This application claims the benefit of Taiwan application Serial No. 103141964, filed Dec. 3, 2014, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates in general to a frequency deinterleaving and time deinterleaving circuit, a method thereof and a receiving circuit of a digital television, and more particularly to a frequency deinterleaving and time deinterleaving circuit, a method thereof and a receiving circuit that can be configured to support multiple digital video standards. 
     Description of the Related Art 
     There have been numerous digital television standards, including Digital Video Broadcasting-Terrestrial (DVB-T), Digital Video Broadcasting-Cable2 (DVB-C2), Digital Video Broadcasting-Terrestrial 2 (DVB-T2), Digital Terrestrial Multimedia Broadcast (DTMB), and Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). These different standards are broadcasted and promoted respectively in different regions. Among these standards, DVB-C2, DVB-T2, DTMB and ISDB-T adopt interleaving-deinterleaving schemes in frequency and time domains to minimize various interferences and/or noises have on transmission data during signal transmission.  FIG. 1  shows a function block diagram of a conventional receiver of a digital television. The receiver  100  of a digital television mainly includes a front-end circuit  110 , a frequency deinterleaving circuit  120 , a time deinterleaving circuit  130 , a demapping circuit  140 , and a decoding circuit  150 . An input signal is usually a modulated signal, e.g., a quadrature amplitude modulation (QAM) signal based on orthogonal frequency division multiplexing (OFDM). The front-end circuit  110  performs operations including but not limiting to fast Fourier transform (FFT), channel estimation, equalization and signal-to-noise (SNR) estimation on the input signal, and outputs an interleaved signal that carries including but not limiting to information such as two quadrature components (I and Q), an SNR, or channel state information (CSI). The information is rearranged in a correct sequence after the frequency deinterleaving circuit  120  and the time deinterleaving circuit  130  perform deinterleaving operations, and is restored to bit information after an operation performed by the demapping circuit  140 . Next, the transmission data is obtained after an operation (e.g., low-density parity check (LDPC) or Viterbi decoding operation) performed by the decoding circuit  150 . It should be noted that, the above DVB-T2 standard further includes a cell interleaving and deinterleaving operation. Therefore, a cell deinterleaving circuit is further included in a DTB-T2-compatible receiver. 
     The time interleaving and deinterleaving operations mainly involve two operation concepts—convolution and row-column operations. The ISDB-T standard and the DTMB standard adopt the convolution operation, and the DVB-T2 standard and the DVB-C2 standard adopt the row-column operation. Further, the frequency interleaving and deinterleaving operations also involve two main operation concepts—look-up table (LUT) and permutation operations. The ISDB-T standard adopts the look-up table operation, and the DTMB, DVB-T2 and DVB-C2 standards adopt the permutation operation. For both frequency deinterleaving and time deinterleaving, a memory (e.g., a static random access memory (SRAM) or a first-in-first-out (FIFO) memory) is provided for temporary data storage. By writing the information into and reading the information from the memory, the sequence of the information is restored. However, implementation details may slightly vary although the same operation concept is adopted. For example, the DVB-T2 standard and the DVB-C2 standard both adopt the row-column operation concept for time interleaving and deinterleaving, the DVB-C2 standard adopts specifically a twisted row-column operation concept. In conclusion, the receiver  100  of different standards requires a memory to implement frequency and time deinterleaving operations for one of different standards. For a receiver  100  compatible to multiple standards, memory devices may be configured inefficiently if each of these standards utilizes an separate circuit for frequency deinterleaving and time deinterleaving. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a frequency deinterleaving and time deinterleaving circuit, a method thereof, and a receiving circuit of a digital television that can be configured to support multiple digital video standards and to save memory utilization. 
     The present invention discloses a frequency deinterleaving and time deinterleaving circuit. The circuit performs a frequency deinterleaving operation and a time deinterleaving operation on an interleaved signal by using a first memory and a second memory, and is adapted for multiple digital video standards. The circuit includes: a frequency deinterleaving control module, configured to generate a first access index according to a setting value; a time deinterleaving control module, configured to generate a second access index according to the setting value; a first address generating unit, configured to generate a first access address according to the first access index; and a second address generating unit, configured to generate a second access address according to the second access index. The setting value corresponds to a digital video standard of the interleaved signal. The first memory is accessed for temporary data of the frequency deinterleaving operation according to the first access address. The second memory is accessed for temporary data of the time deinterleaving operation according to the second access address. 
     The present invention further discloses a receiving circuit of a digital television for processing a digital television signal to generate transmission data. The receiving circuit includes: a front-end circuit, configured to process the digital television signal to generate an interleaved signal; a setting unit, configured to provide a setting value associated with a digital video standard of the digital television signal; a frequency deinterleaving and time deinterleaving circuit, configured to select a frequency deinterleaving operation and a time deinterleaving operation corresponding to different digital video standards according to the setting value, and to process the interleaved signal to generate a deinterleaved signal; a quadrature amplitude modulation (QAM) demapping circuit, configured to demap the deinterleaved signal to generate a demapped signal; and a decoder, configured to decode the demapped signal to generate the transmission data. 
     The present invention further discloses a frequency deinterleaving and time deinterleaving method adapted for multiple digital video standards. The method, which performs a frequency deinterleaving operation and a time deinterleaving operation on an interleaved signal by using a first memory and a second memory, includes: generating a first access index according to a setting value; generating a first access address according to the first access index; accessing the interleaved signal in the first memory according to the first access address to complete the frequency deinterleaving operation; generating a second access index according to the setting value; generating a second access address according to the second access index; and storing accessing the interleaved signal having undergone the frequency deinterleaving operation in the second memory according to the second access address to complete the time deinterleaving operation. The setting value corresponds to a digital video standard of the interleaved signal. 
     The frequency deinterleaving and time deinterleaving circuit, the method thereof, and the receiving circuit of a digital television of the present invention are capable of being configured to support multiple video standards and complete the frequency deinterleaving operation or the time deinterleaving operation through a shared memory, thereby saving circuit costs. 
     The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a function block diagram of a conventional receiver of a digital television; 
         FIG. 2  is a function block diagram of a receiver of a digital television of the present invention; 
         FIG. 3  is a detailed function block diagram of a frequency deinterleaving and time deinterleaving circuit  220  of the present invention; 
         FIG. 4A  and  FIG. 4B  are diagrams of a memory configuration and a memory accessing sequence when a row-column operation unit  384  performs a row-column operation on a DVB-C2 signal, respectively; 
         FIG. 5  is a function block diagram of a QAM demapping circuit  240  according to an embodiment of the present invention; 
         FIG. 6  is a function block diagram of a decoding circuit  260  according to an embodiment of the present invention; 
         FIG. 7  is a flowchart of a frequency deinterleaving and time deinterleaving method according to an embodiment of the present invention; and 
         FIG. 8  is a flowchart of generating a second writing index and a second reading index by a convolution operation method. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention discloses a frequency deinterleaving and time deinterleaving circuit, a method thereof and a receiving circuit of a digital television capable of saving memory utilization. The circuit and method may be applied to a digital television that supports multiple digital video standards. Within the realms of implementation possibility, one person skilled in the art can realize the present invention by equivalent elements or steps based on the disclosure of the present invention; that is, the implantation is not limited by the following non-limiting embodiments. 
       FIG. 2  shows a function block diagram of a receiver  200  of a digital television of the present invention. The receiver  200  includes a front-end circuit  210  that processes digital television signals. In general, digital television signals in the DTMB, DVB-C2, DVB-T2, ISDB-T and DVB-T standards need to undergo FFT, channel estimation, equalization and SNR estimation processes. Thus, in the front-end circuit  210 , one same set of FFT circuit, channel estimation circuit, equalization and SNR estimation circuit may be utilized to process these digital television signals of different standards. Alternatively, the front-end circuit  210  may include multiple sets of the above circuits, and select one of these sets of circuits corresponding to the digital television signal according to a setting value provided by a setting unit  205 . For signals of the four standards of DTMB, DVB-C2, DVB-T2 and ISDB-T, the digital television signal is processed by the front-end circuit  210  to generate an interleaved signal, which the interleaved signal has at least undergone frequency interleaving and time interleaving at a transmitter. For the DVB-T2 standard, the interleaved signal has further undergone cell-interleaving. The above setting value may be predetermined by user scenario of the receiver  200 . For example, for the receiver  200  of a digital television applied in region that adopts the ISDB-T standard, the setting value is set to a code associated with the ISDB-T standard. For example, the setting unit  205  may be implemented by a register. 
     The interleaved signal is inputted into a frequency deinterleaving and time deinterleaving circuit  220 . According to the setting value provided by the setting unit  205 , the frequency deinterleaving and time deinterleaving circuit  220  selects a frequency deinterleaving scheme and a time deinterleaving scheme corresponding to the standard of the digital television signal received by the receiver  200 .  FIG. 3  shows a detailed function block diagram of the frequency deinterleaving and time deinterleaving circuit  220  of the present invention. The frequency deinterleaving and time deinterleaving circuit  220  includes a frequency deinterleaving memory  310 , a time deinterleaving memory  320 , a first address generator  410 , a second address generator  420 , a frequency deinterleaving control module  370 , and a time deinterleaving control module  380 . The first address generator  410  includes a reading address generating unit  330  and a writing address generating unit  340 . The second address generator  420  includes a reading address generating unit  350  and a writing address generating unit  360 . The frequency deinterleaving control module  370  includes a look-up table (LUT) operation unit  372  and a permutation operation unit  374 . The time deinterleaving control module  380  includes a convolution operation unit  382  and a row-column operation unit  384 . The frequency deinterleaving control module  370  generates a first access index according to the setting value provided by the setting unit  205  to control the first address generator  410  to accordingly generate a first access address. The first access index includes a reading index and a writing index for controlling the first address generator  410 . The first access address includes a reading address and a writing address for accessing the frequency deinterleaving memory  310 . The time deinterleaving control module  380  generates a second access index to control the second address generator  420  to accordingly generate a second access address. The second access index includes a reading index and a writing index for controlling the second address generator  420 . The second access address includes a reading address and a writing address for accessing the time deinterleaving memory  320 . The frequency deinterleaving memory  310  is accessed for the temporary data of the frequency deinterleaving operation according to the first access address, and the time deinterleaving memory  320  is accessed for the temporary data of the time deinterleaving operation according to the second access address. More specifically, according to the reading index and the writing index generated by the deinterleaving control module  370 , the reading address generating unit  330  and the writing address generating unit  340  generate the actual reading address and writing address of the frequency deinterleaving memory  310 , respectively. Similarly, according to the reading index and the writing index generated by the time deinterleaving control module  380 , the reading address generating unit  350  and the writing address generating unit  360  generate the actual reading address and writing address of the time deinterleaving memory  320 , respectively. The frequency deinterleaving control module  370  selects the LUT operation unit  372  or the permutation operation unit  374  according to the setting value to perform the frequency deinterleaving operation. Similarly, the time deinterleaving control module  380  also selects the convolution operation unit  382  or the row-column operation unit  384  according to the setting value to perform the time deinterleaving operation. It should be noted that, in the present invention, the term “access” is associated with reading data from a memory and/or writing data to a memory, and is not limited as an operation of simultaneously storing and writing data to/from a same memory. 
     With the collaboration of the reading address generating unit  330  and the writing address generating unit  340 , the frequency deinterleaving control module  370  writes and reads the data of the interleaved signal to/from the frequency deinterleaving memory  310  to complete the frequency deinterleaving operation. For example, when the setting value indicates that the interleaved signal is the ISDB-T standard, the frequency deinterleaving control module  370  selects the LUT operation unit  372  to generate the reading index and the writing index, and the LUT operation unit  372  generates the reading index and the writing index by an LUT scheme. When the setting value indicates that the interleaved signal is one of the DTMB, DVB-T2 and DVB-C2 standards, the frequency deinterleaving control module  370  selects the permutation operation unit  374  to generate the reading index and the writing index, and the permutation operation unit  374  generates the reading index and the writing index according to a frequency deinterleaving rule defined by the standard. Details of frequency interleaving and deinterleaving based on an LUT operation (corresponding to the ISDB-T standard) and frequency interleaving and deinterleaving based on a permutation operation (corresponding to the DTMB, DVB-T2 and DVB-C2 standards) are specified in the respective standards and are generally known to one person skilled in the art, and operation details of the LUT operation unit  372  and the permutation operation unit  374  shall be omitted herein. In conclusion, the frequency deinterleaving control module  370  is capable of determining the frequency deinterleaving scheme to be used according to the signal standard indicated by the setting value. The reading index and the writing index accordingly generated are then converted to a reading address and a writing address by the reading address generating unit  330  and the writing address generating unit  340 , respectively. Therefore, the frequency deinterleaving memory  310  may be shared by signals of different standards to complete the frequency deinterleaving operation, and four frequency deinterleaving memories of conventional receivers corresponding to four signal standards can be simplified into one single frequency deinterleaving memory, thereby significantly reducing the memory utilization requirement. 
     With the collaboration of the reading address generating unit  350  and the writing address generating unit  360 , the time deinterleaving control module  380  writes and reads data of the interleaved signal to/from the time deinterleaving memory  320  to complete the time deinterleaving operation. For example, when the setting value indicates that the interleaved signal is the ISDB-T or DTMB standard, the time deinterleaving control module  380  selects the convolution operation unit to generate the reading index and the writing index. When the setting value indicates that the interleaved signal is the DVB-T2 or DVB-C2 standard, the time deinterleaving control module  380  selects the row-column operation unit  384  to generate the reading index and the writing index. Details of the convolution operation unit  382  and the row-column operation unit  384  for generating the reading index and the writing index are given below. 
     Assume that the convolution operation unit  382  is currently processing an i th  carrier of a j th  OFDM symbol of the interleaved signal. 
     In step 1, a branch parameter b is set. For the ISDB-T standard, the branch parameter b=i; for the DTMB standard, the branch parameter b=mod(i, 52). 
     In step 2, a delay buffer depth L b * is calculated. For the ISDB-T standard, the delay buffer depth L b *=1×(95−mod(b×5.96)), where I=0, 1, 2, 4, 8, 16; for the DTMB standard, the delay buffer depth L b *=M×(52−b), where M=240 or 720. 
     In step 3, a buffer index c b,j * is updated. The buffer index of the b th  branch of the j th  OFDM symbol c b,j *=mod(c b,j-1 *|1,L b *), where c b,-1 * is 0. 
     In step 4, a reading index rptr=c b,j *+Σ m=0   b-1 L m * is generated. The reading address generating unit  350  generates the reading address of the time deinterleaving memory  320  according to this reading index, and the data at this address is read out. 
     In step 5, a writing index wptr-rptr is generated. That is, the writing index is made to be equal to the reading index. The writing address generating unit  360  generates the writing address of the time deinterleaving memory  320  according to this writing index, and a next set of data of the frequency deinterleaved signal is written to this address. 
     In step 6, the value i is increased (i.e., a next carrier is to be processed), and step 1 is iterated. 
     In step 7, when all the carriers of the current symbol have been processed, the value j is increased (i.e., a next symbol is to be processed) until all symbols have been processed. By sequencing the index as well as reading old data and writing new on the same index, the memory is accessed in the manner to simulate the delay buffer adopted by the convolution operation. 
     The row-column operation unit  384  performs the time deinterleaving operation by a unit of one TI block. Each TI block includes an N FEC  number of forward error correction (FEC) blocks, each of which includes an N cell  number of cells. In the row-column operation scheme, an amount of Nr rows×Nc columns in the time deinterleaving memory  320  is used, where Nr is N cell /5 and Nc is N FEC ×5. Initially, the row-column operation unit  384  generates the writing index to write the frequency deinterleaved signal to the time deinterleaving memory  320 . A process of generating the writing index of the i th  cell is as follows. 
     In step 1, a column index C i  is generated. In the DVB-T, DVB-T2 and DVB-C2 standards, the column index C i =mod(i,N c ). 
     In step 2, a row index R i  is generated. In the DVB-T, DVB-T2 and DVB-C2 standards, the row index R i =i divN c . 
     In step 3, the current cell of data is checked whether a data part. Due to differences of the DVB-C2 standard from the DVB-T2 and DVB-T standards, in addition to the data part of the signal, a pilot part is also carried in the frequency deinterleaving and time deinterleaving circuit  220 , but the pilot part should not be rearrange din the time deinterleaving operation. Thus, for the DVB-C2 standard, if the row-column operation unit  384  determines that the current cell is not a data part, a writing operation is not performed. A writing operation is performed when the corresponding cell belongs to a data part. However, for operation a signal of the DVB-T2 and DVB-T standards, one writing index is generated for each cell. 
     In step 4, the value of i is increased (i.e., the next cell is to be processed), and step 1 is iterated until all cells of the TI block have been processed, a next block is to be processed. 
     When the column index C i  and the row index R i  have been generated, the writing address generating unit  360  accordingly generates the writing address, and the cell is written into the time deinterleaving memory  320  according to the writing address. When the data of the entire TI block (excluding the pilot part) is written into the time deinterleaving memory  320 , the row-column operation unit  384  generates the reading index for reading the frequency deinterleaved signal from the time deinterleaving memory  320  to complete the time deinterleaving operation. A process of generating the reading index of the i th  cell is as follows. 
     In step 1, a column index C i  is generated. The column index of the DVB-T standard is C i =mod(i,N c ), the column index of the DVB-T2 standard is C i −i divN r , and the column index of the DVB-C2 standard is C i −mod(i,N c ). 
     In step 2, a row index R i  is generated. The row index of the DVB-T standard is R i =i divN c , the row index of the DVB-T2 standard is R i =mod(i,N r ), and the row index of the DVB-C2 standard is R i =mod(C i ,N r )+(i divN c ),N r ). 
     In step 3, the value of i is increased (i.e., a next cell is to be processed), and step 1 is iterated until all cells have been processed, a next block is to be processed. 
     When the column index C i  and the row index R i  have been generated, the reading address generating unit  350  accordingly generates the reading address. By reading the data according to this reading sequence from the time deinterleaving memory  320 , the time deinterleaved signal can be obtained. In step 2 above, as the row-column operation adopted by the DVB-C2 standard additionally includes a twist component, further operation details are given with an example below.  FIG. 4A  and  FIG. 4B  show diagrams of a memory configuration and a memory accessing sequence when the row-column operation unit  384  performs a row-column operation on a DVB-C2 signal. In this example, N r =6·N c =7. When i=0˜5, C i =i and R i =mod(i+0.6)=i; when i=6, C i =6 and R i =mod(6+0.6)=0; when i=7, C i =6 and R i =mod(0+1.6)=1; and so forth. 
     In conclusion, the time deinterleaving control module  380  determines the time deinterleaving scheme according to the signal standard indicated by the setting value. The generated reading index and writing index are then respectively converted to the reading address and the writing address by the reading address generating unit  350  and the writing address generating unit  360 . Thus, the time deinterleaving memory  320  may be shared by signals of different standards to complete the frequency deinterleaving operation, and four time deinterleaving memories of conventional receivers corresponding to four signal standards can be simplified into one single time deinterleaving memory, thereby significantly reducing the memory utilization requirement. In the embodiment in  FIG. 3 , the frequency deinterleaving memory  310  and the time deinterleaving memory  320  are disposed inside the frequency deinterleaving and time deinterleaving circuit  220 . However, in implementation, without substantially modifying operations of the frequency deinterleaving and time deinterleaving circuit  220 , the frequency deinterleaving memory  310  and the time deinterleaving memory  320  may also be disposed outside the frequency deinterleaving and time deinterleaving circuit  220 . It should be noted that, as far as the DVB-T standard is concerned, the transmitter does not perform any interleaving operation on the signals. Therefore in theory, due to difference of modulation of the DVB-T standard, after the digital television signal is processed by the front-end circuit  210 , the processed digital television signal can be decoded by the decoding circuit  260  without undergoing the processes of the frequency deinterleaving and time deinterleaving circuit  220  and the QAM demapping circuit  240 . However, the memory in the frequency deinterleaving and time deinterleaving circuit  220  is left idle if the frequency deinterleaving and time deinterleaving operation is not performed. To fully utilize hardware resources, when the signal processed by the receiver  200  is a DVB-T signal, the memory in the frequency deinterleaving and time deinterleaving circuit  220  may serve as a buffer memory of the decoding circuit  260  to enhance the stability of the decoding circuit  260 . That is to say, when the signal processed by the receiver  200  of the digital television is a DVB-T signal, the memory in the frequency deinterleaving and time deinterleaving circuit  220  serves as a general buffer. Therefore, the frequency deinterleaving and time deinterleaving circuit  220  need not adjust the sequences of writing data to and reading data from the memory, i.e., the sequences are not changed before entering and after exiting the memory. As previously stated, the column indices of the writing index and the reading index are both C i =mod(i,N c ), and the row indices are both R i =i divN c . Therefore, in  FIG. 2 , when the signal processed by the receiver  200  of the digital television is a DVB-T signal, according to the setting value, the demultiplexer  230  outputs the signal of the frequency deinterleaving and time deinterleaving circuit  220  to the multiplexer  250  while bypassing the QAM demapping circuit  240 , and the multiplexer  250  similarly selects and outputs the processed signal by the QAM demapping circuit  240  according to the setting value to the decoding circuit  260 . 
       FIG. 5  shows a function block diagram of a QAM demapping circuit according to an embodiment of the present invention. The QAM demapping circuit  240  includes a demultiplexer  510 , a DTMB demapping circuit  520 , a DVB-C2 demapping circuit  530 , a DVB-T2 demapping circuit  540 , a cell deinterleaving circuit  545 , an ISDB-T demapping circuit  550 , and a multiplexer  560 . The DTMB demapping circuit  520 , the DVB-C2 demapping circuit  530 , the DVB-T2 demapping circuit  540  and the ISDB-T demapping circuit  550  respectively perform demapping operations on signals of the corresponding signal standards. As the DVB-T2 standard further includes a cell interleaving operation at the transmitter, the receiver is required to process the DVB-T2 signal by the corresponding cell deinterleaving circuit  545 . The demultiplexer  510  outputs the deinterleaved signal via the corresponding path according to the setting value. Similarly, the multiplexer  560  selects the corresponding path according to the setting value and outputs the signal via the selected path as the demapped signal. 
       FIG. 6  shows a function block diagram of a decoding circuit  260  according to an embodiment of the present invention. The decoding circuit  260  includes a demultiplexer  610 , an LDPC decoding circuit  620 , a Vertibi decoding circuit  630  and a multiplexer  640 . The demultiplexer  610  outputs the demapped signal to the appropriate decoding circuit according to the setting value. For example, if the signal is of the ISDB-T standard or of the DVB-T standard, the demapped signal is outputted to the Vertibi decoding circuit  630 ; if the signal is of the DTMB standard, of the DVB-T2 standard, or of the DVB-C2 standard, the demapped signal is outputted to the LDPC decoding circuit  620 . The multiplexer  640  similarly outputs the corresponding decoded signal according to the setting value to obtain the transmission data. 
     In conclusion, in the present invention, the frequency deinterleaving and time deinterleaving operations are completed by using shared frequency deinterleaving memory and time deinterleaving memory. Therefore, in present invention, only one memory is required for the receiver  200  of a digital television supporting multiple standards. The present invention may be applied so as to manufacture television chips compatible to different digital television standards and is advantageous in cost aspect. 
       FIG. 7  shows a flowchart of a frequency deinterleaving and time deinterleaving method according to an embodiment of the present invention. In addition to the above-mentioned frequency deinterleaving and time deinterleaving circuit, the present invention discloses a frequency deinterleaving and time deinterleaving method may adapt for a receiver of a digital television. The method may be performed by the above-mentioned receiver  200  of a digital television or any equivalent devices. As shown in  FIG. 7 , the frequency deinterleaving and time deinterleaving method of the present invention is used to perform a frequency deinterleaving operation and a time deinterleaving operation on an interleaved signal, and includes following steps. 
     In step S 705 : providing a first memory. 
     In step S 710 : generating a first writing index and a first reading index according to a setting value. The setting value indicates a digital video standard of the interleaved signal, e.g., the DVB-T, DVB-T2, DVB-C2, ISDB-T, or DTMB standard. This step performs a frequency deinterleaving operation. The first writing index and the first reading index are generated primarily according to operation concepts—LUT and permutation operations. The ISDB-T standard adopts the LUT operation, and the DTMB, DVB-T2 and DVB-C2 standards adopt the permutation operation. Thus, according to the signal standard indicated by the setting value, this step selects the LUT operation or the permutation operation to generate the first writing index and the first reading index. 
     In step S 720 : generating a first writing address and a first reading address according to the first writing index and the first reading index, respectively. The first writing address may be generated by a writing address generating unit according to the first writing index, and the first reading address may be generated by a reading address generating unit according to the first reading index. 
     In step S 730 : writing to and reading from the interleaved signal in the first memory according to the first writing address and the first reading address, respectively, to complete the frequency deinterleaving operation. After the first writing address and the first reading address are generated, the interleaved signal may be written to the first memory according to the first writing address and read from the first memory according to the first reading address. The sequence of the first writing address and the first reading address are opposite to which of the frequency interleaving operation performed by a transmitter. Thus, after reading the signal, the frequency deinterleaving operation is completed to obtain the frequency deinterleaved signal. 
     In step S 740 : providing a second memory. 
     In step S 750 : generating a second writing index and a second reading index according to the setting value. This step performs a time deinterleaving operation. The second writing index and the second reading index are generated primarily according to two operation concepts—convolution and row-column operations. The ISDB-T standard and the DTMB standard adopt the convolution operation, and the DVB-T2 standard and the DVB-C2 standard adopt the row-column operation. Thus, this step selects the convolution operation or the row-column operation according to the signal standard indicated by the setting value to generate the second writing index and the second reading index. 
     In step S 760 : generating a second writing address and a second reading address according to the second writing index and the second reading index, respectively. The second writing address may be generated by a writing address generating unit according to the second writing index, and the second reading address may be generated by a reading address generating unit according to the second reading index. 
     In step S 770 : writing to and reading from the interleaved signal that has undergone frequency interleaving in the second memory according to the second writing address and the second reading address, respectively, to complete the time deinterleaving operation. After the second writing address and the second reading address are generated, the frequency deinterleaved signal may be written to the second memory according to the second writing address and read from the second memory according to the second reading address. Thus, after reading the signal, the time deinterleaving operation is completed to obtain the deinterleaved signal. 
     Referring to  FIG. 8 , when step S 750  selects the convolution operation to generate the second writing index and the second reading index, steps below are performed. 
     In step S 810 : obtaining a branch parameter b according to a carrier coefficient of an ODFM symbol of the interleaved signal. The interleaved signal is a QAM signal based on OFDM. Similar to the step 1 details of the convolution operation unit  382 , the branch parameter b is generated according to the carrier coefficient i. 
     In step S 820 : obtaining a delay buffer depth L b * according to the branch parameter b. Similar to the step 2 details of the convolution operation unit  382 , the delay buffer depth L b * is calculated according to the branch parameter b. For the ISDB-T and DTMB standards, the delay buffer depth L b ^ is obtained with different calculation methods. 
     In step S 830 : generating the second reading index according to the branch parameter b and the delay buffer depth L b *. Similar to the step 3 and step 4 details of the convolution operation unit  382 , the buffer index c b,j * can be updated according to the branch parameter b and the delay buffer depth L b *, and then the reading index can be generated according to the buffer index C b,j *, the branch parameter b, and the delay buffer depth L b *. That is to say, the reading index is generated according to the branch parameter b and the delay buffer depth L b *. 
     In step S 840 : obtaining the second writing index which is made to equal to the second reading index. Similar to the step 5 details of the convolution operation unit  382 , for the same carrier coefficient, the writing index is made to equal to the reading index. That is, when data is read from an address of the memory, a next set of data is to be written to the same address. 
     Further, when step above-mentioned S 750  selects the row-column operation to generate the second writing index and the second reading index, the second writing index and the second reading index are obtained according to the carrier coefficient of the OFDM symbol of the interleaved signal, row count information of the second memory, and column count information of the second memory. Details of the row-column operation unit  382  are previously described and shall be omitted herein. 
     Further, in step S 710  and/or step S 750  above, if the setting value indicates that the digital video standard of the interleaved signal is DVB-T, the reading index can simply be made to equal to the writing index. That is to say, for the DVB-T standard, the sequences for writing data to the memory and reading data from the memory are not rearranged. Therefore, the first memory and/or the second memory merely serve(s) as buffers for the decoding circuit. 
     One person skilled in the art can understand details and possible equivalent implementation and variations of the methods in  FIG. 7  and  FIG. 8  according to the disclosure of the devices in  FIG. 2  to  FIG. 6 . Without affecting the full disclosure and implementation possibility, repeated description is omitted herein. Further, the shapes, sizes, ratios and sequences of the steps in the drawings are examples for explaining the present invention to one person skilled in the art, not limiting the present invention. Within the realms of implementation possibility, one skilled person in the art would selectively implement part or all technical features of any embodiment of the application or selectively combine part or all technical features of the embodiments of the application based on the disclosure of the present invention with enhanced flexibility. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
A receiving circuit for a digital television is provided. The receiving circuit of the digital television, adapted to process a digital television signal to generate transmission data, includes: a front-end circuit, configured to process the digital television signal to generate an interleaved signal; a setting unit, configured to provide a setting value associated with a digital video standard of the digital television signal; a frequency de-interleaving and time de-interleaving circuit, configured to select a frequency de-interleaving scheme and a time de-interleaving scheme corresponding to different digital video standards according to the setting value, and to process the interleaved signal to generate a de-interleaved signal; a quadrature amplitude modulation (QAM) demapping circuit, configured to demap the de-interleaved signal to generate a demapped signal; and a decoder, configured to decode the demapped signal to generate the transmission data.