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Bit Error Concealment For Audio Coding Systems

The QM arithmetic coder achieves a very good compression result if the context is properly selected to summarize the correlation between coded data. The BEC method includes two distinct aspects: (1) detection of bit errors capable of introducing an audible artifact in an audio output signal, and (2) concealment of the artifact. The obvious approach is to simply declare a packet loss and employ PLC. In particular, the long-term prediction residual for the current frame is held in xwp(XWPOFF:XWPOFF+FRSZ−1), wherein XWPOFF denotes an offset into vector xwp(n) and FRSZ denotes the frame size in samples. [0062] news

such as Hamming, BCH, cyclic, and Reed-Muller codes, the Reed-Solomon code is chosen in our implementation because of its excellent performance on correcting burst errors, which is the most common case Responsive to detecting that the decoded audio frame includes the distortion, operations are performed on the decoded audio signal to conceal the distortion. [0018] A system is also described herein. FIG. 4 is a block diagram that depicts functional elements of bit error feature set analyzer 314 in accordance with one implementation of the present invention. LPC analysis and filtering module 306 analyzes 8 kHz audio signal 114 to calculate the short-term predictor coefficients ai, i=1, 2, . . . , M.

The system of claim 18, wherein the bit error detection module is configured to determine the average signal level of the prediction residual for the decoded audio frame by computing an This condition is often called frame erasure in wireless networks and packet loss in packet networks. For example, if no packets have been lost in the recent past, PLR would be close to zero (or equal to zero).

End-to-end delay is a critical component of any two-way audio communications system and this limits the number of retransmissions in eSCO channels to one or two retransmissions. Because a Bluetooth® radio operates on the globally available unlicensed 2.4 GHz band, it must share the band with other consumer electronic devices that also might operate in this band including Bit stream 112 comprises a CVSD-encoded representation of an audio signal and PCM signal 114 comprises a decoded representation of the same audio signal. In general, re-encoding performs well in highly predictable regions where the concealment signal closely resembles the original signal.

LPC Analysis and Filtering Module 306 [0056] LPC analysis and filtering module 306 is configured to perform a so-called “LPC analysis” on 8 kHz audio signal 114 to update coefficients of If the maximum value of the long-term prediction residual is much greater than the average magnitude, then this tends to indicate that a bursty bit error sufficient to create an audible As a result, annoying “click-like” artifacts may become audible in the audio output when bursty bit errors occur. [0012] Recent versions of the Bluetooth specification (in particular, version 1.2 of the ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: http://0.0.0.5/ Connection to 0.0.0.5 failed.

The method of claim 1, wherein performing operations on the decoded audio signal to conceal the distortion comprises replacing the decoded audio frame with a synthesized audio frame generated in accordance As previously mentioned, bit errors may cause a packet to be discarded. To understand this, consider a signal with no bit errors. The first means are for enabling the processing unit to decode a portion of an encoded bit stream to generate a decoded audio frame, wherein the decoded audio frame comprises a

Because audio processing module 104 does not have access to encoded 64 kb/s bit stream 112, BEC system 110 must detect bit errors and conceal artifacts resulting therefrom without knowledge of Takishima, M. PLC Module 206 [0099] PLC module 206 is configured to determine if the current frame has been lost based on the state of a bad frame indicator (BFI) received from another In one embodiment, bit error decision module 406 makes the final decision by comparing the maximum absolute value xwpmax(k) of the long-term prediction residual for the current frame to the average

BER-based threshold biasing module holds BER constant during periods of active speech. [0043] Generally speaking, BER-based threshold biasing module 202 detects a click only if voice activity is observed for a navigate to this website In theory, eSCO channels eliminate the problem of undetected bit errors in the user-data portion of a packet by supporting the retransmission of lost packets and by providing CRC protection for No. 12/147,781 to Chen, entitled “Low-Complexity Frame Erasure Concealment,” the entirety of which is incorporated by reference herein. Frame erasure and packet loss may result, for example, from corruption of a frame or packet due to bit errors.

Each element depicted in FIG. 2 will now be described. [0037] A. If the pitch track classification is “tracking,” then it is more likely that if a segment of speech from the current frame does not match well with the past, it is The audio decoder is configured to decode a portion of an encoded bit stream to generate a decoded audio frame, wherein the decoded audio frame comprises a portion of a decoded http://onlinetvsoftware.net/bit-error/bit-error-rate-analysis-of-jamming-for-ofdm-systems.php The system is shown in FIG. 1 as BEC system 110.

The method of claim 1, wherein analyzing at least the decoded audio signal to detect whether the decoded audio frame includes the distortion comprises: computing a plurality of pitch predictor taps Your cache administrator is webmaster. Re-Encoding Decision Module 408 [0091] Re-encoding decision module 408 is configured to set a re-encoding flag, denoted rei, that is used to enable or disable re-encoding for the current frame.

As mentioned above, CVSD was designed to be robust to random bit errors but is not robust to bursty bit errors.

In one embodiment, pitch estimator 302 comprises a simple, low-complexity pitch estimator based on an average mean difference function (AMDF). In accordance with the method, a portion of an encoded bit stream is decoded to generate a decoded audio frame, wherein the decoded audio frame comprises a portion of a decoded In this case, the false detection rate should be as low as possible. If it is not, it is limited to such.

The noise pulse differs in at least three very important ways: (1) the noise pulse shape varies from one error frame to the next, (2) the pulse can often consume the In one embodiment, the values of the two detection biasing factors are stored in look-up tables that are referenced based on the current value of BER. [0049] C. HV1 packets provide ⅓ rate FEC on a data payload size of 10 bytes. http://onlinetvsoftware.net/bit-error/bit-error-rate-analysis-jamming-ofdm-systems.php In one embodiment, A VMWL is set to 40. [0073] Note that the above algorithm uses the samples in xwp(n) from the frame preceding the current frame.

If the frame preceding the current frame did not contain a bit-error (in other words, if bei(k−1)=0), then AVM calculator 402 calculates avm in accordance with: [0000] avm = ∑ n The maximum absolute value of the quantized coefficients that can be represented by each Huffman codebook and the number of coefficients in each n-tuple for each codebook is shown in Table