Audio decoding device with soft decision error correction by bit interpolation

• US 6,751,586 B1
• Filed: 08/03/2000
• Issued: 06/15/2004
• Est. Priority Date: 08/05/1999
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Okuno, Daisuke
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): Storm, Donald L.
• Application Number:
  US09/631,584
• Time in Patent Office: 1,412 Days
• Field of Search: 704/226-230, 714/794, 714/795, 375/340, 375/341
• US Class Current: 704/228
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0082 fields explicitly indicating existence of error in data being transmitted, e.g. so that downstream stations can avoid decoding erroneous packet; relays
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178

Abstract

A audio decoding device includes an error correction processing means 13 for generating interpolation process information, a soft decision information generating means 12a for generating a soft decision information indicating a current situation of the transmission line based on coded data, a audio decoding processing means 14 for applying an interpolation process to the audio code in unit of bit based on interpolation information and soft decision information and then decoding the audio code which is subjected to the interpolation process to generate audio data, and a audio output processing means 15 for outputting the audio data.

Claims

1. A audio decoding device comprising:

reception processing means for receiving a signal from a transmission line as a received signal;

demodulation processing means for demodulating the received signal which is received by the reception processing means into coded data;

soft decision information generating means for generating a soft decision information indicating a current situation of the transmission line, based on coded data which are demodulated by the demodulation processing means;

error correction processing means for decoding the coded data to output a audio code and also outputting interpolation process information based on the coded data if it is decided that an uncorrectable error is added to the coded data which are demodulated by the demodulation processing means;

audio decoding processing means for reading interpolation information in a preceding frame based on interpolation process information concerning to the audio code, then applying an interpolation process to the audio code in unit of bit based on interpolation information and soft decision information, and then generating audio data by decoding the audio code which is subjected to the interpolation process if the audio code associated with the coded data, to which the uncorrectable error is added, is received from the error correction processing means; and

audio output processing means for outputting the audio data generated by the audio decoding processing means.

2. A audio decoding device according to claim 1, wherein the error correction processing means stores/holds the audio code and the coded data frame by frame as the interpolation information when the coded data which are demodulated by the demodulation processing means and to which no error is added is decoded to output the audio code, or when an error correction process is applied to the coded data which are demodulated by the demodulation processing means and to which the correctable error is added and then the coded data which are subjected to the error correction process are decoded to output the audio code.

3. A audio decoding device according to claim 2, wherein the soft decision information generating means includes:

data extracting means for extracting a receiving electric field strength from the coded data which are demodulated by the demodulation processing means, and also extracting phase information of symbol points from the coded data, and

soft decision information calculation processing means for generating soft decision information indicating the current situation of the transmission line, based on the receiving electric field strength and the phase information which are extracted by the data extracting means.

4. A audio decoding device according to claim 1, wherein the soft decision information generating means includes:

data extracting means for extracting a receiving electric field strength from the coded data which are demodulated by the demodulation processing means, and also extracting phase information of symbol points from the coded data, and

soft decision information calculation processing means for generating soft decision information indicating the current situation of the transmission line, based on the receiving electric field strength and the phase information which are extracted by the data extracting means.

5. A audio decoding device comprising:

reception processing means for receiving a signal from a transmission line as a received signal;

demodulation processing means for demodulating the received signal which is received by the reception processing means into coded data;

soft decision information generating means for generating a soft decision information indicating a current situation of the transmission line, based on coded data which are demodulated by the demodulation processing means;

error correction processing means for decoding the coded data demodulated by the demodulation processing means to output a audio code and also outputting interpolation process information concerning to the coded data if it is decided that an uncorrectable error is added to the coded data;

error correction processing situation analyzing means for analyzing an error added situation of the audio code which is output from the error correction processing means;

optimization audio decoding processing means for selecting an optimum audio decoding means, based on an analyzed result obtained by the error correction processing situation analyzing means, out of a normal process type audio decoding means which decodes the audio code output from the error correction processing means to generate the audio data, an interpolation process type audio decoding means which applies the interpolation process to the audio code output from the error correction processing means in unit of bit based on the interpolation process information and the soft decision information and then decodes the audio code which is subjected to the interpolation process to generate the audio data, and an optimization process type audio decoding means which applies an optimizing process to the audio code output from the error correction processing means and then decodes the audio code which is subjected to the optimizing process to generate the audio data, and then outputting the audio data generated by a selected audio decoding means; and

audio output processing means for outputting the audio data generated by the audio decoding processing means.

6. A audio decoding device according to claim 5, wherein the soft decision information generating means includes:

data extracting means for extracting a receiving electric field strength from the coded data which are demodulated by the demodulation processing means, and also extracting phase information of symbol points from the coded data, and

soft decision information calculation processing means for generating soft decision information indicating the current situation of the transmission line, based on the receiving electric field strength and the phase information which are extracted by the data extracting means.

7. A audio decoding device according to claim 5, wherein the error correction processing means includes:

error correction demodulation processing means for applying the error correction process to the coded data which are demodulated by the demodulation processing means bit by bit based on the soft decision information which is generated by the soft decision information generating means, and then decoding the coded data which are subjected to the error correction process to output the audio code.

8. A audio decoding device according to claim 5, wherein the error correction processing means includes:

error check bit calculating means for checking whether or not the error is added to the audio code output from the error correction decoding processing means, and then outputting a checked result as an error check bit.

9. A audio decoding device according to claim 8, wherein the error correction processing situation analyzing means includes:

audio code error deciding means for deciding whether or not the error is added to the audio code which is output from the error correction processing means, based on the error check bit supplied from error check bit calculating means.

10. A audio decoding device according to claim 9, wherein the error correction processing situation analyzing means includes:

error correctability deciding means for deciding whether or not the error which is added to the audio code is correctable, based on contents of the audio decoding process associated with the audio decoding means which is selected by a preceding frame stored in a audio decoding process storage buffer, if it is decided by the audio code error deciding means that the error is added to the audio code.

11. A audio decoding device according to claim 10, wherein the optimization audio decoding processing means selects the interpolation process type audio decoding means if it is decided by an error correctability deciding means that the error which is added to the audio code is uncorrectable, and

the selected interpolation process type audio decoding means reads the audio data and the audio code, which are stored in the audio information storage buffer and are concerned with the preceding frame, as the interpolation information based on the interpolation process information concerning to the audio code, then applies the interpolation process to the audio code to which the uncorrectable error is added in unit of bit based on the interpolation information and the soft decision information, and then decodes the audio code which is subjected to the interpolation process to generate the audio data, if the audio code which is output from the error correction processing means and to which the uncorrectable error is added is received.

12. A audio decoding device according to claim 10, wherein the optimization audio decoding processing means selects the optimization process type audio decoding means if it is decided by the error correctability deciding means that the error which is added to the audio code is correctable, and

the selected optimization process type audio decoding means applies an optimizing process to the audio code which is output from the error correction processing means, and then decodes the audio code which is subjected to the optimizing process to generate the audio data.

13. A audio decoding device according to claim 10, wherein the optimization process type audio decoding means includes:

optimizing normal process type audio decoding means for decoding the audio code to generate the audio data if it is decided by the error correctability deciding means that the error which is added to the audio code is correctable.

14. A audio decoding device according to claim 13, wherein the optimization process type audio decoding means includes:

audio decision processing means for calculating a correlation value between the audio data generated by the optimizing normal process type audio decoding means and the audio data in the preceding frame stored in the audio information storage buffer, then deciding whether or not a calculated correlation value is in excess of a threshold value, and

the optimization process type audio decoding means sets the audio data generated by the optimizing normal process type audio decoding means as the audio data generated in the optimization process type audio decoding means if it is decided by the audio decision processing means that the calculated correlation value exceeds the threshold value.

15. A audio decoding device according to claim 13, wherein the optimization process type audio decoding means includes:

interpolation process deciding means for counting sequentially a number of times of the audio decoding process frame by frame by using the optimizing normal process type audio decoding means, and then deciding whether or not the number of times of the audio decoding process exceeds a predetermined number of times if it is decided by the audio decision processing means that the correlation value is not in excess of the threshold value, and

optimizing interpolation process type audio decoding means for applying the interpolation process to the audio code being output from the error correction processing means bit by bit based on the soft decision information and the audio code concerning to the preceding frame which is stored in the audio information storage buffer, then decoding the audio code which is subjected to the interpolation process to generate the audio data, and then setting such audio data as the audio data generated in the optimization process type audio decoding means if it is decided by the interpolation process deciding means that the number of times of the audio decoding process in every frame exceeds the predetermined number of times.

16. A audio decoding device according to claim 9, wherein the optimization audio decoding processing means selects the normal process type audio decoding means if it is decided by the audio code error deciding means that no error is added to the audio code, and

the selected normal process type audio decoding means decodes the audio code which is output from the error correction processing means to generate the audio data.

17. A audio decoding device according to claim 5, wherein the optimization audio decoding processing means includes:

audio decoding process storing means for storing sequentially contents of the audio decoding process, which are concerned with a selected audio decoding means, into a audio decoding process storage buffer every frame of the audio data when the audio data which are generated by the selected audio decoding means are output.

18. A audio decoding device according to claim 5, wherein the optimization audio decoding processing means includes:

audio information storage means for storing sequentially the audio data and the audio code into a audio information storage buffer every frame when the audio data which are generated by the selected audio decoding means are output.

19. A audio decoding device according to claim 5, wherein the optimization process type audio decoding means includes:

audio code optimization processing means for detecting likelihood of respective elements of the audio code which is output from the error correction processing means based on the soft decision information, then applying bit inversion to low likelihood elements of the audio code, and then generating the audio code which is subjected to the bit inversion, if it is decided by the interpolation process deciding means that the number of times of the audio decoding process in every frame does not exceed the predetermined number of times, and

the optimizing normal process type audio decoding means decodes the audio code which is generated by the audio code optimization processing means and which is subjected to the bit inversion to generate the audio data.