JP3103098B2 - PCM audio decoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a PCM audio decoder device that can be used for both the MTSC system and the MUSE system in a satellite broadcast receiving device, for example.

(Prior art) PCM (Pulse Code Modulation)
This signal is transmitted in a certain format as a digital signal called the NTSC system (Technical Problems of Television and FM Broadcasting, Vol. 4 of 1982, and urgent superimposition on broadcast radio waves) Technical Conditions for Warning Signals "and MUSE method (Telecommunications Technology Council, High Definition Television Committee Report, June 1990
Report on "Technical conditions for high-definition television broadcasting" on the 25th.

First, an audio format of the NTSC system, which is a normal broadcasting system, will be described with reference to FIG. 4 and FIG. There are two types of modes, A mode and B mode, which differ in voice quality and number of channels. FIG. 4 (a) shows bit allocation on a bit interleave matrix in A-mode signal multiplexing, FIG. 4 (b) shows bit distribution in A-mode signal multiplexing, and FIG. FIG. 5B shows bit allocation on a bit interleave matrix in mode signal multiplexing, and FIG. 5B shows bit distribution in B mode signal multiplexing. As shown in each figure, one frame is 20
The data is transmitted in units of 1 ms in units of 48 bits. In both modes, one frame consists of a 16-bit frame synchronization signal, 16-bit control code, 1792-bit voice and data, and 224 bits.
In the A mode, 10 bits × 32 samples × 4 channels and range bit bits × 4 channels as level information are added, and 1318 bits are audio data, and the remaining 480 bits are used in the A mode. Is independent data. In B mode, 16 bits x
48 samples × 2 channels, range bits 8 bits × 2
In addition to channels, 1562 bits are audio data,
The remaining 230 bits are independent data. The independent data is used as four channels for transmitting information other than voice. Error correction and detection are performed on 63 bits per row on the interleave matrix.

By the way, the audio signal of the satellite broadcast is transmitted after interleaving in order to disperse these errors when several bits occur consecutively. This is performed by changing the temporal order of data, and is performed by sequentially writing data to the memory in the horizontal direction and sequentially reading data from the memory in the vertical direction and transmitting the data in FIG. Therefore, the receiving apparatus needs to perform deinterleaving, which is the reverse operation. That is, this deinterleaving is an operation of sequentially writing in the vertical direction and sequentially reading out in the horizontal direction.

On the other hand, the format of the audio PCM system of the MUSE system, which is a high definition, will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 (a) shows bit allocation on a bit interleave matrix in A-mode signal multiplexing, FIG. 6 (b) shows bit distribution in A-mode signal multiplexing, and FIG. FIG. 7B shows bit assignment on a bit interleave matrix in mode signal multiplexing, and FIG. 7B shows bit distribution in B mode signal multiplexing. As shown in each figure, one frame is composed of 1350 bits, and is 1 ms in the same way as the NTSC system.
It is transmitted in units. In both modes, one frame is composed of a 16-bit frame synchronization signal, a 22-bit control code, 1168-bit audio and data, and a 128-bit error correction code. As in the case of the system, the number of bits per sample is different, and is 8 bits in the A mode and 11 bits in the B mode. NTSC audio is normal PCM data, but MUSE audio is differential PCM (DP
CM).

Also in the MUSE system, transmission is performed with interleaving in order to disperse the occurrence of errors. In this case, there are two stages of interleaving, bit interleaving and word interleaving. That is, the bit interleaving is performed in the same manner as in the NTSC system as shown in FIGS.
In FIG. 8A, writing is performed in the horizontal direction and reading is performed in the vertical direction.
The time order is changed, such as 1, d17, d2, d18,. This is called word interleaving, and is a per-sample rearrangement. Therefore, the receiving apparatus needs to perform two deinterleaving processes, bit deinterleaving and word deinterleaving.

(Problems to be Solved by the Invention) As described above, the PC of the receiving device that receives both the normal NTSC system and the high-vision MUSE system in satellite broadcasting
The M audio decoder requires a large number of memories to perform both types of deinterleaving, and is uneconomical.

The present invention has been made in view of the above, and an object of the present invention is to use a bit deinterleave memory and a word deinterleave memory of a MUSE system as a bit deinterleave memory of an NTSC system, thereby achieving economy.
A PCM audio decoder device is provided.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, a PCM audio decoder apparatus of the present invention comprises: a first method for performing bit interleaving and word interleaving; and a second method for performing bit interleaving. A PCM audio decoder device for receiving and deinterleaving an audio signal of the first type, using a first memory used for bit deinterleaving the audio signal of the first system, and a first memory A second memory used for word deinterleaving the bit deinterleaved audio signal, and the first and second memories may be used for bit deinterleaving the audio signal of the second scheme. And a control means for performing the control.

(Operation) In the PCM audio decoder device of the present invention, the first and second memories used for bit deinterleaving and word deinterleaving of the audio signal of the first system are used to convert the audio signal of the second system into bits. It is controlled so that it can be used to deinterleave.

(Example) Hereinafter, an example of the present invention is described using a drawing.

FIG. 1 is a block diagram showing a configuration of a PCM audio decoder according to an embodiment of the present invention. The PCM audio decoder device shown in the figure has a first memory 513 and a second memory 514 used for bit deinterleaving and word deinterleaving processing of the MUSE system.
3,514 is also used for NTSC-type bit deinterleaving, thereby sharing the memory, making it economical, and miniaturizing it. Switching between the MUSE system and the NTSC system is performed by a MUSE / NTSC switching signal supplied to the terminal 503. More specifically, the terminal 503 is connected to the changeover switches 510, 512, 519, 520, 521, 527 as shown by the dotted lines, whereby each switch is controlled by a changeover signal from the terminal 503, and when each switch is switched to the M side, the MUSE method When switching to the N side, the NTSC system is used.

In FIG. 1, an input signal is input from an input terminal 501, and a clock is input from a clock input terminal 502. This clock is 1.35 MHz. The input signal input from the input terminal 501 is supplied to the synchronization circuit 504, where 1
A 6-bit synchronization signal is detected, and the position of the synchronization signal is supplied to a timing generation circuit 518 to regulate the timing of the entire PCM decoder.

Further, the input signal is separately supplied to a bit deinterleave circuit 507 through an exclusive OR circuit (XOR) 505. In the MUSE method, one input of the exclusive OR circuit 505 is connected to the low level of the ground via the changeover switch 512, so that the input signal is passed as it is to the bit deinterleave circuit 507. You. Further, the input signal is also supplied to a control code detection circuit 522, where each control code is detected. This control code indicates each mode such as A mode / B mode.

In the case of the MUSE system, the bit deinterleave circuit 507 performs the first operation according to the matrix shown in FIGS. 6A and 7A based on the address from the MUSE bit deinterleave address generation circuit 515. The data is sequentially written in the memory 513 in the vertical direction and read out in the horizontal direction, bit deinterleaving processing is performed, and the resulting output is input to the error correction circuit 508, and error correction is performed in units of 82 bits. Here, the error code is obtained by adding an error check bit of 8 bits to the data of 74 bits (82,74) B
It is a CH code, in which 1-bit error correction and 2-bit error detection are performed.

An error-corrected signal and an error flag indicating that an error has been detected are supplied to a word deinterleave circuit 509 in the case of the MUSE system. The word deinterleave circuit 509 uses the second memory 514 via the changeover switch 519, rearranges the sample data of each channel in time order based on the address from the MUSE word deinterleave address generation circuit, and switches the switch 510. The signal is supplied to the range extending circuit 523 via the input terminal. The range expansion circuit 523 compresses the audio signal according to the audio signal level in one frame, transmits information indicating the degree of compression as range information, and expands the audio signal according to the range information on the receiving side. Return to the original (semi-instantaneous companding method). This output is input to the error correction circuit 524. Here, the error correction circuit 5
If the error could not be corrected in 08, but an error was detected, the error flag indicating the error replaces the erroneous sample data with the previous sample data (retains the previous value) or replaces it with the average value of the previous and subsequent sample values (Average value correction) to suppress noise caused by errors.
The output of the error correction circuit 524 is input to the DPCP decoder 526, returned to the original PCM signal, adjusted to a fixed output format by the output buffer 526, and output from the output terminal 511. The output is thereafter converted to an analog signal via a D / A converter (not shown), and an audio signal is obtained.

In the NTSC system, the input is 2.048 MHz, which is different from the MUSE system. Therefore, the timing generation circuit 518 needs to be largely switched, but many circuit blocks can be shared as they are or by slight switching.

In the case of NTSC, the input signal is a pseudo-random signal (PN)
In order to return this, the output of the PN generation circuit 505 is switched via the changeover switch 512 to the exclusive OR circuit 505.
To obtain an exclusive OR with the input signal.

The output from the exclusive OR circuit 505 is supplied to a bit deinterleave circuit 507. The bit deinterleave circuit uses the first and second memories 513 and 514 and performs bit deinterleave processing based on the address from the NTSC address generation circuit. The error correction is a (63,53) BCH code obtained by adding 7 error check bits to 56-bit data in units of 63 bits. Similar to the MUSE method, 1-bit error correction and 2-bit error detection are performed. Have the ability. In the case of the NTSC system, the word deinterleave circuit 509 is bypassed, and the output from the error correction circuit 508 passes through the changeover switch 510 and is output via the range expansion circuit 523, the error correction circuit 524, and the output buffer circuit 526. . Note that the DPCM decode circuit 525 is bypassed.

Next, the bit deinterleaving and word deinterleaving processing will be described in detail with reference to FIGS. Deinterleaving requires twice as much memory area as interleaved blocks to separate writing and reading. For example, if one frame of data is written to page 0, the data of page 1 is read. In the case of MUSE system,
In the bit deinterleaving, as shown in FIG. 2A, 82 bits × 16 bits × 2 pages = 2624 bits are required. In word interleave, in A mode, 8
Bit x 4 channels x 32 samples x 2 pages = 2048 bits, B mode requires 11 bits x 2 channels x 48 samples x 2 pages = 2112 bits, but the difference between A mode and B mode, and later Since an error flag required for error correction is also required, 1272 × 8 words × 16 bits × 2 pages = 3072 bits are used as a word interleave memory as shown in FIGS. 2 (b) and 2 (c). In the A mode, audio 8 bits + error flag 1 bit = 9 bits are used as one word and used as 9 bits × 8 words. In the B mode, audio 11 bits + error flag 1 bit = 12 bits are used as 1 bit. Word, 12 bits x 6 words. In FIG. 2, the hatched portions are unused portions.

In the case of the NTSC system, word deinterleaving is not required, but bit deinterleaving requires 6332 bits × 32 bits × 2 pages = 4032 bits. Therefore, the third
As shown, a first memory 513 for bit deinterleaving and a second memory 514 for word deinterleaving are shown.
Are used as memory for bit deinterleaving for NTSC. Specifically, the first memory is 63 bits × 32
The second memory is used as a memory for one page of 8 bits × 4 words × 63 bits by slightly changing the address lines such as changing the length and width of the second memory. By using in this way, it is not necessary to add a special memory for the NTSC system.

Incidentally, the memory is defined by the number of data bits × the number of words. In this embodiment, the first memory is 8 bits × 328 words, and the second memory is 12 bits × 256 words. Originally, a 1-bit × n-word memory is possible, but the above-described memory configuration is used in terms of processing efficiency. In general, the number of words is 2 ⁿ for the number n of address lines.
However, when an integrated circuit is used, it is necessary to reduce unnecessary memory and make the memory as small as possible.

A description will be given of the reduction of the memory capacity when this embodiment is adopted. The MUSE system requires at least 2624 bits for bit deinterleaving and 2112 bits for word deinterleaving, while the NTSC system requires at least 4032 bits for bit deinterleaving. Here, when only bit deinterleaving is shared, 4032 bits + 2112 bits are required, and an additional 1212 bits is required. On the contrary,
In this embodiment, only 2624 bits are required for bit deinterleaving and only 2112 bits are required for word deinterleaving, so that it is possible to reduce the memory capacity, reduce the IC chip size, and reduce the cost. Can be planned.

〔The invention's effect〕

As described above, according to the present invention, the first and second signals used for bit deinterleaving and word deinterleaving of the audio signal of the first scheme, respectively.
Is controlled so that it can be used for bit deinterleaving of the audio signal of the second system, so that the memory can be shared and the memory capacity can be reduced. In this case, the chip size can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a PCM audio decoder according to one embodiment of the present invention, FIG. 2 is an explanatory diagram showing a memory map in the MUSE system, and FIG. 3 is an explanatory diagram showing a memory map in the NTSC system. Figures 4 and 5 show NTSC
FIGS. 6 and 7 are explanatory diagrams showing the format of the audio signal of the system, and FIGS. 6 and 7 are explanatory diagrams showing the format of the audio signal. 507: a bit deinterleave circuit, 508: an error correction circuit, 509 ... a word deinterleave circuit, 513 ... a first memory, 514 ... a second memory, 515 ... a MUSE bit deinterleave address generation circuit, 516: NTSC address generation circuit, 517: MUSE word deinterleave address generation circuit.

Claims (1)

(57) [Claims] 1. A PCM audio decoder device for receiving an audio signal of a first system subjected to bit interleaving and word interleaving and an audio signal of a second system subjected to bit interleaving and performing deinterleaving, A first memory used for bit deinterleaving the audio signal of the first system, and a second memory used for word deinterleaving the bit deinterleaved audio signal using the first memory And a control means for controlling the first and second memories to be used for bit deinterleaving of the audio signal of the second system.
M audio decoder device.