JPH1141606A - Picture decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate a changeover circuit for an input signal by a conversion processing without synchronous disturbance by reading out a display of a decoded picture in a form of a sequential picture always at the highest frame rate regardless of whether an inputted picture is a jump picture or the sequential picture. SOLUTION: When a decoded picture is a sequential scanning picture, a picture quality correction part 106 does not perform processing but outputs the sequential scanning picture. Also when the decoded picture is a jump scanning picture, a fixed frame rate read control part 108 controls reading out so that the decoded picture is dealt with by the sequential scanning picture. Thus, regardless of whether an inputted picture is the jump scanning picture or the sequential scanning picture, it is displayed and read out by the sequential scanning picture at the highest frame rate. Also, even when a broadcasting of picture data of a sequential scanning system and of a sequential scanning system is switched, an output can be performed with continuity of the signal maintained and without using a changeover circuit of an input circuit and synchronous disturbance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a set-top box for receiving a digital broadcast signal obtained by multiplexing digital data such as a compressed image or program information, decoding a selected image signal, and outputting the decoded signal. The present invention relates to a decoding device.

[0002]

2. Description of the Related Art In recent years, with the development of digital technology, digital broadcasting services have been realized in which broadcasting video, audio, and data signals are integrally processed as digital signals, and broadcasting is performed using communication satellites and the like. is there. These services use MPEG2 (ISO / IEC-1381).
It is possible to provide broadcasts of tens to hundreds of channels by a compression multiplexing technique typified by, for example, (8).
On the other hand, there is a demand for high quality broadcast images in both analog and digital transmission systems for television broadcasting. In digital broadcasting, the number of scanning lines having approximately the same information amount as that of current analog broadcasting is 525, and the frame rate is high. The transmission of image data of the 60 Hz interlaced scanning method is general (hereinafter referred to as the 525I method), but the number of scanning lines having about twice the amount of information in the original image is 525 lines, and the progressive scanning method with a frame rate of 60 Hz. (Hereinafter referred to as the 525P system) has been studied. FIG. 2 shows an example of a conventional image decoding apparatus, and its operation will be described below.

In FIG. 2, reference numeral 100 denotes a header analyzer, 10
Reference numeral 1 denotes an image decoding unit, and reference numeral 102 denotes a reference frame memory. Reference numeral 103 denotes a display buffer, usually a dual-port memory or the like. Reference numeral 104 denotes an input frame rate dependent read control unit for controlling reading of the display buffer based on the frame rate of the input image, and 105 denotes a control timing signal generation unit used in each processing unit.
In this conventional example, the input signal is a bit stream signal encoded by MPEG2 or the like.

[0006] The input bit stream is input to a header analysis unit 100 and an image decoding unit 101. The header analysis unit 100 performs decoding of image data such as encoding mode information for identifying whether the compressed image data is obtained by encoding a progressive scan image or an interlaced scan image, and frame rate information representing a display cycle of the image. Necessary various header information is extracted and notified to the image decoding unit 101 and the control timing signal generation unit 105. The image decoding unit 101 decodes the image data according to the timing signal from the control timing signal generation unit 105 and the encoding method of each image while referring to the reference frame memory 102 when a reference image is required. The decoded data is stored in the display buffer 1
03, and is read out and output from the input rate-dependent read control unit 104 at a timing synchronized with the display output timing based on the frame rate of the input coded image.

If the decoded data is an image to be referred to in the subsequent image decoding, the reference frame memory 1
02 is also recorded. At this time, if the input bit stream is obtained by encoding a video of the 525I system, the decoding and display output processing are performed by the interlaced scanning system at 525 scanning lines and a frame rate of 60 Hz, and output. In the case of the 525P system, decoding and display output processing are performed and output in a sequential scanning system at 525 scanning lines and a frame rate of 60 Hz. In other words, the conventional image decoding device outputs the input coded image data in an output form corresponding to the state of the original image of the input coded image data, ie, interlaced scanning or sequential scanning.

[0006]

As described above, in the conventional image decoding apparatus, the image data is output in a form corresponding to the state of the original image of the input coded image data, and is now widely used. When watching and recording digital broadcasts simultaneously on a television receiver or VTR,
In a television receiver, input terminals are different between a progressive scan image and an interlaced scan image, and 525 is used for a continuous broadcast.
When switching between P and 525I, there is an undesirable state for the viewer, such as switching of input terminals and switching of display synchronization processing. In addition, images of the progressive scanning method are recorded on the VTR at the same time as viewing and listening, and the progressively scanned images remain 525I output is always required for television receivers that cannot be viewed in
Means for converting to 525I format at the time of 525P;
There is another problem that switching means for switching between the decoded output at the time and the output of the converting means is separately required, which leads to an increase in the circuit scale.

[0007]

In order to solve the above-mentioned problems, an image decoding apparatus according to the present invention always provides a decoded image having the highest frame rate regardless of whether an input image is a skipped image or a sequential image. 525P.
And 525I can be output without deteriorating the synchronization quality even when the mode is switched, and there is no need for a means for switching between the 525I conversion output at the time of 525P and the 525I output at the time of 525I as described above.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image decoding apparatus according to a first aspect of the present invention encodes data obtained by encoding a progressively scanned image by frame encoding or encoding of an interlaced scanned image by frame encoding or field encoding. An image decoding device for decoding data, at least encoding mode information for identifying progressive scanning or interlaced scanning, frame rate information representing a display cycle of an encoded image, and the encoded data. A multiplexed bit stream is input, and coding information obtaining means for obtaining coding mode information and frame rate information from the bit stream, based on coding mode information and frame rate information obtained from the coding information obtaining means, Decoding means for decoding the encoded data, and storing the decoded image data Output buffer means, and display control means for always reading out image data decoded by the output buffer means at the highest frame rate defined by the frame rate information and in a sequential scanning mode during display. It is assumed that.

[0009] Regardless of whether the decoded image is a skipped image or a sequential image, the image is always output in the form of a sequential image, so that even if 525P and 525I are switched, it is possible to output without deteriorating the synchronization quality. Yes, 5 more
There is no need for a means for switching between the 525I conversion output at the time of 25P and the 525I output at the time of 525I.

According to a second aspect of the present invention, there is provided an image decoding apparatus, wherein the display control means in the first aspect converts the sequentially scanned image data read from the output buffer means into an interlaced scanned image. And sequentially outputting the sequentially scanned image data read from the output buffer means and the interlaced scanned image data from the scan conversion means. Regardless of whether the decoded image is an interlaced image or a sequential image, the image is always output in the form of a sequential image, and is converted from the sequential image to the interlaced image so that the synchronization quality is maintained even when 525P and 525I are switched. It is possible to output two types of images.

An embodiment of an image decoding apparatus according to the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIG. 1, a header analysis unit 100, an image decoding unit 101, a reference frame memory 102, a display buffer 103, and a control timing signal generation unit 105 have the same configuration as the conventional example. , 106 are image quality correction units, and 107 is an interlaced scan conversion unit.
Reference numeral 108 denotes a fixed frame rate readout control unit which reads out the data of the display buffer 103 at the highest frame rate of the input image and in the sequential scanning method. For example, in this embodiment, the data is read out at 525P. The operation of the embodiment configured as described above will be described focusing on parts different from the conventional example.

The operation up to the writing to the display buffer 103 is the same as that of the conventional example. The fixed frame rate read control unit 108 always reads the data of the display buffer 103 at 525P regardless of the frame rate or the scanning method of the decoded image. If the decoded image is 52
If the image is a 5P progressively scanned image, the image quality correcting unit 106 outputs the sequentially scanned image without performing any processing. In the interlaced scan converter 107, a method of thinning out the image information from the 525P signal and outputting it is common, but it may be output after performing a filtering process or the like to make the image quality degradation less noticeable.

On the other hand, if the decoded image is an interlaced scan image such as 525I, the fixed frame rate read control unit 108 controls reading so that the decoded images are sequentially treated as images. As a reading method at this time, a method of reading out data within one horizontal period of the decoded image twice at a double speed, or a method of recording data of two consecutive fields in the display buffer 103, and
A method of alternately reading out two consecutive field data in each horizontal period, or recording one field of data in the display buffer 103 and synchronizing the decoding process of the image decoding unit 101 with the display readout, While reading the data from the memory 103 and storing the decoded data, the field data from the display buffer 103 and the decoded field data from the image
A method of alternately reading data every horizontal period is conceivable.

The data read from the display buffer 103 in the progressive scanning method (at a rate of 525 P in this embodiment) is thinned out in the interlaced scanning unit 107 using a line memory or the like so as to obtain an original interlaced scanned image. Output as an interlaced scan image. The image quality correction unit 106 may output the image as it is if the adverse effect on the image quality such as aliasing is ignored, and the processing of the interpolation line inserted for the sequential scanning includes interpolation filtering of the upper and lower lines, In the case of pursuing image quality, it is also possible to further have a frame memory, perform motion detection, perform adaptive line interpolation processing, and output the result.

According to the above embodiment, 52
Even when 5P and 525I broadcasts are switched, it is possible to simultaneously perform sequential scan output and interlaced scan output while maintaining signal continuity. Further, even at the time of switching, only processing is added, and the image quality correction unit 106
A switching circuit for switching the input signal to the interlaced scanning unit conversion unit 107 is not required.

[0017]

As described above, according to the image decoding apparatus of the present invention, the input coded image has the interlaced scan image,
Even in the case of a progressive scan image or when switching from one to the other, there is no synchronization disturbance, and it is possible to simultaneously output a progressive scan image and an interlaced scan image without the need for a circuit for switching input signals in scan conversion processing. Has an effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an image decoding apparatus according to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating an example of a conventional image decoding apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 header analysis unit 101 image decoding unit 102 reference frame memory 103 display buffer 104 input frame rate dependent read control unit 105 control timing signal generation unit 106 image quality correction unit 107 interlaced scan conversion unit 108 fixed frame rate read control unit

Claims (4)

[Claims] An image decoding apparatus for decoding data obtained by encoding a progressively scanned image by frame encoding or data obtained by encoding an interlaced scanned image by frame encoding or field encoding. An input is a bit stream obtained by multiplexing encoding mode information for identifying interlaced scanning, frame rate information indicating a display period of an encoded image, and the encoded data, and the encoding mode information and the frame rate. Coding information obtaining means for obtaining information; decoding means for decoding the coded data based on coding mode information and frame rate information obtained from the coding information obtaining means; and Output buffer means for storing the decoded image data, and image data decoded by the output buffer means. Display control means for reading data at the highest frame rate defined by the frame rate information and in a progressive scanning manner. 2. A display control means comprising: scan conversion means for converting progressively scanned image data read from an output buffer means into an interlaced scan image, wherein the sequentially scanned image data read from the output buffer means and the scan conversion means. 2. The image decoding apparatus according to claim 1, wherein the interlaced scanning image data is output simultaneously. 3. When a field image is decoded by a decoding means, an output buffer means stores at least two field images, and outputs two consecutive field images from the output buffer means. 3. The image decoding apparatus according to claim 1, wherein the image is read out by a sequential scanning method as a frame image. 4. An output buffer means for storing at least one field image when a field image is decoded by a decoding means, wherein the field image read from the output buffer means and the decoding 3. The image decoding apparatus according to claim 1, wherein the field image decoded by the means is read out as a frame image by a sequential scanning method.