JP3067404B2 - Image encoding device and 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 high-efficiency coding for efficiently coding a signal with a smaller code amount for recording, transmission and display for processing a digital signal. More particularly, the present invention relates to an encoding device and a decoding device between image devices having different image rates between a signal source image and a display image, such as a case where the image is displayed on a normal television receiver. .

[0002]

2. Description of the Related Art <2-3 Pulldown> When an image on a film such as a movie is viewed on a normal television, it is necessary to convert the image because the image rate is different. To convert a film of 24 frames per second into a television signal of 60 fields per second, two frames of the film may be converted into 5 fields of the television signal. Also, although the TV signal is interlaced, the film is not originally scanned,
Naturally, it is non-interlaced. Therefore, 2 pieces are 5
When converting into a field, one frame is converted into two fields corresponding to one frame, and the other frame is converted into three fields.
There are duplicate fields. This is shown in FIG. 6, where o is an interlaced odd field and e is an even field. This method is "2-3 pull down"
, One field out of five fields is a repetition of the same field. Such processing can be realized by simply scanning and then converting using a semiconductor memory when converting a film image into an electric signal, or by performing film frame advance in synchronization with the television signal. it can.

<Bidirectional Inter-Frame Prediction> In high-efficiency coding of a moving image, a frame to be coded is predicted by a coded frame by using a correlation between frames of an image signal, and only a prediction error is generated. Is inter-frame predictive coding. In recent years, motion-compensated inter-frame prediction, in which an image is predicted by moving the image in accordance with motion, has become more common. Therefore, there is a method for further improving the efficiency by using bidirectional prediction. This means that the prediction structure is 2 as shown in FIG.
In this stage, one of several frames (P frame) is predicted from only one side (forward direction), and the intervening frame (B frame) is predicted from both directions (forward and reverse directions) from P frame. There is a way to In this method, the B frame has a high prediction efficiency, and the error does not spread to other in the non-recursive prediction, so that the quantization can be set coarsely.
As a result, the efficiency can be considerably increased, and it is used in the MPEG system which is being standardized by ISO / IEC. Note that the same applies to the case where a frame is a field of an interlace signal.

<Configuration of Encoding Apparatus> FIG. 4 shows an example of the configuration of an encoding apparatus for performing bidirectional prediction in a system for encoding a film image as a television signal. Here, it is assumed that the image signal is obtained by simply sequentially (non-interlacing) scanning a film image and converting it into an electric signal. The image signal input from the image input 1 is input to the image rate converter 31.
A 2-3 pull-down process is performed. This processing is built in the telecine device separately from the encoding device, and the encoding device may receive a signal as a television signal of 60 fields per second. The signal converted into the television signal of 60 fields per second is temporarily stored in the field memory 3 in order to change the encoding order in bidirectional prediction. The P (unidirectional prediction) field is output immediately, and the B (bidirectional prediction) field is output after the next P.

The output of the field memory 3 is a prediction subtractor 4
And the prediction signal input from the predictor 9 is subtracted. The output of the prediction subtractor 4, which is the prediction residual, becomes data encoded and compressed by the intra-field encoder 5. The data is fixed in rate in the data buffer 6, output from the data output 7, and guided to the intra-field decoder 12 in the P field. In the intra-field decoder 12, the compressed data becomes a reproduced prediction residual, and the prediction signal is added by the adder 11, to become a reproduced image signal. The reproduced image signal is stored in the field memory 10, delayed, and then guided to the predictor 9. It should be noted that only the P field used for prediction is stored in the field memory 10, and two fields are stored. The predictor 9 generates a prediction signal in accordance with the type of the field to be predicted (P / B) and the image order, and supplies the prediction signal to the prediction subtractor 4. The image counter 8 counts the vertical synchronizing signal of the television signal in the period of the P field, and outputs information of the field type (P / B) and the image order. The field memory 3 and the predictor 9 are controlled by this information.

<Configuration of Decoding Device> FIG. 5 shows the configuration of the decoding device. The compressed data input from the data input 30 passes through the data buffer 31 and is supplied to the intra-field decoder 1.
2 and the prediction signal is added by the adder 11 to become a reproduced image signal. The signal is output from the image output 34 through the switch 33 in the B field. In the P field, the switch 33 is crossed, the reproduced image signal is stored in the field memory 10, and the immediately preceding P field image stored in the field memory 10 is output from the image output 34 through the switch 33. .

[0007] The reproduced image signal stored in the field memory 10 is supplied to a predictor 9. The predictor 9 generates a prediction signal in accordance with the type of the field to be predicted (P / B) and the image order. give. Image order information is input from the image order input 35, and the predictor 9 and the changeover switch 33 are controlled by this. Film images can be encoded with such an encoding / decoding system.
Duplicate fields generated by -3 pull-down will cause duplicate data.

[0008]

When the image rate of the signal source image and that of the transmission display device are different, such as when a film image is viewed on a normal television receiver, the image rate is converted to a standard television signal and then transmitted and displayed. In some cases, the image rate is converted before image data is transmitted and displayed. When high-efficiency coding is applied to transmission, when the image rate is converted to a standard television signal before coding, there are overlapping fields due to the difference in the image rate, and the same image cannot be converted into two.
Useless information is generated. On the other hand, if encoding is performed without converting the image rate and the image rate is converted after decoding, no information is wasted, but an image memory is required to convert the image rate on the decoding side.

The present invention has been made in view of the above points. In a film image and a normal television image, images at intervals where the image time (timing) coincides are independently or unidirectionally predictively encoded and decoded. It is an object of the present invention to provide a film image encoding apparatus and a decoding apparatus which do not require an additional memory for image rate conversion by a decoder by repeatedly displaying only the image on the apparatus and converting the image rate. Is what you do.

[0010]

In order to achieve the above object, first, an image apparatus having a different image rate between a signal source image on the encoding apparatus side and a display image on the decoding apparatus side is used. An image coding apparatus using bidirectional inter-picture prediction, wherein an image is independently coded or unidirectional inter-picture predictive coding is performed at intervals at which image timings of the signal source image and the display image match. The present invention provides an image encoding device characterized by the following.

Second, an image decoding apparatus which uses bidirectional inter-picture prediction between image apparatuses having different image rates between a signal source image on the encoding apparatus side and a display image on the decoding apparatus side. An image decoding apparatus, wherein an image is independently decoded or one-way inter-picture predictive decoding is performed at intervals at which image timings of the signal source image and the display image match. It is.

Third, when encoding an image having a plurality of images having the same contents, only the encoded data of the first image among the images having the same contents is output, and the encoded data of other images having the same contents are encoded. An image encoding apparatus according to the above, wherein the image encoding apparatus is controlled not to output the image.

Fourthly, only the image which has been subjected to independent decoding or one-way inter-picture predictive decoding is output a plurality of times to convert the image rate. The present invention provides a chemical conversion device.

[0014]

According to the present invention, images are independently or unidirectionally predictively encoded at intervals at which the time (timing) of the two images coincides, and only the encoded data of the first image is output for images having the same contents.
Since the encoded data of other images is not output, no useless information is generated. By outputting only the image that has been independently or unidirectionally predicted decoded multiple times by the decoding device and performing image rate conversion, the image of the independent or unidirectional prediction is stored in the image memory for use in inter-image prediction. Since it is stored, the image rate can be converted simply by outputting it.
Therefore, an image memory for converting the image rate is not required. When no conversion is performed, the image rate becomes the same as that of the signal source, and outputs of both image rates are obtained.

[0015]

FIG. 1 is a block diagram showing a first embodiment of an encoding apparatus according to the present invention. The same parts as those in the conventional example of FIG. The encoding apparatus shown in FIG. 4 differs from the encoding apparatus shown in FIG. 4 in that an interlace converter 2 is provided instead of an image rate converter, and a field prediction type (P
The setting of B) and the control based on it are different.

In FIG. 1, an image signal input from an image signal input terminal 1 is converted by an interlace converter 2 from a non-interlace signal to an interlace signal. That is, one frame is converted into two fields, and 24 frames (frames) are converted into 48 fields. The configuration after the field memory 3 is the same as the conventional example, and only the processing content is different. The P field is set to a field that is output twice when the field is converted into 60 fields on the decoding side. This eliminates the need to output the B field twice and eliminates the need for a memory for image rate conversion in the decoding device.

Such a field configuration is as shown in FIG.
The P field is set at intervals at which the image timing matches. FIG. 8 shows the same image at different image rates,
One frame of the film is surrounded by a solid line, and a plurality of squares in the frame constitute a field. The upper (o) field is an odd field, the lower (o) is an even field, numbers are picture numbers, P and B are field prediction types, and the P field is shaded. A field indicated by-indicates a field in which encoded data is not transmitted.

In the state (a) of 48 fields per second, P
It can be seen that the field exists every two frames, with even and odd being replaced each time. The image order in the encoding apparatus of FIG. 1 is as shown in FIG. 1A, and the operation of the field memory and the predictor follows the order. Here, the even-odd order is changed every two frames, because the order of (b) is used as a reference when the image rate is converted to 60 fields per second. The interval of P is always 5 fields in 60 fields (b) per second.

<Second Embodiment> FIG. 2 is a block diagram showing a second embodiment of the encoding apparatus according to the present invention. 1 are given the same reference numerals. The second embodiment corresponds to a case where 2-3 pull-down is performed when a film image is converted into a television signal, and the encoded signal is already 60 fields per second.

In this case, the signal of 60 fields may be returned to 48 fields, and then the encoding process may be performed as in the first embodiment. Is omitted, and only valid 48 fields are encoded. The apparatus configuration is different from the encoding apparatus of FIG. 1 in that the interlace converter 2 is replaced with an image rate converter and a data controller 21 is added.
The field type to be processed is (b) of 60 fields per second in FIG. This is similar to the conventional example in which the interval between P fields is set to 5 fields.

The processing operation is the same as that of the conventional example except that only the overlap field indicated by-(the next field after the P field) is special, and the other is connected to the data controller 21. At the timing of the overlapping field, the data controller 21 is disconnected, and no data is supplied to the data buffer and is not transmitted. At this time, the prediction subtractor 4 and the intra-field encoder 5 need not be operating. The data output in this manner is the same as in the case of the first embodiment in FIG.

In this encoding apparatus, it is necessary to know which field is present in duplicate, and that information is needed. This information is obtained by the frame number if the operation of the image rate converter is specified by the frame number of the output image. Therefore, when an image signal is recorded once on a VTR or the like, it is necessary to use a VTR that can manage frame numbers. If this information is not known, it is determined by matching between two fields. If the image counter is reset with this information, the operation of the encoder can be performed properly. The P field periodically resets the prediction, and that field becomes an independent field.

<Decoding Apparatus> FIG. 3 is a block diagram showing a first embodiment of the decoding apparatus according to the present invention. The same parts as those in the conventional example of FIG. The processing operation is different from that of the conventional decoding device shown in FIG. This decoding device corresponds to both the encoding devices of the first embodiment and the second embodiment.

When an image is output after being converted into 60 fields per second, the decoding device is basically operated in 60 fields, and the image order is as shown in FIG. 8 (b). The operation of No. 9 is in accordance with it. Here, the operation is performed in the overlapping field (P
Only the next field after the field) is special,
Otherwise, the data controller 32 is connected and decoding is performed in the same manner as in the conventional example. At the overlap field timing, the data controller 32 is disconnected, no data is supplied to the intra-field decoder, and no decoding is performed. Instead,
The image of the P field stored in the field memory 10 is repeatedly output.

On the other hand, for a television receiver of 50 fields per second, the image speed is allowed to increase by 4%,
An image of 48 fields per second is output without conversion. In this case, the decoding device is basically operated at 50 fields per second. The image order is as shown in FIG.
The interval of P changes between 5 fields and 3 fields each time. Since the image order changes to a and b, the order of the image data is exchanged in the data buffer 31. The operations of the field memory 12 and the predictor 9 follow the image order shown in FIG. The data controller 32 is always connected. In this way, the same data and the same decoding device can be changed only by changing the processing content of the decoding device, and thus 60 fields per second and 50
(48) It is possible to output an image in both fields.

[0026]

According to the film image encoding apparatus and the decoding apparatus of the present invention, an image signal having a different number of images per second can be used to independently or unilaterally separate images at intervals at which the time (timing) of two images matches. In the same picture, only the encoded data of the first picture is output, and only the picture which is independent or unidirectionally decoded by the picture is output several times. By performing the above conversion, redundant images are not encoded, so that useless information does not occur and encoding efficiency is improved.

Next, in order to convert the image rate in the encoding device, it is only necessary to repeatedly output the independent or unidirectionally predicted image stored in the image memory. No image memory is required. This does not increase the scale of the decoding device.

The proportion of the picture converted by the coding apparatus to the whole picture is increased by repeating the picture of the independent or unidirectional prediction. The image quality of the independent or unidirectional prediction image is better than that of the bidirectional prediction image, so that the average image quality is improved.

Further, since 60 fields per second and 50 fields per second can be reproduced with the same encoded data, the same media can be reproduced in different TV system areas, and the media can be shared. As explained above,
The film image encoding device and the decoding device according to the present invention have extremely excellent effects in practical use.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a (film) image encoding apparatus according to the present invention.

FIG. 2 is a block diagram showing a (film) image encoding apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing an embodiment of a (film) image decoding apparatus according to the present invention.

FIG. 4 is a block diagram showing a conventional example of a film image encoding device.

FIG. 5 is a block diagram showing a conventional example of a film image decoding device.

FIG. 6 is a diagram showing how a film image is converted into a television image.

FIG. 7 is a diagram illustrating a prediction relationship of predictive coding having bidirectional prediction.

FIG. 8 is a diagram showing a configuration of an image at each image rate.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 image input, 2 interlace converter, 3 field memory, 4 predictive subtractor, 5 intra-field encoder, 6, 31 data buffer, 7 data output, 8
Image counter, 9 ... predictor, 10 ... field memory,
11 adder, 12 intra-field decoder, 13 image output, 20 image rate converter, 21, 32 data controller, 33 switch, 30 data input terminal, 34 image output, 35 ... Image order input.

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N ^7/ 24-7/68 H04N 1/41-1/419 H04N 5/253 H04N 7/01

Claims (4)

(57) [Claims] 1. An image encoding apparatus using bidirectional inter-picture prediction between image apparatuses having different image rates between a signal source image on an encoding apparatus side and a display image on a decoding apparatus side, An image coding apparatus, wherein an image is independently coded or one-way inter-picture predictive coding is performed at intervals at which image timings of a signal source image and the display image match. 2. An image decoding apparatus using bidirectional inter-picture prediction between image apparatuses having different image rates between a signal source image on an encoding apparatus side and a display image on a decoding apparatus side, An image decoding apparatus, wherein an image is independently decoded or one-way inter-picture predictive decoding is performed at intervals at which image timings of a signal source image and the display image match. 3. When encoding an image having a plurality of images having the same content, only encoded data of the first image having the same content is output, and encoded data of another image having the same content is not output. 2. The image encoding apparatus according to claim 1, wherein the control is performed in such a manner. 4. An image decoding apparatus according to claim 2, wherein only an image which has been subjected to independent decoding or one-way inter-picture predictive decoding is output a plurality of times to convert an image rate. Device.