JPH0638195A - Video coder - Google Patents

Abstract

PURPOSE:To obtain sufficient picture quality by suppressing quantity of arithme tic operation much needed at the time of the calculation of motion vectors in a conventional coder in the system of a high efficiency coder for a video source employing inter-frame prediction. CONSTITUTION:The coder is provided with a camera control section 7 measuring a moving quantity of a camera 6 at every frame and with a video coding section 10 whose retrieval range is optionally changed at the time of motion vector calculation so that retrieval range is changed depending on the moving quantity of the camera. That is, the video coding section 10 identifies the position in a frame from a frame GOB number, increases the retrieval range of a motion vector in the middle of the frame and decreases the retrieval range of a motion vector at ends of the frame at the characteristic of the motion vector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video coder for high efficiency coding of a video source using interframe prediction.

[0002]

2. Description of the Related Art In recent years, commercialization of communication services using ISDN lines has started, and AV (Audio Visualsua) such as videophones and videoconference systems using such digital lines have been started.
l) Services are drawing attention, and service specifications, protocol specifications, and multimedia multiplexing frame structure specifications for AV services are described in CCITT Recommendation (or Recommendation Draft) H.264.
320, H.M. 242, H.H. 221, H.221. It was announced as 261 mag.

H. In H.261, p × 64 kbit / s (p = 1
The coding and decoding methods for moving image signals at the speeds of (1) to (30) are specified. H. In H.261, since the image signal has a wide frequency band, a video signal high efficiency coding device (video codec) for compressing the image signal has been developed. As a video signal encoding algorithm in this conventional high-efficiency video signal encoding apparatus, a method combining inter-frame prediction using redundancy in the time axis direction and transform encoding for reducing spatial redundancy of prediction error Has been taken.

Motion compensation can be used in the inter-frame prediction. Motion compensation is performed in macroblock units (16
The difference from the previous screen is calculated as a motion vector with (× 16 pixels), and this value is transmitted. The decoding device receives the motion vector in macroblock units and reproduces the image using the previous frame and the motion vector. In order to calculate the value of the motion vector in the video coding unit, the vector that has the smallest error from the macroblock inside the frame of the previous screen to be coded is calculated.

[0005]

However, in this conventional method, for example, if all search ranges are calculated at the time of calculating a motion vector, the amount of calculation increases and the encoding cannot be done in time. On the other hand, if the search range is narrowed, it becomes impossible to follow the movement, and it is not possible to obtain sufficient image quality.

[0006]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, it comprises a movement amount measuring means for measuring the movement amount of the camera for each frame and a designating means for designating a motion vector search range based on the measurement movement amount of the movement amount measuring means, and the motion vector designated by the designating means. A motion vector is calculated within the search range to perform motion compensation.

[0007] For example, the designating means has a function of designating the size of the motion vector search range, and further comprises identification means for identifying the position within the frame. The designating means has the motion vector search range depending on the position of the frame. Change the size of.

[0008]

In the above structure, the search position of the motion vector is changed according to the amount of movement of the camera. For example, if the camera moves to the right, the vector search range is specified on the right side of the macroblock. In addition, the size of the motion vector search range is changed according to the position of the macroblock in the frame. For example, the motion vector search range is increased at the center of the frame and is decreased at the end of the frame. As a result, the amount of vector calculation can be reduced and, for example, the image quality in the central portion of the screen can be improved as compared with the peripheral portion.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a multimedia communication device according to an embodiment of the present invention. In the figure, 1 is a handset which is one of the audio input / output means of this device, 2 is a microphone which is one of the audio input means of this device, 3 is a speaker which is one of the audio output means of this device,
Reference numeral 4 is a voice interface unit, which is a system control unit 1.
In response to the instruction of 4, the switching process is performed to switch the handset 1, the microphone 2 and the speaker 3 as the voice input / output means. Also, the voice interface unit 4 is for on / off hook detection processing for detecting whether the handset 1 is in the on-hook state or the off-hook state, and for canceling the echo when the microphone 2 and the speaker 3 are used as the voice input / output means. The echo canceling process of (1) and the generation of tones such as dial tone, ringing tone, busy tone, and ring tone are also executed.

[0010] 5 is instructed by the system control unit 14,
(64kbps PCM A-law), (64kbps PCM
μ-law), (64bps / 56kbps / 48kbps SB-A
DPCM), (32kbps ADPCM), {16kbps
(For example, APC-AB)}, (8 kbps), and the like, which is a voice encoding / decoding unit that encodes a transmission voice signal and decodes a reception voice signal according to a voice signal encoding / decoding algorithm.

Reference numeral 6 is one of the image inputting means of this apparatus, which is a camera for inputting a self-portrait, etc., 7 is a camera control section for measuring the amount of movement of the camera 6, 8 is an image received from the camera 6 or the other party, A display unit for displaying operation screens and the like, 9 is NTS
A video interface that performs C / CIF conversion, image input device switching processing, input image / received image / operation screen switching processing to the display unit 8, and image signal synthesis processing for displaying them separately on the display unit 8. Ace part, 10 is CC
ITT Recommendation Draft H. 261 is a video encoding / decoding unit that encodes the transmission image according to H.261, and controls the motion-compensated inter-frame prediction in this embodiment. A video decoding unit 11 decodes the received image signal.

Reference numeral 12 is a data terminal for performing data communication, and 13 is a data interface unit that controls the interface between the data terminal 12 and the demultiplexing unit 15. For example, communication data from the data terminal 12 is demultiplexed. Part 15
Output to. 15 is CCITT Recommendation H.264. 221, an audio signal from the audio encoding / decoding unit 5, an image signal from the video encoding unit 10, and a data interface unit 1
3 from the data, BAS from the system control unit 18,
The multiplexing / demultiplexing unit 16 multiplexes each transmission frame unit and separates the reception frame into each unit of the constituent unit to notify each unit. Reference numeral 16 is a line interface for controlling the line according to the ISDN user / network interface. It is a department.

Reference numeral 17 denotes an operation unit such as a keyboard and touch panel used for inputting control information for performing overall control of this device, and 18 includes a CPU, ROM, RAM, auxiliary storage device, etc. for monitoring the state of each unit. In addition, the system control unit according to the present exemplary embodiment controls the entire apparatus, creates an operation / display screen according to the state, executes an application program, and the like.

The camera control section 7, the video interface section 9 and the video encoding section 1 of the present embodiment having the above-mentioned configuration.
The relationship with 0 and the detailed description are shown in FIG. In the configuration of FIG. 2, motion compensation interframe predictive coding is performed. In FIG. 2, 9-1 is included in the video interface unit 9,
NTSC / C for NTSC / CIF conversion of video signals
It is an IF converter. Further, 10-1 is a video coding control unit and 10-2 is a video coding circuit.

The encoding processing operation of the photographing information in the camera 6 of the present embodiment having the above configuration will be described using the flow chart of FIG. First, in step S1, the video signal captured by the camera 6 is sent to the NTSC / CIF converter 9-1 and converted into a CIF signal. The signal converted into the CIF signal is output to the video encoding circuit 10-2.

On the other hand, the camera control section 7 receives the frame synchronization signal from the video encoding control section 10-1 in step S2, measures the rotational movement amount vector (x, y) for each frame of the camera, and then video. Output to the encoding control unit 10-1. The video encoding control unit 10-1 assigns the camera movement amount vector (x, y) obtained from the coordinates shown in FIG. 4 to the conversion diagram shown in FIG. The variable c is calculated. Figure 5
The conversion diagram of is the maximum search range of the motion vector ± 15
(Pixel) × ± 15 (line) is divided into nine blocks 1 to 9 shown in the figure, and each block is numbered. From this figure, the search block position is determined according to the value of the search block position variable c. Video coding control unit 10-1
Outputs the search block position variable c to the video encoding unit 10-2.

The video encoding unit 10-2 then calculates a motion vector that minimizes the prediction error within the block range designated in step S4. As described above, according to the present embodiment, the calculation amount can be reduced by limiting the search range when calculating the motion vector.

[0018]

Other Embodiments In the above description, for example, the video encoding control unit 10-1 converts the camera movement amount vector (x, y) obtained from the coordinates shown in FIG. 4 into the conversion diagram shown in FIG. The search block position is allocated, the search block position corresponding to the value of the search block position variable c is determined, and the search block position variable c is output to the video encoding unit 10-2. The motion vector with the smallest prediction error within the range was calculated.

However, the present invention is not limited to the above example, and the same effects can be achieved by the following method. A second embodiment according to the present invention will be described below with reference to the flow chart of FIG. The flow chart of FIG. 6 is a process corresponding to the one-variable calculation process of step S3 in the process of FIG. 3 in the above-described first embodiment, and in the second embodiment, the search range of step S3 of the first embodiment. Instead of calculation, the search range is calculated by the processing shown in FIG. The other encoding processing and hardware configuration can be the same as those of the first embodiment described above.

In the search range calculation in the second embodiment, the video coding unit 10-2 divides one frame of the CIF format into 12 GOBs as shown in FIG. 7, and assigns numbers to the divided blocks. . Then, in step S11, prior to the motion vector calculation, the GOB numbers to which the corresponding macroblock belongs are "1", "2", "1".
Check whether it is "1" or "12". The GOB numbers to which the corresponding macro block belongs are "1", "2", "1".
If it is "1" or "12", since it is the end of the frame, the process proceeds to step S12 in order to reduce the inspection range, and the motion vector search range is set to a block of 10.times.10.

On the other hand, the G to which the corresponding macroblock belongs
If the OB number is not "1", "2", "11", or "12", since it is the center of the frame, the process proceeds from step S11 to step S13 to increase the inspection range, and the motion vector search range is set to 15 Set to a block of × 15. Then, thereafter, for example, a process substantially similar to step S4 of FIG. 3 is executed to calculate a motion vector that minimizes the prediction error in the search range set by the process of FIG.

By calculating the motion vector that minimizes the prediction error in the search range described above, the amount of calculation of the motion vector can be reduced as described above. In the second embodiment described above, the position in the frame is identified by the GOB number, but the position may be identified by the macroblock unit in the GOB. As a result, finer control can be performed.

The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0024]

As described above, according to the present invention, the calculation amount can be reduced by limiting the search range when calculating the motion vector. Further, the image quality in the central portion of the screen can be improved as compared with the peripheral portion.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention.

FIG. 2 is a block diagram showing a relationship and detailed description with a camera control unit, a video interface unit, and a video encoding unit shown in FIG.

FIG. 3 is a flow chart showing the encoding operation of this embodiment.

FIG. 4 is a diagram showing an example in which a camera movement amount (x, y) of the present embodiment is associated with a movement amount variable.

FIG. 5 is a diagram showing an example in which the motion vector search range of this embodiment is divided into 9 blocks.

FIG. 6 is a flow chart showing a search range setting operation of another embodiment according to the present invention.

FIG. 7 is a diagram showing the positions of GOBs in one frame of a CIF format according to another embodiment.

[Explanation of symbols]

 1 Handset 2 Microphone 3 Speaker 4 Audio interface unit 5 Audio encoding / decoding unit 6 Camera 7 Camera control unit 8 Display unit 9 Video interface unit 10 Video encoding unit 11 Video decoding unit 12 Data terminal unit 13 Operation unit 14 system control unit 15 demultiplexing unit 16 line interface unit

Claims (2)

[Claims] 1. A moving amount measuring means for measuring a moving amount of a camera for each frame, and a designating means for designating a motion vector search range based on the measured moving amount of the moving amount measuring means. A video encoding device characterized by calculating a motion vector within a motion vector search range and performing motion compensation. 2. A discriminating means for discriminating a position in a frame is further provided, and the designating means has a function of designating the size of the motion vector search range, and determines the size of the motion vector search range depending on the frame position. The video encoding device according to claim 1, wherein the video encoding device is changed.