composed of 525 lines (scanning lines), and the data amount of one line is a data amount of 720 pixels.
[0018]
Furthermore, the OA tally used in the following description is information indicating whether video data is used for television broadcasting. For example, when the OA tally is on, it indicates that the video data output from the frame synchronizer is used for television broadcasting, and when the OA tally is off, it indicates that the video data is not used for television broadcasting. .
[0019]
FIG. 1 shows a first embodiment and is a block diagram of a frame synchronizer. FIG. 2 is a diagram showing a memory area of the ring buffer memory.
[0020]
In FIG. 1, a ring buffer memory 100 stores video data for one frame in units of lines. As shown in FIG. 2, the ring buffer memory 100 has a storage capacity for storing video data for at least two frames.
The other station clock generation unit 500 generates an operation clock of the video data (hereinafter referred to as another station clock for convenience) from the asynchronous video data.
[0021]
The write control unit 200 sequentially writes asynchronous video data to the ring buffer memory 100 line by line based on the other station clock generated by the other station clock generation unit 500. The write control unit 200 has a line counter 210 and measures the number of lines written to the link buffer memory 100 with the line counter 210. Further, the writing control unit 200 transmits the measured number of lines to the timing control unit 400.
[0022]
The read control unit 300 sequentially reads the video data stored in the ring buffer memory 100 line by line based on the reference clock. Further, the read control unit 300 has a line counter 310 and measures the number of lines read from the ring buffer 100 by the line counter 310. Further, the read control unit 300 transmits the measured number of lines to the timing control unit 400.
[0023]
Furthermore, the read control unit 300 changes the line read position in accordance with an instruction from the timing control unit 400, and reads the frame twice or skips one frame.
[0024]
Based on the number of lines from the write control unit 200 and the number of lines from the read control unit 300, the timing control unit 400 determines the line difference between the write line by the write control unit 200 and the read line by the read control unit 300. Is calculated.
[0025]
For example, the timing control unit 400 calculates (the number of lines from the read control unit 300−the number of lines from the write control unit 200) to calculate the line difference. Then, the timing control unit 400 monitors the calculated line difference, and determines whether the OA tally is off when the line difference is equal to or less than a preset first threshold value or equal to or greater than a second threshold value. . That is, it is determined whether the video data output from the FS is not used for television broadcasting. As a result of the determination, when the OA tally is off, that is, when the video data output from the FS is not used for television broadcasting and the line difference is equal to or less than the first threshold, the timing control unit 400, as shown in FIG. The read control unit 300 is instructed to read the line back by one frame (525 lines). On the other hand, when the OA tally is off, that is, when the video data output from the FS is not used for television broadcasting and the line difference is equal to or larger than the second threshold, the timing control unit 400 has 1 as shown in FIG. Discard the frame (525 lines) and instruct the read control unit 300 to change the line read position to a position skipped by one frame.
[0026]
Note that the first threshold is a minimum value that prevents the write control unit 200 from catching up with the position of the write line even when the video data is continuously used for about one day in the television broadcast (OA tally is turned on). Value. In the present embodiment, the description will be made assuming that the threshold A = 10 (line). The threshold B is described as 536 (line) in the present embodiment in consideration of skipping one frame.
[0027]
Next, the operation in the above configuration will be described.
[0028]
In the following description, in order to simplify the description, the case where the operation clock (other station clock) of asynchronous video data is slower and faster than the reference clock will be described separately.
[0029]
1) First, the case where the other station clock is slower than the reference clock (when the position of the read line of the read control unit 300 gradually approaches the position of the write line of the write control unit 200) will be described. It is assumed that the read control unit 300 starts operation after the write control unit 200 writes video data for one frame in the ring buffer memory 100. The description will be made assuming that the first threshold is 10 lines.
[0030]
The writing control unit 200 sequentially writes video data of other stations into the ring buffer memory 100 in units of lines. At the same time, the write controller 200 counts up the number of lines in the line counter 210 every time a line is written in the ring buffer memory 100. Then, the write control unit 200 transmits the number of lines indicated by the line counter 210 to the timing control unit 400.
[0031]
On the other hand, the read control unit 300 reads video data from the ring buffer memory 100 line by line according to the reference clock of the local station. At the same time, the read controller 300 counts up the number of lines in the line counter 310 every time video data is read from the ring buffer memory 100 in units of lines. Then, the read control unit 300 transmits the number of lines indicated by the line counter 310 to the timing control unit 400.
[0032]
The timing control unit 400 calculates (the number of lines from the read control unit 300−the number of lines from the write control unit 200) to calculate the line difference. For example, when the number of lines from the write control unit 200 is 780 and the number of lines from the read control unit 300 is 770, the timing control unit 400 calculates (780−770) and sets the line difference “10”. calculate. Then, the timing control unit 400 monitors the calculated line difference, and determines whether the OA tally is off when the line difference is equal to or less than the first threshold value of 10 lines.
[0033]
When the OA tally is off, the timing control unit 400 instructs the read control 300 to return the line position by one frame (525 lines). Receiving this instruction, the read control unit 300 returns the position of the next read line to the previous line position for one frame (525 lines) that has already been read.
[0034]
On the other hand, when the OA tally is still on even though the line difference becomes 10 lines or less of the first threshold, the timing control unit 400 monitors that the OA tally is off and turns off. In such a case, the above operation is performed.
[0035]
2) Next, a case where the clock of the other station is faster than the reference clock of the own station (when the position of the read line of the read control unit 300 gradually moves away from the position of the write line of the write control unit 200) will be described. . The operation until the line difference is obtained in the timing control unit 400 is the same as the operation described above, and thus detailed description thereof is omitted. Further, it is assumed that the read control unit 300 starts an operation after the write control unit 200 writes video data for one frame in the ring buffer memory 100. The description will be given assuming that the second threshold value is 536 lines.
[0036]
  The timing controller 400 monitors the line difference and determines whether the line difference is 536 lines or more. For example, the number of lines from the writing control unit 200 is “
1078 ", the number of lines from the read controller 300 is" 54 "2In the case of "", the timing control unit 400 calculates (1078-542) and calculates the line difference "536". If it is determined that the line difference is 536 or more, the OA tally is turned off. Determine if there is.
[0037]
When the OA tally is off, the timing control unit 400 instructs the read control unit 300 to skip the position of the read line of the read control unit 300 by one frame (525 lines). Upon receiving this instruction, the read control unit 300 changes the position of the next read line to a position skipped by one frame (525 lines).
[0038]
On the other hand, when the line difference becomes equal to or greater than the second threshold value and the OA tally is still on, the timing controller 400 monitors the OA tally being turned off. The above operation is performed.
[0039]
In this way, the present invention provides the first and second thresholds, and only when the video is not used for broadcasting, i.e., when the video may be uncomfortable due to twice reading or discarding of the frame. Since the frame is read twice or discarded by the FS, the frame that gives the viewer a sense of incongruity while the video is broadcast is not read or discarded.
[0040]
A second embodiment will be described.
[0041]
In the first embodiment, the line difference between writing and reading is equal to or less than the first threshold value or equal to or greater than the second threshold value, and the OA tally is off, that is, the video output from the FS is broadcast. Only when there is no frame, the frame is read twice or discarded by FS.
[0042]
However, even when the line difference is equal to or smaller than the first threshold value or equal to or larger than the second threshold value, the OA tally on state may continue for a long time, and the frame may not be read twice or discarded by FS. is there. In this case, there is a possibility that the processing will fail.
[0043]
Therefore, in the second embodiment, a third threshold value and a fourth threshold value are set which may cause the processing to fail when the frame cannot be read twice or discarded by FS. When the line difference is equal to or smaller than the third threshold value or equal to or larger than the fourth threshold value, the frame is read twice or discarded by the FS regardless of whether the OA tally is turned on or off. And
[0044]
In order to achieve the above feature, the third threshold value or the fourth threshold value is set in the timing control unit 400 in addition to the first threshold value and the second threshold value. When the line difference between the writing and reading becomes equal to or smaller than the first threshold and the OA tally is kept on, but the line difference becomes equal to or smaller than the third threshold, OA Regardless of whether the tally is on or off, the frame is read twice by the FS described in the above embodiment. In addition, if the line difference between the write and read becomes equal to or greater than the second threshold and the OA tally on state continues, but the line difference becomes equal to or greater than the fourth threshold, OA Regardless of whether the tally is on or off, the frame is discarded by the FS described in the above embodiment.
[0045]
In this way, by setting the threshold to two stages, it is possible to minimize video data discarding (interlace) or double reading during TV broadcasting while avoiding failure of FS processing.
[0046]
A third embodiment will be described.
[0047]
In the third embodiment, in addition to the OA tally, the first threshold value, and the second threshold condition in the first embodiment, the position of the readout line is a frame (or field) and a frame (or field). It is a condition that it is the boundary of
[0048]
In addition, description is abbreviate | omitted about the thing of the same structure as 1st Embodiment or 2nd Embodiment, and only a different part is demonstrated.
[0049]
The difference from the first embodiment or the second embodiment is that the timing control unit 400 receives the number of lines from the read control unit 300 and determines the boundary of the frame every 525 lines. .
[0050]
The operation of the third embodiment will be described below.
[0051]
In the following description, in order to simplify the description, the case where the operation clock (other station clock) of asynchronous video data is slower and faster than the reference clock will be described separately.
[0052]
1) First, the case where the other station clock is slower than the reference clock (when the position of the read line of the read control unit 300 gradually approaches the position of the write line of the write control unit 200) will be described. It is assumed that the read control unit 300 starts operation after the write control unit 200 writes video data for one frame in the ring buffer memory 100. The description will be made assuming that the first threshold is 10 lines.
[0053]
The writing control unit 200 sequentially writes video data of other stations into the ring buffer memory 100 in units of lines. At the same time, the write controller 200 counts up the number of lines in the line counter 210 every time a line is written in the ring buffer memory 100. Then, the write control unit 200 transmits the number of lines indicated by the line counter 210 to the timing control unit 400.
[0054]
On the other hand, the read control unit 300 reads video data from the ring buffer memory 100 line by line according to the reference clock of the local station. At the same time, the read controller 300 counts up the number of lines in the line counter 310 every time video data is read from the ring buffer memory 100 in units of lines. Then, the read control unit 300 transmits the number of lines indicated by the line counter 310 to the timing control unit 400.
[0055]
The timing control unit 400 calculates (the number of lines from the read control unit 300−the number of lines from the write control unit 200) to calculate the line difference. For example, when the number of lines from the write control unit 200 is 780 and the number of lines from the read control unit 300 is 770, the timing control unit 400 calculates (780−770) and sets the line difference “10”. calculate.
[0056]
In addition, the timing control unit 400 determines the boundary between frames from the number of lines from the read control unit 300.
[0057]
Then, the timing control unit 400 monitors the calculated line difference, and when the line difference is equal to or less than the first threshold value of 10 lines and the line position to be read is a boundary between frames, the OA tally Determine if is off.
[0058]
When the OA tally is off, the timing control unit 400 instructs the read control 300 to return the line position by one frame (525 lines). Receiving this instruction, the read control unit 300 returns the position of the next read line to the previous line position for one frame (525 lines) that has already been read.
[0059]
On the other hand, if the line difference is 10 lines or less of the first threshold and the read line position is at the boundary between frames, the OA tally is still on, and the timing control unit 400 determines the OA tally. Is turned off, and when it is turned off, the above-described operation is performed at the timing of the read line position at the boundary between frames.
[0060]
2) Next, a case where the clock of the other station is faster than the reference clock of the own station (when the position of the read line of the read control unit 300 gradually moves away from the position of the write line of the write control unit 200) will be described. . The operation until the line difference is obtained in the timing control unit 400 is the same as the operation described above, and thus detailed description thereof is omitted. Further, it is assumed that the read control unit 300 starts an operation after the write control unit 200 writes video data for one frame in the ring buffer memory 100. The description will be given assuming that the second threshold value is 536 lines.
[0061]
The timing controller 400 monitors the line difference and determines whether the line difference is 536 lines or more. For example, when the number of lines from the write control unit 200 is “1078” and the number of lines from the read control unit 300 is “540”, the timing control unit 400 calculates (1078-542) and calculates the line difference ” 536 "is calculated.
[0062]
In addition, the timing control unit 400 determines the boundary between frames from the number of lines from the read control unit 300.
[0063]
If the line difference is equal to or greater than the second threshold value (536 lines) and the line position to be read is the boundary between frames, it is determined whether the OA tally is off.
[0064]
When the OA tally is off, the timing control unit 400 instructs the read control unit 300 to skip the position of the read line of the read control unit 300 by one frame (525 lines). Upon receiving this instruction, the read control unit 300 changes the position of the next read line to a position skipped by one frame (525 lines).
[0065]
On the other hand, if the line difference is greater than or equal to the second threshold (536 lines) and the line position to be read is at the boundary between frames, the OA tally is still on, and the timing controller 400 Monitors the turn-off of the OA tally, and when it is turned off, the above operation is performed at the timing when the read line position becomes the boundary between frames.
[0066]
As described above, in the third embodiment, the timing of reading or discarding a frame twice is performed at the boundary between frames, so that there is little damage to only the video that is read or discarded twice.
[0067]
A fourth embodiment will be described.
[0068]
The fourth embodiment is a combination of the first, second, and third embodiments described above. That is, the first, second, third, and fourth threshold values are provided, and the frame is read twice or the frame skipping control is performed at the frame boundary.
[0069]
FIG. 5 is a block diagram of the fourth embodiment.
[0070]
The frame synchronizer according to the fourth embodiment includes a ring buffer memory 101 that stores data for each pixel unit, synchronization separation units 102 and 103 that separate frame synchronization clocks, and a write pointer 104 of the ring buffer memory 101. , Read pointer 105 of ring buffer memory 101, subtractor 106, comparators 107, 108, 109, 110, inverters 111, 112, AND circuits 113, 114, OR circuits 115, 116, and AND circuit 117. , 118, a double reading control unit 119, and an interlace control unit 120.
[0071]
The ring buffer memory 101 is a ring buffer memory in which data is stored for each pixel unit.
[0072]
The synchronization generation unit 102 is a synchronization generation unit that generates a write clock for writing from asynchronous video data.
[0073]
The synchronization generation unit 103 is a synchronization generation unit that generates a one-frame synchronization clock from a reference clock.
[0074]
The subtracter 106 is a subtracter that subtracts the read pointer 105 from the address of the write pointer 104.
[0075]
The comparators 107, 108, 109, and 110 are “High” when the + side input is larger than the − side input, and “Low” when the + side input is smaller than the − side input. Is a comparator. Note that the third threshold value is input to the + side input of the comparator 107, the first threshold value is input to the + side of the comparator 108, the second threshold value is input to the − side input of the comparator 109, and the comparator 110. The fourth threshold value is input to the negative side input.
[0076]
When the output of the AND circuit 117 becomes “High”, the twice-reading control unit 119 performs control for returning the position of the reading pointer 105 by one frame and reading twice.
[0077]
When the output of the AND circuit 118 becomes “High”, the interlace control unit 120 changes the position of the read pointer 105 to a position skipped by one frame and performs read control.
[0078]
Next, the operation in the above configuration will be described in four cases.
[0079]
1) When the difference between the address of the read pointer 105 and the address of the write pointer 104 is smaller than the first threshold and larger than the third threshold
First, when the output of the subtractor 106 becomes smaller than the first threshold value, the output of the comparator 108 changes from “Low” to “High” and is input to the AND circuit 113.
[0080]
On the other hand, the OA tally is “High” when the video output from the FS is used for broadcasting, and “Low” when the video is not used for broadcasting. When the video output from the FS is not used for broadcasting, the AND circuit 113 is inverted by the inverter 111 and “High” is input.
[0081]
Accordingly, since “High” and “High” are input to the AND circuit 113, “High” is output from the AND circuit 113.
[0082]
On the other hand, since the difference between the address of the read pointer 105 and the address of the write pointer 104 is equal to or greater than the third threshold value, the output of the comparator 7 is “Low”.
[0083]
Therefore, since the inputs of the OR circuit 115 are “High” and “Low”, the outputs thereof are “High” and are input to the AND circuit 117.
[0084]
In the AND circuit 117, when the signal output from the sync separation unit 3 as the other input is “High” (the boundary of the frame or field), the output of the AND circuit 117 becomes “High”, and the reading control is performed twice. “High” is output to the unit 119.
[0085]
In response to the “High” signal, the twice reading control unit 119 performs a control of returning the reading position of the reading pointer 105 by one frame and reading twice.
[0086]
2) When the difference between the address of the read pointer 105 and the address of the write pointer 104 is smaller than the third threshold value
First, when the output of the subtractor 106 becomes smaller than the third threshold value, the output of the comparator 107 changes from “Low” to “High” and is input to the OR circuit 115.
[0087]
In the OR circuit 115, since the input from the comparator 107 is “High”, regardless of the “Low” or “High” input from the AND circuit 113, that is, the video output from the FS is used for broadcasting. Regardless of whether or not the output is high, the output is “High”.
[0088]
Therefore, in the AND circuit 117, the output becomes “High” at the timing when the signal output from the synchronization separation unit 3, which is the other input, becomes “High” (frame or field boundary), and the twice-reading control unit 119. “High” is output at the same time.
[0089]
In response to the “High” signal, the twice reading control unit 119 performs a control of returning the reading position of the reading pointer 105 by one frame and reading twice.
[0090]
3) When the difference between the address of the read pointer 105 and the address of the write pointer 104 is larger than the second threshold and smaller than the fourth threshold
First, when the output of the subtractor 106 becomes larger than the second threshold value, the output of the comparator 109 changes from “Low” to “High” and is input to the AND circuit 114.
[0091]
On the other hand, the OA tally is “High” when the video output from the FS is used for broadcasting, and “Low” when the video is not used for broadcasting. When the video output from the FS is not used for broadcasting, the signal input to the AND circuit 114 is inverted by the inverter 112 and “High” is input.
[0092]
Accordingly, since “High” and “High” are input to the AND circuit 114, “High” is output from the AND circuit 114.
[0093]
On the other hand, since the difference between the address of the read pointer 105 and the address of the write pointer 104 is smaller than the fourth threshold value, the output of the comparator 110 is “Low”.
[0094]
Therefore, since the inputs of the OR circuit 116 are “High” and “Low”, the outputs are “High”, and “High” is input to the AND circuit 118.
[0095]
The AND circuit 118 outputs “High” when the signal output from the sync separation unit 3, which is the other input, is “High” (the boundary of the frame or field), and the “High” is sent to the interlace control unit 120. "Is output.
[0096]
In response to the “High” signal, the interlace control unit 120 changes the read position of the read pointer 105 to a position skipped by one frame, and performs read control.
[0097]
4) When the difference between the address of the read pointer 105 and the address of the write pointer 104 is larger than the fourth threshold value
First, when the output of the subtractor 106 becomes larger than the fourth threshold value, the output of the comparator 110 changes from “Low” to “High” and is input to the OR circuit 116.
[0098]
In the OR circuit 116, since the input from the comparator 110 is “High”, regardless of whether the input from the AND circuit 114 is “Low” or “High”, that is, the video output from the FS is used for broadcasting. Regardless of whether or not the output is high, the output is “High”.
[0099]
Therefore, in the AND circuit 118, the output becomes “High” at the timing when the signal output from the sync separation unit, which is the other input, becomes “High” (frame or field boundary), and the interlace control unit 120 receives “ High "is output.
[0100]
In response to the “High” signal, the skip control unit 120 changes the reading position of the reading pointer 105 to a position skipped by one frame, and performs reading control.
[0101]
【The invention's effect】
The present invention provides the first and second threshold values for the difference between the FS writing position and the reading position, and when the video is not used for broadcasting, that is, when the video is read twice or discarded. Since the frame is read twice or discarded by the FS only when there is no problem, the frame that gives the viewer a sense of incongruity while the video is being broadcast is not read or discarded. There is an excellent effect.
[0102]
Furthermore, a third threshold value and a fourth threshold value are set, which may cause the processing to fail when the frame cannot be read twice or discarded by the FS, and the difference between the FS writing position and the reading position is determined. When the threshold value is equal to or lower than the third threshold value or equal to or higher than the fourth threshold value, the frame is read twice or discarded by the FS regardless of whether the OA tally is turned on or off. There is no risk of bankruptcy.
[Brief description of the drawings]
FIG. 1 is a block diagram of a frame synchronizer according to a first embodiment.
FIG. 2 is a diagram showing a memory area of a ring buffer memory;
FIG. 3 is a diagram for explaining control of twice-reading a frame.
FIG. 4 is a diagram for explaining interlaced frame control;
FIG. 5 is a diagram for explaining a fourth embodiment;
[Explanation of symbols]
100 Ring buffer memory
200 Write controller
210 Line counter
300 Read controller
310 line counter
400 Timing control unit
500 Other station clock generator
101 Ring buffer memory
102,103 Sync separator
104 Write pointer
105 Read pointer
106 Subtractor
107, 108, 109, 110 comparator
111, 112 inverter
113, 114 AND circuit
115,116 OR circuit
117, 118 AND circuit
119 Twice reading controller
120 Jump control unit

Claims (7)

A frame synchronizer that synchronizes asynchronous video data with a reference clock,
Storage means for storing video data;
A writing means for writing asynchronous video data into the storage means with a clock of the video data;
Reading means for reading out video data stored in the storage means with a reference clock;
The difference between the writing position of the video data by the writing means in the storage means and the reading position of the video data of the reading means in the storage means is equal to or less than the first threshold or greater than or equal to the second threshold. In this case, it is determined whether the video data read by the reading means is used for television broadcasting, and when the video data is used for television broadcasting, the use of the video data for the television broadcasting is monitored, and the reading means And control means for causing the reading means to read twice for one frame when the video data read in is no longer used for television broadcasting, or to cause the reading means to skip one frame for reading. Frame synchronizer.   When the video data read by the reading unit is used for television broadcasting, the control unit is configured to read the reading when the difference between the writing position and the reading position is equal to or smaller than a third threshold value that is smaller than the first threshold value. Means for reading twice for one frame, and the difference between the writing position and the reading position is not less than a fourth threshold value, which is greater than a second threshold value, even if the video data read by the reading means is used for television broadcasting 2. The frame synchronizer according to claim 1, wherein the frame synchronizer is configured to cause the reading means to skip one frame.   The control means causes the reading means to read twice for one frame when the video data read by the reading means satisfies a frame or field boundary, or the reading means for one frame. 3. The frame synchronizer according to claim 1, wherein the frame synchronizer is configured to skip and perform reading. A frame synchronization method for synchronizing asynchronous video data with a reference clock,
Writing asynchronous video data to the storage device with the clock of the video data;
Reading video data from the storage device with a reference clock;
If the difference between the video data writing position and the reading position in the storage device is equal to or less than the first threshold value or equal to or greater than the second threshold value, is the video data read from the storage device used for television broadcasting? And when the video data is used for television broadcasting, monitoring the use of the video data for television broadcasting;
As a result of the monitoring, when the video data read by the reading means is no longer used for television broadcasting, the reading means reads twice for one frame, or skips the reading means for one frame, and A frame synchronization method characterized by comprising:   Even when the read video data is used for television broadcasting, the difference between the video data writing position and the reading position in the storage device is equal to or smaller than a third threshold value smaller than the first threshold value. 5. The frame synchronization method according to claim 4, further comprising a step of reading the read position of the video data back by one frame and reading it twice.   Even when the read video data is used for television broadcasting, the difference between the video data write position and the read position in the storage device is not less than a fourth threshold value greater than the second threshold value. 6. The frame synchronization method according to claim 4, further comprising a step of reading the video data by advancing the reading position of the video data by one frame.   The timing at which the video data reading position is read back by one frame and the video data reading position is advanced by one frame and the video data is read out is the boundary of the frame or field. 7. The frame synchronization method according to claim 4, wherein the frame synchronization method is performed at different timings.

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