CN100442375C - Audio signal processing circuit capable of modifying digital audio signal - Google Patents

Abstract

An audio signal processing circuit includes an analyzer, a bitstream buffer, an audio signal processor, a first buffer, an IEC burst circuit, and a digital interface. The audio signal processing circuit uses the analyzer to read out the data in the medium and temporarily store the data in the bitstream buffer. The audio signal processor includes a bitstream repair circuit for detecting the bitstream transmitted from the bitstream buffer and repairing the bitstream to conform to a predetermined standard. The modified data is buffered in the first buffer, and a burst preamble is added to the data stored in the first buffer before the data is output via the digital interface using the IEC burst circuit.

Description

Audio signal processing circuit capable of modifying digital audio signal

technical field

The present invention provides an audio signal processing circuit, especially an audio signal processing circuit capable of modifying a digital audio signal. The audio signal processing circuit of the present invention can be used in CD players.

prior art

Please refer to Figure 1, Figure 1 is a schematic diagram of the IEC 60958 data-bursts format. IEC 61937 is an interface specification for defining a non-linear pulse-code modulation (PCM) encoded audio signal bit stream, and the encoded audio signal bit stream uses the specification of IEC 60958. The format of the IEC 60958 interface is composed of a series of IEC 60958 subframes (subframes). Each IEC 60958 subframe is usually used to transport nonlinear pulse code modulation samples, but may also be used to transmit data. Each subframe contains a data burst and padding. The size of the data burst in different subframes may be different, and the function of padding is to maintain the size of each subframe at a specific value. Each data burst consists of a burst-preamble followed by a burst-payload, where the burst-preamble includes four 16-bit words Pa, Pb, Pc, and Pd, and Pa and Pb are The sync word, Pc is the relevant data of the burst capacity, Pc is the number of the bit stream, and the content of the burst capacity is the data of the coded audio signal frame.

Please refer to FIG. 2 . FIG. 2 is a schematic diagram of the structure of an audio signal processing circuit 10 in a conventional optical disc player. The audio signal processing circuit 10 includes an analyzer 12, a bit stream buffer 14, an audio signal processor 16, a second buffer 18, a digital/analog converter 20, an IEC burst circuit 22, and a digital interface twenty four. After an optical disc 26 is inserted into the optical disc player, the data is read by a server (not shown), and the analyzer 12 will temporarily store the digital data in the read optical disc 26 in the bit stream buffer 14, and then process the audio signal The device 16 will decode the digital data stored in the bit stream buffer 14 into a pulse code modulation code, and temporarily store the decoded pulse code modulation code in the second buffer 18, and finally store it in the digital/analog converter 20 The PCM encoded in the second buffer 18 is converted into an analog signal for output. Since the user may not want to use the audio signal processing circuit inside the CD player, but wants to use a more professional decoder/amplifier device to process the digital audio signal, the evaluation of the audio signal processing circuit 10 in the CD player not only provides In addition to playing the digital audio signal data in the optical disc 26 through the above-mentioned decoding program, it can also be connected to a subsequent decoder/amplifier device 28 through the digital interface 24 . The optical disc player converts the digital audio signal data read by the optical disc player from the optical disc 26 into a specific digital audio signal format (for example: IEC 61937/IEC 60958 audio signal format) through the digital interface 24 without decoding. Afterwards, the digital data is transmitted to the decoder/amplifier device 28 outside the CD player for the decoder/amplifier device 28 to process the digital data. However, the data transmitted between the optical disc player and the decoder/amplifier device 28 through the digital interface 24 must comply with the specifications of IEC 61937/IEC 60958, otherwise the decoder/amplifier device 28 cannot decode the digital data, so digital data is used. When the interface 24 is used to connect the optical disc player and the decoder/amplifier device 28, the digital data in the optical disc 26 will be read out by the analyzer 12 and temporarily stored in the bit stream buffer 14, so that the digital data output to the digital interface 24 The data becomes the specification of IEC 60958. Before the digital data stored in the bit stream buffer 14 is transmitted to the digital interface 24, the bit stream is divided into burst loads of appropriate size using the IEC burst circuit 22, a burst preamble is added, and then Add appropriate padding to make the original audio signal bit stream comply with the IEC 60958 specification, and then output the bit stream to the decoder/amplifier device 28 through the digital interface 24 .

It can be seen from the above that the audio signal processing circuit 10 will first temporarily store the digital data read from the optical disc 26 in the bit stream buffer 14, and the digital data stored in the bit stream buffer 14 is decoded by the audio signal processor 16. After being coded by pulse code modulation, it is temporarily stored in the second buffer 18, and the digital/analog converter 20 is used to convert the code stored in the second buffer 18 into an analog signal for output. In addition, the optical disc player can also be connected to the decoder/amplifier device 28 through the digital interface 24 inside the audio signal processing circuit 10, and the digital data stored in the bit stream buffer 14 passes through the IEC burst circuit 22 after each batch of data passes through appropriate After the processing is converted into the IEC 60958 standard, it is sent to the digital interface 24 and output to the decoder/amplifier device 28 for decoding and amplifying the signal. However, the IEC burst circuit 22 only directly converts the format of each batch of data stored in the bit stream buffer 14, and does not check the content of the data itself, so the data that does not fully comply with the digital music specification (for example: caused by poor quality data) The audio signal bit stream compiled by the audio signal encoding software and hardware) will also be output to the decoding/amplifying device 28 via the digital interface 24, causing the decoding/amplifying device 28 to receive the audio signal that does not fully meet the digital audio signal specification. The phenomenon that the data cannot be decoded or the sound pops occurs.

Other related technologies can refer to US Patent 5,794,181, US Patent 5,884,048, US Patent 6,272,153, US Patent 6,128,579, and US Patent 6,122,619.

Contents of the invention

Therefore, the main object of the present invention is to provide an apparatus and method for modifying digital audio signals to solve the above problems.

A preferred embodiment of the present invention provides an audio signal processing circuit, which includes an analyzer for reading raw data in the medium; a bit stream buffer connected to the analyzer for temporarily storing the analysis The bit stream of the data read by the device; an audio signal processor is connected to the bit stream buffer, and the audio signal processor includes a bit stream repair circuit for detecting the bit stream transmitted from the bit stream buffer and Repairing it to meet a predetermined standard specification; a first buffer, connected to the audio signal processor, used to temporarily store the modified bit stream of the bit stream repairing circuit; an IEC burst circuit, connected to the first a buffer for dividing the bit stream into appropriately sized burst loads, adding burst preambles, and adding appropriately sized padding so that the original audio signal bit stream conforms to the specifications of IEC 60958; and a digital interface connecting The IEC burst circuit is used to output the bit stream transmitted from the IEC burst circuit.

Description of drawings

Figure 1 is a schematic diagram of the IEC 60958 data-bursts format.

Fig. 2 is a schematic diagram of the structure of a known optical disc player.

FIG. 3 is a schematic diagram of the structure of an optical disc player according to an embodiment of the present invention.

FIG. 4 is a flow chart of modifying a bit stream using an audio signal processing circuit according to an embodiment of the present invention.

FIG. 5 is a flow chart of changing the decoding method of the decoder/amplifier device using the audio signal processing circuit of the embodiment of the present invention.

FIG. 6 is a schematic diagram of checking bit stream errors using an audio signal processing circuit according to an embodiment of the present invention.

Description of reference symbols

10 Known audio signal processing circuit 12 Analyzer

14-bit stream buffer 16 audio signal processors

18 second buffer 20 digital/analog converter

22IEC burst circuit 24 digital interface

26 discs 28 decoder/amplifier device

30 The audio signal processing circuit of the embodiment of the present invention

32 audio signal processor 34 decoding circuit

36-bit stream repair circuit 38 first buffer

Detailed ways

Please refer to FIG. 3 . FIG. 3 is a schematic diagram of the structure of an optical disc player in a preferred embodiment of the present invention. For convenience of description, the same elements in FIG. 3 and FIG. 1 have the same functions and use the same reference numerals. The audio signal processing circuit 30 includes an analyzer 12, a bit stream buffer 14, an audio signal processor 32, a second buffer 18, a digital/analog converter 20, a first buffer 38, an IEC burst circuit 22, and a digital interface 24. The audio signal processor 32 includes a decoding circuit 34 and a bit stream restoration circuit 36 . After the optical disc 26 is inserted into the audio signal processing circuit 30, the analyzer 12 will read out the digital data in the optical disc 26 and temporarily store it in the bit stream buffer 14, and then the decoding circuit 34 of the audio signal processor 32 will store the digital data stored in the bit stream buffer 14. The digital data in the stream buffer 14 is decoded into a pulse code modulation code, and the decoded pulse code modulation code is temporarily stored in the second buffer 18, and finally the digital/analog converter 20 stores the code in the second buffer 18 The pulse code modulation code is converted into an analog signal as an output. The audio signal processing circuit 30 of this embodiment also provides a general decoding program to play the digital audio signal data in the optical disc 26, but unlike the known technology, when the optical disc player is connected to the decoder/amplifier device 28, the audio signal The processing circuit 30 first uses the bit stream repair circuit 36 of the audio signal processor 32 to check and repair the digital data stored in the bit stream buffer 14, and checks or repairs the completed bit stream repair circuit 36. The data is temporarily stored in the first buffer 38, and then the format of the digital audio signal data is arranged by the IEC burst circuit 22 to make it conform to the IEC 60958 standard, and then sent to the digital interface 24 for output.

Please refer to FIG. 4 . FIG. 4 is a flow chart of modifying the bit stream by the audio signal processing circuit 30 of the present embodiment. Before each batch of data stored in the bit stream buffer 14, there will be a sync word as the separation of each batch of data. When there is no error in the data content but only a displacement, the format cannot fully comply with the digital audio signal specification. When required, if the data is directly format-converted and output without checking the sync word of each batch of data, it may cause a decoding error in the decoder/amplifier device 28 and produce popping sounds. For example, for the MPEG audio signal, the sync word is a designated bit group, and its value is 0xfff. In order to prevent the above-mentioned errors caused by the displacement, the audio signal processing circuit 30 transmits the data to the IEC burst by the bit stream buffer 14. Before the circuit 22, the bit stream repair circuit 36 of the audio signal processor 32 is used to check the data, and then the corrected data is temporarily stored in the first buffer 38, and then the format is converted and output.

The steps to check are as follows:

Step 110: find out the synchronization word in the bit stream buffer 14, and set the index sft=0, and proceed to step 120;

Step 120: check whether the synchronous word is a designated bit group, if yes, proceed to step 130, otherwise proceed to step 140;

Step 130: copy the bit stream in the bit stream buffer 14 to the first buffer 38 and offset sft bits, end this bit stream inspection, start from step 110, and carry out the inspection of the next bit stream;

Step 140: Set the index sft=sft+1, indicating that the offset of one bit has been checked, and proceed to step 150;

Step 150: After the synchronization bit is shifted to the left by one bit, the highest bit is discarded, and a lowest bit is added, and the process returns to step 120.

After the bit stream is processed through the above steps, the incorrect displacement can be eliminated, and the bit stream after being checked by the bit stream repair circuit 36 of the audio signal processor 32 is temporarily stored in the first buffer 38, and finally the IEC burst circuit 22 is used to sort it out The format of the digital audio signal data is then transmitted to the decoder/amplifier device 28 via the digital interface 24 . In this way, the compatibility between the audio signal processing circuit 30 and the decoder/amplifier device 28 can be increased.

Please refer to FIG. 5 . FIG. 5 is a flow chart of the audio signal processing circuit 30 changing the decoding mode of the decoding/amplifying device 28 according to the second embodiment of the present invention. In some cases, the data sent by the audio signal processing circuit 30 cannot be correctly decoded due to poor design of the decoder/amplifier device 28. At this time, the audio signal processing circuit 30 can use the audio signal processing The bit stream repair circuit 36 of the device 32 is used to change the content of the data read from the optical disc 26, so that the decoder/enlarger device 28 can operate normally. For example, in an MPEG audio signal, there is a 2-bit field (field) called mode (mode), and the mode field records the playback effect of the audio signal, which can usually be divided into mono, dual mono and Stereo (stereo) three modes, where mono means only one channel has sound, and dual and stereo means that two channels play different sounds, making the sound stereoscopic. Some decoding/enlarging machine devices 28 cannot correctly identify the dual-sound mode, so although these decoding/enlarging machine devices 28 can correctly play the monophonic mode with mono and play the stereo mode with two channels, when the mode field is dual-sound , but it is often played in mono, the user can easily feel that there may be a compatibility problem between the CD player and the decoder/amplifier device 28. The audio signal processing circuit 30 in this embodiment can use the bit stream restoration circuit 36 of the audio signal processor 32 to change the mode field in the data from the optical disc 26 from dual sound to stereo sound, so that these decoding/amplifier devices 28 Just can play the CD 26 data of double sound with double sound. Since most of the decoder/amplifier devices 28 can correctly identify the two-channel mode, the compatibility between the CD player and various decoder/amplifier devices 28 can be improved through the digital audio signal processing of this embodiment. improved. The steps that the bit stream restoration circuit 36 of the audio signal processor 32 changes the mode field are as follows:

Step 210: find out the synchronization word of the data bit stream in the bit stream buffer 14, and copy the synchronization word into the first buffer 38;

Step 220: Retrieve the bit stream until the field of the mode is found, and store the data obtained by the bit stream buffer 14 in the first buffer 38;

Step 230: analyzing the data from the mode field in the bitstream buffer 14;

Step 240: changing the original pattern into a new pattern, and storing the new pattern data in the first buffer 38;

Step 250 : Retrieve the remaining bit stream until the end of the bit stream, and store the data obtained from the bit stream buffer 14 in the first buffer 38 .

In addition to changing the mode field, the bit stream repair circuit 36 of the audio signal processor 32 can also be used in copyright management. General copyrights can be divided into non-copyable (no copy), copyable (copyalways) and copyable once ( copy once). When the copyright field of the optical disc 26 is non-copyable, the optical disc 26 can only be used for reading and playing. When the copyright field of the optical disc 26 is copyable, the optical disc 26 can be copied. If the copyright field of the optical disc 26 can be copied once, the bit stream repair circuit 36 of the audio signal processor 32 will change the copyright field to non-copyable after the first copy.

Please refer to FIG. 6 . FIG. 6 is a schematic diagram of the audio signal processing circuit 30 checking bit stream errors in the third embodiment of the present invention. Another function of the bit stream repair circuit 36 of the audio signal processor 32 is to check whether there is an error in the data bit stream, and the audio signal processing circuit 30 uses the analyzer 12 to read out the data in the optical disc 26 and temporarily store it in the bit stream buffer After the device 14, the bit stream repairing circuit 36 will check each field in the data bit stream wherein, as shown in Figure 6, first find out the synchronization word of the bit stream, then check the header (header), item by item. Auxiliary information (side information), scale factor (scale factor), audio signal sample (audio sample), and supplementary data (ancillary data) and other fields, when checking out that the data content of any field contains errors, the bit stream repair circuit 36 It will try to repair, if the repair is successful, the data will be temporarily stored in the first buffer 38, and then continue to check the next field, if it cannot be repaired successfully, then abandon this batch of data bit streams and start the inspection of the next batch of data bit streams In other words, the bit stream repair circuit 36 will not pass any data containing errors, because for the decoder/amplifier device 28, and considering the user's listening experience, the silence caused by the loss of data is more important than the error of the data The resulting pops have a much lesser impact on the sound quality.

As can be seen from the above, the audio signal processing circuit 30 of the present invention not only provides a general decoding program to play the digital data in the optical disc 26, but also adds a bit stream restoration circuit 36 in the audio signal processor 32 to process the data temporarily stored in the bit stream. The digital data in the stream buffer 14 includes functions such as modifying the displacement of the bit stream, modifying the data content in the bit stream, checking the data content in the bit stream and trying to repair it, and the data in the bit stream buffer 14 passes through the audio signal processor The bit stream repair circuit 36 of 32 is temporarily stored in the first buffer 38 after processing, and then the burst preamble is added by the IEC burst circuit 22 to become the specification of IEC 60958, and the data is transmitted to the decoder/amplifier device 28 through the digital interface 24, This increases the compatibility between the audio signal processing circuit 30 and the decoder/amplifier device 28 .

Compared with the known technology, the known audio signal processing circuit directly uses the IEC burst circuit to convert the digital data stored in the bit stream buffer into the IEC 60958 specification when the digital interface is used to connect to the decoder/amplifier device, and then the The digital interface is output to the decoder/amplifier device. Since the IEC burst circuit does not check the content of the digital data stored in the bit stream buffer, data that contains errors or does not fully meet the specifications is also transmitted to the decoder/amplifier device. A phenomenon that causes the decoder/amplifier device to fail to decode or produce popping sounds. When the audio signal processing circuit of the present invention uses a digital interface to connect to the decoder/amplifier device, it first uses the bit stream restoration circuit of the audio signal processor to process the data in the bit stream buffer and temporarily stores it in the first buffer, Then the IEC burst circuit converts the data stored in the first buffer into IEC 60958 specifications, so that the data bit stream containing errors can be removed, or the audio signal data that does not fully meet the specifications can be corrected, so that the decoding/amplifier device can Correctly decode digital audio signal data to increase compatibility.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (19)

1. audio signal treatment circuit, be used for producing one second bit stream that meets a digital interface standard specification according to one first bit stream, this first bit stream has many group digital datas, and each group digital data has a plurality of fields, and this audio signal treatment circuit includes:

One bit stream buffering device is used for the numerical data of temporary this first bit stream;

One bit stream is repaired circuit, is connected in this bit stream buffering device, is used for detecting at least one field of these a plurality of fields in these many group digital datas and at least one field of revising these a plurality of fields according to a predetermined standard specification;

One first impact damper is connected in this bit stream and repairs circuit, is used for keeping in the numerical data after this bit stream is repaired circuit modification; And

One IEC burst circuit is connected in this first impact damper, is used for that those amended numerical datas are divided into a plurality of burst carrying capacity and each carrying capacity of bursting and adds the preamble of bursting, to form this second bit stream.

2. audio signal treatment circuit as claimed in claim 1 should predetermined standard specification be the MPEG audio signal wherein.

3. audio signal treatment circuit as claimed in claim 1, wherein this first bit stream is obtained by reading a CD.

4. audio signal treatment circuit as claimed in claim 1, it also includes:

One decoding circuit is connected in this bit stream buffering device, is used for the bitstream decoding that transmits by this bit stream buffering device;

One second impact damper is connected in this decoding circuit, is used for keeping in the bit stream that this decoding circuit decoding produces; And

One digital/analog converter is connected in this second impact damper, and the bit stream translation that is used for being transmitted by this second impact damper is an analog signal.

5. audio signal treatment circuit as claimed in claim 4, wherein this decoding circuit and this bit stream are repaired circuit by an audio signal processor that comprehensively is this audio signal treatment circuit.

6. audio signal treatment circuit, be used for producing one second bit stream that meets a digital interface standard specification according to one first bit stream, this first bit stream has many group digital datas, each group digital data has a plurality of fields, these a plurality of fields have a synchronization character field, and this audio signal treatment circuit includes:

One bit stream buffering device is used for the numerical data of temporary this first bit stream;

One bit stream is repaired circuit, be connected in this bit stream buffering device, be used for finding out near the desired location of the synchronization character field in these many group digital datas the synchronization character in these many group digital datas and revise these many group digital datas according to the physical location of the synchronization character of having found out;

One first impact damper is connected in this bit stream and repairs circuit, is used for keeping in the numerical data after this bit stream is repaired circuit modification; And

One IEC burst circuit is connected in this first impact damper, is used for those amended numerical datas are divided into a plurality of carrying capacity and add the preamble of bursting on each bursts carrying capacity of bursting, to form this second bit stream.

7. audio signal treatment circuit as claimed in claim 6, wherein this first bit stream is obtained by reading a CD.

8. audio signal treatment circuit as claimed in claim 6, it also includes:

One decoding circuit is connected in this bit stream buffering device, is used for the bitstream decoding that transmits by this bit stream buffering device;

One second impact damper is connected in this decoding circuit, is used for keeping in the bit stream that this decoding circuit decoding produces; And

One digital/analog converter is connected in this second impact damper, and the bit stream translation that is used for being transmitted by this second impact damper is a simulating signal.

9. audio signal treatment circuit as claimed in claim 8, wherein this decoding circuit and this bit stream are repaired circuit by an audio signal processor that comprehensively is this audio signal treatment circuit.

10. one kind is used for producing according to one first bit stream the method for one second bit stream meet a digital interface standard specification, and this first bit stream has many group digital datas, and each group digital data has a plurality of fields, and this method includes:

(a) detect at least one field of these a plurality of fields in these many group digital datas and at least one field of revising these a plurality of fields according to a predetermined standard specification; And

(b) those amended numerical datas are divided into a plurality of carrying capacity and add the preamble of bursting of bursting, to form this second bit stream in each carrying capacity of bursting.

11. method as claimed in claim 10, wherein this first bit stream is obtained by reading a CD.

12. method as claimed in claim 10 should predetermined standard specification be the MPEG audio signal wherein.

13. method as claimed in claim 10, it also includes:

The decode numerical data of this first bit stream; And

With decoded digital data conversion is simulating signal.

14. method as claimed in claim 10, wherein step (a) also includes:

If have any skew in the numerical data of this first bit stream, then cast out at least one position, be to meet this predetermined standard specification with this first bit stream reparation of river.

15. method as claimed in claim 10, wherein step (a) also includes:

Change a field of set of number data in the numerical data of this first bit stream, being to meet this predetermined standard specification with this first bitstream modification.

16. method as claimed in claim 15, wherein reformed field are to be a copyright management field.

17. method as claimed in claim 15, wherein this reformed field is to be an audio signal pattern field.

18. method as claimed in claim 10, wherein step (a) also includes:

If exist in the numerical data of this first bit stream and anyly can't then give up at least one error bit, being to meet this predetermined standard specification with this first bit stream reparation according to the error bit of this predetermined standard specification reparation success.

19. method as claimed in claim 10, wherein step (a) also includes:

Revise the mistake in the field of numerical data of this first bit stream, being to meet this predetermined standard specification with this first bit stream reparation.

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