JP4055014B2 - Data transmission device - Google Patents

Description

  The present invention relates to a data transmission apparatus capable of transmitting high bit rate video data and the like, and in particular, a transformer capable of transmitting digital data stored in a hard disk or the like by converting the bit rate to a bit rate that can be transmitted on a transmission line. The present invention relates to a data transmission apparatus having a coding function.

  In recent years, DVD / HDD recorders and personal computers equipped with a PVR (Personal Video Recorder) function have been widely used, and video assets that individuals can view at home have also increased. In addition, it is required to enjoy contents such as video information stored on a DVD / HDD recorder or a personal computer at a place where the user wants to view the content, and a client such as a television or a personal computer using a home network. Technologies that enable output to equipment have been proposed. As a technique for transmitting a large amount of data such as video data and audio data at high speed and in real time, for example, IEEE 1394 is adopted as a connection interface for digital television, digital video, and the like.

  Recently, in order to simplify the connection between devices, a DVD / HDD recorder, a personal computer, a liquid crystal monitor, and the like can be connected using a wireless LAN. As a typical technique of this wireless LAN, there is IEEE 802.11 standardized by IEEE, and the one using the 2.4 GHz band is the mainstream. The 2.4 GHz band is called an ISM (Industrial, Scientific and Medical) band, and is a frequency band used for industrial, medical, and household microwave ovens. In Japan, 2.400-2.497 GHz is a wireless LAN. Assigned to.

  Here, for example, in a communication device (particularly a portable communication terminal) that performs data transmission via a wireless LAN or the like, the power that can be supplied may be limited, and thus a technique for suppressing power consumption is required.

  For example, Patent Document 1 discloses a technique for suppressing wasteful power consumption by stopping the operation of an internal circuit when a normal output cannot be obtained in a portable digital broadcast receiver. Similarly, Patent Document 2 discloses a technique for reducing power consumption by stopping the power source of a modulation unit or the like when a reception level is below a certain level in a digital broadcast receiving apparatus.

  Further, in Patent Document 3, in a recording / playback apparatus with a built-in router including a recording / playback unit and a communication unit, the power supplied to the recording / playback unit and the communication unit can be controlled independently, and the recording / playback unit is used. A technique for supplying power to the unit only when a command is received is disclosed.

  In addition, in an AV data processing apparatus that performs decoding processing and encoding processing of digital video data, maximum CPU power (high clock frequency) is required for decoding processing and encoding processing, and power consumption becomes relatively large. Technologies that reduce power consumption are also required in the field.

  For example, Patent Document 4 discloses a technique for shifting to a power saving mode by controlling the clock frequency supplied to a CPU according to the type of application program that is running. Specifically, the CPU clock frequency is maximized when the encoder and decoder operate, and the CPU clock frequency is reduced or stopped when not operating.

On the other hand, as a technique for realizing streaming distribution of video data, a transcoding technique for converting and transmitting the bit rate of encoded video data (for example, MPEG2-TS) according to the environment of the user's communication band is examined. Has been. By using this transcoding technique, it is possible to flexibly cope with band fluctuations in a transmission line having temporal band fluctuations, and to realize high-quality video data streaming delivery. As a technique similar to this transcoding technique, for example, there is a data transmission system in which the transmission rate of video and audio data is changed to minimize degradation when the communication state deteriorates (Patent Document 5). .
JP 2003-158691 A JP 2004-364000 A JP 2004-64209 A JP 2004-164203 A JP 2004-336730 A

  The transcoding technique described above is realized by a transcoder including a decoder and an encoder. Specifically, the original digital data is decoded and encoded to a bit rate suitable for the bandwidth variation of the transmission path. To do. For this reason, power consumption becomes relatively large.

  In addition, a buffer is usually provided in the preceding stage of the decoder and the subsequent stage of the encoder, and a delay occurs in the transmission of digital data. Therefore, the data supply path cannot be easily changed. Therefore, even when the bandwidth of the transmission path is sufficiently free and it is not necessary to perform the bit rate conversion, the transcoder performs the bit rate conversion, which wastes power.

  The present invention has a transcoding function capable of converting the bit rate of digital data, can transmit digital data using a transmission line such as a wireless LAN, and can control power supply by switching the data supply path. It is an object of the present invention to provide a data transmission device that can be reduced.

The present invention has been made to solve the above-described problems, and provides a bit rate detecting means for detecting a bit rate of data that can be transmitted on a transmission line, and a data supply for supplying digital data including video data or audio data. Means, bit rate conversion means for converting the bit rate of the digital data supplied by the data supply means based on the result detected by the bit rate detection means, and a transmission side for storing the bit rate converted digital data A data transmission apparatus having a buffer and a communication means for transmitting and receiving digital data, wherein the transmission side buffer is configured to be able to input digital data output from the bit rate conversion means or the data supply means, Based on the result detected by the bit rate detection means. Data supply control means for inputting the digital data output from the data supply means to either the bit rate conversion means or the transmission side buffer, and the data supply control means is stored in the data supply means. When the digital data being processed is data that does not require bit rate conversion, the reading operation from the data supply means is stopped and the digital data output from the data supply means is directly input to the transmission side buffer. The digital data already input to the bit rate conversion means is all bit-rate converted and stored in the transmission side buffer, and then the read operation from the data supply means is resumed. .

  Furthermore, the power supply control means for controlling the power supply to the bit rate conversion means is provided, and the power supply control means is provided when the digital data stored in the data supply means is data that does not require bit rate conversion. The power supply to the bit rate conversion means is stopped.

  As a result, even if data transmission is delayed through the bit rate conversion means, the digital data read from the data supply means is sequentially stored in the transmission side buffer, and seamless digital data is transmitted. be able to.

  Specifically, a buffer accumulation amount monitoring unit for monitoring the data accumulation amount of the transmission side buffer is provided, and the data supply control unit includes digital data stored in the data supply unit as data that does not require bit rate conversion. In some cases, the read operation from the data supply means is stopped, and the read operation from the data supply means is performed based on the fact that the buffer storage amount monitoring means causes the free space of the transmission side buffer to exceed a predetermined value. I started again. That is, when all bit rate conversion processing of digital data already input from the data supply means is completed in the bit rate conversion means, the digital data is not supplied from the bit rate conversion means to the transmission side buffer, and the free space of the buffer increases. To do. From this, it can be determined that all the digital data already input to the bit rate converting means has been bit rate converted and stored in the transmission side buffer when the free capacity of the buffer becomes equal to or greater than a predetermined value.

  According to the present invention, in the data transmission apparatus, when it is not necessary to convert the bit rate of the digital data stored in the data supply unit, the digital data output from the data supply unit is transmitted without going through the bit rate conversion unit. Since the switching control is performed so as to input to the side buffer, the bit rate conversion process is omitted, and the power can be saved. At this time, by stopping the power supply to the bit rate conversion means, the power consumption can be further reduced.

Further, the data supply control means stops the reading operation from the data supply means when conversion of the bit rate of the digital data stored in the data supply means is unnecessary, and has already been inputted to the bit rate conversion means. Since the digital data is bit rate converted and stored in the transmission side buffer, the read operation from the data supply means is resumed, so that it can cope with the data transmission delay caused by the bit rate conversion means. it can. That is, by switching the data supply path after interrupting (deliberately delaying) the read operation from the data supply means, the digital data read from the data supply means is sequentially stored and combined in the transmission side buffer. Thus, seamless digital data can be transmitted.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a data transmission system according to the present embodiment.

  A data transmission system 100 according to the present embodiment includes a video transmission device 10 that transmits digitized video data and the like, and a video reception device 20 that receives the digital video data transmitted from the video transmission device 10. The Here, it is assumed that the video transmission device 10 and the video reception device 20 perform data transmission, for example, in the 2.4 GHz band using a wireless LAN defined by, for example, IEEE 802.11g (communication speed: 54 Mbps).

  FIG. 2 is a schematic configuration diagram of the video transmission device 10. As shown in FIG. 2, the video transmission device 10 includes a hard disk 11 that stores digital video data, a transcoder 12 that converts the bit rate of the digital video data stored in the hard disk 11, a transmission-side buffer 13, a wireless A LAN communication unit 14, a high frequency amplification unit (RF) 15, an antenna 16, and a transmission side control unit 17 are configured. Here, the video transmission device 10 can be, for example, a DVD / HDD recorder or a personal computer having a wireless communication function.

  The hard disk (data supply means) 11 stores digital video data compressed and encoded in accordance with, for example, the MPEG2 system.

  The transcoder (bit rate conversion means) 12 includes a TC input buffer 121 provided on the input side, an MPEG decoder 122, an MPEG encoder 123, and a TC output buffer 124 provided on the output side. The bit rate of the supplied digital video data is converted according to the band fluctuation of the communication channel. Specifically, the digital video data supplied from the hard disk 11 is once decoded by the MPEG decoder 122 and encoded again by the MPEG encoder 123 to a bit rate suitable for the bandwidth of the communication channel. At this time, bit rate control suitable for the bandwidth of the communication channel is executed based on operation control from the transmission side control unit 17 described later.

  For example, when the bit rate of the digital video data stored in the hard disk 11 is 100 Mbps, a problem occurs when the transmission is performed by a wireless LAN (communication speed to 54 Mbps) based on IEEE802.11g, so the bit rate is converted to a communication speed or lower. For example, it may be converted to 50 Mbps.

  The transmission side buffer 13 stores the digital video data bit rate converted by the transcoder 12 or the digital video data output from the hard disk 11. The wireless LAN communication unit 14 performs protocol processing and modulation / demodulation processing on the digital video data output from the transmission side buffer 13. The high frequency amplifying unit 15 amplifies the RF signal by high frequency and transmits the amplified RF signal to the video receiving device 20 via the antenna 16. For example, the RF signal is transmitted through a communication channel having a frequency band with a center frequency of 2.412 GHz.

  The transmission side control unit 17 includes a CPU, a RAM, and a ROM (not shown). Various control programs are stored in the ROM, and the CPU operates according to the control programs in the ROM while using the RAM as a work area. For example, the transmission side control unit 17 monitors a change in the data accumulation amount of the transmission side buffer 13 (buffer accumulation amount monitoring unit), and thereby detects a bit rate that can be transmitted in the communication channel (bit rate detection unit). Specifically, since the communication speed can be estimated from the change in the data accumulation amount of the transmission side buffer 13, the bit rate that can be transmitted can be detected based on the communication speed. Then, the transcoder 12 is controlled so as to convert the digital video data supplied from the hard disk 11 into a bit rate corresponding to the band fluctuation.

  Furthermore, the transmission side control unit 17 converts the digital video data output from the hard disk 11 to either the transcoder 12 or the transmission side buffer 13 based on the bit rate detected from the change in the data accumulation amount of the transmission side buffer 13. (Data supply control means). Specifically, when the bit rate of the digital video data stored in the hard disk 11 is smaller than the bit rate that can be transmitted in the communication channel (that is, the communication speed), it can be transmitted normally without converting the bit rate. The data supply path is switched so that the digital video data output from the hard disk 11 is input to the transmission side buffer 13. Thereby, since the bit rate conversion process by the transcoder 12 is omitted, power saving can be achieved.

  Further, the transmission-side control unit 17 functions as a power supply control unit that controls power supply to the transcoder 12. That is, the transmission-side control unit 17 stops the power supply to the transcoder 12 when the conversion of the bit rate of the digital video data stored in the hard disk 11 is unnecessary. Thereby, power consumption can be further reduced.

  FIG. 3 is a schematic configuration diagram of the video reception device 20. As shown in FIG. 3, the video reception device 20 includes an antenna 21, a high frequency amplification unit (RF) 22, a wireless LAN communication unit 23, a reception side buffer 24, an MPEG decoder 25, an output unit 26, a reception And receives the digital video data transmitted from the video transmission device 10 and outputs the digital video data. Here, the video receiver 20 can be, for example, a liquid crystal monitor having a wireless communication function.

  The antenna 21 receives the RF signal transmitted from the video transmission device 10 via the communication channel, and supplies the received RF signal to the high frequency amplification unit 22. The high frequency amplification unit 22 amplifies the RF signal received by the antenna 21 at a high frequency and supplies the amplified RF signal to the wireless LAN communication unit 23. The wireless LAN communication unit 23 performs protocol processing and modulation / demodulation processing on the digital video data supplied from the high frequency amplification unit 22. The reception side buffer 24 sequentially stores the digital video data supplied from the wireless LAN communication unit 23.

  The MPEG decoder 25 decompresses and decodes the digital video data supplied from the receiving side buffer 24. The output unit 26 outputs the digital video data supplied from the MPEG decoder 25.

  The receiving side control unit 27 includes a CPU, a RAM, and a ROM (not shown). Various control programs are stored in the ROM, and the CPU operates according to the control programs in the ROM while using the RAM as a work area.

  In the video transmission apparatus 10 according to the present embodiment, when the bit rate of the digital video data stored in the hard disk 11 is not required to be converted, the digital data output from the hard disk 11 is not transmitted through the transcoder 12 but the transmission side buffer 13. Therefore, the bit rate conversion process is omitted and power saving can be achieved. Further, at this time, power supply to the transcoder 12 is stopped, so that power consumption can be further reduced.

  Here, when the data supply path is switched during the transmission of the digital video data, if data is read simultaneously with the switching of the data supply path, the data is read from the hard disk 11 due to the data transmission delay in the transcoder 12. In some cases, the combined digital video data may not be seamlessly combined. And in such a case, the malfunction that the video reproduced | regenerated with the video receiver 20 interrupts arises. For this reason, in the present embodiment, this is dealt with by executing the following data supply path switching control process.

  FIG. 4 is a flowchart showing the switching control when switching the data supply path. In this data supply path switching control, a control program is executed by the transmission side control unit 17 of the video transmission apparatus 10, and each circuit is controlled according to this.

  First, the transmission side control unit 17 detects the communication speed (bandwidth variation) of the communication channel based on the change in the data accumulation amount of the transmission side buffer 13 (step S101). This detection of the communication speed is a process executed even during normal data transmission. Further, based on the detected communication speed, the bit rate of data that can be transmitted on the communication channel can be detected, and the bit rate at which the transcoder 12 converts the bit rate of the digital video data can be determined.

  Next, it is determined whether the bit rate of the digital video data stored in the hard disk 11 is lower than the communication speed (step S102). Here, if the bit rate of the digital video data stored in the hard disk 11 is lower than the communication speed, it can be normally transmitted at the bit rate without converting the bit rate.

  Next, when it is determined in step S102 that the bit rate of the digital video data stored in the hard disk 11 is smaller, it is determined whether power is supplied to the transcoder 12 (step S103). When it is determined that the power is not supplied to the transcoder 12 (that is, the data supply path is the hard disk 11 → the transmission side buffer 13), the process proceeds to step S101.

  If it is determined in step S103 that power is supplied to the transcoder 12 (that is, the data supply path is from the hard disk 11 to the transcoder 12), the process proceeds to step S104, and the data reading operation from the hard disk 11 is stopped. Thus, the data supply path is switched from the hard disk 11 to the transmission side buffer 13.

  Next, it is determined whether there is a certain amount or more in the transmission side buffer 13 (step S105). Specifically, it is performed based on the data accumulation amount of the transmission side buffer 13 by the buffer accumulation amount monitoring means. Here, when all the bit rate conversion processing of the digital video data already input from the hard disk 11 is completed in the transcoder 12, the digital video data is not supplied from the transcoder 12 to the transmission side buffer 13. As a result, the free space of the buffer increases. Thus, by determining whether or not the free space of the buffer has become a predetermined value or more, all the digital video data already input to the transcoder 12 (TC input buffer 121) is converted to the bit rate and stored in the transmission side buffer 13. It can be determined whether or not.

  If it is determined in step S105 that the transmission side buffer 13 has a certain space or more, the digital video data reading operation from the hard disk 11 is resumed (step S106), and the power supply to the transcoder 12 is stopped. (Step S107). As a result, the leading edge of the digital video data supplied directly from the hard disk 11 to the transmission side buffer 13 is seamlessly combined with the trailing edge of the digital data previously supplied to the transcoder 12.

  On the other hand, if it is determined in step S102 that the bit rate of the digital video data stored in the hard disk 11 is higher, it is determined whether power is supplied to the transcoder 12 (step S108). If it is determined that power is supplied to the transcoder 12 (that is, the data supply path is from the hard disk 11 to the transcoder 12), the process proceeds to step S112, and bit rate conversion is performed in accordance with the band.

  If it is determined in step S108 that power is not supplied to the transcoder 12 (that is, the data supply path is from the hard disk 11 to the transmission side buffer 13), the data reading operation from the hard disk 11 is stopped and the data supply path is stopped. Is switched from the hard disk 11 to the transcoder 12 (step S109).

  Next, power supply to the transcoder 12 is started (step S110), and the digital video data reading operation from the hard disk 11 is resumed (step S111). Then, the process proceeds to step S112, and bit rate conversion is performed in accordance with the band.

  As described above, in this embodiment, when the conversion of the bit rate of the digital video data stored in the hard disk 11 is unnecessary, the reading operation from the hard disk 11 is stopped and the digital video already input to the transcoder 12 is stopped. The read operation from the hard disk 11 is resumed after the data is bit-rate converted and stored in the transmission buffer 13. As a result, even when data transmission is delayed through the transcoder 12, the digital video data read from the hard disk 11 is sequentially stored in the transmission side buffer 13, and the seamless digital video data is transmitted. can do.

  As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.

  For example, in the above-described embodiment, the 2.4 GHz band wireless LAN defined by IEEE802.11g has been described, but other transmission technologies can also be used. For example, a 5.2 GHz band wireless LAN defined by IEEE802.11a, a 2.4 GHz band wireless LAN defined by IEEE802.11b, an optical wireless LAN, or the like can be used. Further, the present invention can be applied not only to wireless transmission technology but also to wired transmission technology.

  In the above embodiment, when the bit rate of the digital video data stored in the hard disk 11 is not required to be converted, the data supply path is switched and the power supply to the transcoder 12 is stopped. Since the bit rate conversion process is omitted simply by switching the supply path, power saving can be achieved.

It is a schematic block diagram of the data transmission system of this embodiment. 2 is a schematic configuration diagram of a video transmission device 20. FIG. 2 is a schematic configuration diagram of a video receiving device 30. FIG. It is a flowchart which shows a data supply path | route switching control process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Video transmission apparatus 11 Hard disk 12 Transcoder 121 TC input buffer 122 MPEG decoder 123 MPEG encoder 124 TC output buffer 13 Transmission side buffer 14 Transmission side wireless LAN communication part 15 High frequency amplification part 16 Antenna 17 Transmission side control part 20 Video reception apparatus 21 Antenna 22 High-frequency amplification unit 23 Reception-side wireless LAN communication unit 24 Reception-side buffer 25 MPEG decoder 26 Output unit 27 Transmission-side control unit 100 Data transmission system

Claims (4)

Bit rate detection means for detecting the bit rate of data that can be transmitted on the transmission line, data supply means for supplying digital data including video data or audio data, and the bit rate of the digital data supplied by the data supply means A data transmitting apparatus comprising: a bit rate converting means for converting based on a result detected by the bit rate detecting means; a transmission side buffer for storing the digital data subjected to the bit rate conversion; and a communication means for transmitting / receiving the digital data. Because
The transmission side buffer is configured to be able to input digital data output from the bit rate conversion means or the data supply means,
Data supply control means for inputting the digital data output from the data supply means to either the bit rate conversion means or the transmission side buffer based on the result detected by the bit rate detection means;
Power supply control means for controlling power supply to the bit rate conversion means;
Buffer accumulation amount monitoring means for monitoring the data accumulation amount of the transmission side buffer,
When the digital data stored in the data supply means is data that does not require bit rate conversion,
The power supply control means stops power supply to the bit rate conversion means,
The data supply control means stops reading operation from the data supply means, performs switching control so that the digital data output from the data supply means is directly input to the transmission side buffer, and the buffer accumulation amount monitoring means The data transmission device restarts the reading operation from the data supply means when the free capacity of the transmission side buffer becomes equal to or greater than a predetermined value. Bit rate detection means for detecting the bit rate of data that can be transmitted on the transmission line, data supply means for supplying digital data including video data or audio data, and the bit rate of the digital data supplied by the data supply means A data transmitting apparatus comprising: a bit rate converting means for converting based on a result detected by the bit rate detecting means; a transmission side buffer for storing the digital data subjected to the bit rate conversion; and a communication means for transmitting / receiving the digital data. Because
The transmission side buffer is configured to be able to input digital data output from the bit rate conversion means or the data supply means,
Based on the result detected by the bit rate detecting means, data supply control means for inputting the digital data output from the data supply means to either the bit rate conversion means or the transmission side buffer,
The data supply control means stops the read operation from the data supply means and outputs from the data supply means when the digital data stored in the data supply means is data that does not require bit rate conversion. The digital data is switched to be directly input to the transmission side buffer, and all the digital data already input to the bit rate conversion means is bit rate converted and stored in the transmission side buffer before the data supply means. A data transmitting apparatus , wherein the reading operation from the computer is resumed . Power supply control means for controlling power supply to the bit rate conversion means,
3. The power supply control means stops power supply to the bit rate conversion means when the digital data stored in the data supply means is data that does not require bit rate conversion. The data transmission device described in 1. Buffer accumulation amount monitoring means for monitoring the data accumulation amount of the transmission side buffer;
The data supply control means stops the reading operation from the data supply means when the digital data stored in the data supply means is data that does not require bit rate conversion, and the buffer accumulation amount monitoring means 4. The data transmission apparatus according to claim 2, wherein the reading operation from the data supply unit is resumed when the free capacity of the transmission side buffer becomes equal to or greater than a predetermined value.

Images