JP2001008203A - Dynamic image transmission method and dynamic image transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely reproduce dynamic image data in real time without causing deficiency in dynamic image data or data overflow at a receiver side device even in the case that the dynamic image data are transmitted via a communication channel at a transmission rate different from a coding rate in a dynamic image transmission system where compressed dynamic image data are transmitted via a communication channel. SOLUTION: A system adopting this dynamic image transmission method is provided with a receiver side device B1, that receives dynamic image data, and the receiver side device B1 is provided with a timing conversion section 10 that converts contents of a synchronizing field instructing timing for expansion processing of the dynamic image data received when a transmission rate of a communication channel 5 differs from a coding rate and with a dynamic image expansion section 12 that applies expansion processing to the dynamic image data after being converted by this timing conversion section 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving image transmission system for transmitting a moving image through a wired or wireless communication line, such as a video conference system or a video telephone.

[0002]

2. Description of the Related Art A conventional moving picture transmission system of this type will be described with reference to FIGS. Note that, in order to facilitate understanding, it is assumed that one-way video transmission is performed. Therefore, the description will be made separately for a transmission-only device and a reception-only device. If so, each device has both a transmission function and a reception function.

[0003] Figure 6 is a block diagram showing a configuration of a transmission side apparatus A ₀ of the moving image data constituting the moving image transmission system, FIG. 7 is a block diagram showing a configuration of a receiving side apparatus B ₀ of the moving image data.

In FIG. 6, reference numeral 1 denotes a moving image generating unit for generating moving image data of a camera or a video recorder, etc., 2 a moving image compressing unit for compressing moving image data, and 3 a semiconductor memory for storing the compressed moving image data. Department. The storage unit 3 is provided because the moving image data generated by the moving image generating unit 1 may not always be transmitted in real time depending on the degree of congestion of the communication line 5 or the like, and the moving image data can be temporarily stored. That's why.

[0005] 4 the communication unit to transmit the moving picture data, 5 wired or wireless communication line connecting the transmitting side apparatus A ₀ with the receiving-side apparatus B _0, the first switch 6, 7 second Switch. Both switches 6 and 7 output the compressed video data to the communication line 5 in real time,
It can be switched manually depending on whether the data is once stored in the storage unit 3 and then output to the communication line 5.

On the other hand, in FIG. 7, reference numeral 5 denotes the communication line, 14 denotes a communication unit for receiving moving image data from the communication line 5, and 13 denotes a storage unit such as a semiconductor memory for storing moving image data. What provided the storage unit 13 can watch videos as needed video data sent from the sending device A ₀ instead of displaying in real time, and had been temporarily stored That's why.

Reference numeral 12 denotes a moving image decompressing unit for expanding received moving image data, 11 denotes a moving image display unit such as a liquid crystal display or a CRT for displaying moving image data, 16 denotes a third switch, and 17 denotes a third switch.
Is a fourth switch. The switches 16 and 17 are manually switched depending on whether the received compressed video data is output to the video decompression unit 12 in real time or temporarily stored in the storage unit 13 and then output to the video decompression unit 12. It has become.

Next, the operation of the conventional moving picture transmission system having the above configuration will be described below.

[0009] First, the operation of the transmitting-side apparatus A _0.

The moving image data obtained by the moving image generator 1 is input to the moving image compressor 2. The moving image compression unit 2 performs compression for reducing the moving image data from the moving image generation unit 1 to a data amount that can be transmitted through the communication line 5. In this case, conventionally, processing is performed so that the encoding rate when compressing and encoding moving image data always coincides with the transmission rate of the communication line 5.

Here, as a processing method for the moving image compression unit 2 to compress and encode moving image data, a frame compression method that compresses only within a frame and a frame that further reduces the data amount by utilizing the correlation between the preceding and succeeding frames. There is between compression. Usually, the transmission form of the moving image via the communication line 5 is IT
H. UT, which is recommended as a video coding method for videophones of the UT standard. 261, H .; 263,
Intra-frame compression and inter-frame compression are used together.

For example, as shown in FIG. 8, with respect to moving image data transmitted in frame units, the first frame,
The eighth and fifteenth frames are frames compressed using only intra-frame compression (hereinafter, referred to as I-frames), and the other frames require difference information between preceding and following frames. Is a frame compressed by using inter-frame compression (hereinafter, referred to as a P frame).

The compression mode in which the I frame and the P frame are mixed at a predetermined ratio in this manner is as follows.

Since the compression rate of the P frame is higher than that of the I frame, transmitting only the P frame can reduce the transmission rate per unit time, which is convenient.
If only the frames are transmitted continuously, errors accumulate on the receiving side and distortion of the reproduced image increases, and if the screen is switched and the correlation between the previous and next frames is lost, the P frame is used instead. This is to avoid inconveniences such as an increase in the amount of data.

[0015] Here, now, when transmitting to the receiving side apparatus B ₀ side in real time while compressing the video data from the video generating unit 1 video compression unit 2 includes a first switch 6 second Are switched so as to be connected to each other. As a result, the output of the moving image compression unit 2 is input to the communication unit 4 via the switches 6 and 7.

When the moving image data compressed by the moving image compression unit 2 is temporarily stored in the storage unit 3, the first switch 6
Is connected to the storage unit 3. Thereby, the moving image data obtained by the compression by the moving image compression unit 2 is stored in the storage unit 3 via the first switch 6. Then, when transmitting the moving image data stored in the storage unit 3, the second switch 7 is connected to the storage unit 3 side. Then, the moving image data stored in the storage unit 3 is read and input to the communication unit 4 via the second switch 7.

The communication unit 4 performs predetermined encoding and modulation of the moving image data according to the type of the communication line 5 (wired, wireless, etc.) and outputs it.

In this manner, the moving image data from the transmitting device A ₀ can be transmitted to the receiving device B ₀ in real time via the communication line 5, and can be transmitted after being temporarily stored in the storage unit 3. it can.

[0019] Next, the operation of the receiving-side apparatus B _0.

The communication unit 14 receives a signal transmitted via the communication line 5, performs predetermined demodulation and decoding, and outputs compressed moving image data.

When displaying the transmitted moving image data in real time, the third switch 16 is switched so that the output of the communication unit 14 is connected to the moving image decompression unit 12, and the fourth switch 17. Turn off. Therefore, the moving image data from the communication unit 14
The video data is input to the video decompression unit 12 via the, and is decompressed into the original video data, and then output to the video display unit 11.

On the other hand, when moving image data is temporarily stored in the storage unit 13, the fourth switch 17 is turned on. Thereby, the moving image data from the communication unit 14 is
Is stored in the storage unit 13 via the. Next, when reading out the moving image data stored in the storage unit 13, the third switch 16 is connected to the storage unit 13 side. Then, the moving image data read from the storage unit 13 is input to the moving image expanding unit 12 via the third switch 16 and is expanded into the original moving image data, and the expanded moving image data is displayed on the moving image display unit 1.
1 is displayed.

As described above, the receiving side device B ₀ demodulates and decodes the signal received from the communication line 5 in real time.
In addition to expanding and reproducing the moving image data, the storage unit 1 temporarily stores the desired compressed moving image data in response to a storage request.
3, the stored data can be read out and reproduced again.

[0024]

[SUMMARY OF THE INVENTION Incidentally, in the case of using the storage unit 13 provided on the receiving device B ₀ also coding rate is not consistent with the transmission rate, and receives the video data, and, The received moving image data can be appropriately expanded. For example, even when moving image data is transmitted using the communication line 5 having a transmission rate higher than the encoding rate, the received moving image data is temporarily stored in the storage unit 13, and then, from the storage unit 13, If the stored moving image data is read out at a speed suitable for the expansion processing in the moving image expansion unit 12, the moving image data can be reproduced and displayed without any problem.

As described above, when temporarily storing the received moving image data in the storage unit 13, there is a case where it is desired to monitor in advance whether or not the transmitted moving image data is the desired one and confirm it. At that time, it is necessary to display the received moving image data on the moving image display unit 11 in real time without storing it in the storage unit 13.

However, if an attempt is made to display a moving image on the moving image display unit 11 in real time in a state where the encoding rate does not match the transmission rate, the following problem occurs. This will be further described with reference to FIG.

The coding rate in the moving picture compression section 2 is F,
Assuming that the transmission rate of the communication line 5 is R, in the conventional moving image transmission system, processing is performed such that the encoding rate F always matches the transmission rate R (that is, R = F).

[0028] Here, video data output from the transmitting device A _0, as shown in FIG. 8, both the data length of a mix of the I and P frames are roasted, also P frame Although each data length has a length, here, for ease of understanding, it is limited to a P frame as an example,
In addition, it is assumed that all P frames have the same data length. In this case, each P-frame, as shown in FIG. 9 (b), will be transmitted with a period t ₀ adapted to the transmission rate R of the communication line 5.

In the moving picture decompression section 12 of the receiving side apparatus B ₀ , the received moving picture data is reproduced at a predetermined reproduction timing (cycle t).
₀ ), the encoding rate F and the transmission rate R are balanced, so that the entire system can handle moving image data without excess or deficiency.

On the other hand, as shown in FIG. 9A, when the transmission rate R is higher than the encoding rate F of the moving image data transmitted from the transmitting apparatus A ₀ (R> F), Moving image data output from the communication unit 4 (when P frames are used)
Is transmitted on the communication line 5 with a period t ₁ (<t ₀ ).

In this case, when the receiving apparatus B ₀ expands the received moving image data at the same predetermined reproduction timing (period t ₀ ) as in the case of R = F, the moving image expanding section 12 There than the amount capable decompression processing video data, who the amount of moving image data communication unit 14 receives increases, resulting in overflow data at the receiving side apparatus B ₀ is will be disconnected communication line 5 is generated , Video data cannot be reproduced in real time.

On the other hand, as shown in FIG. 9C, when the transmission rate R is smaller than the coding rate F of the moving image data transmitted from the transmitting apparatus A ₀ (R <F), the communication unit 4 Is transmitted on the communication line 5 with a period t ₂ (> t ₀ ).

In this case, when the received moving image data is expanded at the same predetermined expansion timing (period t ₀ ) as in the case of R = F in the receiving side device B ₀ , the moving image expansion unit 12 than the amount capable decompression processing video data, who the amount of moving image data communication unit 14 receives is reduced, insufficient amount of data required to result in video decompression on the receiving side apparatus B ₀ is generated , Video data cannot be reproduced in real time.

Therefore, according to the present invention, even when the encoding rate is different from the transmission rate of the communication line, the moving picture data can be reliably reproduced in real time without causing the shortage of the moving picture data or overflow of the data in the receiving apparatus. It is an object to provide a moving image transmission system as described above.

[0035]

Means for Solving the Problems To solve this problem, the present invention is as follows.

(1) In a moving image transmission method for transmitting compressed moving image data via a communication line, if the transmission rate of the communication line and the encoding rate are different on the receiving side of the moving image data, the received moving image data The content of the synchronization field indicating the timing of decompression processing is converted, and the moving image data is decompressed based on the information of the converted synchronization field.

(2) In a moving image transmission system for transmitting compressed moving image data via a communication line, a receiving device for receiving the moving image data is provided, and the receiving device includes a transmission rate and a coding rate of the communication line. A timing converter that converts the content of a synchronization field that indicates the timing of expanding the received moving image data when the moving image data is different from the moving image data, and a moving image expander that expands the moving image data converted by the timing converter. Is provided.

With the above-described configuration, the moving picture transmission system of the present invention can reliably transmit moving picture data and perform display and recording in real time even at a coding rate different from the transmission rate of the communication line. Become.

[0039]

Embodiments of the present invention will be described below.

According to the moving image transmission method of the present invention, when transmitting the compressed moving image data through a communication line,
If the transmission rate of the communication line and the encoding rate are different on the receiving side of the moving image data, the content of the synchronization field indicating the timing of expanding the received moving image data is converted, and the converted synchronization field is converted. The moving image data is decompressed based on the above information.

According to the moving image transmission method of the present invention, when transmitting the compressed moving image data through a communication line,
On the receiving side of the moving image data, while temporarily storing the received moving image data when the encoding rate is lower than the transmission rate of the communication line, whether the received moving image data is a frame compressed using only intra-frame compression or not. The stored video data is continuously output at the same timing as the encoding rate from the detection of a frame within one frame to the detection of the frame compressed within the next frame. On the other hand, if a frame compressed using only intra-frame compression is detected, reading of the stored moving image data is stopped for a predetermined time, and reading of the moving image data from the frame is restarted. The expanded moving image data is expanded at the same timing as the encoding rate.

According to a third aspect of the present invention, there is provided a moving picture transmission system comprising a receiving apparatus for receiving moving picture data when transmitting compressed moving picture data via a communication line. And a timing converter for converting the contents of a synchronization field for instructing the timing for expanding the received moving image data when the transmission rate and the encoding rate are different from each other, and expanding the moving image data converted by the timing converting unit. A moving image decompression unit for processing is provided.

According to a fourth aspect of the present invention, there is provided a moving picture transmission system including a receiving apparatus for receiving moving picture data when transmitting compressed moving picture data via a communication line. A storage unit for temporarily storing received moving image data when the encoding rate is smaller than the transmission rate of the transmission rate, and monitoring whether the received moving image data is a frame compressed using only intra-frame compression, From the detection of a frame of one intra-frame compression to the detection of the next intra-frame compressed frame, moving image data is continuously read from the storage unit at the same timing as the encoding rate, while only intra-frame compression is performed. When a frame compressed using is detected, reading of the moving image data from the storage unit is stopped for a predetermined time, and then reading of the moving image data from the frame is performed. Resuming timing controller, and the moving image expanding section for expanding processing video data after read out from the storage unit at the same timing as the encoding rate,
It is characterized by having.

According to a fifth aspect of the present invention, there is provided a moving picture transmission system according to the third or fourth aspect, further comprising a transmitting apparatus for transmitting moving image data, wherein the transmitting apparatus comprises a code for transmitting data. A coding rate negotiating unit for determining a coding rate and transmitting the determined coding rate to the receiving side device; and a compression control unit controlling compression of moving image data in the moving image compressing unit according to the coding rate determined by the coding rate negotiating unit. The receiving side apparatus is provided with a coding rate negotiation section for transmitting information on the coding rate notified from the transmitting side apparatus to the timing conversion section.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a transmitting side device of a moving image transmission system according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram showing a configuration of a receiving side device of the same system. The same reference numerals are given to portions corresponding to the prior art shown in FIGS. 6 and 7.

In FIG. 1, A indicates the entire transmitting side device, 1 is a moving image generating unit, 2 is a moving image compressing unit, 3 is a storage unit,
The communication unit 5 is the communication line, the 6 first switch, 7 is a second switch, the above structure is the same as that of the conventional transmitting apparatus A ₀ shown in FIG. 6, Here, detailed description is omitted.

The transmitting apparatus A according to the first embodiment further includes a coding rate negotiating unit 9 for determining a coding rate of moving image data, and a coding rate determined by the coding rate negotiating unit 9. A compression control unit 8 for controlling the moving image compression unit 2 is provided.

On the other hand, in FIG. 2, B ₁ indicates the whole of the receiving side apparatus, 11 is a moving image display unit, 12 is a moving image decompression unit, 1
3 is a storage unit, 14 is a communication unit, 5 is a communication line, 16 is a third
Switch, 17 is a fourth switch, because the above structure is the same as that of the conventional receiving device B ₀ shown in FIG. 7, a detailed description thereof will be omitted.

The receiving-side apparatus B ₁ of the _first embodiment further includes a timing converter 1 for converting a synchronization field indicating a decompression timing included in the received moving image data.
0, a decompression controller 18 for selecting video data to be decompressed,
An encoding rate negotiating unit 19 for determining an encoding rate of transmission data, and a fifth switch 20 and a sixth switch 21 for selecting whether to display moving image data after the timing conversion are provided.

The third and fourth switches 16 and 17 are controlled by the timing converter 10 so that the fifth and sixth switches 2
0 and 21 are switched by the extension control unit 18, respectively.

Next, the operation of each section of the moving picture transmission system having the above configuration will be described in detail.

Here, it is assumed that the communication line 5 is line-connected at the transmission rate R, and that a session for transmitting a moving image is established between the transmitting device A and the receiving device B _1. .

In this state, a user who uses the transmission side apparatus A has a moving picture recorded at a coding rate F different from the transmission rate R, for example, F = αR (α is a coefficient, α> 0, α ≠ 1). When the transmission is instructed by the data, the coding rate negotiating unit 9 of the transmitting device A sends the coding rate of the moving image data to the coding rate negotiating unit 19 of the receiving device B ₁ via the communication line 5. F is notified. At the same time, the coding rate negotiating unit 9 of the transmitting device A also provides the information of the coding rate F to the compression control unit 8.

[0055] Further, the receiving-side apparatus when requesting the transmission of the moving image data coding rate F against B ₁ users transmitting apparatus A, the coding rate negotiation unit 1 of the receiving side apparatus B ₁
9 transmits a transmission request under the coding rate F to the coding rate negotiating unit 9 of the transmitting apparatus A via the communication line 5. The coding rate negotiating unit 9 of the transmitting device A
In accordance with this, information on the coding rate F is given to the compression control unit 8.

The compression control section 8 controls the moving picture compression section 2 based on the information on the coding rate F from the coding rate negotiation section 9 and compresses and codes the moving picture data at the coding rate F.

When transmitting the compressed moving image data to the receiving device B ₁ in real time, the output of the moving image compressing unit 2 is transmitted to the communication unit 4 via the first and second switches 6 and 7.
Is input to When the output of the moving image compression unit 2 is temporarily stored in the storage unit 3 via the first switch 6, the moving image data read from the storage unit 3 is input to the communication unit 4 via the second switch 7. .

The communication section 4 outputs moving image data (I frame and P frame) compressed and encoded at the encoding rate F. At that time, the communication unit 4, in order to inform the reproduction timing of the video data in the receiving-side apparatus B _1, and transmits the additional information that the synchronization field for the moving image data to be transmitted in advance (I and P frames). The reproduction timing based on this synchronization field is set to the timing of the period t ₀ for P frames, for example, so as to conform to the transmission rate R of the communication line 5.

On the other hand, when the moving image data received via the communication line 5 is displayed in real time without being stored in the storage unit 13 in the receiving device B ₁ , the third switch 1
6 is connected to the fifth switch 21 side, and the fourth switch 17 is turned off.

In this state, the moving picture data coding rate negotiating section 19 recognizes the coding rate F of the moving picture data and supplies the information to the decompression control section 18. Accordingly, the decompression control section 18 responds to this. Fifth switch 20 and sixth switch 2
Switch 1.

That is, when the encoding rate F (= αR) matches the transmission rate R (α = 1), it is necessary to adjust the reproduction timing when the moving image data is expanded in the moving image expansion unit 12. Therefore, the output of the communication unit 14 is switched to be directly connected to the moving image decompression unit 12 without passing through the timing conversion unit 10.

If the coding rate F (= αR) does not match the transmission rate R (α ≠ 1), the moving image decompression unit 12
Since it is necessary to adjust the reproduction timing at the time of expanding the moving image data in the
Is output from the moving image decompression unit 1 via the timing conversion unit 10.
The fifth and sixth switches 20 and 21 are switched so as to be connected to the second switch.

The timing converter 10 rewrites the synchronization field indicating the reproduction timing included in each frame by the following procedure each time an I frame or a P frame included in the moving image data is received from the communication unit 4.
Output to the moving image decompression unit 12.

Now, as shown in FIG. 3, when α = 1
Each frame I ₁ , P ₁₁ , P ₁₂ ,..., I ₂ , P (when the coding rate F matches the transmission rate R)
_21, P _22, the reception time for ...... is, t _I1, t _P11, t
It is assumed that _P12 ,..., _TI2 , _tP21 , _tP22,.

Under the condition of α = 1, t _P12 −t _P11 = t _P13 −t _P12 =... = T ₀ as long as the P frames have the same data length.
It has become.

At the time of transmission, the synchronization field for adjusting the reproduction timing added to each frame is f
(t _I1 ), f (t _P11 ), f (t _P12 ), ..., f (t _I2 ), f (t _P21 ), f
(t _P22 ), ... Here, f (t) is a calculation formula for determining the value of the synchronization field, for example, H.2
In the case of the 63 standard, it is given by f (t) = 29.97t mod 256 (where mod represents the remainder of the division).

When α ≠ 1, the timing converter 10 determines whether each frame I ₁ , P ₁₁ , P ₁₂ ,..., I ₂ , P ₂₁ , P
_The synchronization field obtained by receiving ₂₂ ,... _{Is represented} by f (t _I1
・ Α), f (t _P11・ α), f (t _P12・ α), ……, f (t _I2・
α), f (t _P21 · α), f (t _P22 · α),...

This means the following.

When 0 <α <1, that is, when the transmission rate R is higher than the coding rate F (= αR) (F <R), the same data as shown in FIG. The period at the time of reception of the long P frame is t ₁ (<t ₀ ).

However, when the receiving apparatus B ₁ expands the received moving image data using the same synchronization field (period t _{0 for a} P frame) as when R = F (that is, α = 1), the unit time becomes in the T, than the amount the video decompression unit 12 can be extended processing video data, who the amount of moving image data communication unit 14 receives increases, resulting in data video decompression unit 12 of the receiving-side apparatus B ₁ Overflow occurs.

Therefore, when 0 <α <1, the timing converter 10 sets the synchronization field to f (t _I1.
α), f (t _P11 • α), f (t _P12 • α), ……, f (t _I2 • α), f
By rewriting as (t _P21 · α), f (t _P22 · α),..., the reproduction timing when the moving image data received by the moving image expansion unit 12 is expanded is advanced. That is,
The moving image data is decompressed at an early timing in conformity with the large transmission rate R. As a result, the moving image decompression unit 1
In 2, the overflow of the moving image data is eliminated.

On the other hand, when α> 1, that is, when the transmission rate R is smaller than the coding rate F (= αR) (F> R)
In FIG. 9, as shown in FIG. 9 (c), the reception cycle of P frames having the same data length is t ₂ (> t ₀ ).

However, when the receiving apparatus B ₁ expands the received moving image data with the same synchronization field (period t _{0 in} the case of a P frame) as in the case of R = F (that is, α = 1), the unit time becomes in the T, than the amount the video decompression unit 12 can be extended processing video data, who the amount of moving image data communication unit 14 receives is reduced, resulting in data required for a video decompression on the receiving side apparatus B ₁ Insufficient quantity.

Therefore, when α> 1, the timing converter 10 sets the synchronization field to f (t _I1 · α), f
(t _P110 • α), f (t _P12 • α), ……, f (t _I2 • α), f (t _P21
.Alpha.), F ( _{t.sub.P22.alpha.} ),..., Thereby delaying the reproduction timing when the moving image data received by the moving image expansion unit 12 is expanded. That is, the moving image data is decompressed at a later timing in conformity with the transmission rate R being small. As a result, there is no shortage of moving image data in the moving image decompression unit 12.

FIG. 4 is a characteristic diagram showing the relationship between the reproduction timing (horizontal axis) at which the decompression process is performed and the received moving image data amount (vertical axis) so that the above description can be visually understood. .

In FIG. 4, the straight line indicated by L ₀ is α = 1 (R = F)
For, when the straight line shown by L ₁ is 0 <α <1 for (F <R),
Straight line shown by L ₂ indicates the case of α> 1 (F> R), respectively.

When it is assumed that moving image data is reproduced at the timing indicated by the black circle on the straight line L1 when α = 1, the timing conversion unit 10 rewrites the synchronization field, and when 0 <α <1, Has a straight line L ₁
Video data at the timing shown by white circles in the top is to be reproduced, and when the alpha> 1, the moving image data is to be reproduced at timing indicated by triangles of the straight line L _2.

As described above, according to the first embodiment,
Even when moving image data is transmitted in a state where the encoding rate F and the transmission rate R are different, a moving image can be displayed in real time in accordance with the transmission rate R.

Therefore, when the transmission rate R is higher than the coding rate F (when 0 <α <1), the user having the receiving side apparatus B ₁ can change the content of the moving image during reception of the moving image data. It can be confirmed in real time in the fast forward playback state. If the transmission rate R is smaller than the coding rate F (when α> 1), the receiving apparatus B
_The user having ₁ can check the content of the moving image in real time while receiving the moving image data in real time.

When the moving image data is temporarily stored in the storage unit 13, the fourth switch 17 is turned on, and the moving image data is not input to the timing conversion unit 10. Therefore, the information in the dynamic synchronization field TR is not rewritten. However, when the moving image data stored in the storage unit 13 is read out at a speed suitable for the expansion processing in the moving image expansion unit 12, the moving image data can be expanded by the moving image expansion unit 12 without any problem.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to the drawings.

In the second embodiment, the configuration of the transmitting side device A constituting the moving picture transmission system is the same as that of FIG. 1, so that the detailed description is omitted here.

FIG. 5 is a block diagram showing the configuration of the receiving side device B2 of the moving picture transmission system according to the _second embodiment, in which parts corresponding to those of the prior art shown in FIG. .

In FIG. 5, B ₂ indicates the entirety of the receiving apparatus, 11 is a moving image display unit, 12 is a moving image decompression unit, 13 is a storage unit, 14 is a communication unit, 5 is a communication line, and 16 is a third unit. The switch 17 is a fourth switch.
The same is because those of the conventional receiving device B ₀ shown in a detailed description will be omitted.

The receiving apparatus B ₂ of the _second embodiment further includes a coding rate negotiating unit 19 for determining a coding rate of transmission data, and a timing control unit 22 for monitoring output data from the communication unit 14. Is provided.

Then, the third and fourth switches 16 and 17
Are switched by the timing control unit 22.

Next, the operation of each section of the moving picture transmission system having the above configuration will be described.

When the communication line 5 is line-connected at the transmission rate R and a session for transmitting a moving image is established between the transmitting side and the receiving side, the transmission rate is stored in the storage unit 3 of the moving image transmission system on the transmitting side. Coding rate F lower than R
(= ΑR) (0 <α <1), when the user of the transmission-side moving image transmission system instructs transmission of the moving image data,
Or if the user of the receiving video transmission system requests the transmission to the transmitting side, the encoding rate negotiation unit 19 of the receiving-side apparatus B ₂ from the coding rate negotiation unit 9 of the transmitting side, the video data Coding rate F (= αR) (0 <α <
1) is notified via the communication line 5.

In response to this, the moving picture data coding rate negotiating section 19 recognizes the coding rate F of the moving picture data and gives the information to the timing control section 22, and accordingly, the timing control section 22 The third switch 16 and the fourth switch 17 are switched.

That is, when the coding rate F is equal to the transmission rate R
(Α = 1), it is not necessary to adjust the reproduction timing when the moving image data is decompressed.
The switch 17 is turned off, and the output of the communication unit 14 is directly transmitted to the moving image decompression unit 1 without passing through the storage unit 13.
The third switch 16 is switched so as to be connected to the second switch.

When the encoding rate F does not match the transmission rate R (0 <α <1), it is necessary to adjust the reproduction timing when the moving image data is expanded in the moving image expansion unit 12. The timing control unit 22 turns on the fourth switch 17 and switches the third switch 16 so that the output of the storage unit 13 is provided to the moving image decompression unit 12.

Next, the timing control unit 22
For video data output from the polygonal line L ₃ in FIG. 4
The writing and reading operations to and from the storage unit 13 are performed at the timings indicated by.

[0093] That is, I ₁ in between (e.g. FIG. 8 from one single I-frame until it receives the next I-frame-
Until video data) of the P _16, stores those video data sequentially in the memory unit 13, moving image expanding unit 1 moving image data stored is read at the same rate as the encoding rate F
Output to 2.

When detecting the next I frame (for example, I _{2 in} FIG. 8) included in the moving image data from the communication unit 4, the timing control unit 22 stores the moving image expanding unit 1 in the storage unit 13.
After temporarily stopping the read operation of the moving image data to the _second frame and adjusting the time, an instruction is given to restart reading from the I2 frame.

The moving image decompression unit 12 decompresses the moving image data read from the storage unit 13 at a predetermined coding rate F.

In this way, the broken line L in FIG.
_{In 3} , the gradient from when a certain one I frame is received to when the next I frame is received matches the gradient of the straight line L ₀ when α = 1.

Therefore, in the second embodiment, the coding rate F (= αR) (0 <α <
Even when transmitted via the communication line 5 the video data recorded in 1), rather than the fast-forward reproduction (in the case of the straight line L ₁₎ and slow reproduction (in the case of the straight line L _2), when the normal reproduction (the straight line L
_The moving image can be displayed and recorded in the same state as in the case of ( ₀ ).

In each of Embodiments 1 and 2 described above, the coding rate negotiating units 9 and 19 are provided. However, the coding rate between the transmitting apparatus A and the receiving apparatuses B ₁ and B ₂ is determined. When F is negotiated and set in advance, the coding rate negotiation units 9 and 19 can be omitted.

[0099]

According to the moving picture transmission system of the present invention, the following effects can be obtained.

(1) Even when moving image data is transmitted via a communication line having a transmission rate different from the encoding rate, the moving image data is reliably reproduced in real time without causing shortage or overflow of the moving image data on the receiving side. You can check the contents.

(2) Also, when moving image data recorded at a low encoding rate is received via a communication line having a high transmission rate, the receiver can reproduce the contents of the recorded image in the normal reproduction state during reception. You can check.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a transmission-side device of a moving image transmission system according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a receiving device of the moving image transmission system according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an operation of a timing conversion unit according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the reproduction timing of moving image data and the amount of moving image data on the receiving side according to the present invention.

FIG. 5 is a block diagram showing a configuration on a receiving side of the moving image transmission system according to the second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a transmission-side device of a conventional moving image transmission system.

FIG. 7 is a block diagram showing a configuration of a receiving side device of a conventional moving image transmission system.

FIG. 8 is a diagram showing a transmission form of a frame compressed as a moving image;

FIG. 9 is an explanatory diagram showing a state in which data overflow or insufficient data of moving image data occurs due to coincidence or inconsistency between an encoding rate and a transmission rate.

[Explanation of symbols]

 Reference Signs List 1 moving image generation unit 2 moving image compression unit 3,13 storage unit 4,14 communication unit 5 communication line 6,7 switch 8 compression control unit 9,19 coding rate negotiation unit 10 timing conversion unit 11 moving image display unit 12 moving image decompression unit 16 , 17 switch 18 extension control unit 20, 21 switch 22 timing control unit

Claims (5)

[Claims] 1. A moving image transmission method for transmitting compressed moving image data via a communication line, comprising the steps of: receiving a moving image data on a receiving side of the moving image data if the transmission rate and the coding rate of the communication line are different; A moving image transmission method, comprising: converting the content of a synchronization field indicating the timing of decompression processing; and performing decompression processing on the moving image data based on the information of the converted synchronization field. 2. A moving image transmission method for transmitting compressed moving image data via a communication line, wherein the receiving side of the moving image data temporarily receives the moving image data when the encoding rate is lower than the transmission rate of the communication line. It is monitored whether or not the received moving image data is a frame compressed using only intra-frame compression, and after detecting a frame of one certain intra-frame compression, the next moving image data is compressed. Until a frame is detected, the stored moving image data is continuously read at the same timing as the encoding rate. On the other hand, when a frame compressed using only intra-frame compression is detected, the stored moving image data is read. Is stopped for a predetermined period of time, and then reading of the moving image data from the frame is resumed. Video transmission method characterized by decompression processing at the same timing as. 3. A moving image transmission system for transmitting compressed moving image data via a communication line, comprising a receiving device for receiving the moving image data, the receiving device comprising: A timing converter that converts the content of a synchronization field that indicates the timing of expanding the received moving image data when the rate is different, and a moving image expander that expands the moving image data converted by the timing converter. , A moving image transmission system. 4. A moving image transmission system for transmitting compressed moving image data via a communication line, comprising: a receiving device for receiving the moving image data, wherein the receiving device has a code rate higher than a transmission rate of the communication line. A storage unit for temporarily storing received moving image data when the image data rate is low, and monitoring whether or not the received moving image data is a frame compressed using only intra-frame compression. From the detection of a frame to the detection of a frame compressed in the next frame, moving image data is continuously read from the storage unit at the same timing as the encoding rate, and compressed using only intra-frame compression. When a frame is detected, the reading of the moving image data from the storage unit is stopped for a predetermined time and then the reading of the moving image data from the frame is restarted. A moving image transmission system, comprising: a moving control unit; and a moving image decompression unit that decompresses the moving image data read from the storage unit at the same timing as the encoding rate. 5. The moving image transmission system according to claim 3, further comprising: a transmitting device that transmits moving image data, wherein the transmitting device determines a coding rate of the transmission data and performs the reception. An encoding rate negotiation unit to be transmitted to the side device; and a compression control unit that controls the compression of the moving image data in the moving image compression unit based on the encoding rate determined by the encoding rate negotiation unit. And a coding rate negotiation unit for transmitting coding rate information notified from the transmission side device to the timing conversion unit.