Video output apparatus and output video changeover control method

When a changeover instruction is input to video output changeover control section 108, power control section 112 turns on the power to changeover target video output section 102. Timing change section 111 synchronizes sync signal Y output by changeover target video output section 102 with sync signal X output by changeover source video output section 101. Power control section 112 turns off the power to changeover source video output section 101.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a video output apparatus and output video changeover control method used for a moving image digital transmission apparatus and storage apparatus.

2. Description of the Related Art

With the increasing level of integration of communication terminal apparatuses, etc. in recent years, a plurality of video output means (signal sources) such as a camera and circuit for processing stored video data are mounted on a single apparatus. Since such an apparatus having a plurality of signal sources is normally provided with only one display apparatus such as an LCD (liquid crystal display) panel, signals from a plurality of signal sources are switched and displayed as appropriate. That is, in the above apparatus, a plurality of signal sources is configured to share one display means. A signal source normally outputs a set of a video signal and sync signal.

When an apparatus having such a plurality of signal sources switches between those signal sources, sync signals are sometimes not output to a display apparatus at fixed intervals, which results in a problem of causing disturbance on images displayed until sync signals and video signals become stable, giving the user unpleasant impression.

A technology to reduce this disturbance of images displayed is disclosed in the Unexamined Japanese Patent Publication No.HEI 7-134577 (hereinafter referred to as “conventional example 1”) as a “Display apparatus”. When images displayed are switched by a changeover between signal sources, etc., the display apparatus described in this conventional example 1 displays fixed colors such as black on a display screen only for a predetermined period and displays images free of disturbance when the video signals and sync signals of the target signal source become stable.

Then, conventional example 2, which is a technology to reduce disturbance of images displayed and is different from conventional example 1 will be explained. This conventional example 2 uses a sync signal common to all signal sources by supplying a sync signal output from one signal source to other signal sources. Thus, conventional example 2 can eliminate discrepancies between sync signals during a changeover and thereby reduce disturbance of images displayed.

However, conventional examples 1 and 2 have the following problems. That is, conventional example 1 displays images in a single color during a changeover, giving the user an unpleasant impression. Conventional example 2 always needs to operate the signal source to supply sync signals even when a video signal output from another signal source is displayed, having a problem of increasing power consumption.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a video output apparatus and output video changeover control method capable of changing video signals by hiding the changeover of images displayed from the user and suppressing power consumption to a low level.

This object can be attained by changing the output timing of a sync signal of the target signal source to the output timing of a sync signal of the signal source to be changed when signal sources to supply video signals to the display apparatus are changed. More specifically, the object of the present invention is attained by generating a reset signal synchronized with the sync signal to be changed and synchronizing the target sync signal with this reset signal and thereby synchronizing the target sync signal with the sync signal to be changed

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one example is illustrated by way of example, in which;

With reference now to the attached drawings, embodiments of the present invention will be explained in detail below.

FIG. 1is a block diagram showing a configuration of a video output apparatus according to Embodiment 1 of the present invention. Video output section101creates predetermined sync signal X and video signal X corresponding to this sync signal X, outputs video signal X to video signal selection section103and outputs sync signal X to first sync signal selection section104and second sync signal selection section109. On the other hand, video output section102creates predetermined sync signal Y and video signal Y corresponding to this sync signal Y, outputs video signal Y to video signal selection section103and outputs sync signal Y to first sync signal selection section104and second sync signal selection section109. These video output section101and video output section102output, for example, a video signal stored in memory and a video signal captured from an image pickup apparatus such as a camera. That is, video output section101and video output section102are the signal sources that supply a video signal and sync signal to a display apparatus such as an LCD (liquid crystal display) panel, which is not shown. The internal configurations of these video output section101and video output section102will be described later.

As a video sync signal, two kinds of sync signals are used, a vertical sync signal for synchronization in the vertical direction and a horizontal sync signal for synchronization in the horizontal direction. These sync signals have same control such as a changeover, and therefore the vertical sync signal and horizontal sync signal are collectively called a “sync signal” and the path through which this sync signal passes is expressed with one transmission path line.

Upon acquiring a changeover instruction instructing that an image displayed be changed and indicating the target video output section (that is, signal source) from input terminal107, video output changeover control section108controls video signal selection section103and first sync signal selection section104so that video signal selection section103and first sync signal selection section104select the video signal and sync signal output from the target video output section indicated by the changeover signal above. According to the control of video output changeover control section108, video signal selection section103selects either video signal X or video signal Y as the target video signal and outputs the selected video signal from output terminal105to a display apparatus, which is not shown. In this way, either video signal X or video signal Y output from video output section101or video output section102is selected by video signal selection section103and output as the output video signal.

According to the control of video output changeover control section108, first sync signal selection section104selects either video signal X or video signal Y as the target sync signal and outputs the selected sync signal from output terminal106to a display apparatus, which is not shown.

In this way, video output section101and video output section102serve as the signal sources that supply a video signal and sync signal to a display apparatus (not shown) provided in the posterior stage of the video output apparatus according to this embodiment.

Upon acquiring a changeover instruction from input terminal107, video output changeover control section108controls second sync signal selection section109so that second sync signal selection section109selects the source sync signal to be changed. According to the control of video output changeover control section108, second sync signal selection section109selects either sync signal X or sync signal Y as the source sync signal to be changed and outputs the selected sync signal to reset signal generation section110.

Furthermore, upon acquiring a changeover instruction, video output changeover control section108controls reset signal generation section110to generate a reset signal. According to the control of video output changeover control section108, reset signal generation section110generates a reset signal synchronized with a sync signal output from the source video output to be changed and outputs the generated reset signal to timing change section111. Timing change section111outputs the reset signal to the target video output section, that is, video output section101or video output section102at an appropriate timing and thereby synchronizes the sync signal (here, sync signal X or sync signal Y) output from this target video output section with the reset signal.

On the other hand, video output changeover control section108is configured to include power control section112, and when a changeover instruction is input to video output changeover control section108, power control section112outputs a power control signal that instructs whether the power to the target video output section should be turned on or off.

As described above, a power control signal or reset signal is input to the target video output section, that is, video output section101or video output section102. Upon acquiring a power control signal instructing the power to be turned on, target video output section101or video output section102turns on the power, drives the sync signal generation circuit included in the video output section and turns on power to a video signal supply circuit equipped with a circuit that reconstructs a video signal from the signal stored in video signal memory and an output circuit that outputs a video signal, etc. so as to enable a video signal to be output.

Then, a configuration of the video output apparatus according to this embodiment will be explained in detail with reference toFIG. 2.FIG. 2is a block diagram showing part of a configuration of the video output apparatus of this embodiment. InFIG. 2, the same components as those inFIG. 1are assigned the same reference numerals and detailed explanations thereof will be omitted. InFIG. 2, of the components shown inFIG. 1, the descriptions of video signal selection section103, first sync signal selection section104, output terminal105, output terminal106, input terminal107, video output changeover control section108, second sync signal selection section109, reset signal generation section110and power control section112will be omitted.

As shown in thisFIG. 2, video output section101is configured to include sync signal generation circuit201and video signal supply circuit202, and video output section102is configured to include sync signal generation circuit203and video signal supply circuit204.

When the count of reference clocks reaches a predetermined number, sync signal generation circuit201outputs sync signal X to video signal supply circuit202as well as first sync signal selection section104and second sync signal selection section109shown inFIG. 1. Upon reception of sync signal X from sync signal generation circuit201, video signal supply circuit202outputs a video signal captured by a picture pickup apparatus (not shown) such as a camera, a video signal stored in memory (not shown) beforehand and a video signal, etc. transmitted from an external apparatus to video signal selection section103as video signal X. Furthermore, when the count of reference clocks reaches a predetermined number, sync signal generation circuit203outputs sync signal Y to video signal supply circuit204as well as first sync signal selection section104and second sync signal selection section109shown inFIG. 1. Upon reception of sync signal Y from sync signal generation circuit203, video signal supply circuit204outputs a video signal captured by a picture pickup apparatus (not shown) such as a camera, a video signal stored in memory (not shown) beforehand and a video signal, etc. transmitted from an external apparatus to video signal selection section103as video signal Y. A video signal with a large amount of data is normally compressed using a coding system such as JPEG and MPEG and stored in memory.

Immediately after receiving a reset signal from timing change section111, sync signal generation circuit201and sync signal generation circuit203output sync signal X or sync signal Y. That is, inputting of a reset signal from timing change section111changes the output timing of a sync signal output from the sync signal generation circuit (that is, sync signal generation circuit201or sync signal generation circuit203) equipped with the target video output section.

Then, with reference toFIG. 3, the internal configurations of sync signal generation circuit201and sync signal generation circuit203will be explained.FIG. 3is a block diagram showing the internal configuration of sync signal generation circuit201. Sync signal generation circuit203has almost the same configuration as that of sync signal generation circuit201, and therefore only a detailed explanation of sync signal generation circuit201will be given, whereas a detailed explanation of sync signal generation circuit203will be omitted. Sync signal generation circuit201is provided with counter303that outputs a horizontal sync signal and counter304that outputs a vertical sync signal.

In sync signal generation circuit201above, a reference clock is input from input terminal301to counter303and counter304. Counter303counts reference clocks and when the count of reference clocks reaches a predetermined number, counter303outputs a horizontal sync signal. The horizontal sync signal is output to counter304and at the same time output from output terminal305to outside the circuit. Counter304counts reference clocks and when the count of reference clocks reaches a predetermined number, counter304outputs a vertical sync signal in synchronization with the horizontal sync signal. The vertical sync signal is output from output terminal306to outside the circuit.

On the other hand, through input terminal302, the reset signal output from timing change section111is input to counter303and counter304. When the reset signal is input to counter303and counter304, the count of reference clocks counted so far is reset to “0” and counting of reference clocks is restarted at the time of reset. Moreover, counter303outputs a horizontal sync signal triggered by the reset signal from timing change section111and counter304outputs a vertical sync signal triggered by the reset signal from timing change section111. That is, counter303and counter304output a horizontal sync signal and vertical sync signal, respectively for every predetermined number of clocks in horizontal and vertical directions from the time at which the reset signal is input. This predetermined number of clocks is changed as appropriate according to the configuration of the apparatus, etc. In this embodiment, suppose this predetermined number of clocks is M clocks in the horizontal direction and N clocks in the vertical direction. Then, counter303outputs a horizontal sync signal every time the number of reference clocks countered reaches M clocks and counter304outputs a vertical sync signal every time the number of reference clocks countered reaches N clocks.

Next, the changeover operation of the video output section (that is, signal source of the output video signal) in the video output apparatus in the above configuration will be explained with reference toFIG. 4.FIG. 4is a flow chart to explain the operation of changing the supply source of a video signal. In this embodiment, the case where the signal source of an output video signal is changed from video output section101to video output section102will be explained as an example.

First, in step (hereinafter referred to as “ST”)401, a changeover instruction instructing that the signal source of an image to be displayed on the display apparatus be changed from video output section101to video output section102is input from input terminal107to video output changeover control section108. Then, in ST402, a power control signal is input from power control section112to video output section102, which is the target video output section (signal source) and the power to video output section102is turned on.

Then, in ST403, video output changeover control section108instructs second sync signal selection section109to select sync signal X from video output section101to be changed. Second sync signal selection section109selects sync signal X and outputs to reset signal generation section110.

Then, in ST404, video output changeover control section108instructs reset signal generation section110to output a reset signal to timing change section111. Reset signal generation section110generates a reset signal synchronized with sync signal X generated by source video output section101to be changed output from second sync signal selection section109and outputs the reset signal to timing change section111. The operation of generating this reset signal will be described later.

In ST405, the reset signal is output from timing change section111that has acquired the reset signal to target video output section102at an appropriate timing, that is, the timing at which reset signal generation section110generates a reset signal (hereinafter referred to as “reset signal generation timing”) or the timing that arrives every N clocks from the reset signal generation timing (hereinafter referred to as “change timing”). Thus, a reset signal is output from timing change section111at the “reset signal generation timing” that matches the output timing of sync signal X at source video output section101to be changed or the “change timing” that matches the output timing of sync signal X at same source video output section101to be changed. That is, the reset signal output from timing change section111is synchronized with sync signal X output by source video output section101.

Then, in ST406, counter303and counter304equipped with video output section102are reset based on a reset signal output from timing change section111. That is, when a reset signal is input, the counts of counter303and counter304provided for sync signal generation circuit203are reset to “0”. This makes counter303and counter304restart counting of reference clocks at the time at which the reset signal is input, and therefore a horizontal sync signal or vertical sync signal is output for every N clocks from the time at which the reset signal is input from timing change section111. That is, sync signal Y output from target video output section102is synchronized with the reset signal and at the same time synchronized with sync signal X at source video output section101to be changed.

Then, in ST407, after waiting for a predetermined time until video signal Y output from video output section102becomes stable, the process moves on to ST408. In ST408, video output changeover control section108instructs video signal selection section103and first sync signal selection section104to select an output signal from image output section102. In this way, video signal selection section103outputs video signal Y whose signal source is video output section102as an output video signal. On the other hand, first sync signal selection section104outputs sync signal Y whose signal source is video output section102as an output sync signal.

Then, in ST409, a power control signal is input from video output changeover control circuit108to video output section101and the power to video output section101is turned off.

Then, the operation of changing the video output sections (that is, signal sources) will be explained with reference toFIG. 5AtoFIG. 5G.

The signal shown inFIG. 5Ais a reference clock input to counter303and counter304. The reference clock is a cyclic signal that has a certain accurate time interval and is used as a reference to establish synchronization.

The signal shown inFIG. 5Bis a pulse signal including a vertical sync signal (hereinafter referred to as “VSYNC”) generated by sync signal generation circuit201provided for video output section101. In sync signal generation circuit201provided for video output section101, clock303and clock304count reference clocks and the pulse signal turns ON when this count reaches N clocks and rectangular vertical sync signals501to505made up of a rising section and falling section are output. That is, clock303and clock304output VSYNC for every N reference clocks. Here, sync signal generation circuit201outputs both a vertical sync signal and horizontal sync signal, but since the operation of generating a vertical sync signal is almost the same as the operation of generating a horizontal sync signal, for simplicity of explanations, only a vertical sync signal (VSYNC) will be shown inFIG. 5AtoFIG. 5G, whereas detailed explanations of the horizontal sync signal will be omitted.

The signal shown inFIG. 5Cis a signal instructing the generation of a reset signal (hereinafter referred to as “reset generation instruction signal”) output by video output changeover control section108. This reset generation instruction signal506is output to reset signal generation section110by video output changeover control section108that has acquired a changeover instruction from input terminal107.

The signal shown inFIG. 5Eis reset signal507output from reset signal generation section110to timing change section111. Reset signal generation section110extracts one of VSYNC's generated after receiving a reset generation instruction signal output from video output changeover control section108as a reset signal and outputs to timing change section111.FIG. 5DandFIG. 5Edescribe the case where the VSYNC′ generated at the earliest timing after the reset generation instruction signal is received is extracted as a reset signal and output to timing change section111as an example. After receiving the reset signal, timing change section111outputs this reset signal to target video output section102at an appropriate timing, that is, the reset signal generation timing or a change timing that arrives every N clocks from the reset signal generation timing.FIG. 5Eshows change timing513that arrives N clocks after the reset signal generation timing and change timing514that arrives 2N clocks (that is, N clocks after change timing513) after the reset signal generation timing as an example of the “change timing” above.

InFIG. 5DandFIG. 5E, a reset signal is extracted from VSYNC′, which is inverted VSYNC, but in the case where VSYNC is not a pulse signal as shown in the figure but a level signal made up of a low signal that lasts for a certain period of time or high signal that lasts for a certain period of time, it is also possible to generate a reset signal at a timing that matches the level rising section or falling section.

The signal shown inFIG. 5Fis a pulse signal including a vertical sync signal output from target video output section102.FIG. 5Fshows the case where a reset signal is input from timing change section111to target video output section102at change timing513and immediately after the reset signal is input, video output section102outputs a sync signal.

Before inputting a reset signal, counter304of target video output section102counts reference clocks. When this count reaches N clocks, the pulse signal turns ON, rectangular vertical sync signals508to510made up of a rising section and falling section as shown inFIG. 5Fare output. When reset signal507is output from timing change section111at change timing513, counter304outputs vertical sync signal511and resets the number of reference clocks counted until reset signal507is input and restarts counting of reference clocks. In this way, counter304outputs a vertical sync signal every N clocks from change timing513.

Thus, until reset signal507is received at change timing513, video output section102outputs vertical sync signals508to510generated at the own timing, receives reset signal507and then outputs vertical sync signal511and vertical sync signal512at a timing synchronized with reset signal507, that is, a timing synchronized with a sync signal output from video output section101to be changed.

Therefore, as shown inFIG. 5G, from output terminal106, a vertical sync signal from source video output section101to be changed is output before change timing513and a vertical sync signal from source video output section102from change timing513on (that is, simultaneously with change timing513or after change timing513). The vertical sync signal output from this output terminal106is output always at constant intervals irrespective of before or after change timing513as is apparent fromFIG. 5G.

As shown above, according to this embodiment, when target video output section102is selected from among a plurality of video signal output sections (that is, video output section101and video output section102) to change an image to be supplied to the display apparatus according to a changeover instruction input from input terminal107, the output timing of sync signal Y output from target video output section is changed by timing change section111. Since timing change section111changes the timing in such a way that sync signal Y output by target video output section102is synchronized with sync signal X output by source video output section101to be changed, the sync signal output to the display apparatus has a constant interval before and after the changeover takes place. Thus, the display apparatus always receives a sync signal with a constant interval, producing an effect that images displayed are not disturbed. Thus, the user of the video output apparatus according to this embodiment can comfortably change images without being annoyed by disturbance of images displayed.

Furthermore, in this embodiment, reset signal generation section110generates a reset signal synchronized with source video output section101to be changed and timing change section111changes the output timing of a sync signal in target video output section102based on this reset signal, and therefore it is not necessary to continue operation of source video output section101even after display apparatus are changed.

That is, since the generation timing (that is, reset signal generation timing) of the reset signal generated by reset signal generation section110matches the output timing of the sync signal output from source video output section101to be changed, timing change section111can acquire the output timing of sync signal X output from source video output section101by acquiring a reset signal without the need to acquire sync signal X output from source video output section101. Timing change section111synchronizes the output timing of a sync signal at target video output section102with the output timing of a sync signal at source video output section101acquired based on a reset signal. In this way, the output timing of a sync signal at source video output section102to be changed is synchronized not “directly” with the output timing of a sync signal at source video output section101but “via a reset signal”.

Changing the output timing of a sync signal at source video output section102to be changed according to the control of reset signal generation section110and timing change section111in this way determines the output timing of a sync signal at target video output section102independently of source video output section101, that is, without direct connection with source video output section101.

As described above, after a reset signal is generated, it is not necessary to continue to operate source video output section101. Therefore, in this embodiment, after video signal selection section103and first sync signal selection section104change the video signal and sync signal to be selected, power control section112performs control turning off the power to source video output section101. Thus, the video output apparatus according to this embodiment can reduce power consumption more than the conventional video output apparatus.

In contrast to the changeover operation explained in this embodiment, in the case where a changeover is made from video output section102to video output section101, video output section101, which becomes the changeover target in this case, outputs a sync signal synchronized with the output timing of a sync signal at video output section102, which becomes the changeover source in this case based on the reset signal output from timing change section111. From this point too, it is apparent that video output section102is independent of video output section101with respect to the output timing of a sync signal.

This embodiment has described the case where a sync signal and a video signal corresponding to this sync signal are output from the two video output sections (that is, signal sources) of video output section101and video output section102, but the present invention is not limited to this and all that is required is that a plurality of video output sections (that is, signal sources) that output to a display apparatus a sync signal and a video signal corresponding to this sync signal be provided according to the type of the video signal displayed on the display apparatus.

Furthermore, in this embodiment, the sync signal generation circuit (that is, sync signal generation circuit201or sync signal generation circuit203) provided for the target video output section outputs a sync signal immediately after receiving a reset signal from timing change section111. However, the sync signal generation circuit provided for the target video output section can also be configured to generate a sync signal N clocks after receiving a reset signal instead of outputting a sync signal immediately after receiving the reset signal.

The video output apparatus according to the present invention demonstrates outstanding effects especially when mounted on a communication terminal apparatus. This is because a communication terminal apparatus is often carried with the user and used connected to a power supply with a limited capacity such as batteries, and thus a reduction of power consumption is essential.

Hereinafter, a case where the video output apparatus according to Embodiment 1 of the present invention is mounted on a communication terminal apparatus will be explained with reference toFIG. 6.FIG. 6is a block diagram showing a configuration of the communication terminal apparatus according to Embodiment 2 of the present invention. InFIG. 6, the same components as those inFIG. 1according to Embodiment 1 are assigned the same reference numerals as those inFIG. 1and detailed explanations thereof will be omitted.

Reception apparatus602applies predetermined radio reception processing such as frequency conversion to a signal received from antenna601and generates a baseband signal. Demodulation apparatus603applies predetermined demodulation processing such as QPSK or 16QAM to the baseband signal generated by reception apparatus602. Decoding apparatus604applies predetermined decoding processing to the demodulated signal and obtains a reception video signal. The reception video signal obtained by decoding apparatus604is output to video output section609.

Video output apparatus607has the same configuration as that of the video output apparatus shown inFIG. 1in Embodiment 1. For simplicity of explanations, descriptions of output terminal105, output terminal106, input terminal107, video output changeover control section108, second sync signal selection section109and reset signal generation section110are omitted.

Timing change section111in this video output apparatus607outputs a rest signal to video output section101, video output section102and video output section610to synchronize the sync signal after the changeover with the sync signal before the changeover. Image output section101outputs the reception video signal received from decoding apparatus604to video signal selection section103and outputs sync signal X to first sync signal selection section104. That is, in this embodiment, video output section101serves as a signal source of reception video signals.

Video output section102stores predetermined video signals in the manufacturing stage of the communication terminal apparatus according to this embodiment. In this Specification, a video signal stored in this video output section102is called “stored video signal”. Video output section102outputs this stored video signal to video signal selection section103and outputs sync signal Y to first sync signal selection section104.

Image pickup apparatus605is configured to include image pickup section609such as a camera and video output section610. Image pickup section609takes pictures of targets such as persons and landscape, etc. and captures these pictures as video signals. In this Specification, a video signal captured from image pickup section609is called “image pickup signal”. This image pickup signal is output from image pickup section609to video output section610. Video output section610has a configuration similar to that of video output section101and video output section102and outputs image pickup signals captured by image pickup section609to video signal selection section103. Furthermore, video output section610generates sync signal Z through a sync signal generation circuit (not shown) equipped inside and outputs sync signal Z generated to first sync signal selection section104.

Video signal selection section103selects one of a reception video signal, stored video signal or image pickup signal as the target video signal and outputs the selected signal to display apparatus608. On the other hand, first sync signal selection section104selects one of sync signal X, sync signal Y or sync signal Z as the sync signal, the changeover target, and outputs the selected sync signal to display apparatus608.

Display apparatus608synchronizes the video signal output from video signal selection section103with the sync signal output from first sync signal selection section104and displays the video (image) on the LCD panel.

Then, the operation of changing a video signal supplied to display apparatus608in the communication terminal apparatus in the above configuration will be explained. Here, a case where a video signal supplied to display apparatus608is changed from a reception video signal to an image pickup signal, that is, a case where the signal source of the video signal supplied to display apparatus608is changed from video output section101to video output section610will be explained as an example.

Before starting the changeover operation, an image formed based on the reception video signal is displayed on display apparatus608. This reception video signal is the reception signal received from antenna601, which has been converted to a baseband signal by reception apparatus602, demodulated by demodulation apparatus603, decoded by decoding apparatus604and input to video output section101.

First, when a changeover instruction instructing that the signal source of an image to be displayed on display apparatus608be changed from video output section101to video output section102is input, the power to video output section610, which is the target video output section (signal source) is turned on. More specifically, a sync signal generation circuit (not shown) included in video output section610is driven and at the same time the power to a video signal supply circuit (not shown) equipped with a coding circuit (not shown) that encodes an image pickup signal captured by image pickup section609, a decoding circuit that decodes coded data and an output circuit that outputs the decoded image pickup signal to the outside of image pickup apparatus605, etc. so as to enable the image pickup signal to be output.

Then, timing change section111that has acquired a reset signal generated based on a changeover instruction outputs a reset signal to target video output section610at an appropriate timing. This allows the output timing of sync signal Z output from target video output section610to be changed and synchronization between sync signal Z and sync signal X output from source video output section101to be changed to be established.

In image pickup apparatus605, an image pickup signal captured from image pickup section609is output to video signal selection section103and sync signal Z generated by video output section610is output to first sync signal selection section104. Then, after waiting for a predetermined time until the image pickup signal and sync signal Z become stable, video signal selection section103supplies the image pickup signal to display apparatus608and first sync signal selection section104supplies sync signal Z to display section608. Display section608synchronizes the supplied image pickup signal with sync signal Z and displays the image corresponding to the supplied image pickup signal on the LCD panel.

Finally, a power supply control signal is input to video output section101and the power to video output section101is turned off.

As shown above, this embodiment mounts video output apparatus607according to Embodiment 1 on a communication terminal apparatus, and therefore it is possible to reduce power consumption of the communication terminal apparatus without causing disturbance in an image displayed on display apparatus608. This embodiment prevents a display image from being disturbed especially when the image taken by image pickup section609such as a camera is displayed while a video signal is being downloaded through antenna601.

In this embodiment, display apparatus608forms a display image on an LCD panel, but the present invention is not limited to this and it is also possible to form the display image on a CRT, EL (electro-luminescence) panel, LED matrix display apparatus, etc. Furthermore, this embodiment describes the case where the signal source that supplies a video signal to display apparatus608is changed from video output section101to video output section610, but the present invention is not limited to this and it is possible to change the signal source from an arbitrary video output section to another video output section.

As described above, when the signal source that supplies a video signal to a display apparatus is changed, the present invention can reduce power consumption of a communication terminal apparatus without disturbing display images on the display apparatus by changing the output timing of a sync signal of the target signal source to the output timing of a sync signal of the signal source to be changed.

This application is based on the Japanese Patent Application No.2000-45503 filed on Feb. 23, 2000, entire content of which is expressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is ideally suited to the field of a video output apparatus and output video changeover control method used for a motion picture digital transmission apparatus and storage apparatus.