EP1303856A1 - Method for concealing transmission errors in digital audio data - Google Patents
Method for concealing transmission errors in digital audio dataInfo
- Publication number
- EP1303856A1 EP1303856A1 EP01953895A EP01953895A EP1303856A1 EP 1303856 A1 EP1303856 A1 EP 1303856A1 EP 01953895 A EP01953895 A EP 01953895A EP 01953895 A EP01953895 A EP 01953895A EP 1303856 A1 EP1303856 A1 EP 1303856A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- channel
- digital audio
- errors
- audio data
- audio channel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 60
- 230000005540 biological transmission Effects 0.000 title claims abstract description 59
- 230000005236 sound signal Effects 0.000 claims description 3
- 238000001228 spectrum Methods 0.000 abstract description 9
- 238000001514 detection method Methods 0.000 description 8
- 238000007493 shaping process Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 125000004122 cyclic group Chemical group 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000005070 sampling Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000005562 fading Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005923 long-lasting effect Effects 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/005—Correction of errors induced by the transmission channel, if related to the coding algorithm
Definitions
- the invention is based on a method for concealing transmission errors in digital audio data according to the preamble of the independent claim.
- the method according to the invention for concealing transmission errors in digital audio data with the features of the independent patent claim has the advantage over the fact that the concealment of errors is initialized with start values. This is the concealment of errors
- the method according to the invention enables improved error concealment with little additional effort.
- the method according to the invention can be used on all available audio decoders.
- individual error strategies can be implemented in order to carry out a corresponding shaping of the audio spectrum depending on the number of transmission errors.
- Various audio compression methods can also be used with the method according to the invention.
- the reception quality calculated at the beginning of the audio channel set is the start values for the initialization of the error concealment supplies.
- Current bit error rate values and / or checksum errors and / or scale factor errors are thus used for error concealment, so that the error concealment adapts to the reception quality of the received audio data. This is possible because of the
- Signal processing line in a radio receiver that uses the method according to the invention must first fill the individual blocks of signal processing with data and therefore, for example, the bit error rate resulting from the channel decoding before the start of the
- Audio playback is available. This means that this current data can advantageously be used when concealing errors.
- Error concealment is advantageous in that the reception quality from the previously set audio channel is used for the initialization of error concealment with the currently set audio channel.
- the previously set audio channel provides data on the
- reception quality is calculated from the bit error rate and / or the number of scale factor errors and / or the number of checksum errors. These values result from the Channel or source decoding. This means that values that are created for other tasks are also used.
- the error concealment of the digital audio data is carried out by equalization. This enables the spectrum to be shaped so that the subjective impression of a listener of transmission errors is minimized. This is based on an equalizer function.
- an analog audio program or audio channel was initially set, for example an FM channel, the reception quality of which is used to conceal the transmission errors of this previously set audio channel, which is based on the reception field strength and / or synchronization attempts .
- This reception quality is compared with a predetermined quality measure in order to determine whether the reception quality is still sufficient.
- the radio receiver performs a check of the reception quality of an alternative digital audio channel (DAB), for example in transmission breaks or at least for the duration of a frame, in order, if necessary, to use this digital audio channel, which, when reception is good, is better
- DAB digital audio channel
- Radio receiver is able to process both analog and digital audio channels. Fault concealment in FM can also be done by reducing bandwidth or level. This is the case, for example, with an FM-DAB switchover.
- a Another way of determining the reception quality for an FM audio program is to evaluate a digital carrier, such as the RDS (Radio Data Signal), for example.
- An advantageous further development of the method according to the invention consists in that after switching from an analog audio channel to a digital audio channel and vice versa, there is initially a short muting, at most one second, in order to determine a corresponding reception quality for the currently set digital audio channel for the initialization of the error concealment , A listener will find this more pleasant than a poor concealment of errors.
- the duration of the storage of the reception quality of the previously set digital audio channel is compared with a threshold value, so that reception qualities that only give an impression of a distant past are not used for the initialization of the error concealment.
- a distant past concerns, for example, transmission error numbers that were calculated at least 2 to 3 seconds ago. A vehicle may already have covered such a distance within 2 to 3 s, so that the reception conditions and thus the reception quality may have changed significantly.
- a radio receiver has appropriate means to carry out the method according to the invention.
- Figure 1 is a block diagram of a radio receiver for
- FIG. 2 is a flowchart of the inventive method.
- an error concealment that is used for a certain number of transmission errors that cannot be corrected by the channel decoding must be initialized.
- such an error concealment is therefore initialized with start values, the error concealment then being adapted by a reception quality which results from the currently set digital audio channel, and after the channel decoding, the error concealment of the transmission errors in the digital audio data is then carried out.
- the start values are calculated either from the current number of transmission errors of the set digital audio channel or from a number of transmission errors from a previously set digital audio channel.
- the bit error rate and / or the number of scale factor errors and / or the number of checksum errors flow into the number of transmission errors.
- the starting values are adjusted accordingly by comparing the channel error protection levels of the first and second audio channels.
- the Channel error protection level denotes how much data is added to the user data in order to detect or correct transmission errors at the receiving end.
- Reception quality for this audio channel is calculated, for example, from the reception field strength and the synchronization attempts and compared with a predetermined quality measure in order to check the reception quality of the audio channel.
- a number of transmission errors of equivalent digital audio channels is checked so that a switchover can be carried out if necessary.
- a short muting must also be provided at the beginning in order to determine the number of transmission errors of the newly set digital audio channel for a corresponding error concealment. The reverse is also possible.
- the number of transmission errors of the previously set digital audio channel is too old, the number of transmission errors of the currently set digital audio channel is also used to initialize the concealment of errors.
- the error concealment itself is carried out by shaping the audio spectrum.
- the method according to the invention enables a switchover, in particular in unfavorable reception situations, to a subjectively better hearing impression of received ones Audio programs.
- Currently evaluated data are used.
- the method according to the invention relates in particular to digital audio data which is digital
- Broadcast transmission procedures are transmitted. This particularly includes DAB (Digital Audio Broadcasting).
- DRM Digital Radio Mondiale
- DVB Digital Video Broadcasting
- OFDM Orthogonal Frequency Division Multiplex
- the OFDM is a suitable method for overcoming the frequency-selective fading. The frequency-selective fading will then not have a drastic effect on the reception of digital audio data, since the digital audio data are distributed over many subcarriers which do not influence one another. The subcarriers are on different frequencies that are close together.
- Error detection which is implemented in the source decoding and works by means of a checksum, forms a second stage in order to recognize and correct errors. If an error is detected, previously stored data will replace current error-containing data. There is thus an error concealment, but since audio data which follow one another in time have a close correlation to one another, it is a good estimate to replace data which is currently faulty. This affects frame errors that are recognized by checksum errors, and Scale factor errors, which are also determined by checksum errors.
- the audio signals are divided into frequency ranges on the transmission side.
- the frequency value with the greatest signal power is used as a so-called scale factor for each frequency range.
- the remaining signal values in this frequency range are normalized to this scale factor. This considerably reduces the distance from the smallest signal power to the largest signal power.
- the scale factors are then transmitted to the receiver with the standardized audio data.
- CRC Cyclic Redundancy Check
- the error detection for the scale factors is used for the method according to the invention. Ie the number of errors, which is determined in the scale factors, determines which measure the method according to the invention takes with regard to the equalization.
- the digital audio data are still spectrally encoded.
- the well-known MPEG methods or Dolby-AC3 are used for this.
- DAB uses MPEG-1,2 Layer 2 coding.
- DAB Downlink Adaptive Binary Arithmetic Coding
- checksums Cyclic Redundancy Code
- CRC Cyclic Redundancy Code
- the audio decoder uses these two checksums to identify whether errors have occurred in the frame. If the first checksum calculation detects an ISO CRC error, the frame cannot be decoded. There may have to be a frame repetition with the last one received correctly
- the device If it is not possible, the device is muted. In the case of the second checksum calculation, the frame can still be decoded in the event of an error; however, since some scale factors are damaged, they are corrected by previously correctly received scale factors replaced. These measures can help to overcome individual, very short-term reception problems. In normal cases, however, the reception conditions change very quickly, which is why the audio decoder constantly switches back and forth between activated audio output and, if necessary, a muting. This sounds very uncomfortable and does not do justice to a digital high-end receiver that is supposed to provide audio playback in CD quality. Problems arise in particular when activating, i.e. switching on audio channels. If an audio channel is activated and the audio quality is very poor, it is usually switched through anyway. This is where the method according to the invention begins.
- FIG. 1 shows a radio receiver that uses the method according to the invention for concealing transmission errors in digital audio data.
- An antenna 1 is connected to an input of a high-frequency receiver 2.
- An output of the high-frequency receiver 2 leads to an analog-digital converter 3.
- the data output of the analog-digital converter 3 is connected to a data input of a channel decoder 5.
- a data output of the channel decoding 5 leads to an input of a demultiplexer 4 with error detection.
- a first data output of demultiplexer 4 leads to dequantization 6.
- a second data output of demultiplexer 4 leads to a second data input of dequantization 6.
- a third data output of demultiplexer 4 leads to equalization 11, which in turn is connected to a third data input of dequantization 6 ,
- a data output of dequantization 6 leads to a filter bank 7, which is itself connected to a digital-to-analog converter 8.
- the output of the digital-to-analog converter 8 is at an audio amplifier 9 connected.
- the signals amplified by the audio amplifier are transmitted by a loudspeaker 10.
- a processor which the radio receiver has, carries out the channel decoding 5 and the demultiplexing 4
- Source decoding can also be implemented on a processor.
- Error detection must also be factually considered for source decoding. On the basis of this last-mentioned error detection, error concealment occurs, with the replacement of frames or scale factors.
- the DAB signals which are received with the antenna 1, are filtered in the high-frequency receiver 2, amplified and converted into an intermediate frequency.
- the converted signals are then digitized by the analog-digital converter 3.
- the channel decoding 5 carries out the calculation of the bit errors and, if necessary, an error correction. With the channel decoding 5, a determination of the bit error rate is possible.
- the resulting data stream is divided by the demultiplexer 4 into the audio data and page information.
- This page information relates in particular to data about the dequantization 6 of the digital audio data. This side information is then transmitted for dequantization 6. Furthermore, the demultiplexer 4 carries out a
- the equalization 11 initializes the concealment of errors at the beginning of a set audio channel (subchannel). For this purpose, the equalization 11, if another digital audio channel had previously been set, uses the transmission error number of this previously set digital audio channel and its
- Channel error protection to fill the concealment with start values. This is necessary because at the beginning of a set audio channel, the statistics about the errors that occur in this currently set audio channel are based on a small database. The currently calculated data can therefore provide a distorted picture. The previously set and the currently set audio channel can still differ in the channel error protection. This means that one channel uses more data for channel error protection than the other. This must be taken into account when calculating the start values for the concealment of errors.
- By muting at the beginning of a new audio channel setting it is possible to determine a sufficient database for the initialization of the error concealment. During muting, the transmission errors for the new audio channel are determined and counted.
- the number of transmission errors of the previously set audio channel is adopted, if the channel error protection is the same, and a corresponding one
- Equalization is stopped.
- the equalization is carried out here by shaping the audio spectrum. This means that the spectral components of the audio spectrum are weighted differently with the equalization, so that, for example, higher frequency components are filtered out in order to improve the subjective hearing impression in the event of disturbances. This can be done until muted. A simple level reduction is also possible.
- the corresponding set of equalizer values is then selected and loaded on the basis of the transmission error number or the reception quality.
- the equalizer values can also be calculated using a predetermined equation.
- a set of equalizer values can be loaded from the memory in order to then calculate new sets of equalizer values based on these equalizer values.
- the initialization of error concealment is therefore only activated when switching to another audio program (audio channel) or when switching on a radio receiver.
- a switchover is also present, for example, in the case of an automatic alternative frequency switchover.
- This technique is used in FM programs and DRM because transmitters are transmitted on alternative frequencies. If there is no previously set audio channel, as is the case when switching on, then currently calculated values of the digital audio data of the currently set audio channel are used for the initialization of the error concealment, which are determined, for example, during a muting. These values then at least give an indication of the extent to which the transmission error number must lead to error concealment. If the number of transmission errors is below a predetermined threshold value, no error concealment is carried out at all, then there is undisturbed radio reception.
- transmission error numbers of the previously set audio channel have been stored for a longer period of time, ie longer than 3 seconds, for example, then these values are also no longer used because they are no longer are characteristic of the current transmission conditions in a motor vehicle.
- the equalization 11 then delivers corresponding equalizer values for the dequantization 6.
- the dequantization 6 is part of the source decoding.
- the scale factors to which the digital audio data are based are used to perform the dequantization.
- the shaping of the audio spectrum is possible.
- the resulting audio spectrum is then subjected to an inverse discrete cosine transformation in the filter bank 7 in order to complete the audio decoding.
- the audio decoding is here at DAB according to the MPEG-1.2 Layer 2 standard.
- the decoded audio data are then converted by a digital-to-analog converter 8 into analog signals in order to be amplified by the audio amplifier 9 and reproduced by the loudspeaker 10 become.
- the decoded audio data present at the output of the audio decoder 7 are present as PCM data (pulse code modulation).
- This data can also be switched to a multimedia bus in order to be used by other components of this multimedia bus, for example a loudspeaker system, for playback.
- a sampling rate converter is used after the filter bank 7 in order to convert the sampling rate to the bus transmission rate, for example. Even if other audio data, for example decoded with MP 3, has been decoded by the radio receiver, a sampling rate conversion may be necessary.
- the radio receiver which is a digital receiver as shown above, is able to receive both DAB and FM. Then the error concealment, if an FM audio channel was selected first and then a DAB channel, by a Sniffer function prepared. That is to say, the radio receiver checks the number of transmission errors in equivalent digital audio channels in short time intervals in order to automatically switch over when the reception quality of the FM channel deteriorates. This also applies in the opposite case if, in the event of poor reception, DAB switches to an equivalent FM audio channel. The reception quality of equivalent FM channels is then determined here during a frame. Such equivalent channels are also transmitted as accompanying information or they are already stored in the radio receiver.
- the reception quality can be determined from the reception field strength (signal field strength), the synchronization attempts, the
- Baseband energy and other parameters can be determined. This reception quality is compared with a predetermined quality measure, which is determined empirically. If the reception quality is better than the quality measure, then there is an acceptable reception, if the reception quality is below the quality measure, then an existing digital audio channel is switched to, provided that the digital audio channel has a number of transmission errors that enable good reception (no muting) ,
- the FM channel can have a digital carrier (RDS), which can be used to determine the number of transmission errors.
- RDS digital carrier
- the number of transmission errors that is determined for a digital audio channel is also compared with a predetermined quality measure in order to be able to make an objective statement about the reception quality. Even with an FM channel, bandwidth concealment can be used to conceal errors. Depending on the reception quality, the bandwidth is gradually reduced. Switching from a digital audio channel to an analog audio channel is preferably carried out only when the device is muted or when the error is concealed.
- the inventive method is shown as a flow chart.
- a user of the radio receiver which was shown in FIG. 1, selects an audio channel in which digital audio data are transmitted.
- the radio receiver receives the digital audio data contained in the digital radio signals by means of the antenna 1 of the radio-frequency receiver 2 and the analog-digital converter 3.
- a data stream is present at the output of the analog-digital converter 3.
- the channel decoding in block 5 from FIG. 1 is then carried out with the determination of the bit error rate.
- the demultiplexer 4 then performs the demultiplexing of the audio frames in audio data and page information. Furthermore, the frame errors and the
- Scale factor error determined. These error measures, including the bit error rate, are then transmitted to the equalization 11, which thus, and possibly with a previously set audio channel, initializes the error concealment or adapts it later to the current reception quality.
- the start values for error concealment are thus calculated from the audio channel previously set, namely from the number of transmission errors.
- the channel error protection, the previously set audio channel and the currently set audio channel compared to adjust the starting values accordingly.
- method step 15 the initialization of the error concealment is started.
- method step 16 it is checked whether a channel had previously been set for which the number of transmission errors had been determined. If this is the case, the channel error protection is compared in method step 17.
- step 19 it is also checked whether the number of transmission errors of the previously set audio channel has been stored for a shorter time than a set threshold value. If this is the case, then in method step 20 the initialization of the start values with the previously calculated number of transmission errors of the previously set
- Audio channels initialized, taking channel error protection into account.
- the error concealment is then started in method step 21, which is then adapted to the current state by means of currently calculated transmission error numbers of the currently set audio channel.
- method step 18 If it was determined in method step 16 that no digital audio channel had previously been set and thus there was no number of transmission errors for the initialization of the error concealment, then in method step 18 the currently calculated number of transmission errors, which results from the bit error rate that results from the channel decoding, the checksum error number which is calculated by a CRC (Cyclic Redundancy Check) and which
- Scale factor error count calculated. This then starts the initialization with start values in method step 20, and then again in method step 21 Continue concealing errors with currently calculated transmission error numbers.
- method step 19 If it was determined in method step 19 that the number of transmission errors of the previously set audio channel had already been stored for a longer time than the set threshold value (for example 3 s), this number of transmission errors is deleted and only the number of transmission errors of the currently set audio channel is used, so that the process then jumps to method step 18 and continues as shown above.
- the set threshold value for example 3 s
Landscapes
- Engineering & Computer Science (AREA)
- Computational Linguistics (AREA)
- Signal Processing (AREA)
- Health & Medical Sciences (AREA)
- Audiology, Speech & Language Pathology (AREA)
- Human Computer Interaction (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Detection And Prevention Of Errors In Transmission (AREA)
- Circuits Of Receivers In General (AREA)
- Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
- Noise Elimination (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10034783A DE10034783A1 (en) | 2000-07-18 | 2000-07-18 | Method for concealing transmission errors in digital audio data |
DE10034783 | 2000-07-18 | ||
PCT/DE2001/002557 WO2002007149A1 (en) | 2000-07-18 | 2001-07-13 | Method for concealing transmission errors in digital audio data |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1303856A1 true EP1303856A1 (en) | 2003-04-23 |
EP1303856B1 EP1303856B1 (en) | 2004-10-06 |
Family
ID=7649242
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP01953895A Expired - Lifetime EP1303856B1 (en) | 2000-07-18 | 2001-07-13 | Method for concealing transmission errors in digital audio data |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP1303856B1 (en) |
JP (1) | JP4813747B2 (en) |
CA (1) | CA2415424C (en) |
DE (2) | DE10034783A1 (en) |
ES (1) | ES2228914T3 (en) |
WO (1) | WO2002007149A1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE527866C2 (en) * | 2003-12-19 | 2006-06-27 | Ericsson Telefon Ab L M | Channel signal masking in multi-channel audio system |
US7835916B2 (en) | 2003-12-19 | 2010-11-16 | Telefonaktiebolaget Lm Ericsson (Publ) | Channel signal concealment in multi-channel audio systems |
EP3340497A1 (en) * | 2016-12-22 | 2018-06-27 | Nxp B.V. | Error concealment with redundant data streams |
EP3340498B1 (en) | 2016-12-22 | 2022-07-13 | Nxp B.V. | Receive path quality information |
WO2021200151A1 (en) * | 2020-03-30 | 2021-10-07 | ソニーグループ株式会社 | Transmission device, transmission method, reception device, and reception method |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2507972B2 (en) * | 1993-08-20 | 1996-06-19 | 日本電気株式会社 | Line quality monitoring device |
JPH08242215A (en) * | 1995-03-06 | 1996-09-17 | Mitsubishi Electric Corp | Digital sound broadcasting receiver |
JP3345557B2 (en) * | 1996-10-14 | 2002-11-18 | アルパイン株式会社 | Digital audio broadcast receiving apparatus and receiving method |
DE19959037B4 (en) * | 1999-12-08 | 2004-04-29 | Robert Bosch Gmbh | Process for decoding digital audio data |
-
2000
- 2000-07-18 DE DE10034783A patent/DE10034783A1/en not_active Ceased
-
2001
- 2001-07-13 JP JP2002512969A patent/JP4813747B2/en not_active Expired - Fee Related
- 2001-07-13 WO PCT/DE2001/002557 patent/WO2002007149A1/en active IP Right Grant
- 2001-07-13 EP EP01953895A patent/EP1303856B1/en not_active Expired - Lifetime
- 2001-07-13 CA CA002415424A patent/CA2415424C/en not_active Expired - Fee Related
- 2001-07-13 DE DE50104018T patent/DE50104018D1/en not_active Expired - Lifetime
- 2001-07-13 ES ES01953895T patent/ES2228914T3/en not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
---|
See references of WO0207149A1 * |
Also Published As
Publication number | Publication date |
---|---|
DE50104018D1 (en) | 2004-11-11 |
WO2002007149A1 (en) | 2002-01-24 |
DE10034783A1 (en) | 2002-02-07 |
CA2415424A1 (en) | 2003-01-08 |
JP4813747B2 (en) | 2011-11-09 |
ES2228914T3 (en) | 2005-04-16 |
CA2415424C (en) | 2007-10-02 |
JP2004504744A (en) | 2004-02-12 |
EP1303856B1 (en) | 2004-10-06 |
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