JP2006211509A - Encoding apparatus, stc correction method used therein, encoding system, transmission system, and audio transmission/reception system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct an STC value that becomes a source of a PTS value, if the STC value is not correct. <P>SOLUTION: An audio encoding unit 10 of an encoding system comprises an encoding processing section 11, a PTS generating section 12 and an STC monitoring section 13. The STC monitoring section 13 computes a differential value between a present STC value a<SB>n</SB>given to an audio frame at a present time point and a previous STC value that became a source of a PTS value given to an audio frame at a time point preceding to the audio frame of the present time point for one frame and determines whether the differential value is settled within an allowable range of an STC value increase amount in the case where an STC value given for each of a plurality of audio frames increases time-sequentially by the same value all the time and if it is determined that the differential value is settled within the range, the present STC value a<SB>n</SB>is adopted as an STC value c<SB>n</SB>that becomes a source of a PTS value to be given to the audio frame at the present time point, but if not, an arithmetic value with the STC value increase amount added to the previous STC value is adopted as an STC value c<SB>n</SB>that becomes a source of the PTS value given to the audio frame at the present time point. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an encoding apparatus, an STC correction method used in the encoding apparatus, an encoding system, a transmission system, and a voice transmission / reception system, and more particularly to an STC automatic correction method for an encoding apparatus.

  Conventionally, a transmission system having a video and audio encoding unit for encoding video and audio signals independently, and multiplexing and transmitting the encoded signals of independent video and audio signals to one transmission path, A system is known that includes a video and audio decoding unit that separates and independently decodes video and audio encoded signals from multiplexed signals (see, for example, Patent Document 1). ).

  In this system, the time information of the signal is added to the encoded video and audio signals in the transmission system so that the video and audio can be reproduced at the correct time in the reception system. For example, the transmission system is called “PTS (Presentation Time Stamp)” that is added in units of audio frames based on time information called “STC (System Time Clock)” that is common within the transmission system in audio coding. The reproduction time information is created, and the created PTS is sent to the reception system together with time reference information called “PCR (Program Clock Reference)”. In the reception system, an STC in the reception system is generated from the PCR of the received audio frame, and an audio signal composed of the audio frame is reproduced based on the time information of the PTS.

  Here, when the STC value is passed to the speech encoding unit in the transmission system, for example, the STC value is destroyed, the supply of the STC value is stopped, and the STC value reference is independent of the speech encoding unit. When a situation such as switching occurs, the PTS, which is time information in units of audio frames, is not correctly added, and as a result, the audio signal decoded in the reception system is delayed in synchronization or not reproduced at the correct time. Inconvenience may occur.

In order to avoid this, a method of automatically calculating the STC internally in the speech encoding unit and adopting it as the time information of the speech frame can be considered. However, with this method alone, it is impossible to detect the deviation between the STC value of the system time information and the STC value that is automatically calculated internally. As a result, there is a possibility that a desired reproduction cannot be performed in the reception system.
JP-A-10-51750

  As described above, when adding a PTS value representing the playback time of a voice, the STC value serving as a reference when adding the PTS value is destroyed, stopped, or the STC value reference is independent of the voice encoding unit. When a situation such as switching occurs, the correct time information of the audio frame is lost, and there is a possibility that the desired reproduction cannot be performed in the reception system, and in the worst case, it becomes a phenomenon in which synchronization with the decoded video signal cannot be achieved. May cause serious problems in system operation.

  The present invention has been made in consideration of such a conventional situation, and when the time information of a voice frame always increases with the same value in voice coding, when the STC value that is the basis of the PTS value is not correct. The purpose is to automatically correct the STC value.

  In order to achieve the above object, the STC correction method used in the encoding apparatus according to the present invention inputs and encodes a speech signal, and for each of a plurality of time-sequential speech frames constituting the encoded speech signal, This is an STC correction method used in an encoding apparatus that outputs a PTS (Presentation Time Stamp) value representing reproduction time information generated based on an STC (System Time Clock) value representing time information given in time series. The previous STC based on the current STC value given to the current voice frame among the plurality of voice frames and the PTS value given to the voice frame at a predetermined frame earlier than the current voice frame. A calculation step for calculating a difference value with respect to a value, and an ST in which the calculated difference value is always increased in time series with the same STC value given for each of the plurality of audio frames. It is determined whether or not it is within the allowable range of the C value increase amount, and if it is determined that it is within the allowable range, the STC value that is the basis of the PTS value assigned to the current audio frame is used as the STC value. When the STC value is adopted and when it is determined that it is not within the allowable range, the correction value obtained by correcting the current STC value is adopted as the STC value that is the basis of the PTS value given to the current audio frame. And a processing step.

  In the present invention, the correction value is preferably a calculated value obtained by adding the STC value increase amount to the previous STC value.

  In the processing step, when it is determined that the difference value is not within the allowable range of the STC value increase amount continuously for a predetermined number of times, an STC value serving as a reference for the STC value increase amount is determined as the current STC value. You may have the step which switches to a value.

  The encoding apparatus according to the present invention inputs and encodes a speech signal, and for each speech frame that is continuous in a plurality of time sequences constituting the encoded speech signal, STC (time information given in time sequence) An encoding apparatus that outputs a PTS (Presentation Time Stamp) value representing reproduction time information generated based on a System Time Clock value, and is provided to a current audio frame among the plurality of audio frames An arithmetic means for calculating a difference value between the current STC value and the previous STC value that is a source of the PTS value given to the audio frame at a time point before the current audio frame, and the calculated difference It is determined whether or not the value is within the allowable range of the STC value increase amount when the STC value given for each of the plurality of audio frames always increases with the same value in time series, and is within the allowable range Judged If the current STC value is adopted as the STC value that is the basis of the PTS value given to the current audio frame, and it is determined that the current audio frame is not within the allowable range, And a processing unit that employs a correction value obtained by correcting the current STC value as an STC value that is a source of the assigned PTS value.

  In the present invention, the correction value is preferably a calculated value obtained by adding the STC value increase amount to the previous STC value.

  The processing means determines an STC value as a reference for the STC value increase amount when the difference value is determined not to be within the allowable range of the STC value increase amount for a predetermined number of times. You may have a means to switch to a value.

  An encoding system according to the present invention includes a plurality of the encoding apparatuses according to any one of the above, wherein the plurality of encoding apparatuses have different allowable ranges of the STC value increase amount.

  A transmission system according to the present invention includes any one of the encoding devices described above, and transmits an audio signal encoded by the encoding device.

  An audio transmission / reception system according to the present invention includes a transmission system that includes the encoding device according to any one of the above and that transmits an audio signal encoded by the encoding device, and an audio signal transmitted by the transmission system. A receiving system for receiving, wherein the receiving system has a decoding device for decoding the audio signal encoded by the encoding device.

  According to the present invention, when the STC value, which is the time information of the audio frame, always increases at the same value, the increase / decrease amount of the STC value that is the source of the PTS value given to the audio frame is the current STC value. By monitoring based on the difference value from the previous STC value, it is possible to detect STC value fluctuation, instantaneous deviation of STC value, and switching of STC value reference, thereby correcting the STC value when the STC value is not given correctly. As a result, it is possible to ensure the validity of the PTS value assigned to the audio frame.

  Embodiments of the present invention will be described below with reference to the drawings.

  The encoding system according to the present embodiment encodes a video signal by a video encoding method of a predetermined standard such as MPEG-2 (Moving Picture Coding Experts Group-phase 2) video standard, and converts an audio signal to MPEG-2 AAA (Advanced TS (Transport Stream) consisting of a packet sequence such as PES (Packetized Elementary Stream) based on the MPEG-2 system standard, etc., from the encoded video and audio data, encoded by a predetermined audio encoding method such as Audio Coding It is applied to a transmission system that generates and transmits signals and the like.

  FIG. 1 shows a main part configuration of the encoding system of this embodiment.

  The encoding system shown in FIG. 1 is a time information common to the speech encoding unit 10 and the speech encoding unit 10 that encodes a speech signal using a speech encoding method such as MPEG-2 AAA. An STC unit 20 that supplies an STC and an operation unit 30 that can be operated by the operator such as various settings are provided. In addition, an encoding device that encodes a video signal (not shown), a multiplexing device that multiplexes the encoded audio and video signals into one TS signal, and the like are included. In the following description, since the configuration other than the speech encoding unit 10 is not directly related to the present invention, the description thereof is omitted.

The speech encoding unit 10 generates an encoding processing unit 11 that encodes an input speech signal, and generates a PTS value that is reproduction time information based on the STC value given from the STC unit 20, thereby encoding the processing unit 11. And a PTS generator 12 to be supplied to. Additionally, as a processing unit with STC correcting method of the present invention, in the present embodiment, the difference value between the current STC value _{a n} and the previous STC value the displacement detection of STC value _{a n} given from the STC unit 20 performed based on [Delta] d, when detecting the instantaneous deviation of the STC values _{a n,} etc. for correcting the current STC value _{a n} at the correct STC value _{c n,} as required by monitoring the increase and decrease in the STC value An STC monitoring unit 13 for correction is provided.

  Here, the principle of the STC correction method used in the encoding system of the present invention will be described with reference to FIGS.

  This STC correction method automatically corrects the adopted STC value when there is a problem with the STC value adopted when the time of the voice frame always increases with the same value in speech coding. Automatic correction is performed while monitoring the fluctuation of the value, 2) the instantaneous deviation of the STC value, and 3) the switching of the STC value reference. For this reason, the present STC correction method includes a) means for detecting STC value deviation from the difference between the current STC value and the previous STC value, and b) when detecting an instantaneous deviation of STC value, the current STC value is set to the correct STC value. And c) means for adopting the current STC value as a reference for calculating a correct STC value when the deviation of the STC value is continuously detected within the specified time.

  2 to 5, the horizontal axis represents real time, and the vertical axis represents the STC value adopted by the speech encoding unit 10. AF1 is the first audio frame input to the audio encoding unit 10 as an audio signal to be encoded at a certain time, and AF2 is input to the audio encoding unit 10 as an audio signal to be encoded following the first audio frame AF1. The second audio frame, AF3, is input to the audio encoding unit 10 as an audio signal to be encoded following the second audio frame AF2, and AF4 is the third audio frame AF3. Is the fourth audio frame that is input to the audio encoding unit 10 as an audio signal to be encoded.

  Also, t1 is the time when the speech encoding unit 10 acquires the STC value a1 for the first speech frame AF1, and t2 is the moment when the speech encoding unit 10 acquires the STC value a2 for the second speech frame AF2. , T3 is the time when the speech encoding unit 10 acquired the STC value a3 for the third speech frame AF3, and t4 is the time when the speech encoding unit 10 acquires the STC value a4 for the fourth speech frame AF4. Indicates the time of the moment.

Also, a _n (n is a positive integer, n = 1 to 4 in the example in the figure, and so on) is supplied from the external STC generation unit 20 to the current speech frame input, and the speech encoding unit 10 STC in the obtained current STC value, b _n is the previous STC value before adopted in the speech frame, c _n is STC value adopted in the current speech frame, [Delta] d is adopted in the previous speech frame This is a difference value between the value and the STC value supplied from the outside and acquired by the speech encoding unit 10 for the current speech frame input, and indicates a _n −b _n . Δe is an increment value of an ideal STC value to be acquired in the current voice frame, and is an ideal STC that increases by unit time for each voice frame input from the previous STC value adopted in the previous voice frame. Indicates the amount of increase in value.

A graph straight line L1 in FIGS. 2 to 5 shows a time-series change line of STC values that serve as a reference for an ideal external STC value that increases by unit time for each voice frame input. Graph line L2 shown in FIG. 5, the time-series change in the STC value when switching the STC value as a reference of the ideal external STC value slide into increased unit time for each speech frame input to the current STC value a _n A straight line is shown.

Although not noted in the figure, Delta] f represents the tolerance of the difference value Δd between the current STC value a _n and the previous STC value b _n, the value is a fixed value that is specified. Scale M1 is a range of tolerance Δf of difference value Δd at the timing of time t1 (upper limit = r2-b1, lower limit = r1-b1), and scale M2 is tolerance of difference value Δd at the timing of time t2. The range of the difference Δf (upper limit = r3-b2, lower limit = r2-b2), the scale M3 is the range of the tolerance Δf of the difference Δd at the timing of time t3 (upper limit = r4-b3, lower limit = r3-b3) and the scale M4 indicate the range of the tolerance Δf of the difference value Δd at the timing of time t4 (upper limit = r5-b4, lower limit = r4-b4).

Hereinafter, four cases will be described with reference to FIGS.
(Case 1)
The example of FIG. 2, STC value a _n supplied from the outside indicates an ideal case in which slide into increased unit time for each speech frame when the speech frame input.

In this case, a difference value Δd (= a1-b1) between the current STC value a1 given from the STC generation unit 20 at the timing of time t1 and the previous STC value b1 that is the basis of the PTS value given in the previous voice frame. Is within the range of the tolerance Δf shown in the scale M1 (upper limit = r2-b1, lower limit = r1-b1), and at this time, the STC value c1 that is the source of the PTS value to be assigned to the current speech frame A1 is adopted. That is, the STC value c1 has a relationship of a1 = c1.
(Case 2)
Example of FIG. 3 shows an example in which STC value a _n supplied from the outside during the speech frame input is not increased unit time for each speech frame, is representative of the change and its method of correcting STC value .

  In this case, a difference value Δd (= a2−b2) between the current STC value a2 given from the STC generation unit 20 at time t2 and the previous STC value b2 that is the basis of the PTS value given in the previous voice frame. Is within the range of the tolerance Δf indicated by the scale M2 (upper limit = r3-b2, lower limit = r2-b2). At this time, the STC value c2 that is the basis of the PTS value to be assigned to the current speech frame As, a2 is adopted. That is, the STC value c2 has a relationship of a2 = c2.

The example of FIG. 3 shows the case where the external STC value is larger than the ideal increment Δe, but the external STC value is within the allowable range Δf even when the external STC value is smaller than the ideal increment. _An is adopted.

Further, in order to notify a receiving system (not shown) that a PTS value has been created using a corrected STC value instead of a true STC, a PES header part in a PES packet generated by the encoding processing unit 11 A flag is superimposed on the user data. By doing so, the receiving system (not shown) can inspect the correctness with the corrected STC value. Further, it is desirable to output an alarm corresponding to the circumstances in which the speech encoding unit 10 performed the correction. By doing so, appropriate measures can be taken in the host system (not shown).
(Case 3)
The example of FIG. 4, STC value a _n of the outside when the speech frame input shows an example in which no increase unit time for each speech frame represents the instantaneous deviation and the correction method of the STC value.

  In this case, a difference value Δd (= a3−b3) between the current STC value a3 given from the STC generation unit 20 at the timing of time t3 and the previous STC value b3 that is the basis of the PTS value given in the previous voice frame is In this case, the value of b3 + Δe is adopted as the STC value c3 that is the basis of the PTS value to be given to the current voice frame. That is, the STC value c3 has a relationship of c3 = b3 + Δe, and is an ideally increased value of the STC value.

  In the example of FIG. 4, a case where the external STC value is larger than the ideal increment Δe is shown, but even when the external STC value is smaller than Δ, if it is not within the allowable range Δf, the STC value is A value of bn + Δe is adopted.

In addition, a flag is set in the user data in the PES header portion in the PES packet generated by the encoding processing unit 11 in order to notify the reception system that the PTS value has been created using the corrected STC value instead of the true STC. Is superimposed. By doing so, the receiving system (not shown) can inspect the correctness with the corrected STC value. Further, it is desirable to output an alarm corresponding to the circumstances in which the speech encoding unit 10 performed the correction. By doing so, appropriate measures can be taken in the host system (not shown).
(Case 4)
FIG. 5 shows the STC value reference switching and the correction method showing the situation where the external STC value is switched. A straight line L2 in FIG. 5 is a straight line representing an increase in the switched external STC.

  In this case, the difference between the current STC values a2 and a3 given from the STC generation unit 20 and the previous STC values b2 and b3 based on the PTS value given in the previous audio frame at the timings t2 and t3. The values Δd (= a2−b2) and Δd (= a3−b3) are not within the tolerance Δf indicated by the scales M2 and M3. At this time, the values Δd (= a2−b2) are based on the PTS values to be added to the current speech frame. As the STC values c2 and c3, b2 + Δe and b3 + Δe are adopted, respectively. That is, the STC values c2 and c3 are in a relationship of c2 = b2 + Δe and c3 = b3 + Δe, and are ideally increased STC values.

However, when the STC values (b2 + Δe, b3 + Δe) that are ideally increased at the timings of times t2 and t3 are employed, and the STC values (b4 + Δe) that are ideally increased at the timings of the next time t4 are also employed. For this, an ideal STC value (b _n + Δe) is adopted three times in succession.

  When the ideal STC value is continuously adopted as described above, it is considered that the STC value changing straight line that serves as a reference for the increase in the ideal external STC value is changed from the straight line L1 to the straight line L2, and at time t4. At the timing, the STC value (b4 + Δe) that is ideally increased is discarded as the STC value c4 that is the basis of the PTS value to be assigned to the current speech frame, and the current STC value a4 given from the STC generation unit 20 is adopted. Is done. The number of times of “3 times continuously” is merely an example and can be set to an arbitrary value.

  Note that even if the switching of STC is in the direction of decreasing STC value as opposed to the example of FIG. 5, the concept of the determination of the difference and the range of allowable range is common, and it depends on the situation of increase / decrease of STC value. The operation also includes performing an appropriate correction process.

  Further, the encoding processing unit 11 notifies the receiving system (not shown) that the PTS value has been created using the corrected STC value instead of the true STC and that the STC reference has been switched. A flag is superimposed on the user data in the PES header part in the generated PES packet. By doing so, the receiving system (not shown) can inspect the correctness with the corrected STC value. Further, it is desirable to output an alarm according to the background of the correction from the speech encoding unit 10. By doing so, appropriate measures can be taken in the host system.

  FIG. 6 shows an internal configuration example of the STC monitoring unit 13 based on the principle of the STC correction method.

  The STC monitoring unit 13 is functionally a control unit 131 responsible for the control center, and each unit operating under the control of the control unit 131, that is, a current STC value buffer 132, a previous STC value buffer 133, a subtractor 134, a continuous correction A number setting table 135, an STC value calculation reference table 136, and a determination unit 137.

Among them, the current STC value buffer 132, STC values _{a n} input from the STC generation unit 20 is temporarily stored as a current STC value _{a n.}

The front STC value buffer 133, STC value _{c n} output from the STC monitoring unit 13 to the PTS generating portion 12 is temporarily stored as a previous STC value _{b n.}

Subtractor 134 calculates the difference value Δd in the current STC value _{a n} and the previous STC value _{b n} from both buffers _{132,133 (= a n -b n)} .

  In the continuous correction number setting table 135, the continuous correction number x designated through the operation unit 30 or the like is set.

  The STC value calculation reference setting table 136 includes an ideal STC value reference value (for example, an STC value along the straight line L1 in FIGS. 2 to 5) that increases by unit time for each voice frame input, and its A tolerance Δf indicating the allowable range of the increase amount is set.

Judging unit 137, the difference value Δd output from the subtractor 134, on the basis of the set value of both tables 135 and 136, to detect the deviation of the current STC value _{a n} and the previous STC value _{b n,} accordingly It determines STC value _{c n} to be adopted.

  FIG. 7 is a flowchart for explaining the operation of the STC monitoring unit 13.

  First, the continuous correction number x in the continuous correction number setting table 135 is initially set (step St1), and the STC value and the tolerance Δf as the STC value calculation reference in the STC value calculation reference table 136 are initially set (step St2). .

Then, enter the STC value _{a n} given from the STC generation unit 20, and temporarily stored in the current STC value buffer 132 as the current STC value _{a n} (step St3), and the current STC value _{a n} of the current STC value buffer 132 Then, a difference value Δd (= a _n −b _n ) from the previous STC value b _n temporarily stored in the previous STC value buffer 133 is calculated (step St4).

Next, it is determined whether or not the difference value Δd = 0 between the current STC value a _n and the previous STC value b _n (step St5). If YES (Δd = 0), the difference is given to the current voice frame. as STC value _{c n} underlying the PTS value, employing the current STC value _{a n (c n = a n} ) ( step St6). This case corresponds to Case 1 described above.

  If the determination in step St5 is NO (Δd = 0 is not true), it is determined whether or not the difference value Δd satisfies the condition of the tolerance Δf, that is, the upper limit value of Δf ≧ the lower limit value of Δd ≧ Δf. (Step St7).

In this decision, YES if the (meet the conditions of Delta] f upper limit ≧ [Delta] d ≧ Delta] f lower limit), the STC value _{c n} underlying the PTS value applied to the current speech frame, the current STC value _{a n} It was adopted _(c n _{= a} n) _(step St8), and outputs a control signal _{S n} to the PTS generating portion 12 in this regard (step St9). PTS generating unit 12, the control signals _{S n,} recognizes that deviates than ideal STC value of the current STC value _{a n} adopted as STC value _{c n} is intended to be within the scope of the tolerance Delta] f, Necessary processing, such as outputting an alarm related to this, is performed. This case corresponds to the case 2 described above.

For NO (Delta] f does not satisfy the condition of upper limit ≧ [Delta] d ≧ Delta] f lower limit) is determined in the step St 7, as STC value c _n underlying the PTS value applied to the current speech frame, ideal The STC value “b _n + Δe” is adopted (c _n = b _n + Δe) (step St10), the continuous correction number x is incremented (step St11), and the condition of x ≧ setting value (for example, 3 times) Is determined (step St12).

In case of YES (satisfies the condition of x ≧ set value) in this determination, as STC value _{c n} to be outputted to the PTS generating portion 12 discards the value of _{"b n} + .DELTA.e" current STC value a adopted _{n (c} n _{= a} n) (step St 13), employs a current STC value _{a n} as STC value as a reference value of an ideal STC value, switches the STC value calculation criteria (step St14 ), and outputs the control signal _{S n} in this regard to the PTS generating portion 12 (step St15). In addition, the number of continuous corrections x is initialized (x → 0) (step St16) to prepare for detection of switching of the STC value calculation reference again. PTS generating portion 12, a control signal by the _{S n,} although the current STC value _{a n} is outside the range of tolerance Delta] f, the current STC value a as STC values _{c n} underlying the PTS value applied to the current speech frame _n it is employed, and recognizes that the STC value as a reference value of an ideal STC value is switched to the current STC value a _n, etc. for outputting an alarm on this, performs the necessary processing. This case corresponds to Case 4 described above.

For the NO (not yet satisfy the conditions of x ≧ set value) in the determination, and outputs a control signal _{S n} in this regard to the PTS generating portion 12 (Step St17). PTS generator 12 recognizes that the ideal STC value to outside the range of the current STC value _{a n} is tolerance Δf _{(b n} + Δe) is employed by the control signals _{S n,} warning about this To perform necessary processing. This case corresponds to the case 3 described above.

When the process of step St6, St9, St15 is completed, outputs the STC value _{c n} adopted in accordance with each case 1 to 4 above the PTS generating portion 12 and the front STC value buffer 133 (step St18).

  The processes in steps St3 to St18 are repeatedly executed until it is determined in step St19 that the process is finished.

  Therefore, according to the present embodiment, when the STC value, which is the time information of the voice frame in the voice coding unit, always increases in time series with the same value, the STC that is the source of the PTS value given to the voice frame By monitoring the amount of increase / decrease in the value, the STC value variation, the STC value instantaneous deviation, and the STC value reference switching are detected. If the STC value that is the basis of the PTS value is incorrect, the STC to be adopted The value can be automatically corrected. Accordingly, it is possible to ensure the validity of the PTS value given to each encoded audio frame.

  Therefore, a reception system having a decoding device that decodes an encoded audio signal can output a decoded signal based on desired time information. In addition, by detecting the switching of the STC and switching the reference STC at that time, the validity of the PTS value is ensured, and the output environment in the reception system is also consistent with the transmission system side equipped with the decoding device. It can be the right thing. In addition, it is possible to prevent unauthorized time information from being added to a speech encoded signal, and to prevent inconvenience in an operation system using the time information. In addition, it is convenient from an operational point of view that even when the time information as the system is switched, it can be automatically followed without performing various settings and controls.

  Note that the above-described internal configuration and operation (see FIGS. 7 and 8) of the STC monitoring unit 13 in the speech encoding unit 10 are merely examples, and the present invention is not limited to this, and this STC correction method. Any internal configuration and operation are applicable as long as they follow the principle (see FIGS. 2 to 5).

  As another embodiment of the present invention, a configuration may be adopted in which the result of detecting the STC value deviation by the speech encoding unit is notified to the outside. According to this, it is possible to easily implement the embodiment implemented by the audio encoding unit in the part that performs the PTS addition processing in the video encoding unit, the part that multiplexes the video encoded signal and the audio encoded signal, etc. It is possible to implement.

  In addition, the following application system is also conceivable by providing switch means capable of switching between valid / invalid of the STC correction method.

  For example, as an example of a system using only an audio signal, a virtual effect with multiple audio channels is possible. In the case of 4-channel audio encoding, two 2-channel audio encoding units are provided, and the aforementioned PTS value increase amount tolerance Δf is prepared separately. For example, one of the two speech encoding units is provided with a tolerance Δf of the PTS value increase amount by disabling the present STC correction method by the switch means, and the other speech encoding unit has a switch By disabling the present STC correction method by means, the PST value increase amount tolerance Δf is not provided, but the shifted STC value supplied from the outside is added as it is. In this way, by supplying an STC that is favorably shifted, a ringing sound can be realized at the time of a sound effect or the like. This virtual effect time can be changed by a PTS value increase amount tolerance Δf that can be arbitrarily set. This can also be realized by speech decoding which is contrary to speech encoding.

It is a schematic block diagram which shows the principal part structure of the encoding system which concerns on embodiment of this invention. It is a graph explaining the ideal case where the STC value supplied from the outside at the time of audio | voice frame input increases by unit time for every audio | voice frame. It is a graph explaining the case where the STC value supplied from the outside at the time of voice frame input does not increase by unit time for each voice frame (within an allowable range). It is a graph explaining the case where the STC value supplied from the outside at the time of voice frame input does not increase by unit time for each voice frame (outside the allowable range). It is a graph explaining the case where the reference | standard of the STC value supplied from the outside at the time of audio | voice frame input switches. It is a schematic block diagram which shows the internal structure of a STC monitoring part. It is a schematic flowchart explaining operation | movement of an STC monitoring part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Speech encoding part 11 Encoding process part 12 PTS generation part 13 STC monitoring part 20 STC generation part 30 Operation part 131 Control part 132 Current STC value buffer 133 Previous STC value buffer 134 Subtractor 135 STC value calculation reference table 136 Continuous correction Number table 137 determination unit

Claims (9)

Generates an audio signal based on STC (System Time Clock) value representing time information given in time series for each audio frame that is continuous in a plurality of time series. An STC correction method used in an encoding device that outputs a PTS (Presentation Time Stamp) value representing reproduced time information,
A current STC value given to a current voice frame among the plurality of voice frames, and a previous STC value based on a PTS value given to a voice frame at a predetermined frame before the current voice frame; A calculation step for calculating a difference value of
The calculated difference value determines whether or not the STC value given for each of the plurality of audio frames is within an allowable range of an STC value increase amount when the STC value always increases in the same time series, and When it is determined that the current STC value is within the allowable range, the current STC value is adopted as the STC value that is the basis of the PTS value assigned to the current audio frame, and the current STC value is determined not to be within the allowable range And an STC correction method for use in an encoding apparatus, comprising a processing step of using a correction value obtained by correcting the current STC value as an STC value that is a source of a PTS value assigned to the current speech frame. .   The STC correction method used in the encoding apparatus according to claim 1, wherein the correction value is a calculated value obtained by adding the STC value increase amount to the previous STC value.   In the calculation step, when it is determined that the difference value is not within the allowable range of the STC value increase amount continuously for a predetermined number of times, an STC value serving as a reference for the STC value increase amount is determined as the current STC value. The STC correction method used in the encoding apparatus according to claim 1, further comprising a step of switching to a value. Generates an audio signal based on STC (System Time Clock) value representing time information given in time series for each audio frame that is continuous in a plurality of time series. An encoding device that outputs a PTS (Presentation Time Stamp) value representing the playback time information,
A current STC value given to a current voice frame among the plurality of voice frames, and a previous STC value based on a PTS value given to a voice frame at a predetermined frame before the current voice frame; Computing means for calculating the difference value of
The calculated difference value determines whether or not the STC value given for each of the plurality of audio frames is within an allowable range of an STC value increase amount when the STC value always increases with the same value in time series, When it is determined that the current STC value is within the allowable range, the current STC value is adopted as the STC value that is the basis of the PTS value assigned to the current audio frame, and the current STC value is determined not to be within the allowable range And a processing unit that employs a correction value obtained by correcting the current STC value as an STC value that is a source of the PTS value assigned to the current speech frame.   5. The encoding apparatus according to claim 4, wherein the correction value is a calculated value obtained by adding the STC value increment to the previous STC value.   The processing means determines an STC value as a reference for the STC value increase amount when the difference value is determined not to be within the allowable range of the STC value increase amount for a predetermined number of times. 6. The encoding apparatus according to claim 4, further comprising means for switching to a value. A plurality of the encoding devices according to any one of claims 4 to 6,
The encoding system, wherein the plurality of encoding devices have different allowable ranges of the STC value increase amount.   A transmission system comprising the encoding device according to any one of claims 4 to 6 and transmitting an audio signal encoded by the encoding device. A transmission system comprising the encoding device according to any one of claims 4 to 6 and transmitting an audio signal encoded by the encoding device;
A receiving system for receiving an audio signal sent by the sending system;
The speech transmission / reception system, wherein the reception system includes a decoding device that decodes the speech signal encoded by the encoding device.

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