KR100522121B1 - MPEG encoder to limit DCT coefficient according to buffer status - Google Patents

Abstract

The present disclosure relates to an MPEG encoder that limits the DCT coefficient according to the buffer state by observing the state of the buffer and selecting and encoding a region of the DCT coefficient to be variably discarded according to the state of the buffer. The apparatus of the present invention comprises a DCT for discrete cosine transforming the data in the time domain into the data in the frequency domain, a selection mode decision logic for determining the selection mode according to the fullness signal and the external selection signal of the buffer and outputting a coefficient processing signal; A coefficient processing logic that receives the signal converted from the DCT and determines the area of the coefficient to be discarded according to the selected mode from the selection mode decision logic, and outputs the coefficient processing logic to quantize the signal processed from the coefficient processing logic; And a VLC that receives the quantized signal from the quantizer and variably encodes it, and a buffer that stores the signal encoded by the VLC and outputs the fullness of bits to the selection mode decision logic. Accordingly, the present invention provides an effect of improving data quality of a decoded image by coding data more efficiently according to a buffer state.

Description

MP encoder that limits the DCT coefficient according to the buffer status

The present invention relates to an MPEG encoder. More specifically, the present invention relates to an MPEG encoder that monitors the state of a buffer and selects and encodes a region of the DCT coefficient to be variably discarded according to the state of the buffer. It is about.

In digital satellite broadcasting, digital cable TV, and high-definition TV, which are gaining attention all over the world recently, MPEG (compression / extension) algorithm that encodes and transmits video and audio signals into digital signals or records them on a medium, decodes them, and plays them back. Moving Picture Expert Group) is being adopted.

Most picture coding standards, including H.263 of the ITU, perform motion estimation and discrete cosine transform (DCT). These transform coefficients are quantized, and the quantized coefficients are subjected to variable length coding (VLC) to obtain final encoded image data. The encoded image data is once stored in a buffer, multiplexed with the encoded audio data and other data, and transmitted at a constant bit rate through a limited capacity transmission channel. However, if the value of the quantized discrete cosine transform coefficient is not 0, all of them are variable length coded and stored in the buffer. That is, it is variable-length coded regardless of the buffer's fullness.

However, in the above characteristics adjustment, even if the quantization interval that increases in proportion to the buffer's fullness has a relatively large value, if there is a coefficient in the high frequency region having a large value in the discrete cosine transform region, the coefficients are quantized. Is coded without being ignored. In general, in variable-length coding, many of these coefficients are allocated, so when the coefficients are high in the buffer fullness, the buffer fullness does not decrease as intended and is decoded due to the relatively large quantization interval. There was a problem that the state of the image quality is poor.

Accordingly, an object of the present invention is to reduce the number of bits allocated by discarding the coefficient of the high frequency component to the discrete cosine transform coefficient when the buffer is high in accordance with the state of the buffer to solve the above-described problem, thereby quantizing The present invention provides an MPEG encoder that restricts the DCT coefficient according to the buffer state to improve the image quality by reducing the interval, thereby coding a coefficient belonging to a relatively low frequency region.

In order to achieve the above object, the MPEG encoder restricting the DCT coefficient according to the buffer state according to the present invention includes a DCT for discrete cosine transforming the data in the time domain into the data in the frequency domain, the buffer fullness signal and the external selection signal. A selection mode decision logic for determining a selection mode and outputting a coefficient processing signal, and a region of coefficients to be discarded according to a mode selected from the selection mode decision logic by receiving a signal converted from the DCT to remove coefficients and output the coefficients. A coefficient processing logic, a quantizer for quantizing a signal processed from the coefficient processing logic, a VLC for variably encoding the quantized signal from the quantizer, and a signal encoded in the VLC, and storing the fullness of the bit. Contains a buffer that outputs to the selection mode decision logic.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an MPEG encoder according to an embodiment of the present invention. As shown, the apparatus of the present invention receives a selection mode decision logic 10 that receives a selection signal from the outside and a fullness signal of a buffer and outputs a counting signal, and a discrete cosine transform by receiving an image signal and a motion compensation signal. It includes a DCT (20). A coefficient processing logic 30 is connected to an output terminal of the selection mode decision logic 10 and the DCT 20, and an output terminal of the coefficient processing logic 30 receives data and processes coefficients to quantize the quantizer 40. ) Is connected. Also, the VLC 50 is connected to the quantizer 40 so that the encoded data is stored in the buffer 60 after being variably encoded.

The operation of the MPEG encoder for limiting the DCT coefficient according to the buffer state according to the present invention configured as described above will be described in detail.

The DCT 20 shown in FIG. 1 performs discrete cosine transform on a block basis as shown in FIG. 3, and one block has a size of 8 × 8, and the result of the discrete cosine transform is the DCT 20. It has an effect that energy is gathered in the vicinity of the low frequency component (bright part of FIG. 3) by the energy packing property of. In particular, the image signal is excellent in this effect in nature. The signal input to the DCT 20 is in the form of an intra or inter block. Here, the signal of the intrablock is an input video signal, and the interblock is a signal obtained by subtracting the input video signal and the motion compensated signal. The DCT 20 performs discrete cosine transforming the data in the time domain into the data in the frequency domain through a predetermined process as described above. The discrete cosine transformed DCT 20 output signal is input to the coefficient processing logic 30, and the coefficient processing logic 30 receives the coefficient processing signal from the selection mode decision logic 10 to count coefficients of the area to be discarded (FIG. 3). Remove the dark part). The selection mode decision logic 10 receives a function selection signal, a unit selection signal, and the like from the outside, and a buffer fullness signal from the buffer 60. Here, a function selection signal, a macroblock, a slice, and a picture for selecting one of the functions of the linear case of FIG. 2A or the non-linear function of FIG. 2B. : When the unit selection signal for selecting one of I (Intra), P (Predictive), and B (Bidirectional) picture is input from the outside to the selection mode decision logic 10, the selection mode decision logic 10 is set to the mode. By selecting the to determine the area of the DCT coefficients to be discarded, which will be described below with reference to FIGS. The selection mode decision logic 10 selects the case of M ₁ of FIG. 3A, the case of M ₂ of FIG. 3B, and the case of M ₃ of FIG. 3C, and outputs the coefficient processing signal to the coefficient processing logic 30. The coefficient processing logic 30 processes the coefficients by removing coefficients of the DCT coefficient region (dark portion of FIG. 3) to be received from the selection mode decision logic 10 and outputs them to the quantizer 40. do. The quantizer 40 quantizes the discrete cosine transformed input coefficient signal and outputs the quantized signal to the VLC 50. Quantized data through the quantizer 40 is input to the VLC 50 for high efficiency of incubation. The VLC 50 allocates and encodes a small number of bits when the output level is high according to the frequency of appearance of the input signal. The VLC 50 allocates and encodes a large number of bits when the output level is low. The buffer 60 stores the encoded video signal and continuously outputs the fullness of the buffer 60 to the selection mode decision logic 10.

2A and 2B are graphs showing embodiments of the coefficient determination range designation mode according to the buffer fullness of the apparatus of FIG. 1, and FIGS. 3A, 3B and 3C are examples of the DCT coefficient region to be discarded according to the designation mode of FIG. It is a figure which shows an example.

As shown in Figs. 2 and 3, as the fullness of the buffer increases, the area where the coefficients are discarded (dark part of Fig. 3) becomes wider. FIG. 2A is a linear function, and FIG. 2B is a nonlinear function, which is selected from the outside. In Figs. 2A and 2B, B is the size of the buffer and the selection mode M ₃ is selected if the fullness of the bit buffer is between N ₂ and N ₃ . An example of M ₃ is shown in FIG. 3C, where the darker portion of M ₃ is the area to be discarded. As the area to be discarded becomes wider, the number of coefficients that are coded decreases so that the number of allocated bits decreases, thereby reducing the fullness of the buffer. As the fullness of the buffer decreases, the quantization interval that increases and decreases in proportion to the fullness of the buffer decreases, so that the coefficients corresponding to the low frequency region (bright part of FIG. 3) are more precisely quantized. As shown in Fig. 2, if the fullness of the buffer 60 is _{equal to} or less than N ₀ , which is an arbitrary state, there is no area to be discarded. In other words, if the buffer state is sufficient enough, all coefficients are coded.

As described above, the present invention provides an effect of improving data quality of a decoded image by coding data more efficiently according to a buffer state.

1 is a block diagram of an MPEG encoder according to an embodiment of the present invention;

2A and 2B are graphs showing an embodiment of each of the coefficient determination range designation mode according to the buffer fullness of the apparatus of FIG. 1;

3A, 3B and 3C illustrate an embodiment of a DCT coefficient region to be discarded according to the designation mode of FIG.

※ Explanation of code for main part of drawing

10: Selection mode decision logic 20: DCT (Discrete Cosine Transform)

30: coefficient processing logic 40: quantizer

50: Variable Length Coding (VLC) 60: Buffer

Claims (5)

In the MPEG encoder, DCT for discrete cosine transforming data in the time domain into data in the frequency domain; A selection mode decision logic which receives a fullness signal of a buffer, an external function selection signal, and a unit selection signal to determine a selection mode and output a coefficient processing signal; A coefficient processing logic that receives the signal converted from the DCT, determines a region of coefficients to be discarded according to the mode selected by the selection mode decision logic, and removes and outputs the coefficients; A quantizer for quantizing the signal processed from the coefficient processing logic; A VLC variable-encoded by receiving the quantized signal from the quantizer; And An MPEG encoder storing a signal encoded by the VLC and limiting a DCT coefficient according to a buffer state, the buffer including a buffer for outputting the fullness of bits to the selection mode decision logic; The method of claim 1, wherein the DCT is An MPEG encoder for limiting a DCT coefficient according to a buffer state, which is applied to both an intrablock type signal and an interblock type signal. The method of claim 1, wherein the function selection signal is a signal for selecting one of a function in the case of linear and a function in the case of non-linear. And a linear encoder which linearly or nonlinearly selects a coefficient determination range designation mode to be discarded according to the fullness of the buffer in the selection mode decision logic. The method of claim 1, wherein the unit selection signal is MPEG encoder for limiting the DCT coefficient according to the buffer state, characterized in that the signal for selecting one of the macroblock, slice and picture unit. The method of claim 4, wherein the picture unit of the unit selection signal is MPEG encoder for limiting the DCT coefficient according to the buffer state, characterized in that it comprises at least one of three, I picture, P picture and B picture.

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