KR20010019935A - Decorder and method for selectivly decording specific picture type video signal - Google Patents

Abstract

PURPOSE: A video decoder and a method for selectively decoding MPEG video data of a specific picture type are provided to select and output only a desired, specific picture type upon a high speed retrieval without having a circuit for discriminating a specific picture type. CONSTITUTION: A variable length decoder(300) decodes all MPEG video data regardless of their picture type in a normal refresh mode according to a picture selection signal applied from the outside, and selectively decodes a MPEG video data of a specific picture type in a high speed retrieval mode. An inverse scan(202) inverse-scans DCT coefficients of a video data outputted from the VLD(300). An inverse quantizer(204) quantizes the inverse scanned DCT coefficients of the video data. An inverse discrete cosine transform(206) performs an inverse discrete cosine transformation of the quantized DCT coefficients of the video data.

Description

Video decoder and method capable of selective decoding for specific picture type MPEG video data {DECORDER AND METHOD FOR SELECTIVLY DECORDING SPECIFIC PICTURE TYPE VIDEO SIGNAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video decoders, and more particularly, to video decoders and methods capable of selectively decoding only certain types of picture types from moving picture experts (MPEG) video data during high-speed search.

With the recent expansion of digital communication technology and the integration of high density semiconductor (VLSI) and signal processing (DSP) technology, video data, audio data and other data that have been generated and processed heterogeneously and independently in the past are used as information sources or media. It can be processed and used in a wide variety of forms without distinction. In this environment, the need for standardization of international data transmission standard for digital data transmission and sharing between different devices has emerged, and according to these needs, Joint Picture Experts Group and moving picture transmission for still picture transmission MPEG and the like have been standardized.

According to the MPEG standardization, digital video data and audio data are compressed, multiplexed and transmitted, and compressed and transmitted video and audio data are decoded. According to this provision, digital data is further compressed by Discrete Cosine Transform, Quantization, Scan, and finally by Variable Length Coding. The compressed and transmitted data is restored after undergoing a variable length decoding, inverse quantization, and inverse discrete cosine transform.

FIG. 1 is a schematic block diagram of an MPEG decoder device for decoding MPEG data input after being processed by MPEG. In general, MPEG data is composed of a hierarchical data stream such as a transport stream (TS), a packetized elementary stream (PES), and an elementary stream (ES). The ES is a stream in which video or audio is encoded and compressed. PES is a stream that separates each ES by packetizing each ES, and TS is a stream in which video PESs or audio PESs are mixed into packets of 188 byte units. A PS is also a stream of video PESs or audio PESs mixed into packets of inconsistent length. It is common for a stream to be transmitted / received in the form of PS (Program Stream) or TS between the MPEG encoder and the MPEG decoder. In this case, the PS is designed for use in a relatively error-free environment and is suitable for applications such as software processing in a multimedia application, and TS is suitable for storage or transmission in a medium that is easy to lose packets or noisy. It is designed for use in environments with the same error.

Referring now to FIG. 1, the MPEG decoder device 100 typically consists of a TS decoder 102, a video decoder 104, and an audio decoder 106 as in FIG. 1. The TS decoder 102 decodes a TS input from a digital TV receiver or a VCR and sends video PESs to the video decoder 104 and audio PESs to the audio decoder 106. Video decoder 104 then decodes and reconstructs the video PESs, and audio decoder 106 decodes and reconstructs the audio PESs.

FIG. 2 illustrates a detailed block configuration of the video decoder 104 of FIG. 1. Referring to FIG. 2, the video decoder 104 includes a variable length decorator (VLD) 200. Inverse Scan 202, Inverse Quantizer 204, Inverse Discrete Cosine Transform (IDCT) 206, Motion Compensation 208, Frame It is composed of a frame (210). The VLD 200 restores a bit stream of the input MPEG video data to an original fixed length code. The inverse scan unit 202 rearranges DCT coefficients arranged one-dimensionally through a zigzag scan or an alternative scan after undergoing a discrete cosine transform and quantization process during transmission. The inverse quantization unit 204 restores the quantized DCT coefficients to their original values. The inverse discrete cosine transforming unit 206 restores the DCT coefficients restored through inverse quantization to the original screen through inverse discrete cosine transform. The motion compensation unit 208 motion-compensates the original image restored by the inverse discrete cosine transform unit 206 and finally outputs the motion. The frame memory 210 temporarily stores a screen output from the motion compensator, which is used to restore other screens.

However, the MPEG video decoder as described above is composed of a GOP (Group Of Pictures) structure of I (Intra), B (Bidirectionally Predictive), and P (Predictive) pictures to play only the role of simply playing the input MPEG video data stream. Therefore, in order to perform high-speed search, there was a problem that a separate circuit for selecting only a specific type of picture type from the outside and applying it to the MPEG video decoder 104 must be provided.

As described above, the conventional MPEG video decoder is composed of a GOP structure of I, B, and P pictures, and merely plays a role of simply playing an input MPEG video data stream. There was a problem that a separate circuit for selecting and applying only to the MPEG decoder had to be provided.

Accordingly, an object of the present invention is to provide a video decoder and method capable of selectively decoding only a specific type of picture type among MPEG video data.

1 is a block diagram of a conventional MPEG decoder device;

FIG. 2 is a block diagram of a video decoder in the MPEG decoder of FIG. 1;

3 is a block diagram of a video decoder according to an embodiment of the present invention;

4 is an operation control flow diagram for selectively decoding only a specific picture type according to an embodiment of the present invention.

5 is a diagram illustrating a GOP configuration of MPEG video data according to an embodiment of the present invention.

The present invention for achieving the above object, in the video decoder, in the normal playback mode according to the picture selection signal applied from the outside to decode and output all the MPEG video data input regardless of the picture type, in the fast search mode VLD which selects and decodes only a specific picture type from the input MPEG video data, and an inverse scan unit which inversely scans DCT coefficients of video data output from the VLD, and inverse quantizes DCT coefficients of the inversely scanned video data. And an inverse discrete cosine transform unit for IDCT outputting the DCT coefficients of the dequantized video data.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description and in the accompanying drawings, in order to provide a more thorough understanding of the present invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

3 illustrates a detailed block configuration of a video decoder implemented to selectively perform decoding of only a specific type of picture type according to an embodiment of the present invention. Referring to FIG. 3, when the VLD 300 of the video decoder 302 according to an embodiment of the present invention decodes and outputs only a specific type of picture type for high-speed search in the video decoder 104 as described above, Unlike in the prior art, in which a separate circuit for selecting only a picture type of a specific type, that is, extracting picture-related information for each picture included in the video ES and inputting it to the video decoder 104 in advance is needed, Decodes the picture type of each picture from the video data stream input through the TS decoder 102 according to the applied picture selection signal, decodes only the picture type corresponding to the picture selection signal, and outputs the remaining picture types without decoding. Discarded. That is, since the extraction of the picture-related information is performed in the process of processing the VLD 300, as in the embodiment of the present invention, it is preferable to select only a picture type of a specific type from the VLD 300 itself. It is much more efficient by avoiding duplicate execution of.

Hereinafter, the operation of the VLD 300 according to an embodiment of the present invention will be described in more detail. First, in the case of NTSC MPEG data, the MPEG video data stream (PES) is generally composed of 2 frames per second I picture, 8 frames P picture, and 20 frames B picture. At this time, for example, the picture selection signal "1" is a high-speed search mode control signal for decoding and displaying only I pictures for high-speed search, and the picture selection signal "0" typically decodes and displays all I, B, and P pictures. If the picture selection signal "1" is applied, the VLD 300 decodes and outputs only the I picture of the input video data stream, and discards the remaining B and P pictures without decoding. do. In contrast, when the picture selection signal "0" is applied, I, B, and P pictures are decoded and output as in the normal case of the input video data stream.

4 is a flowchart illustrating an operation control for allowing only a specific type of picture type to be selected and output from the VLD 300 in the video decoder 302 according to an embodiment of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 3, 4, and 5.

First, in describing the embodiments of the present invention, for convenience of description, the MPEG video data input to the VLD 300 is inputted after the video data stream compressed and stored in the MPEG standard on the storage medium is read from the storage medium through a video reproducing apparatus such as a VCR. Assume that the data is

First, when a video data stream compressed to MPEG standard is read and applied from a storage medium in response to a playback request from a user in a normal playback mode, the VLD 300 recognizes that a video signal is input in step 400 and in step 402. Proceed to to check the logic level of the picture selection signal to check whether the current playback mode is the normal playback mode or the fast search mode.

In this case, the user sets the high speed search mode through key operation when the high speed search is required while playing and watching MPEG video data stored in the storage medium in the normal playback mode as described above. The fast search mode means a mode in which only a specific picture type is selected and reproduced from the I, B, and P pictures, unlike the normal playback mode in which all of the I, B, and P pictures are decoded and output. Since only a specific type of picture type is selected and reproduced among B and P pictures, high-speed playback is possible, and high-speed search is possible. At this time, if there is a command for setting the fast search mode by the user as described above, a picture selection signal for this is generated and applied to the VLD 300. The picture selection signal is, for example, in response to a mode setting command from the user. As a control signal applied from a microcomputer (not shown) to the VLD 300, the VLD 300 may operate according to the current operation mode.

Then, in step 402, the VLD 300 recognizes the current setting mode according to the logic state of the picture selection signal. At this time, the picture selection signal having a logic high, that is, "1" state, is searched at high speed. This is a fast search mode control signal that decodes and displays only I pictures, and a logic low, i.e., a picture selection signal having a status of "0", is a normal playback mode in which all I, B, and P pictures are decoded and displayed. If the control signal is previously set, the VLD 300 proceeds to step 404 when the logic level of the picture selection signal is "0" in step 402. Decodes the input I, B, P pictures and outputs them. Accordingly, each picture decoded from the VLD 300 undergoes a process of inverse quantization, inverse discrete cosine transform, and the like, and is then compensated for and displayed on the screen.

On the contrary, when the logic level of the picture selection signal is "1", the VLD 300 recognizes that the current operation mode is the fast search mode, and proceeds to step 406 to examine the picture type of the input video signal. As shown in FIG. 5, when an I picture type video signal is input among the picture types input, the process proceeds to step 404 to decode and reproduce the video signal. In contrast, a B and P picture type video signal is input. In this case, the process proceeds to step 408 where the video data stream is reproduced at high speed by being discarded without decoding.

As described above, the present invention has an advantage in that the video decoder can selectively output only a specific type of desired picture type without providing a separate circuit for selecting a specific type of picture type at high speed search.

Claims (2)

In a video decoder, In normal playback mode, the MPEG video data input is decoded and output regardless of the picture type in normal playback mode according to the picture selection signal applied from the outside.In the fast search mode, only a specific picture type is selected from the input MPEG video data. Variable length decoding unit to decode and output the result; An inverse scan unit for inverse scanning the discrete cosine transform coefficients of the video data output from the variable length decoding unit; An inverse quantizer for inversely quantizing the ideal cosine transform coefficients of the inversely scanned video data; And at least an inverse discrete cosine transform unit for outputting the inverse cosine transform coefficients of the inverse quantized video data by inverse discrete cosine transform. In a video decoder including at least a variable length decoding unit, an inverse scan unit, an inverse quantization unit, and an inverse discrete cosine transform unit, a selective decoding method for a specific picture type among MPEG video data, When the MPEG video data is input, checking whether the picture selection signal applied from the outside is a normal playback mode control signal or a fast search mode control signal; If the picture selection signal is a control signal for commanding normal reproduction, decoding and outputting the input MPEG video data regardless of the picture type; And when the picture selection signal is a control signal for commanding a fast search, decoding and outputting only a specific picture type of the input MPEG video data. Selective decoding method for.