JP2012004944A - Videophone device, videophone system, videophone method and videophone control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a videophone device suppressing degradation of the signal-to-noise ratio of a reception signal when the reception signal level is lowered so as to be unlikely to cause interruption of a phone call.SOLUTION: When a reception signal level is lowered, the resolution of an image which is displayed on a display device 3 or generated by a camera 4 is lowered, so that noise due to harmonics generated by the display device 3, the camera 4, and a CPU 2 which are components of a videophone device itself is suppressed. Since noise generated from the inside is suppressed, the signal-to-noise ratio of the reception signal is improved, so that noise in the image displayed on the display device 3 or the image transmitted to a telephone conversation partner is suppressed and the phone call becomes unlikely to be interrupted.

Description

  The present invention relates to a videophone device, a videophone system, a videophone method, and a videophone control program, and in particular, controls the resolution of an image displayed on a display device or an image generated by a camera based on the quality of a received signal such as a received signal level. Thus, the present invention relates to a videophone that suppresses interruption of a call when the quality of a received signal deteriorates.

  In mobile phone videophones, the reception environment of radio waves changes due to movement and the communication quality changes, so the received signal level and signal-to-noise ratio fluctuate, and the image displayed on the display device and sent to the terminal of the communication partner Often the quality of the image varies significantly. The communication quality is expressed by the signal level of the received signal and the signal-to-noise ratio.

  The mobile videophone device includes a display device including a transmission / reception unit, an LCD, a camera using a high-pixel-number element such as a CCD as a light receiving element, and a control unit including a CPU that controls the display device and the camera. . The radio wave received by the antenna is converted into a received signal by the transmission / reception unit. This received signal is processed by the control unit, sent to the display device, and displayed as an image on the display device. An image captured by the camera is processed by the control unit, sent to the transmission / reception unit, converted into a high-frequency transmission signal by the transmission / reception unit, and sent to the antenna.

  In a portable videophone device that communicates with high-resolution images, the display device, camera, and control unit perform signal processing at a high bit rate. When the display device, camera, and CPU perform signal processing at a high bit rate, the level of harmonics of the clock frequency increases, and the harmonics are mixed into the received signal as noise, making it easy to reduce the signal-to-noise ratio of the received signal. Become. In particular, when the received radio wave intensity is low and the received signal level is low, if the level of harmonic noise generated from the display device, camera, CPU, etc. is high, the received signal that is output from the transceiver and processed by the CPU The signal to noise ratio is reduced. If the signal-to-noise ratio is low, not only will the image displayed on the display device be noisy or distorted, it will be difficult to see the image, but the probability that the call will be interrupted will be high.

  For videophone systems, the image to be sent to the mobile phone of the other party depends on whether the other party is watching the display (display device) of the mobile phone or not, that is, depending on the necessity of the image. A technique for controlling the frame rate and reducing unnecessary communication traffic is disclosed in Japanese Patent Application Laid-Open No. 2007-110312.

  In addition, in order to control the communication speed of an image as in the videophone system of Patent Document 1, two types of high and low speeds are prepared as the frame rate of an image to be transmitted. If the communication speed is realized, there is a possibility that the frame rate is frequently switched. However, a technique (mobile videophone) for avoiding frequent switching of the frame rate is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2009-259259. -141543).

  In the videophone of Patent Document 2 (FIG. 1), two levels of high and low thresholds for determining the received signal strength are prepared, and when the low frame rate is set in the camera unit, the high level threshold is set. When the received signal strength exceeds the high level threshold, a high-speed frame rate setting command is output to the camera unit. On the other hand, when the high frame rate is set in the camera unit, a low frame rate setting command is output to the camera unit when the received signal strength has interrupted the low level threshold using the low level threshold.

JP 2007-110212 A (paragraphs 0020-0030) JP 2009-141543 A (summary, FIG. 1)

  In the videophone system described in Patent Document 1 described above, even if the communication traffic can be reduced, the degradation of communication quality such that the signal-to-noise ratio of the received signal is reduced when the received signal level is low is suppressed. However, the probability of blocking the call cannot be reduced.

  In addition, in the mobile videophone described in Patent Document 2, the signal-to-noise ratio of the received signal is low when the received signal level is low even if the switching of the frame rate can be suppressed frequently. It is impossible to suppress the deterioration of communication quality and reduce the probability of interruption of a call.

  When communication quality degradation such as a decrease in the signal-to-noise ratio of the received signal due to a decrease in the received signal level occurs, a lot of noise is added to the image displayed on the display device, the image is disturbed, and further communication is not possible. Blocked. As described above, in the videophone device, the signal processing speed in the display device, the camera, and the control unit is much higher than that of the voice-only phone device, so that the internally generated noise level is high and the reception signal level is low. However, there is a problem to be solved that the communication quality is lower than that of a voice-only telephone device and that the call is easily interrupted.

  Accordingly, an object of the present invention is to provide a videophone device, a videophone system, a videophone method, and a videophone control in which a decrease in the signal-to-noise ratio of a received signal is suppressed when a received signal level is reduced, and a call is hardly interrupted. To provide a program.

  In order to solve the above-described problems, a videophone device, a videophone system, a videophone method, and a videophone control program according to the present invention employ the following characteristic configuration.

  (1) The videophone apparatus according to the present invention is characterized in that the resolution of at least one of the image displayed on the display device or the image output from the camera is controlled based on the quality of the received signal.

  (2) The videophone system according to the present invention is a videophone system that performs videophone communication with each other, wherein the terminal includes a display device that displays an image transmitted from a communication partner terminal, and a communication partner terminal. A videophone system, comprising: a camera that outputs an image to be transmitted to the camera; and a control unit that controls the resolution of at least one of the display device and the image based on the quality of a received signal.

  (3) The videophone method according to the present invention is a videophone method in which a plurality of terminals perform videophone communication with each other. The terminal displays an image transmitted from a communication partner terminal on a display device, and performs communication. An image is transmitted to the other terminal, and the resolution of at least one of the image displayed on the display device or the image transmitted to the other terminal is controlled based on the quality of the received signal. And

  (4) A videophone control program according to the present invention is characterized in that the videophone method described in (3) is implemented as a program executable by a computer.

  According to the present invention, there is provided a videophone device, a videophone system, a videophone method, and a videophone control program in which a decrease in a signal-to-noise ratio of a received signal is suppressed when a received signal level is reduced and a call is hardly interrupted. Can be provided.

It is a figure which shows the structure of the portable video telephone apparatus which is one embodiment of this invention. 3 is a flowchart showing a flow of processing in the mobile videophone device of FIG. 1. 3 is a time chart showing a relationship between a received signal level and image resolution in the mobile videophone device of FIG. 1. The embodiment shown in FIG. 3 is modified so that the received signal level (threshold value) for switching the resolution of the image has hysteresis, and the received signal level and the image in the other embodiment of the portable videophone device of the present invention. It is a time chart which shows the relationship with resolution. It is a time chart which shows the relationship between the received signal level and the resolution of an image in another embodiment of this invention which deform | transformed the carrying of the implementation shown in FIG. In the embodiment of FIG. 1, it is a schematic diagram which shows the example (A) of the high resolution image displayed on a display apparatus, and the example (B) of a low resolution image.

  Preferred embodiments of a videophone device, a videophone system, a videophone method, and a videophone control program according to the present invention will be described below with reference to the accompanying drawings. In the following description, the videophone device and the videophone method according to the present invention will be mainly described. However, a videophone system can be implemented by providing a plurality of the videophone devices, and the videophone method is executed by a computer. Needless to say, it may be implemented as a possible videophone control program, or may be recorded on a computer-readable recording medium.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The present invention relates to an image or a camera displayed on a display device when the quality of a received signal (at least one of the received signal level or the signal-to-noise ratio of the received signal) falls below a predetermined threshold in a videophone device. The main feature is to reduce the resolution of an image to be captured. With this feature, it is possible to suppress a decrease in the signal-to-noise ratio in the received signal and to prevent the interruption of the call. That is, according to the present invention, when the quality of the received signal deteriorates due to a decrease in the received signal level or the like, the display device, the camera, and the control unit which are constituent elements of the own videophone device are generated by reducing the resolution of the image to be handled. The main feature is to reduce noise.

(Embodiment of the present invention)
Next, an example of the configuration of the videophone device according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an embodiment of a portable videophone device according to the present invention. As shown in FIG. 1, the videophone device 10 includes a transmission / reception unit 1, a CPU (corresponding to the control unit described above) 2, a display device 3, and a camera 4, and an antenna 11 is attached. Radio waves received by the antenna 11 are demodulated by the transmission / reception unit 1 and converted into reception signals. This received signal is processed by the CPU 2, sent to the display device 3, and displayed as a real-time moving image on the display device 3. An image captured by the camera 4 is processed by the CPU 2, sent to the transmission / reception unit 1, modulated by the transmission / reception unit 1, converted into a high-frequency transmission signal, and sent to the antenna 11. The CPU 2 controls the transmission / reception unit 1, the display device 3, and the camera 4. The display device 3 and the camera 4 have two operation modes of low resolution and high resolution as image resolution, and operate in one of the low resolution and high resolution modes under the control of the CPU 2.

FIG. 2 is a flowchart showing the flow of processing in the mobile videophone apparatus of FIG. In the operation description of FIG. 2, the CPU 2 is assumed to simultaneously switch the resolution of the display device 3 and the camera 4 to a high resolution or a low resolution. Further, CPU 2, the display device 3 and to switch the resolution of the camera 4 from high resolution to low resolution, pre-stores a threshold E _T as a reference value of the received signal level to determine whether to switch from low resolution to high resolution reversed Suppose you are.

First, a videophone call is started with high resolution (S01). Then the received signal level to determine whether a less threshold E _T (S02). If the received signal level is not below the threshold E _T to maintain a high-resolution (S03). Again received signal level after a predetermined time has elapsed is determined whether equal to or less than a threshold value E _T (S02). If the received signal level is below the threshold E _T switch to low resolution (S04). After switching to the low resolution to the determination of whether the received signal level is the threshold value E _T over again after a predetermined time has elapsed (S05). If the received signal level is not the threshold E _T or more to maintain a low resolution (S06). A certain time after the received signal level again to determine whether the threshold value E _T or more (S05). If the received signal level is the threshold value E _T or switch to a higher resolution (S07). After switching to the high resolution to the determination of whether the received signal level is below the threshold E _T after a predetermined time has elapsed (S02).

FIG. 3 is a time chart showing the relationship between the received signal level and the image resolution in the mobile videophone apparatus of FIG. In the embodiment of FIG. 3 also, the resolutions of the display device 3 and the camera 4 are simultaneously switched to a high resolution or a low resolution. The time chart of FIG. 3 shows the operation of the portable videophone device of FIG. 1 when the received signal level decreases and increases with time. Switch to low resolution at time t1 when the received signal level falls below falling threshold E _T over time. Switch to high resolution time t2 when the time further elapses received signal level equal to or greater than a threshold value E _T.

FIG. 4 is a modification of the embodiment shown in FIG. 3, and the received signal level in another embodiment of the portable videophone device of the present invention is provided with hysteresis in the threshold value of the received signal level for switching the image resolution. 3 is a time chart showing the relationship between the image resolution and the image resolution. Also in the embodiment of FIG. 4, it is assumed that the resolutions of the display device 3 and the camera 4 are simultaneously switched to a high resolution or a low resolution. In the time chart of FIG. 4, it is shown that the high threshold E _TH and the low threshold E _TL are set as the threshold E _T for evaluating the received signal level. In the embodiment of FIG. 3, the switching from the high resolution to the low resolution, the reception signal level of the reference value for determining whether to switch back from the low resolution to the high resolution is one of the threshold E _T, received In an environment where the signal level is near the threshold, the resolution of the image is frequently switched. Therefore, as shown in FIG. 4, the threshold value when changing from high resolution to low resolution (low threshold value E _TL ) and the threshold value when changing from low resolution to high resolution (high threshold value E _TH ) are set to different values. As a result, it is possible to reduce the flutter of switching between high resolution and low resolution. Here, the received signal level is RSCP: Received Signal Code Power or RSSI: Received Signal Strength Indicator.

FIG. 5 is a time chart showing the relationship between the received signal level and the image resolution in another embodiment of the present invention, which is a modification of the embodiment shown in FIG. In the time chart of FIG. 5, the hysteresis in the threshold of the received signal level for switching the resolution of the image displayed on the display device of the portable television device and the threshold of the received signal level for switching the resolution of the image sent to the communication partner. to set the hysteresis each independently, instead of the high threshold _{E TH} of Fig. 4, a first high threshold _{E TH1} and a second high threshold _{E TH2} provided, instead of the low threshold _{E TL,} the It shows that a low threshold E _{TL1 of} 1 and a second low threshold E _TL2 are provided. In the embodiment of FIG. 5, the display device 3 and the camera 4 have different timings for switching to high resolution or low resolution.

In the videophone device according to the embodiment of the present invention described with reference to the time charts of FIGS. 3 and 4, the resolution of the image displayed on the mobile phone device and the resolution of the image coming to the other party are controlled simultaneously. On the other hand, in the videophone apparatus according to the embodiment of the present invention shown in the time chart of FIG. 5, the threshold value (low threshold value E _TL ) when changing from high resolution to low resolution and low resolution to high resolution are shown. Each of the threshold _values (high threshold value E _TH ) at the time of change has two stages. That is, the first low threshold E _TL1 and the second low threshold E _TL2 are provided as the low threshold E _TL , and the first high threshold E _TH1 and the second high threshold E _TH2 are provided as the high threshold E _TH. Provided.

At time t1 when the received signal level becomes equal to or lower than the first low threshold E _TL1 , first, the image to be displayed on the display device 3 of the own mobile phone is set to a low resolution, and noise generated from the display device 3 is reduced. Furthermore, at time t2 when the received signal level becomes equal to or lower than the second low threshold E _TL2 , the resolution of the image generated by the camera 4 is set to low resolution, the image coming to the other party is set to low resolution, and noise generated from the camera 4 is reduced. To reduce. Then, at time t4 the reception signal levels is made the second time t3 and first becomes more high threshold E _TH2 or more high threshold E _TH1, is displayed on the display device 3 of the image and their phone sends it to the other party The resolution of the image is switched to high resolution in order.

  FIG. 6 is a schematic diagram schematically showing an image displayed on the display device 3 in the embodiment of the present invention described with reference to FIGS. 1 to 5, and (A) is displayed at a high resolution. An image of a certain person is shown, and (B) is an image of the same person when displayed at a low resolution. Reference numerals 100 and 200 denote heads, 101a, 101b, 201a and 201b denote eyes, 102 and 202 denote mouths, and 110 and 210 denote body parts. Since FIG. 6A is a high-resolution image, the outline of the human body is expressed with natural roundness. On the other hand, since FIG. 6B is a low-resolution image, the outline of the human body is unnaturally expressed with a square shape. However, even in the low-resolution image of FIG. 6B, the main elements of the person are expressed, so that it can generally withstand the use as an image in a videophone. When the reception signal level is the same, the low-resolution image in FIG. 6B has less noise and image disturbance in the low-resolution image in FIG. 6A than in the high-resolution image.

According to the embodiment of the present invention described above, the following remarkable effects can be obtained.
1. 1. In an environment where the reception level of radio waves is low, the communication quality can be improved and the communication sustainability can be improved by reducing the image resolution of the videophone device. 2. In an environment where the reception level of radio waves is low, the current consumption can be reduced by reducing the resolution of the videophone device. In the embodiment shown in FIG. 5 in which the resolution switching threshold is divided into two stages, the time during which the resolution at the communication partner is degraded can be shortened.

  In the embodiment described above, the method for reducing the noise generated by the mobile phone itself by reducing the image resolution for the videophone and improving the communication quality in the environment where the received signal level is low has been described. However, the present invention can also be applied to applications such as mobile navigation and online games. When an application such as mobile navigation or online game is installed on a mobile terminal and the application is activated, the camera image of the mobile terminal is not transmitted, only the navigation and game images are received and displayed on the display device. Done. In this way, the present invention is applied to an application that does not transmit an image but only receives an image, and lowers the resolution of the image displayed on the screen of the display device of the portable terminal in an environment where the reception signal level is low. Thus, the noise generated by the display device and the CPU can be reduced, and the communication quality can be improved in the same manner as in the case of performing bidirectional communication of image transmission and reception.

  In the embodiment described above, the CPU 2 stores a threshold value in advance, compares the received signal level with the threshold value, and determines whether the quality of the received signal has changed to such an extent that the resolution of the image needs to be changed. Deciding. In the present invention, the quality of the received signal may be determined not only by the received signal level but also by the signal-to-noise ratio of the received signal, or by weighting the received signal level and the signal-to-noise ratio. The quality can be evaluated. For example, the received signal level S and the signal-to-noise ratio R are weighted 6 and 3, respectively, 6S + 3R is the received signal quality Q (= 6S + 3R), and the received signal quality Q is compared with a threshold value, The resolution switching timing may be determined.

  The present invention has been specifically described with reference to the embodiment. However, the present invention is not limited to these embodiments, and of course extends to various forms within the scope described in the claims.

1 transceiver 2 CPU
3 Display device 4 Camera 10 Mobile videophone 11 Antenna 100, 200 Head 101a, 101b, 201a, 201b Eye 102, 202 Mouth 110, 210 Body

Claims (10)

  A videophone device, wherein the resolution of at least one of an image displayed on a display device or an image output from a camera is controlled based on a quality of a received signal. A control unit for controlling the display device and the camera and evaluating the quality of the received signal;
The control unit evaluates the quality of the received signal based on at least one of a signal level or a signal-to-noise ratio of the received signal, and controls the resolution based on the evaluation. The videophone device according to 1. In the display device and the camera, two types of resolution, high resolution and low resolution, are set in advance,
The videophone apparatus according to claim 2, wherein the control unit performs the evaluation based on a comparison between a quality of the received signal and a predetermined threshold value. The controller is
When the display device or the camera is set to the high resolution, in the first case where the quality of the received signal changes from a state higher than the threshold to a state lower than the threshold, the display device or Control to change the resolution of the camera from the high resolution to the low resolution, respectively;
When the display device or the camera is set to the low resolution, in the second case where the quality of the received signal varies from a state lower than the threshold to a state higher than the threshold, the display device or The videophone apparatus according to claim 3, wherein control is performed to change the resolution of the camera from the low resolution to the high resolution. The controller is
High threshold and low threshold are stored as the threshold,
In the first case, the low threshold is used as the threshold,
5. The videophone device according to claim 4, wherein, in the second case, the high threshold is used as the threshold. The controller is
Storing a first high threshold and a second high threshold lower than the first high threshold as the high threshold;
Storing a first low threshold and a second low threshold lower than the first low threshold as the low threshold;
In the first case relating to the display device, the first low threshold is used as the low threshold,
In the first case relating to the camera, the second low threshold is used as the low threshold,
In the second case relating to the display device, the first high threshold is used as the high threshold,
The videophone apparatus according to claim 5, wherein, in the second case relating to the camera, the second high threshold is used as the high threshold.     7. The television according to claim 2, wherein the control unit evaluates the quality of the received signal by weighting each of a signal level of the received signal and a signal-to-noise ratio. Telephone device.   A videophone system that performs videophone communication with each other, wherein the terminal includes a display device that displays an image transmitted from a communication partner terminal, a camera that outputs an image transmitted to the communication partner terminal, A videophone system comprising: a control unit that controls the resolution of at least one of the display device and the camera based on the quality of a received signal.   A videophone method in which a plurality of terminals perform videophone communication with each other, wherein the terminal displays an image transmitted from a communication partner terminal, transmits an image to the communication partner terminal, and transmits the image to the communication partner terminal. A videophone method, comprising: controlling a resolution of at least one of the image displayed on a display device or the image transmitted to the counterpart terminal based on a quality of a received signal.   10. A videophone control program that implements the videophone method according to claim 9 as a program executable by a computer.

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