JP2947302B2 - Image encoding / decoding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image code capable of coping with an enormous jitter delay generated in a high-speed packet network without impairing real-time performance when transmitting and receiving a compression-coded moving image signal using a high-speed packet network. The present invention relates to a decryption device.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of an image encoding / decoding apparatus using a high-speed packet network as a communication network. In the figure, 1 is an encoding unit, 3 is a packet transmitting unit, 4 is a packet receiving unit, 5 is a decoding unit, 20 is an input image signal, 21 is coded data, 24 is a packet to be transmitted, and 25 Is a received packet, 26 is packet-decomposed data, and 27 is a decoded image signal.

In the transmitting station, the input image signal 2
0 uses the temporal / spatial redundancy of the image signal in the encoding unit 1 to compress the amount of information by using, for example, inter-frame encoding, vector quantization, orthogonal transform encoding, or the like alone or in combination. Do. The encoded data 21 is divided by the packet transmission unit 3 for each frame, or for dividing one frame into a plurality of blocks, and for each block or several blocks, or for each predetermined fixed length data amount, Further, it converts the packet into a packet in which information necessary for transmission and reception is added as a header and sends the packet to a high-speed packet network. In the receiving station, the packet receiving unit 4 receives the packet 25 sent from the high-speed packet network, removes the header from the packet, and performs packet disassembly for extracting only the data sequence. The data 26 is decoded by the decoding unit 5 to obtain a moving image signal 27.

Here, transmission and reception of a moving image signal without frame thinning using this apparatus will be considered. In this case, for example, Karlsson and M.S. Ve
terli “Packet Video and I
ts Integrationinto the Ne
work architecture “IEEEjo”
urnal on Selected Areas i
n Communications, Vol. 7, N
o. 5, June 1989, there is a problem of jitter delay and a problem of signal synchronization between a transmitting station and a receiving station, which are one of the properties of a packet network. The packet network has a function of temporarily storing packets in an exchange when communication paths coexist and transmitting the packets when a communication path becomes free. Therefore, the time required from the transmission of a packet to the reception of the packet differs for each packet. The difference between the average required time for transmitting and receiving packets and the time required for each packet to actually transmit and receive is called jitter delay. On the other hand , when encoding / decoding an image without performing frame thinning, the receiving station must independently perform video processing by synchronizing video frames equal to the image signal input at the transmitting station. As a result, a significant jitter delay occurs, and data contained in a packet received after the synchronization of the receiving station cannot be decoded, resulting in a problem that an image is disturbed.

This will be described with reference to FIG. The horizontal axis is the actual time, the vertical axis is the local time at each point,
The lines A, B, C and D respectively correspond to the points shown in FIG. Lines A and D represent the frame numbers of the input and output image signals. A circle on line B indicates the time at which the packet is sent out, and a line on line C indicates the time at which the packet is received. The time between A and B is the time required for encoding and packetizing the image signal, and the time between CD is the time required for decomposing the packet and decoding the image signal. B
C is the average time required for a packet to be transmitted on the high-speed packet network. An image signal is input to the encoding unit 1 at a constant cycle. The transmitting station encodes and packetizes all the input frames without thinning them out and transmits them. In the figure, since a significant jitter delay occurs on a high-speed packet network for a packet x composed of a part of the encoded data of the image signal of the frame 3, it is the receiving station that receives the packet. Later than frame sync,
The image signal of frame 3 cannot be decoded. As a result, the disturbance of the image occurs, which affects the image of the subsequent frames.

As one of the solutions, for example, K. S
akai, T .; Hamano, T .; Awazu and
K. Matsuda “An Experimenta
lHDTV Codec for ATM Network
rks "VISICOM'90 Third Inte
national Workshop on Pac
As in kret Video, there is a method in which a jitter delay is estimated in advance by calculation and a memory buffer capable of absorbing the jitter delay is provided in the receiving station. However, this method cannot solve the problem when an unexpectedly large jitter delay occurs. Providing a large-capacity memory buffer that can absorb this delay will always cause a large delay between the transmitting station and the receiving station, real-time performance such as a video conference or videophone conversation with the other party. This is a major drawback for services that require.

[0007]

As described above, each of the transmitting station and the receiving station has its own video frame synchronization, and uses a high-speed packet network to transmit and receive an image without performing frame thinning. In a high-speed packet network, when a large jitter delay occurs, the image is distorted. If a large buffer is provided in the receiving station to take measures against the jitter delay, a large delay time always occurs, which causes a video conference or videophone call. However, such a service that requires real-time performance is a drawback.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image encoding / decoding apparatus capable of coping with a severe jitter delay without deteriorating the real-time property. Aim.

[0009] An image encoding / decoding apparatus according to the present invention comprises:
The transmitting station encodes the image signal and transmits it, and the receiving station
Synchronizes the video frame by receiving the encoded video signal
In an image encoding / decoding device configured to decode every interval
The transmitting station encodes the image signal and encodes the encoded data.
Means for outputting the encoded data to the image quality.
Means for layering into multiple components according to the degree of influence
High degree of influence on image quality among layered encoded data
Packetized data of the threshold component is transmitted first.
Means for receiving the packetized data.
Means for receiving the encoded data, and the video frame
Received within the video frame synchronization time
Means for decoding the encoded data.

[0010] In the next invention, the image signal is transmitted by the transmitting station.
And transmits the encoded image on the receiving station side.
Receive signal and decode every video frame synchronization time
In the image encoding / decoding apparatus described above, the transmitting station
Band splits the image signal into multiple components from low frequency components to high frequency components
Means for encoding the band-divided signal and encoding
Means for outputting as data, and
Means for packetizing and transmitting low-frequency components first
On the other hand, the receiving station transmits the packetized encoded data.
Means for receiving the data, and
The encoded data received within the video frame synchronization time
Means for decoding the data.

Further , in the next invention, the image signal is transmitted from the transmitting station side.
And transmits the encoded image on the receiving station side.
Receive signal and decode every video frame synchronization time
In the image encoding / decoding apparatus described above, the transmitting station
Means for encoding an image signal and outputting it as encoded data
Means for locally decoding the encoded data; and
Encoding the difference between the signal and the locally decoded signal
Means for outputting as difference value code data;
The data is first packetized and transmitted, and then the difference value
Means for packetizing encoded data and sending it out.
On the other hand, the receiving station receives the packetized data
Means for performing the video frame synchronization every video frame synchronization time.
Means for decoding the data received within the frame synchronization time
And

[0012]

In the image encoding / decoding apparatus configured as described above, the coded data of the input signal is hierarchized in accordance with the magnitude of the influence on the image quality, and the components having the greater influence are packetized first. Because of the transmission, when a significant jitter delay occurs in the high-speed packet network, even if the image is decoded using the data obtained from the packet received within the video frame synchronization of the receiving station, the image formation is greatly affected. It is possible to decode an image without loss of data and without disorder.
In addition, since a countermeasure against jitter delay can be taken without providing a large buffer in the receiving station, image communication can be performed without impairing real-time performance.

Further, the input signal is subdivided into a plurality of components by sub-band encoding, encoding is performed in accordance with the property of the signal of each band, and the encoded data of the low-frequency component is packetized first. Because of the transmission, if a significant jitter delay occurs in the high-speed packet network, even if the image is decoded using the data obtained from the packet received within the video frame synchronization held by the receiving station, the image formation is performed in the same manner as described above. There is no loss of data having a large effect, and it is possible to decode an image without disturbance without impairing the real-time property.

Further, encoding of the input signal and encoding of a difference signal between the input signal and the local decoded signal according to the property of the difference signal are performed, and the data obtained by encoding the input signal is first processed, followed by the difference signal Of the encoded data of the input signal by decoding the encoded data of the input signal, of the data obtained from the packet received within the video frame synchronization held by the receiving station by packetizing the encoded data of As a supplementary signal, an image without disturbance is obtained without impairing the real-time property as described above.

[0015]

[Embodiment 1] FIG. 1 is a block diagram of an image encoding / decoding apparatus showing one embodiment of the present invention. 1 is an encoding unit, 2 is a layering unit, 3 is a packet sending unit, 4 is a packet receiving unit, 5 is a decoding unit, 20 is an input video signal, 2
1 is coded data, 22 is coded data having a large effect on image quality, 23 is coded data having a small effect on image quality, 24 is a transmitted packet, 25 is a received packet, and 26 is packet-decomposed. Data 27 is a decoded image signal.

In the image encoding / decoding apparatus configured as described above, in the transmitting station, the hierarchization unit 2 converts the encoded data 21 into data 22 having a large effect on image quality.
And small data 23. The method of the hierarchical, when using the discrete cosine transform (DCT) is a type of orthogonal transform coding in the coding unit 1 if e example,
It is assumed that the low-frequency component of the conversion coefficient has a large effect on the image quality, and the high-frequency component has a small effect on the image quality. Also, when performing coding using correlation with other frames such as inter-frame coding and motion compensation prediction,
Data having little effect on the image quality after the hierarchization is not used for local decoding performed by the encoding unit 1. By doing so, when the receiving station decodes the image without using all of the encoded data as described later, it is possible to prevent the disturbance and error of the image from being propagated to subsequent frames. The packet transmission unit 3 packetizes the data, but first packetizes data having a large effect on the image quality and transmits the data to a high-speed packet network. At the receiving station, a significant jitter delay occurs in the high-speed packet network, and when all the packets constituting one frame of data cannot be received within the video frame synchronizing time of the receiving station, the video frame synchronization is performed. The decoding unit 5 decodes the image signal 27 using the data included in the packet received therein, thereby obtaining an image signal 27. When all packets constituting one frame of data can be received within the video frame synchronization time without causing a delay in the high-speed packet network, all the data is decoded and an image signal 27 is obtained.

In the above embodiment, the coded data is hierarchized into two components, a low-frequency component and a high-frequency component.
It is also possible to hierarchize into a plurality of components of three or more components, packetize from low-band components to high-band components, and send the packets to a high-speed packet network.

Embodiment 2 FIG. FIG. 2 is a block diagram of an image encoding / decoding apparatus showing one embodiment when subband encoding is used. In the figure, 6 is a band dividing unit, 7 is a low-band component coding unit, 8 is a high-band component coding unit, 9 is a low-band component decoding unit, 10 is a high-band component decoding unit, and 11 is a band. Synthesis section,
28 is a low-frequency component signal, 29 is a high-frequency component signal, 30,
Reference numeral 32 denotes encoded data of a low-frequency component; 31, 33, encoded data of a high-frequency component; 34, decoded data of a low-frequency component; 35, decoded data of a high-frequency component; .

In the transmitting station, the input image signal is band-divided by the band dividing section 6 into a low-frequency component signal 28 and a high-frequency component signal 29. Each signal is encoded by the encoding unit 6, and data is sent to the packet sending unit 3. In the packet transmission unit 3, the encoded data 3
0 is first packetized and transmitted to the high-speed packet network.
In the receiving station, the packet receiving unit 4 divides the data inside the received packet into low-frequency component data 32 and high-frequency component data 33 and sends them to the decoding units 9 and 10. The signals 34 and 35 decoded by the respective decoding units are synthesized in the band synthesizing unit 11 to obtain the image signal 27. At the receiving station,
If all the packets constituting one frame of data cannot be received within the video frame synchronization of the receiving station due to the jitter delay, the image signal 27 is obtained using the data obtained from the received packet.

Here, the band is divided into two components, a low-frequency component and a high-frequency component. However, the present invention can be applied to a method in which the frequency is divided into a plurality of three or more components.

Embodiment 3 FIG. FIG. 3 shows that the transmitting station has two encoding units.
This is an embodiment for an apparatus having one local decoding unit. In the figure, 12 is a local decoding unit, 13 is an encoding unit,
14 is a decoding unit, 36 is a local decoded signal, 37 is a differential signal between the input signal and the local decoded signal, 38 and 39 are coded data of the differential signal, 40 is a decoded signal of the differential signal, The same is true.

At the transmitting station, the input signal 20 is encoded to obtain encoded data 21. The encoded data 21 is locally decoded by the local decoding unit 12, and the local decoded signal 3
6 is obtained. Next, a difference between the local decoded signal 36 and the input signal 20 is obtained to obtain a difference signal 37. This difference signal 3
The power of 7 is generally small. The difference signal 37 is encoded by the encoding unit 13 to obtain encoded data 38. The packet transmission unit 3 converts the encoded data of data 2
1 is first packetized and sent to a high-speed packet network. In the receiving station, the packet is decomposed by the packet receiving unit 3 and is divided into encoded data 26 of the input signal and encoded data 39 of the locally decoded signal. The decoding units 5 and 14 decode the encoded data to obtain the image signal 27 and the decoded difference signal 40. Difference signal 4
0 serves as a supplementary signal of the image signal 27. When the receiving station cannot receive all the packets constituting one frame of data within the video frame synchronization of the receiving station due to the jitter delay, the image signal 41 is obtained using the data obtained from the received packet. .

Here, an example in which the transmitting station includes one local decoding unit and two encoding units has been described. However, the local decoding of the encoded data 38 is further performed, and the difference signal from the difference signal 37 is obtained. It is also possible to provide a plurality in multiple stages, such as obtaining.

[0024]

Since the present invention is configured as described above, it has the following effects.

The coded data of the input signal is hierarchized, and a packet having a large influence on the image quality is transmitted first. Alternatively, the input signal is divided into bands, and the band is coded according to the band. Since the packet transmission is performed first from the encoded data, if a significant jitter delay occurs in the high-speed packet network, the image is decoded by using the data obtained from the packet received within the video frame synchronization held by the receiving station. Also, it is possible to decode an image without disturbance without any loss of data having a large effect on image formation and without impairing the real-time property.

Following the encoded data of the input signal,
Since the encoded data of the differential signal is transmitted in packets, when decoding an image from data obtained from the packet received within the video frame synchronization of the receiving station, the decoded differential signal decodes the encoded data of the input signal. It plays a supplementary role in the obtained image signal and achieves the same effect as described above.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image encoding / decoding apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an image encoding / decoding device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of an image encoding / decoding device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a conventional image encoding / decoding device.

FIG. 5 is a diagram showing a frame and a packet transmission time and a reception time of an image signal at a transmitting station and a receiving station in a conventional image encoding / decoding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Encoding means 2 Hierarchical means 3 Packet sending means 4 Packet receiving means 5 Decoding means 6 Band division means 7 Encoding means 8 Encoding means 9 Decoding means 10 Decoding means 11 Decoding means 12 Local decoding means 13 Encoding means 14 Decoding means

Continuation of front page (56) References JP-A-63-73786 (JP, A) JP-A-2-57034 (JP, A) JP-A-3-22780 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) H04N 7/24

Claims (3)

(57) [Claims] 1. A transmitting station encodes an image signal and transmits it.
The receiving station receives the encoded image signal and displays it.
Image coding for decoding every image frame synchronization time
In the decoding device, the transmitting station encodes the image signal and outputs the encoded image signal as encoded data.
And a plurality formed in accordance with the degree of influence of the encoded data to the image quality
Means for hierarchization in minutes and the effect on image quality of the hierarchized encoded data
Packetize the encoded data of the component with the highest degree first
While having a means for sending, the receiving station includes means for receiving the packetized encoded data, when the video frame synchronization for each of the video frame synchronization time
Means for decoding the encoded data received within the interval.
An image encoding / decoding apparatus characterized in that: 2. A transmitting station encodes and transmits an image signal.
The receiving station receives the encoded image signal and displays it.
Image coding for decoding every image frame synchronization time
In the decoding device, the transmitting station divides the image signal into a plurality of components from a low-frequency component to a high-frequency component.
Means for encoding the band-divided signal into encoded data.
Means for outputting the encoded data,
Means for receiving the packetized coded data, and means for synchronizing the video frame at each video frame synchronization time.
Means for decoding the encoded data received within the interval.
An image encoding / decoding apparatus characterized in that: 3. A transmitting station encodes and transmits an image signal.
The receiving station receives the encoded image signal and displays it.
Image coding for decoding every image frame synchronization time
In the decoding device, the transmitting station encodes the image signal and outputs the encoded image signal as encoded data.
If, means for locally decoding said encoded data, a difference value between the image signal and said local decoded signal marks
Means for encoding and outputting the encoded data as differential value encoded data; and
Means for packetizing and transmitting the differential value encoded data
While having the bets, the receiving station includes means for receiving the packetized data, the time of the video frame synchronization for each of the video frame synchronization time
Means for decoding the data received within the interval.
An image encoding / decoding device characterized by the following .