JPH0376487A - Video frame synchronization device - Google Patents

Abstract

PURPOSE:To prevent deterioration in picture quality by eliminating or inserting a frame so as to send a signal at a transmission section with a reference frame frequency smaller than a frame frequency of a reception section thereby avoiding delete of frames at the reception section. CONSTITUTION:A frame insertion/delete section 24 uses a frame delete signal from a frame control section 23 to delete a data by one frame from a video input signal whose transmission frame frequency is fsnd. On the other hand, the frame insertion signal is used to repeat the same frame of the video input signal to insert the frame. Then a transmission section T sends the video data with a frame frequency fref (<frcd) to the reception section R. Thus, the transmission section T sends the video data with a smaller frame frequency fred than the reception frame frequency frcd of the reception section R, then it is not required to delete the frame at the reception section R to avoid deterioration of picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video frame synchronization device used in a video encoding device or the like.

2. Description of the Related Art In general, in a video encoding device, a transmitter transmits a video signal with a frame frequency f snd, and when a receiver receives this video signal, it processes the video signal with a frame frequency f rcd.

Therefore, since the frame frequency f snd of the transmitter and the frame frequency f rcd of the receiver are different, f sn
If d > f rcd, the video frame is deleted in the receiving section as shown in FIG. 3(a), and if f snd < f rcd, the receiving section deletes the video frame as shown in FIG. 3(b). By inserting a video frame in the transmitter and receiver, the frequency of the video frame must be synchronized between the transmitter and receiver.

FIG. 2 shows a conventional video frame synchronization device, in which the left side of the figure is a transmitter t, and the right side of the figure is a receiver r.

In the transmitter t shown in FIG. 2, 1 is a subtracter that subtracts the prediction signal stored in the frame memory 2 from the video input signal of the transmission frame frequency f snd, and outputs a prediction error signal; a quantizer that quantizes the prediction error signal from the subtracter 2 with a quantization step size characteristic determined according to the residual buffer amount of the transmission buffer memory 8;
4 adds the quantized signal from the quantizer 3 and the predicted signal stored in the frame memory 2 and outputs a reproduced signal;
This is an adder that stores the prediction signal in the frame memory 2.

5 is a Huffman encoder that outputs a Huffman encoded signal based on the quantized signal from the quantizer 3; 6 is a frame header generator that generates a frame header; 7 is a Huffman encoded signal from the Huffman encoder S; This multiplexer multiplexes the frame headers from the frame header generation section 6, and this multiplexed data is temporarily stored in the transmission buffer memory 8 and sent out to the transmission line 9 at a constant transfer rate.

In the receiving section r, 11 is a frame ladder counter that detects frame headers from the transmission path 9 and counts the number Nh thereof, and 12 is a receiving frame frequency f red
The receiving section frame counter 13 counts the number of frames for reception Nrcd and outputs the number of frames for reception Nh from the ladder counter 11 and the number of frames for reception Nrcd from the receiving section frame counter 12. When Nrcd > THu, a decrement command and a frame deletion command are output to the frame ladder counter 11 and frame insertion/deletion section 15, respectively, and on the other hand, when Nh - Nrcd <THI (<THu),
This is a frame control unit that outputs an increment command and a frame insertion command to the frame ladder counter 11 and frame insertion/deletion unit 15, respectively.

Reference numeral 14 denotes a reception buffer memory that temporarily stores data from the transmission path 9, and a frame insertion/deletion unit 15 extracts one frame from the data from the reception puffer memory 14 in response to a frame deletion command from the frame control unit 13. On the other hand, dummy frame data (data obtained by encoding all the difference data rOJ) is inserted into the data from the reception buffer memory 14 by the frame insertion command.

16 is a demultiplexer that separates the frame header from the data from the frame insertion/deletion unit 15 and outputs a Huffman encoded signal; 17 is a Huffman decoder that Huffman decodes the Huffman encoded signal separated by the demultiplexer 16; , 18 is an adder that adds the prediction error signal Huffman-decoded by the Huffman decoder 17 and the prediction signal stored in the frame memory 19 and outputs it as a video signal. It is stored in the frame memory 19 as a predicted signal.

That is, in the above conventional example, when the transmitter t transmits data at the transmission frame frequency f snd, the receiver r receives the frame header number Nh from the ladder counter 11 and the reception frame frequency from the receiver frame counter 12. The number of frames Nrcd is compared, and if Nh - Nrcd > THu, the frame is deleted, and if Nh - Nrcd (THI (< THu), the frame is inserted, so the frame synchronization between the transmitter t and the receiver r is You can take it.

Problems to be Solved by the Invention However, in the above-mentioned conventional video frame synchronization device,
If the reception frame frequency f rcd is smaller than the transmission frame frequency f snd (frcd<fsnd),
Since the receiver r deletes one frame every certain number of frames, one frame of prediction error is lost due to this deletion,
There is a problem that image quality deteriorates.

SUMMARY OF THE INVENTION In view of the above conventional problems, it is an object of the present invention to provide a video frame synchronization device in which image quality does not deteriorate even when the frame frequencies of transmitting and receiving sections differ.

Means for Solving the Problems In order to achieve the above object, the present invention deletes or inserts frames so that the transmitter transmits at a reference frame frequency lower than the frame frequency of the receiver.

Effect of the Invention With the above-described configuration, frames are not deleted in the receiving section, and therefore, image quality does not deteriorate.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a video frame synchronization device according to the present invention, in which the left side of the figure is a transmitter T, and the right side of the figure is a receiver.

In the transmitter T, 21 counts the transmission frame synchronization signal of frequency f snd, and calculates the number N of transmission frames.
The transmitter frame deletion signal 22 that outputs the transmitter T and snd is a line clock counter that divides the line clock and outputs the reference frame number Nref. It is the number of frames at a common reference frame frequency f ref of the receiving section R, and f ref < f red (where f rcd is the frame frequency of the receiving section R).

23 outputs a frame deletion signal when the difference between the number of transmission frames N5nd counted by the transmitter frame counter 21 and the reference frame number NrefO counted by the line clock counter (N5nd - Nref) is incremented by one; a frame control unit that outputs a frame insertion signal when decremented by one;
24 deletes one frame worth of data from the video human input signal of the transmission frame frequency f snd by the frame deletion signal from the frame control unit 23, and deletes the same frame of the video input signal by the frame insertion signal. This is a frame insertion/deletion unit that inserts frames by repeating them.

25 subtracts the predicted signal stored in the frame memory 26 from the video signal from the frame insertion/deletion unit 24;
The subtracter 27 that outputs a prediction error signal is a quantizer that quantizes the prediction error signal from the subtracter 25 with the characteristics of the quantization step size determined according to the residual bar x77iL of the transmission buffer memory 32. , 28 is an adder that adds the quantized signal from the quantizer 27 and the predicted signal stored in the frame memory 26, outputs a reproduced signal, and stores the reproduced signal in the frame memory 26 as a predicted signal.

29 is a Huffman encoder that outputs a Huffman encoded signal based on the quantized signal from the quantizer 27; 3o is a frame header generator that generates a frame header; 31 is a Huffman encoded signal from the Huffman encoder 29; This multiplexer multiplexes the frame headers from the frame header generation section 30, and this multiplexed data is temporarily stored in the transmission buffer memory 32 and sent out to the transmission line 33 at a constant transfer rate.

In the reception unit R, 41 is a line clock counter that divides the line clock and outputs the reference frame number Nref, and 42 counts the reception frame frequency frcd and outputs the reception frame number Nrcd. The receiving unit frame counter 43 is a line clock counter 41
The difference between the number of reference frames Nref from
This is a frame control unit that outputs a frame insertion signal when cd -Nref) is incremented by one.

44 is a reception buffer memory that temporarily stores data from the transmission path 33; 45 is a reception buffer memory that temporarily stores data from the transmission path 33; and 45, dummy frame data (all differential data r
This is a frame insertion unit that inserts OJ encoded data).

46 is a demultiplexer that separates the frame header from the data from the frame insertion unit 45 and outputs a Huffman encoded signal; 47 is a Huffman decoder that performs Huffman reconstruction of the Huffman encoded signal separated by the demultiplexer 46; 48 is a prediction error signal Huffman-decoded by the Huffman decoder 47 and a frame memory 49.
This is an adder that adds together the predicted signals stored in the frame memory 49 and outputs it as a video signal, and this video signal is stored in the frame memory 49 as a predicted signal for the next frame.

Next, the operation of the above embodiment will be explained.

In FIG. 1, the frame system wJ12 in the transmitter T
3 is the difference (
When 'N5nd - Nref ) is incremented by one, a frame deletion signal is output, and when it is decremented by one, a frame insertion signal is output.

The frame insertion/deletion unit 24 receives a frame deletion signal from the frame control unit 23 to control the frame frequency f for transmission.
Data for one frame is deleted from the video input signal of snd, and on the other hand, a frame is inserted by repeating the same frame of the video input signal using a frame insertion signal.

Therefore, the transmitter T transmits the video data to the receiver R at the frame frequency f ref, (, < f rcd ).

The frame control unit 43 in the receiving unit R receives the reference frame number N ref from the line clock counter 41 and the number of reception frames N r from the receiving unit frame counter 42.
A frame insertion signal is output when the difference in cd (Nrcd - Nref) is incremented by one.

Here, since f ref < f red , it is possible that the difference (Nrcd - Nref) is decremented, and the frame control unit 43 does not output a frame deletion signal.

Therefore, according to the above embodiment, the transmitter T is the receiver R.
On the other hand, since the video data is transmitted at a frame frequency f ref smaller than the receiving frame frequency f rcd of the receiving unit R, the receiving unit R does not delete frames and the image quality does not deteriorate.

Further, since the receiving section R inserts a frame using the receiving frame frequency f rcd, frame synchronization with the transmitting section T can be achieved.

As described in detail, the present invention deletes or inserts frames so that the transmitter transmits at a reference frame frequency lower than the frame frequency of the receiver. There is no need to delete the image, so the image quality does not deteriorate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a video frame synchronization device according to the present invention, FIG. 2 is a block diagram showing a conventional video frame synchronization device, and FIG. 3 is a diagram showing frame deletion or insertion. It is an explanatory diagram. T...Transmission unit, R...Reception unit, 21...Transmission unit frame counter, 22.41...Line clock counter, 23.43...Frame control unit, 24...Frame insertion/ Deletion unit, 42... Receiving unit frame counter, 45... Frame insertion unit.

Claims (2)

[Claims] (1) Delete or insert a frame so that the transmitter transmits at a reference frame frequency lower than the frame frequency of the receiver, and the receiver receives the video signal from the transmitter,
A video frame synchronization device characterized in that a frame is inserted so as to be output at its own frame frequency based on the reference frame frequency. (2) The video frame synchronization device according to claim (1), wherein the transmitting section and the receiving section each generate a reference frame frequency by frequency-dividing a line clock.