JP4093034B2 - Content transmission / reception system and content transmission apparatus - Google Patents

Description

【００６８】
指令部１３２は、ステップＳ２３０で求めた蓄積増減度△ｖ及び調整テーブルからクロック調整量△ｆを求める（Ｓ２３１）。指令部１３２はクロック調整量△ｆの情報を指令情報として送受信データ生成抽出部１４を介してオーディオデータ受信装置３に送信する（Ｓ２３２）。
【００６９】
オーディオデータ受信装置３は指令情報を受信する（Ｓ２３３）。システム制御部３３は受信したクロック調整量△ｆ分だけ復調用のクロック信号の周波数を低くするようにクロック生成部３０に指令する。その結果、復調用のクロック信号が調整される（Ｓ２３４）。
【００７０】
同様に、時刻ｔ７においては、蓄積量差△Ｄ＝Ｄ１―Ｄ３となる。よって、蓄積量差△Ｄの絶対値が所定値ＤＣを越えるため（Ｓ２２９）、蓄積増減度△ｖが求められ（Ｓ２３０）、クロック調整量△ｆが求められる（Ｓ２３１）。その結果、復調用のクロック信号の周波数が高くなるように調整される（Ｓ２３４）。
【００７１】
以上の動作を繰り返して、クロック調整が行われる。よって、本実施の形態によるオーディオシステムは、オーディオデータ送信装置１又はオーディオデータ受信装置３内のＦＩＦＯメモリ１２，３２の蓄積しているオーディオデータが枯渇又は溢れることを防止できる。また、急激なクロック調整は行われないため、ジッタの発生を抑制できる。そのため、本実施の形態によるオーディオシステムは音のとぎれ等を起こすことなく、スムースに再生動作を行うことができる。
【００７２】
なお、本実施の形態では、コンテンツをオーディオデータとして、コンテンツ送受信システムをオーディオシステムとして説明したが、コンテンツが映像データであってもよい。また、コンテンツにオーディオデータと映像データとが含まれていてもよい。
【００７３】
以上、本発明の実施の形態を説明したが、上述した実施の形態は本発明を実施するための例示に過ぎない。よって、本発明は上述した実施の形態に限定されることなく、その趣旨を逸脱しない範囲内で上述した実施の形態を適宜変形して実施することが可能である。
【図面の簡単な説明】
【図１】本発明の実施の形態によるオーディオシステムの構成を示す機能ブロック図である。
【図２】図１に示したオーディオシステムの動作を示すフロー図である。
【図３】図２中のステップＳ２２の詳細を示すフロー図である。
【図４】図１に示したオーディオシステムの動作を説明するためのタイミング図である。
【符号の説明】
１ オーディオデータ送信装置
２ ネットワーク
３ オーディオデータ受信装置
１１ オーディオデータ受信部
１２，３２ ＦＩＦＯメモリ
１３，３３ システム制御部
１４，３４ 送受信データ生成抽出部
１５，３５ インターフェース
３０ クロック生成部
３１ オーディオ復調部
１３１，３３１ 監視部
１３２ 指令部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a content transmission / reception system, and more particularly, to a content transmission / reception system including a content transmission device that transmits content and a content reception device that receives content transmitted from the content transmission device.
[0002]
[Prior art]
In recent years, an audio system using a network such as a LAN (local area network) or the Internet has attracted attention. The audio system includes one or more audio data transmitting apparatuses and a plurality of audio data receiving apparatuses. The audio data transmitting device transmits audio data as digital data to the audio data receiving device. The audio data receiving device receives the audio data transmitted from the audio data transmitting device, and accumulates the audio data in a FIFO (First-In First-Out) memory provided therein. The accumulated audio data is demodulated from a digital signal to an analog signal and output (reproduced) from the audio data receiving apparatus.
[0003]
In a conventional audio system, there may be a difference between the sampling frequency of the audio data transmitting apparatus and the sampling frequency of the audio data receiving apparatus. In this case, there is a difference between the amount of audio data output from the audio data transmitting device and the amount of audio data output from the audio data receiving device. For this reason, the accumulated data in the FIFO memory provided in the audio data transmitting apparatus or the audio data receiving apparatus is depleted or overflowed. As a result, the reproduction of the audio data is interrupted or the reproduction is not smoothly performed. .
[0004]
As a solution to such a problem, the inventions described in Patent Documents 1 to 3 below synchronize the sampling frequency clock in the audio data receiving apparatus.
[0005]
However, these inventions include the following problems. That is, in these inventions, the audio data receiving apparatus adjusts the clock based on the amount of audio data stored in the FIFO memory in the audio data receiving apparatus within a predetermined period. For example, when the accumulated amount of audio data accumulated within a predetermined period is larger than a predetermined threshold, the data amount output from the audio data transmitting device is larger than the data amount output from the audio data receiving device. Because there are many, the clock frequency is increased. As a result, the data amount output from the audio data transmitting device is adjusted to be equal to the data amount output from the audio data receiving device. On the other hand, when the accumulation amount of audio data accumulated within a predetermined period is smaller than a predetermined threshold value, the clock frequency is reduced.
[0006]
In such an invention, there is no problem when the amount of audio data transmitted from the audio data transmitting apparatus per unit time is substantially constant, but there is a problem when the amount of audio data transmitted per unit time varies. Arise. For example, when audio data is not transmitted to the audio data receiving device because the network connecting the audio data transmitting device and the audio data receiving device is congested, or when the audio data transmitting device cannot transmit audio data for some reason, The audio data stored in the FIFO memory in the audio data receiving apparatus is greatly reduced. At this time, since the audio data receiving apparatus tries to reduce the output amount per unit time of the audio data stored in the internal FIFO memory, the audio data receiving apparatus greatly reduces the clock frequency. Therefore, in such a case, there is a problem that jitter occurs.
[0007]
In order to prevent such a large fluctuation of the clock frequency, it is conceivable to extend the period for monitoring the amount of audio data accumulated in the FIFO memory of the audio data receiving apparatus. This is because if the monitoring period is lengthened, the clock frequency is not affected by a rapid fluctuation in a short period.
[0008]
However, if the monitoring period is extended, the opportunity to synchronize the clock frequency is reduced. Therefore, there is a conventional problem that the audio data stored in the FIFO memory of the audio data transmitting apparatus or the audio data receiving apparatus is exhausted or overflows. Arise.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 2-279037
[Patent Document 2]
JP-A-4-322532
[Patent Document 3]
JP-A-6-326696
[Problems to be solved by the invention]
An object of the present invention is to provide a content transmission / reception system capable of smoothly reproducing content including audio data or video data without sound or video being interrupted.
[0010]
[Means for Solving the Problems]
A content transmission / reception system according to the present invention is a content transmission / reception system including a content reception device that receives content and a content transmission device that transmits content via an electric communication line.
[0011]
The content receiving device includes a first storage unit, a first monitoring unit, a transmission unit, a demodulation unit, and a clock generation unit. The first storage means stores content. The first monitoring means monitors the amount of content that has been stored in the first storage means. The transmission unit transmits the first accumulation amount information obtained by the first monitoring unit to the content transmission device. The demodulating means demodulates the content stored in the first storage means in response to the clock signal. The clock generation means generates a clock signal. The content referred to here may be audio data or video data. Further, both audio data and video data may be included.
[0012]
The content transmission apparatus includes a second storage unit, a second monitoring unit, and a command unit. The second storage means stores content. The second monitoring unit monitors the storage amount of the content stored in the second storage unit to obtain second storage amount information. The instruction means instructs the clock generation means to adjust the frequency of the clock signal based on the first accumulation amount information and the second accumulation amount information transmitted from the content receiving device.
[0013]
According to the present invention, the clock signal generated from the clock generation unit of the content receiving device is adjusted based on the first and second accumulation amount information. That is, the clock signal for determining the output speed of the content in the first storage means is adjusted in response to the change in the content storage amount in the first storage means and the change in the content storage amount in the second storage means. Therefore, it is possible to prevent the content stored in the first storage unit in the content receiving device from being exhausted or overflowing. As a result, the content receiving apparatus can reproduce the content without interrupting it.
[0014]
Preferably, the command unit instructs to adjust the frequency of the clock signal when it is determined that the accumulated amount of the first storage unit is larger than the first predetermined amount based on the first accumulated amount information.
[0015]
Thereby, it is possible to prevent the clock signal from being adjusted until the amount of content stored in the first storage unit is small. In addition, by setting the first predetermined amount close to the total capacity of the first storage unit, it is possible to prevent the first storage unit from being exhausted.
[0016]
Preferably, the command unit instructs to adjust the frequency of the clock signal when the variation amount of the accumulation amount of the second storage unit exceeds the second predetermined amount based on the second accumulation amount information.
[0017]
As a result, even if the content storage amount suddenly decreases or increases in the second storage unit, the command unit does not command the adjustment of the clock signal unless the variation amount exceeds the second predetermined amount. Therefore, it is possible to prevent the command means from excessively adjusting the clock signal in response to a sudden decrease or increase in the content storage amount. As a result, the occurrence of jitter can be prevented.
[0018]
Preferably, the first monitoring unit requests the content from the content transmission device when the accumulated amount of the content accumulated in the first storage unit is smaller than the third predetermined amount, and the command unit The requested content is read from the second storage means.
[0019]
Thereby, it is possible to prevent the content from being depleted in the first storage unit in the content receiving apparatus. In addition, since the content transmitting apparatus transmits the requested content, the first storage means does not overflow the content.
[0020]
Preferably, the command unit commands the adjustment amount of the frequency of the clock signal based on the variation amount and the time until the variation amount exceeds the second predetermined amount.
[0021]
As a result, the instruction means does not instruct the clock generation means to always adjust the clock signal by a fixed amount, but instructs the frequency adjustment of the clock signal in accordance with the fluctuation amount of the content accumulation amount of the second accumulation means. can do.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is incorporated.
[0023]
In the embodiment of the present invention, a content is described as audio data, and a content transmission / reception system is described as an audio system.
[0024]
FIG. 1 is a functional block diagram showing the configuration of an audio system according to an embodiment of the present invention. Referring to FIG. 1, the audio system includes an audio data transmitting device 1 and an audio data receiving device 3. The audio data transmitting device 1 and the audio data receiving device 3 are connected via the network 2. The network 2 is, for example, a LAN or the Internet.
[0025]
The audio data receiving device 3 includes a clock generation unit 30, an audio demodulation unit 31, a FIFO memory 32, a system control unit 33, a transmission / reception data generation / extraction unit 34, and an interface 35.
[0026]
The interface 35 receives audio data transmitted from the audio data transmitting apparatus 1 and command information described later. Further, the interface 35 transmits received accumulation amount information, which will be described later, to the audio data transmitting apparatus 1 via the network 2. The transmission / reception data generation / extraction unit 34 receives the audio data and the command information transmitted from the audio data transmitting device 1, and transmits the audio data to the FIFO memory 32 and the command information to the system control unit 33. The FIFO memory 32 stores the audio data output from the transmission / reception data generation / extraction unit 34. The stored audio data is output to the audio demodulator 31 in the order of the stored audio data in response to the read clock signal transmitted from the audio demodulator 31. The clock generation unit 30 generates a clock signal as a standardized frequency for audio data demodulation, and outputs the generated clock signal to the audio demodulation unit 31.
[0027]
The system control unit 33 controls the operation of the audio data receiving device 3. Specifically, the system control unit 33 performs demodulation control of the audio demodulation unit 31 when reproducing audio data. Further, the system control unit 33 receives the command information transmitted from the audio data transmitting device 1 and instructs the clock generation unit 30 to adjust the clock based on the command information.
[0028]
The system control unit 33 includes a monitoring unit 331. The monitoring unit 331 checks the amount of audio data stored in the FIFO memory 32 every predetermined period. The monitoring unit 331 outputs the checked audio data accumulation amount information (hereinafter referred to as reception accumulation amount information) to the transmission / reception data generation / extraction unit 34. Further, based on the received information amount information checked by the monitoring unit 331, the system control unit 33 outputs an audio data transfer request to the transmission / reception data generation / extraction unit 34.
[0029]
The transmission / reception data generation / extraction unit 34 receives the reception accumulation amount information or the audio data transfer request output from the system control unit 33, converts the reception accumulation amount information or the audio data transfer request into a data format according to the protocol, and the interface 35 and the network. 2 to the audio data transmitting apparatus 1 via
[0030]
The audio data transmitting apparatus 1 includes an audio data receiving unit 11, a FIFO memory 12, a system control unit 13, a transmission / reception data generation / extraction unit 14, and an interface 15.
[0031]
The audio data receiving unit 11 receives audio data from the outside. When the audio data transmitted from the outside is digital, the audio data receiving unit 11 receives the audio data, extracts sampling frequency information from the audio data, and transmits it to the system control unit 13. In addition, the audio data receiving unit 11 transmits the received audio data to the FIFO memory 12. When the audio data transmitted from the outside is analog, the audio data receiving unit 11 performs analog-digital conversion on the received audio data. The subsequent operation of the audio data receiving unit 11 is the same as when the audio data is digital.
[0032]
The FIFO memory 12 stores audio data based on the write clock signal transmitted from the audio data receiving unit 11. The audio data is read in the order stored in the FIFO memory 12.
[0033]
The system control unit 13 controls the operation of the audio data transmission device 1. The system control unit 13 includes a monitoring unit 131 and a command unit 132. The monitoring unit 131 checks the amount of audio data stored in the FIFO memory 12 every predetermined period. The monitoring unit 131 transmits the checked audio data storage amount information (hereinafter referred to as transmission storage amount information) to the command unit 132. The command unit 132 demodulates the output from the clock generation unit 30 in the audio data receiving device 3 based on the transmission accumulated amount information and the received accumulated amount information transmitted from the audio data receiving device 3 via the network 2. Instructs adjustment of the clock signal. The system control unit 13 stores therein the state of the data amount stored in the FIFO memory 32 in the audio data receiving device 3 as a “steady state flag”. Here, the steady state flag is “1” as the steady state when the data storage amount of the FIFO memory 32 exceeds 90% of the total capacity, and the data storage amount of the FIFO memory 32 is less than 90% of the total capacity. Then, the unsteady state becomes “0”. The command unit 132 sets the steady state flag in the control unit 13 to “0” or “1” based on the received received amount information.
[0034]
In FIG. 1, one audio data transmitting apparatus and one audio data receiving apparatus are representatively shown, but a plurality of audio data transmitting apparatuses and a plurality of audio data receiving apparatuses may be provided.
[0035]
The operation of the audio system having the above circuit configuration will be described.
[0036]
2 to 4 are a flowchart and timing chart for explaining the operation of the audio system.
[0037]
2 and 4, the command unit 132 in the audio data transmitting apparatus 1 resets the steady state flag at the start of operation (S1). As a result, the steady state flag in the system control unit 13 becomes “0”. Subsequently, the audio data is stored in the FIFO memory 12 via the audio data receiving unit 11 (S2). In this case, when the audio data transmitting device 1 has not received a data transfer request from the system control unit 33 in the audio data receiving device 3 (S3), the monitoring unit 131 determines that the amount of data stored in the FIFO memory is the reference amount. Whether or not C is exceeded is determined every predetermined period (S4). Here, the reference amount C = 50% of the total storage amount of the FIFO memory 12 + the total storage amount of the FIFO memory 32. The reference amount C may be another amount.
[0038]
As a result of the determination by the monitoring unit 131, when it is determined that the amount of data stored in the FIFO memory 12 exceeds the reference amount C, the system control unit 13 reads the amount of data exceeding the reference amount C from the FIFO memory 12. (S5). The read audio data is erased without being transmitted to the audio data receiving device 3. After the data is read from the FIFO memory 12, the process returns to step S2 and the data is written to the FIFO memory 12.
[0039]
On the other hand, if the monitoring unit 131 determines that the amount of data stored in the FIFO memory 12 does not exceed the reference amount C in step S4, the process returns to step S2 and data is continuously written in the FIFO memory 12.
[0040]
By the above operation, until the data transfer request is received from the audio data receiving device 3, the audio data transmitting device 1 writes or reads the audio data so that the amount of data stored in the FIFO memory 12 becomes the reference amount C. Thus, until the data transfer request is received, the data storage amount in the FIFO memory 12 does not exceed the reference amount C, so that it does not become full. Therefore, it is possible to prevent a situation in which the audio data transmitting apparatus 1 cannot capture desired audio data because the amount of data stored in the FIFO memory 12 at the time of data transfer request is full.
[0041]
Subsequently, when a data transfer request is transmitted from the audio data receiving device 3 at time t0 in FIG. 4 (S6), the audio data transmitting device 1 receives the data transfer request (S3). At this time, the system control unit 13 starts reading data for the amount requested from the FIFO 12 (S7). The audio data receiving device 3 requests a data amount for the capacity of the FIFO 32 to be full by a data transfer request.
[0042]
The read data is converted into a protocol for transfer via the network 2 by the transmission / reception data generation / extraction unit 14 and output from the interface 15. The output data is received by the interface 35, the data format is converted by the transmission / reception data generation / extraction unit 34, and stored in the FIFO memory 32 (S8). As a result, as seen after time t0 in FIG. 4, the amount of data stored in the FIFO memory 12 decreases and the amount of data stored in the FIFO memory 32 increases.
[0043]
At time t1, which is the process of accumulating audio data in the FIFO memory 32, the audio data receiving device 3 performs an audio data reproduction operation (S9). The reproduction operation is performed based on an external command. By the reproduction operation, the accumulated data in the FIFO memory 32 is demodulated by the audio demodulator 31 and output to the outside. Therefore, the degree of increase in the accumulated amount of the FIFO memory 32 decreases after time t1.
[0044]
While the FIFO memory 32 is receiving audio data, the monitoring unit 331 determines whether or not the amount of data stored in the FIFO memory 32 is in an unsteady state at predetermined time intervals (S10).
[0045]
When the FIFO memory 32 is in an unsteady state as a result of the determination by the monitoring unit 331 during data reception (S10), the system control unit 33 transmits an unsteady signal to the audio data transmitting apparatus 1 (S11). When the audio data transmitting apparatus 1 receives the unsteady signal (S12), the command unit 132 sets the steady state flag to “0” (S13). When the audio data transmitting apparatus 1 receives the unsteady signal (S12), if the steady state flag is already “0”, the command unit 132 maintains the steady state flag as “0”.
[0046]
On the other hand, during data reception, the FIFO memory 32 is in a steady state at time t2 in FIG. At this time, the monitoring unit 331 determines that the FIFO memory 32 is in a steady state (S14). Therefore, the system control unit 33 transmits a steady signal to the audio data transmitting apparatus 1 (S15). When the audio data transmitting apparatus 1 receives the steady signal (S16), the system control unit 13 sets the steady state flag to “1” (S17). When the audio data transmitting apparatus 1 receives a steady signal (S16), if the steady state flag is already “1”, the command unit 132 maintains the steady state flag as “1”.
[0047]
At time t3 in FIG. 4, the system control unit 13 reads all audio data for the request specified by the data transfer request from the FIFO memory 12. Therefore, the audio data transmitting apparatus 1 ends the reading operation (S18).
[0048]
At time t3, the audio data receiving device 3 receives data for the data transfer request. Therefore, the audio data receiving device 3 finishes the writing operation to the FIFO 32 (S19). The operation in step S18 and the operation in step S19 are performed at substantially the same timing.
[0049]
At time t3 when reading of data for the data transfer request is completed in step S18, the system control unit 13 performs a clock adjustment processing operation (S22).
[0050]
FIG. 3 is a flowchart showing the detailed operation of step S22 in FIG.
[0051]
Referring to FIG. 3, system control unit 13 in audio data transmitting apparatus 1 determines whether the stored steady state flag is “1” or “0” (S221). When the steady state flag is “0”, a timer described later stops counting (S222).
[0052]
When the steady state flag is “1”, the system control unit 13 determines whether a timer (not shown) in the monitoring unit 131 is operating (S223). In FIG. 4, the timer is not operating at time t3 when the clock adjustment processing is performed for the first time after receiving the data transfer request. In this case, the system control unit 13 resets the timer count in the monitoring unit 131 (S224), and then starts the timer count (S225). The timer counts every predetermined period. The monitoring unit 131 investigates the data accumulation amount of the FIFO memory 12 at time t3 and stores the value as the initial FIFO memory accumulation amount (S226). In FIG. 4, the initial FIFO memory storage amount is D1.
[0053]
Returning to FIG. 2 again, the audio data transmitting apparatus 1 determines whether or not the audio data receiving apparatus 3 has finished the reproduction operation (S24). For example, when the audio data receiving device 3 finishes the reproduction operation, a stop notification is transmitted to the audio data transmitting device 1 (S23). When the stop notification is received from the audio data receiving device 3, the audio data transmitting device 1 also ends its operation.
[0054]
If the audio data receiving device 3 does not end the playback operation and continues to perform the playback operation, the audio data transmitting device 1 does not receive a stop notification (S24). At this time, the operation of the audio data transmitting apparatus 1 returns to step S2.
[0055]
Next, an operation in which the audio data receiving device 3 transmits a data transfer request will be described.
[0056]
Referring to FIG. 2, after the reception of the data for the data transfer request is completed (S19, time t3 in FIG. 4), the monitoring unit 331 in the audio data receiving device 3 stores the accumulated data in the FIFO memory 32 every predetermined period. Is less than the prescribed amount DC2 (S20). Here, the specified amount DC2 may be specified as a percentage, for example, as a percentage of the total capacity of the FIFO memory 32, or may be specified as the number of bits.
[0057]
In FIG. 4, the audio data receiving device 3 finishes receiving audio data at time t3 (S19). From time t3 to time t4, the accumulated data in the FIFO memory 32 decreases due to reproduction, but the accumulated data is larger than the specified amount DC2. Therefore, the monitoring unit 331 determines that the accumulation amount of the FIFO memory 32 is larger than the specified amount DC2. As a result, the audio data receiving device 3 continues the reproduction operation (S21).
[0058]
On the other hand, the accumulated data in the FIFO memory 32 becomes less than the specified amount DC2 at time t4. At this time, the system control unit 33 outputs a data transfer request to the audio data transmitting apparatus 1 (S6). At this time, as described above, the system control unit 33 requests a data amount for the data storage amount of the FIFO memory 32 to be full.
[0059]
With the above operation, the audio data receiving device 3 stores the audio data in the FIFO memory 32 and then outputs a data transfer request every time the stored data becomes smaller than the predetermined amount DC2. As a result, the audio data receiving device 3 can always hold a predetermined amount of audio data in the FIFO memory 32 and can prevent the stored data from being exhausted.
[0060]
The audio data transmitting apparatus 1 that has received the data transfer request again at time t4 performs the operations after step S3 again. Then, after reading out the requested audio data at time t5 (S18), the clock adjustment processing operation is performed again (S22).
[0061]
Referring to FIG. 3, since audio data transmitting apparatus 1 has performed the clock adjustment processing once after receiving the data transfer request (time t3 in FIG. 4), the timer is already in operation (S223). In this case, the monitoring unit 131 investigates the amount of data stored in the FIFO memory 12 and stores the value (S227).
[0062]
Thereafter, the command unit 132 obtains the difference between the data storage amount stored by the monitoring unit 131 and the initial FIFO memory storage amount D1 as the storage amount difference ΔD by the following equation (1) (S228).
[0063]
Accumulated amount difference ΔD = Stored data accumulated amount−D1 (1)
Next, the command unit 132 determines whether or not the calculated absolute value of the accumulated amount difference ΔD exceeds a predetermined value DC (S229). Assuming that the amount of accumulated data at time t5 in FIG. 4 is D2, the accumulated amount difference ΔD = D2−D1. Therefore, in this case, since the absolute value of the accumulation amount difference ΔD is smaller than the predetermined value DC, the clock adjustment process is not performed and the process is terminated.
[0064]
Since the subsequent operation is the same as described above, it will not be repeated.
[0065]
The audio data transmitting device 1 and the audio data receiving device 3 repeat the above-described operation. As a result, in the clock adjustment processing operation at time t6 in FIG. 4, if the data accumulation amount at time t6 is D3, the accumulation amount difference ΔD = D3-D1 at time t6. In this case, since the absolute value of the accumulated amount difference ΔD exceeds the predetermined value DC (S229), the command unit 132 obtains the accumulated amount increase / decrease degree Δv by the following equation (2) (S230).
[0066]
Accumulated amount increase / decrease Δv = accumulated amount difference ΔD / timer count value (2)
The command unit 132 has an adjustment table as shown in Table 1. Referring to Table 1, the adjustment table records a clock adjustment amount Δf corresponding to the accumulation increase / decrease degree Δv.
[0067]
[Table 1]

[0068]
The command unit 132 obtains the clock adjustment amount Δf from the accumulation increase / decrease degree Δv obtained in step S230 and the adjustment table (S231). The command unit 132 transmits the information of the clock adjustment amount Δf as command information to the audio data receiving device 3 via the transmission / reception data generation / extraction unit 14 (S232).
[0069]
The audio data receiving device 3 receives the command information (S233). The system control unit 33 instructs the clock generation unit 30 to lower the frequency of the demodulation clock signal by the received clock adjustment amount Δf. As a result, the demodulation clock signal is adjusted (S234).
[0070]
Similarly, at time t7, the accumulation amount difference ΔD = D1−D3. Therefore, since the absolute value of the accumulation amount difference ΔD exceeds the predetermined value DC (S229), the accumulation increase / decrease degree Δv is obtained (S230), and the clock adjustment amount Δf is obtained (S231). As a result, the frequency of the demodulation clock signal is adjusted to be higher (S234).
[0071]
Clock adjustment is performed by repeating the above operation. Therefore, the audio system according to the present embodiment can prevent the audio data stored in the FIFO memories 12 and 32 in the audio data transmitting apparatus 1 or the audio data receiving apparatus 3 from being exhausted or overflowing. In addition, since rapid clock adjustment is not performed, occurrence of jitter can be suppressed. For this reason, the audio system according to the present embodiment can smoothly perform a reproduction operation without causing a break in sound.
[0072]
In the present embodiment, the content is described as audio data and the content transmission / reception system is described as an audio system. However, the content may be video data. In addition, the content may include audio data and video data.
[0073]
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of an audio system according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an operation of the audio system shown in FIG.
FIG. 3 is a flowchart showing details of step S22 in FIG. 2;
4 is a timing chart for explaining the operation of the audio system shown in FIG. 1; FIG.
[Explanation of symbols]
1 Audio data transmitter
2 network
3 Audio data receiver
11 Audio data receiver
12,32 FIFO memory
13, 33 System control unit
14, 34 Transmission / reception data generation and extraction unit
15,35 interface
30 Clock generator
31 Audio demodulator
131,331 monitoring unit
132 Command section

Claims (6)

A content transmission / reception system comprising a content reception device that receives content and a content transmission device that transmits the content to the content reception device via an electric communication line,
The content receiving device is:
First storage means for storing the content;
First monitoring means for monitoring the storage amount of the content stored in the first storage means to obtain first storage amount information;
Means for transmitting the first accumulation amount information obtained by the first monitoring means to the content transmission device;
Demodulation means for demodulating the content stored in the first storage means in response to a clock signal;
Clock generating means for generating the clock signal,
The content transmission device includes:
Second storage means for storing the content;
Second monitoring means for monitoring the storage amount of the content stored in the second storage means to obtain second storage amount information;
The clock generation so as to adjust the frequency of the clock signal based on the second accumulation amount information obtained by the second monitoring means and the first accumulation amount information transmitted from the content receiving device. A content transmission / reception system comprising command means for commanding the means. The content transmission / reception system according to claim 1,
The command means instructs to adjust the frequency of the clock signal when it is determined that the accumulated amount of the first storage means is greater than a first predetermined amount based on the first accumulated amount information. The content transmission / reception system characterized by the above-mentioned. The content transmission / reception system according to claim 2,
The command means instructs to adjust the frequency of the clock signal when the fluctuation amount of the accumulation amount of the second storage means exceeds a second predetermined amount based on the second accumulation amount information. The content transmission / reception system characterized by the above-mentioned. The content transmission / reception system according to claim 2 or 3,
The first monitoring unit requests the content from the content transmission device when the accumulated amount of the content accumulated in the first storage unit is smaller than a third predetermined amount,
The content transmission / reception system, wherein the command means receives a request for the content and reads the requested content from the second storage means. The content transmission / reception system according to claim 3,
The content transmission / reception system characterized in that the command means commands an adjustment amount of the frequency of the clock signal based on the variation amount and a time until the variation amount exceeds the second predetermined amount. A content receiving apparatus comprising: a first storage unit that stores content; a demodulation unit that demodulates the content stored in the first storage unit in response to a clock signal; and a clock generation unit that generates the clock signal. A content transmission device that transmits content,
Second storage means for storing the content;
Monitoring means for monitoring the storage amount of the content stored in the second storage means to obtain second storage amount information;
The storage amount information of content in the first storage means, based on the first storage amount information transmitted from the content receiving device and the second storage amount information obtained by the monitoring means, A content transmission apparatus comprising: instruction means for instructing the clock generation means to adjust the frequency of the clock signal.

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