|Publication number||US8102872 B2|
|Application number||US 11/123,478|
|Publication date||Jan 24, 2012|
|Filing date||May 5, 2005|
|Priority date||Feb 1, 2005|
|Also published as||CN101208740A, CN101208740B, EP1849158A2, EP1849158B1, US20060171419, WO2006084003A2, WO2006084003A3|
|Publication number||11123478, 123478, US 8102872 B2, US 8102872B2, US-B2-8102872, US8102872 B2, US8102872B2|
|Inventors||Serafin Diaz Spindola, Peter J. Black, Rohit Kapoor|
|Original Assignee||Qualcomm Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (16), Non-Patent Citations (9), Referenced by (15), Classifications (6), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims benefit of U.S. Provisional Application No. 60/649,192 entitled “Method for Discontinuous Transmission and Accurate Reproduction of Background Noise Information” filed Feb. 1, 2005, which is hereby incorporated by reference.
The present invention relates generally to network communications. More specifically, the present invention relates to a novel and improved method and apparatus to improve voice quality, lower cost and increase efficiency in a wireless communication system while reducing bandwidth requirements.
CDMA vocoders use continuous transmission of 1/8 frames at a known rate to communicate background noise information. It is desirable to drop or “blank” most of these 1/8 frames to improve system capacity while keeping speech quality unaffected. There is therefore a need in the art for a method to properly select and drop frames of a known rate to reduce the overhead required for communication of the background noise.
In view of the above, the described features of the present invention generally relate to one or more improved systems, methods and/or apparatuses for communicating background noise.
In one embodiment, the present invention comprises a method of communicating background noise comprising the steps of transmitting background noise, blanking subsequent background noise data rate frames used to communicate the background noise, receiving the background noise and updating the background noise.
In another embodiment, the method of communicating background noise further comprises the step of triggering an update of the background noise, when the background noise changes, by transmitting a new prototype rate frame.
In another embodiment, the method of communicating background noise further comprises the step of triggering by: filtering the background noise data rate frame, comparing an energy of the background noise data rate frame to an average energy of the background noise data rate frames, and transmitting an update background noise data rate frame, if a difference exceeds a threshold.
In another embodiment, the method of communicating background noise further comprises the step of triggering by: filtering the background noise data rate frame, comparing a spectrum of the background noise data rate frame to an average spectrum of the background noise data rate frames, and transmitting an update background noise data rate frame, if a difference exceeds a threshold.
In another embodiment, the present invention comprises an apparatus for communicating background noise comprising a vocoder having at least one input and at least one output, wherein the vocoder comprises a decoder having at least one input and at least one output and an encoder having at least one input and at least one output, at least one smart blanking apparatus having a memory and at least one input and at least one output, wherein a first of the at least one input is operably connected to the at least one output of the vocoder and the at least one output is operably connected to the at least one input of the vocoder, a de-jitter buffer having at least one input and at least one output, wherein the at least one output is operably connected to a second of the at least one input of the smart blanker; and a network stack having at least one input and at least one output, wherein the at least one input is operably connected to the at least one input of the de-jitter buffer and the at least one input is operably connected to the at least one output of the smart blanking apparatus.
In another embodiment, the smart blanking apparatus is adapted to execute a process stored in memory. The process includes instructions to transmit the background noise, blank subsequent background noise data rate frames used to communicate the background noise, receive the background noise, and update the background noise.
Further scope of applicability of the present invention will become apparent from the following detailed description, claims, and drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which:
The word “illustrative” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “illustrative” is not necessarily to be construed as preferred or advantageous over other embodiments.
During a full duplex conversation, there are many instances when at least one of the parties is “silent.” During these “silence” intervals, the channel communicates background noise information. Proper communication of the background noise information is a factor that affects the voice quality perceived by the parties involved in a conversation. In IP based communications, when one party goes silent, a packet may be used to send messages to the receiver indicating that the speaker has gone silent and that background noise should be reproduced or played back. The packet may be sent at the beginning of every silence interval. CDMA vocoders use continuous transmission of 1/8 rate frames at a known rate to communicate background noise information.
Landline or wireline systems send most speech data because there are not as many constraints on bandwidth as with other systems. Thus, data may be communicated by sending full rate frames continuously. In wireless communication systems, however, there is a need to conserve bandwidth. One way to conserve bandwidth in a wireless system is to reduce the size of the frame transmitted. For example, many CDMA systems send 1/8 rate frames continuously to communicate background noise. The 1/8 rate frame acts as a silence indicator frame (silence frame). By sending a small frame, as opposed to a full or half rate frame, bandwidth is saved.
The present invention comprises an apparatus and method of conserving bandwidth comprising dropping or “blanking” “silence” frames. Dropping or “blanking” most of these 1/8 rate silence (or background noise) frames improves system capacity while maintaining speech quality at acceptable levels. The apparatus and method of the present invention is not limited to 1/8 rate frames, but may be used to select and drop frames of a known rate used to communicate background noise to reduce the overhead required for communication of the background noise. Any rate frame used to communicate background noise, may be known as a background noise rate frame and may be used in the present invention. Thus, the present invention may be used with any size frame as long as it is used to communicate background noise. Furthermore, if the background noise changes in the middle of a silence interval, the present smart blanking apparatus updates the communication system to reflect the change in background noise without significantly affecting speech quality.
In CDMA communications, a frame of known rate may be used for encoding the background noise when the speaker goes silent. In an illustrative embodiment, a 1/8 rate frame is used in a Voice over Internet Protocol (VoIP) system over High Data Rate (HDR). HDR is described by Telecommunications Industry Association (TIA) standard IS-856, and is also known as CDMA2000 1xEV-DO. In this embodiment, a continuous train of 1/8 rate frames is sent every 20 milliseconds (msec) during a silence period. This differs from full rate (rate 1), half rate (rate 1/2) or quarter rate (rate 1/4) frames, which may be used to transmit voice data. Although the 1/8 rate packet is relatively small, i.e., has fewer bits, compared to a full rate frame, packet overhead in a communication system may still be considerable. This is especially true since a scheduler may not differentiate between voice packet rates. A scheduler allocates system resources to the mobile stations to provide efficient utilization of the resources. For example, the maximum throughput scheduler maximizes cell throughput by scheduling the mobile station that is in the best radio condition. A round-robin scheduler allocates the same number of scheduling slots to the system mobile stations, one at a time. The proportional fair scheduler assigns transmission time to mobile stations in a proportionally (user radio condition) fair manner. The present method and apparatus can be used with many types of schedulers and is not limited to one particular scheduler. Since a speaker is typically silent for about 60% of a conversation, dropping most of these 1/8 rate frames used to transmit background noise during the silence periods provides a system capacity gain by reducing the total amount of data bits transmitted during these silence periods.
The reason that the speech quality is mostly unaffected comes from the fact that the smart blanking is performed in such a way that background noise information is updated when required. In addition to enhanced capacity, using 1/8 rate frame smart blanking reduces the overall cost of transmission because bandwidth requirements are lessened. All these improvements are done while minimizing the effect on the perceived voice quality.
The smart blanking apparatus of the present invention may be used with any system in which packets are transferred, such as many voice communication systems. This includes but is not limited to wireline systems communicating with other wireline systems, wireless systems communicating with other wireless systems, and wireline systems communicating with wireless systems.
Production of Background Noise
In an illustrative embodiment described herein, there are two components to background noise generation. These components include the energy level or volume of the noise and the spectral frequency characteristics, or “color” of the noise.
This method of generating background noise is not limited to CDMA vocoders. A variety of other speech vocoders such as Enhanced Full Rate (EFR), Adaptive Multi Rate (AMR), Enhanced Variable Rate CODEC (EVRC), G.727, G.728 and G.722 may apply this method of communicating background noise.
Although there are an infinite number of energy levels and spectral frequency characteristics for the background noise 89 during a silence interval and for the voice during a conversation, the background noise 89 during silence intervals can usually be described by a finite (relatively small) number of values. To reduce the required bandwidth for communication of background noise information, the spectral and energy noise information for a particular system may be quantized and encoded into codebook entries 71, 73 stored in one or more codebooks 65. Thus, the background noise 35 appearing during a silence interval can usually be described by a finite number of the entries 71, 73 in these codebooks 65. For example, a codebook entry 73 used in an Enhanced Variable Rate Codec (EVRC) system may contain 256 different 1/8 rate constants for power. Typically, any noise transmitted within an EVRC system will have a power level corresponding to one of these 256 values. Furthermore, each number decodes into 3 power levels, one for each subframe inside an EVRC frame. Similarly, an EVRC system will contain a finite amount of entries 71 which correspond to the frequency spectrums associated with encoded background's noise 35.
In one embodiment, an encoder 80 located in the vocoder 60 may generate the codebook entries 71, 73. This is illustrated in
If the rate determinator 122, with input from the model parameter estimator 100, decides to encode a silence frame, the first switch 110 routes the model parameters 105 to a 1/8 rate encoder 120 and the vocoder 60 outputs 1/8 rate frame parameters 119. A packet formatting module 124 contains the apparatus which puts those parameters 119 into a formatted packet 125. If a 1/8 rate frame 70 is generated as illustrated, the vocoder 60 may output a packet 125 containing codebook entries corresponding to energy (FGIDX) 73, or spectral energy values (LSPIDX1 or LSPIDX2) 71 of the voice or silence sample 85.
A rate determinator 122 applies a voice activity detection (VAD) method and rate selection logic to determine what type of packet to generate. The model parameters 105 and an external rate command signal 107 are input to the rate determinator 122. The rate determinator 122 outputs a rate decision signal 109.
The 1/8 Rate Frame
In the illustrated embodiment shown in
Blanking 1/8 Rate Frames
In an exemplary embodiment, a method of blanking 1/8 rate frames 70 may be divided between the transmitting device 150 and the receiving device 160. This is shown in
Since both cell phones shown in
It should be pointed out that the each cell phone user both transmits speech (speaks) and receives speech (listens). Thus, the smart blanking apparatus 140 may also be one block or apparatus at each cell phone which performs both the transmitting and the receiving steps. This is illustrated in
Further, a time warper 190 may be used with the smart blanking apparatus 140. Speech time warping is the action of expanding or compressing the duration of a speech segment without noticeably degrading its quality. Time warping is illustrated in
Classifying 1/8 Rate Frames
1. Transitory 1/8 Rate Frames
In the illustrative embodiment, frames may be classified according to their positioning after a talk spurt. Frames immediately following a talk spurt may be termed “transitory.” They may contain some remnant voice energy in addition to the background noise 89 or they may be inaccurate because of vocoder convergence operation such as, for example, when the encoder is still estimating background noise. Thus, the information contained within these frames varies from the current average volume level of the “noise.” These transitory frames 205 may not be good examples of the “true background noise” during a silence period. On the other hand, stable frames 210 contain a minimal amount of voice remnant which is reflected in the average volume level.
2. Stable Noise Frames
Those frames following the “transitory” noise frames 205 during a silence interval may be termed “stable” noise frames 210. As stated above, these frames display minimal influence from the last talk spurt, and thus, provide a good representation of the sampled input background noise 89. One skilled in the art will recognize that stable background noise 35 is a relative term because background noise 35 may vary considerably.
Differentiating Transitory from Stable Frames
There are several methods for differentiating transitory 1/8 rate frames 205 from stable 1/8 rate frames 210. Two of those methods are described below.
Fixed Timer Discrimination
In one embodiment, the first N frames of a known rate may be considered transitory. For example, analysis of multiple speech segments 89 showed that there is a high probability that 1/8 rate frames 70 may be considered stable after the fifth frame. See
In another embodiment, a transmitter 150 may store the filtered energy value of stable 1/8 rate frames 210 and use it as a reference. After a talk spurt, encoded 1/8 rate frames 70 are considered transitory until their energies fall within a delta of the filtered value. The spectrum usually is not compared because generally if the energy of the frame 70 has converged there is a high probability that its spectral information had converged too.
However, there is the probability that the background noise 35 characteristics could change substantially from one silence period to another resulting in a different filtered energy value for a stable 1/8 rate frame 210 than the one currently stored by the transmitter 150. Consequently, the energy of encoded 1/8 rate frames may not fall within a delta of the filtered value. To address this problem, a converging time-out may also be used to make the differential discrimination method more robust. Thus, the differential method may be considered an enhancement to the fixed timer approach.
Smart Blanking Method
In one embodiment, a method of blanking 1/8 data rate frames or 1/8 rate frames employing transitory frame values 205 may be used. In another embodiment, stable frame values 210 may be used. In a third embodiment, a method of blanking may employ the use of a “prototype 1/8 rate frame” 215. In this third embodiment, the prototype 1/8 data rate frame 215 is used for reproduction of the background noise 35 at the receiver side 160. As an illustration, during initialization procedures, the first transmitted or received 1/8 rate frame 70 may be considered to be the “prototype” frame 215. The prototype frame 215 is representative of the other 1/8 rate frames 70 being blanked by the transmitter 150. Whenever the sampled input background noise 89 changes, the transmitter 150 sends a new prototype frame 215 of known value to the receiver 160. Overall capacity may be increased since each user will require less bandwidth because fewer frames are sent.
Transmitter Side Smart Blanking Method
In the illustrative embodiment the transmitter side 150 transmits at least the first N transitory 1/8 rate frames 205 after a talk spurt. It then blanks the remaining 1/8 rate frames 70 in the silence interval. Test results indicate that sending just one frame produces good results and sending more than one frame improves quality insignificantly. In another embodiment, subsequent transitory frames 205, in addition to the first one or two, may be transmitted.
For operation in unreliable channels (High PER), the transmitter 150 can send the prototype 1/8 rate frame 215 after sending the last transitory 1/8 rate frame 205. In a preferred embodiment, the prototype frame 215 is sent (40 to 100 milliseconds) after the last transitory 1/8 rate frame 205. In one embodiment, the prototype frame 215 is sent 80 milliseconds after the last transitory 1/8 rate frame 205. This delayed transmission has the goal of improving the reliability of the receiver 160 to detect the beginning of a silence period, and transition to the silence state.
In the illustrative embodiment, during the rest of the silence interval, the transmitter 150 sends a new prototype 1/8 rate frame 215 if an update of the background noise 35 has been triggered and if the new prototype 1/8 rate frame 215 is different than the last one sent. Thus, unlike the systems disclosed in the prior art in which the 1/8 frame 70 is transmitted every 20 milliseconds, the present invention transmits the 1/8 frame 70 when the sampled input background noise 89 has changed enough to have an impact in perceived conversation quality and trigger the transmission of a 1/8 frame 70 for use at the receiver 160 to update the background noise 35. Thus, the 1/8 rate frame 70 is transmitted when needed, producing a huge savings in bandwidth.
If the frame is a silence frame, then the system checks whether it is in a silence state (at the step 320). If the system is not in a silence state, such as, for example, when silence state=false, the system transitions to a silence state at the step 325 and sends a silence frame to the receiver (at the step 330). If the system is in a silence state, e.g., when silence state=true, the system checks whether the frame is stable or not (at the step 335).
If the frame is a stable frame 210 (at the step 335), the system updates statistics (at the step 340) and checks to see if an update 212 is triggered (at the step 345). If an update 212 is triggered, the system builds a prototype (at the step 350) and sends a new prototype frame 215 to the receiver 160 (at the step 355). If an update 212 is not triggered, the transmitter 150 will not send a frame to the receiver 160 and returns to the step 300 to receive a frame.
If the frame is not stable (at the step 335), the system may transmit transitory 1/8 rate frames 205 (at the step 360). However, this feature is optional.
Receiver Side Smart Blanking
In the illustrative embodiment, on the receiver side 160, the smart blanking apparatus 140 keeps track of the state of the conversation. The receiver 160 may provide the received frames to a decoder 50 as it receives the frames. The receiver 160 transitions to silence state when a 1/8 rate frame 70 is received. In another embodiment, transition to silence state by the receiver 160 may be based on a time out. In yet another embodiment, transition to silence state by the receiver 160 may be based on both the receipt of a 1/8 rate 70 and on a time out. The receiver 160 may transition to active state when a rate different than a 1/8 rate is received. For example, the receiver 160 may transition to an active state either when a full rate frame or a half rate frame is received.
In the illustrative embodiment, when the receiver 160 is in the silence state, it may play back the prototype 1/8 rate frame 215. If a 1/8 rate frame is received during silence state, the receiver 160 may update the prototype frame 215 with the received frame. In another embodiment, when the receiver 160 is in the silence state, if no 1/8 rate frame 70 is available, the receiver 160 may play the last received 1/8 rate frame 70.
The receiver 160 receives a frame (at the step 400). First, it determines if it's a voice frame (at the step 405). If it is, yes, then it sets its silence state=false (at the step 410), then the receiver plays the voice frame (at the step 415). If the received frame is not a voice frame, then the receiver 160 checks if it is a silence frame (at the step 420). If the answer is yes, the receiver 160 checks if the state is a silence state (at the step 425). If the receiver 160 detects a silence frame, but the silence state is false, e.g., the receiver 160 is in the voice state, the receiver 160 transitions to a silence state (at the step 430) and plays the received frame (at the step 435). If the receiver 160 detects a silence frame, and the silence state is true, the receiver updates the prototype frame 215 (at the step 440) and plays the prototype frame 215 (at the step 445).
As stated above, if the received frame is not a voice frame, then the receiver 160 checks if it is a silence frame. If the answer is no, then no frame was received (e.g. it is an erasure indication) and the receiver 160 checks if the state is a silence state (at the step 450). If the state is silence, e.g., silence state=true, a prototype frame 215 is played (at the step 455). If the state is not silence, e.g., silence state=false, the receiver 160 checks if N consecutive erasures 240 have occurred (at the step 460). (In smart blanking, an erasure 240 is essentially a flag. Erasures 240 may be substituted by the receiver when a frame is expected, but not received). If the answer is no, then N consecutive erasures 240 have not occurred and the smart blanking apparatus 140 coupled to the decoder 50 in the receiver 160 plays an erasure 240 to the decoder 50 (at the step 465) (for packet loss concealment). If the answer is yes, N consecutive erasures 240 have occurred, the receiver 160 transitions to the silence state (at the step 470) and plays a prototype frame 215 (at the step 475).
In one embodiment, the system in which the smart blanking apparatus 140 and method is used is a Voice over IP system where the receiver 160 has a flexible timer and the transmitter 150 uses a fixed timer which sends frames every 20 milliseconds. This is different from a circuit based system where both the receiver 160 and transmitter 150 use a fixed timer. Thus, since a flexible timer is used, the smart blanking apparatus 140 may not check for a frame every 20 milliseconds. Instead, the smart blanking apparatus 140 will check for a frame when asked to do so.
As stated earlier, when time warping is used, a speech segment 89 can be expanded or compressed. The decoder 50 may run when the speaker 235 is running out of information to play back. If the decoder 50 needs to run it will try to get a new frame from the de jitter buffer 180. The smart blanking method is then executed.
Flatness of Background Noise
In the illustrative embodiment, when the decoder 50 detects a 1/8 rate frame 70, the receiver 160 may use only one 1/8 rate frame 70 to reproduce background noise 35 for the entire silence interval. In other words, the background noise 35 is repeated. If there is an update 212, the same updated 1/8 rate frame 212 is sent every 20 milliseconds to generate background noise 35. This may lead to an apparent lack of variance or “flatness” of the reconstructed background noise 35 since the same 1/8 rate frame may be used for extended periods of time and may be bothersome to the listener.
In one embodiment, to avoid “flatness,” erasures 240 may be fed into a decoder 50 at the receiver 160 instead of the prototype 1/8 rate frame 215. This is illustrated in
In another embodiment, random background noise 35 may be “blended” together. This involves blending a prior 1/8 rate frame update 212 a with a new or subsequent 1/8 rate frame update 212 b, gradually changing the background noise 35 from the prior 1/8 frame update value 212 a to the new 1/8 frame update value 212 b. Thus, a randomness or variation is desirably added to the background noise 35. As shown, the background noise energy level can gradually increase (arrow pointing upward from prior 1/8 frame update value 212 a to the new 1/8 frame update value 212 b) or decrease (arrow pointing downward from prior 1/8 frame update value 212 a to the new 1/8 frame update value 212 b) depending on if the energy value in the new update rate frame 212 b is greater or less than the energy value in the prior rate update frame 212 a. This is illustrated in
This gradual change in background noise 35 can also be accomplished using codebook entries 70 a, 70 b in which the frames sent take on codebook entry values that lie between the prior 1/8 frame update value 212 a and the new 1/8 frame update value 212 b, gradually moving from the prior codebook entry 70 a representing the prior 1/8 update frame 212 a to the codebook entry 70 b representing the new update frame 212 b. Each interim codebook entry 70 aa, 70 ab is chosen to mimic an incremental change, Δ, from the prior 212 a to the new update frame 212 b. For example, in
Triggering a 1/8 Rate Prototype Update
In the illustrative embodiment, a transmitter 150 sends an update 212 to the receiver 160 during a silence period if an update of the background noise 35 has been triggered and if the new 1/8 rate frame 70 contains a different noise value than the last one sent. This way, background information 35 is updated when required. Triggering may be dependent on several factors. In one embodiment, triggering may be based on a difference in frame energy.
In another embodiment, triggering may be based on a spectral difference. Such an embodiment is illustrated by the process 1400 of
As stated above, both changes in background noise 35 volume or energy and changes in background noise 35 frequency spectrum can be used as a trigger 175. In previously run trials of the smart blanking method and apparatus, two decibel (2 db) changes in volume have triggered update frames 212. Also, variation in frequency spectrum of 40% has been used to trigger frequency changes 212.
Calculating Spectral Differences
As stated earlier a Linear Prediction Coefficient (LPC) filter (or Linear Predictive Coding filter) is used to extract the frequency characteristics of the background noise 35. Linear predictive coding is a method of predicting future samples of a sequence by a linear combination of the previous samples of the same sequence. Spectral information is usually encoded in a way that the linear differences of the coefficients 72 produced by two different codebooks 65 are proportional to the codebooks' 65 spectral differences. The model parameter estimator 100 shown in
In the illustrative embodiment implementing an ECRV vocoder 60, the spectral differences can be calculated using the following two equations.
In the above equations, LSPIDX1 is a codebook 65 containing “low frequency” spectral information and LSPIDX2 is a codebook 65 containing “high frequency” spectral information. The values n and m are two different codebook entries 71. The value qrate is a quantized LSP parameter. It has three indexes, k, i, j. The value k is the table number that changes for LSPIDX1 and LSPIDX2, where k=1, 2. i is one quantized element that belongs to the same codebook entry 71, where k=1, 2, 3, 4, 5. The value j is the codebook entry 71, e.g., the number that is actually transmitted over the communication channel. The value j corresponds to m and n. The values m and n are used in the above equations instead of j because two variables are needed since the difference between two codebooks is being calculated. In
Each codebook entry 71 decodes to five numbers. To compare the two codebook entries 71 from different frames, the sum of the absolute difference of each of the five numbers is taken. The result is the frequency/spectral “distance” between these two codebook entries 71.
The variation of frequency spectrum codebook entries 71 for “Low Frequency” LSPs and “High Frequency” LSPs is plotted in
Building a New Prototype 1/8 Rate Frame
When an update is required, a new prototype 1/8 rate frame 70 may be built based on the information contained in a codebook 65.
In one embodiment, the transmitter 150 keeps a filtered value of the average energy of every stable 1/8 rate frame 210 produced by the encoder 80 in an “energy codebook” 65 such as a FGIDX codebook 65 stored in memory 130. When an update is required, the average energy value in the FGIDX codebook 65 closest to the filtered value is transmitted to the receiver 160 using the prototype 1/8 rate frame 215.
In another embodiment, a transmitter 150 keeps a filtered histogram of the codebooks 65 containing spectral information, generated by an encoder 80. The spectral information may be “low frequency” or “high frequency” information, such as a LSPIDX1 (low frequency) or LSPIDX2 (high frequency) codebook 65 stored in memory 130. For a 1/8 rate frame update 212, the “most popular” codebook 65 is used to produce an updated value for the background noise 35 by selecting an average energy value in the spectral information codebook 65 whose histogram is closest to the filtered value.
By keeping a histogram of the last N codebook entries 71, some embodiments avoids having to calculate a codebook entry 71 which represents the latest average of the 1/8 rate frames. This represents a reduction in operating time.
A set of thresholds 245 that trigger prototype updates may be set up in several ways. These methods include but are not limited to using “fixed” and “adaptive” thresholds 245. In an embodiment implementing a fixed threshold, a fixed value is assigned to the different thresholds 245. This fixed value may target a desired tradeoff between overhead and background noise quality. In an embodiment implementing an adaptive threshold, a control loop may be used for each of the thresholds 245. The control loop targets a specific percentage of updates 212 triggered by each of the thresholds 245.
The percentage used as targets may be defined with the goal of not exceeding a target global overhead. This overhead is defined as the percentage of updates 212 that are transmitted over the total number of stable 1/8 rate frames 210 produced by the encoder 80. The control loop will keep track of a filtered overhead per threshold 245. If the overhead is above the target it would increase the threshold 245 by a delta, otherwise it decreases the threshold 245 by a delta.
Keep Alive Packet Trigger
If the period of time in which a packet is not sent exceeds a threshold time, the network upon which communication is taking place or the application implementing the voice communication can become confused and think that communication between the two parties has terminated. It will then disconnect the two parties. To avoid this situation from occurring, a keep alive packet is sent before the threshold time has expired to update the prototype. Such a process 1600 is illustrated in
Additional Application for the Smart Blanking Method
The algorithm defined in this document can be easily extended to be used in conjunction with RFC 3389 and cover other vocoders not listed in this application. These include but are not limited to G.711, G.727, G.728, G.722, etc.
Those of skill in the art would understand that information and signals may be represented by using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Those of ordinary skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An illustrative storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
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|International Classification||G10L19/012, H04L12/403|
|Cooperative Classification||G10L19/24, G10L19/012|
|Jun 22, 2005||AS||Assignment|
Owner name: QUALCOMM INCORPORATED, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SPINDOLA, SERAFIN DIAZ;BLACK, PETER J.;KAPOOR, ROHIT;REEL/FRAME:016385/0093
Effective date: 20050504
Owner name: QUALCOMM INCORPORATED, CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SPINDOLA, SERAFIN DIAZ;BLACK, PETER J.;KAPOOR, ROHIL;REEL/FRAME:016385/0376
Effective date: 20050504
|Jun 24, 2015||FPAY||Fee payment|
Year of fee payment: 4