JP2002077828A - Data stream recorder/reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reproduction quality of reproduced data when recording and reproduction are performed simultaneously by a data stream recorder/ reproducer by using a buffer memory efficiently and reducing the load of transferring reproduced data from a recording medium. SOLUTION: The data stream recorder/reproducer comprises a stream intake section (11), buffer memories (30, 31 and 32) for temporarily storing stream data received from the intake section, a random access storage unit (13) for storing stream data received from the buffer memory, a section (14) for reproducing stream data received from the buffer memory or the storage unit, and a section (35) for managing and controlling the buffer memory. The memory managing section determines the data in the stream data taken in to be held in the buffer memory until it is transferred to the stream reproducing section based on the stream reproducing position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data stream recording / reproducing apparatus having a time shift function,
The present invention relates to a technique for efficiently using a buffer memory in such a device.

[0002]

2. Description of the Related Art A time shift device is capable of receiving a video and / or audio data stream of a program (program) content such as a satellite, cable, or terrestrial digital broadcast via a tuner or the like to make random access. A data stream is read out from a given position of the storage medium in a time-shifted form, reproduced and displayed and / or sound-emitted while being sequentially recorded on a large-capacity storage medium (for example, a hard disk). is there. Writing data to the storage medium and reading data from the storage medium
Usually, this is performed via a buffer memory. In this way, also for the content being recorded on the storage medium, normal reproduction or trick play is performed from an arbitrary position on the recording medium where the content is recorded, for example, a recording position several minutes before.

FIG. 14 is a schematic diagram of the usual time shift device. The time shift device includes a stream capturing unit 111, a stream reproducing unit 114, a buffer unit 114 including a recording and reproducing buffer memory and a memory managing unit (not shown), and a storage device 113 such as a hard disk device. It is composed of Storage device 113
Includes a well-known storage medium such as a hard disk, a recording head and a pickup, and a disk drive unit, which are not shown. The stream capture unit 111 captures an image and audio digital data stream from a signal source such as a satellite broadcast receiving tuner, for example, and passes it to the buffer unit 12. The buffer unit 114 temporarily stores the stream data in a buffer memory and writes the stream data to a storage device 113 including a random access storage medium.
On the other hand, the stream reproducing unit 114 instructs the buffer unit 112 to read data from a specific position on the storage medium in accordance with a user's instruction, and responds to the instruction.
2 reads the stream data from a specific position on the storage medium and supplies it to the playback unit 114,
Reproduces the read stream data by performing decoding, DA conversion, and the like. The decoded and DA converted signal is supplied to a display and / or a speaker. By operating the capturing unit 111 and the reproducing unit 114 continuously in parallel and simultaneously, it is possible to reproduce the stream data being recorded or just recorded while capturing the data stream from the signal source.

[0004]

However, in the time shift apparatus, when reproducing in the time shift mode,
For example, there is a problem that the reproduction quality of reproduction data tends to be low due to dropping of image frames of data or occurrence of block noise. A time-shift device must simultaneously write stream data to a storage medium and read stream data from a storage medium at high speed, but the processing capability of the processor or controller of the device is limited, and the storage capacity of the device is limited. Since the priority is given to writing stream data to the medium, the data transfer rate for playback from the storage medium generally tends to be limited by the processing power of the processor or controller, thereby reducing the amount of playback data. The inventor has noticed that the reproduction quality tends to be low. Therefore, by efficiently using a buffer memory that can be accessed at a higher speed than a large-capacity storage medium such as a hard disk, the load on the transfer of the reproduction data from the storage medium is reduced as much as possible. The inventor recognized that it could be improved.

One of the objects of the present invention is to provide a data stream recording / reproducing apparatus which performs recording and reproduction simultaneously.
The use of a buffer memory in an efficient manner.
Another object of the present invention is to reduce the load on transfer of reproduced data from a storage medium in a data stream recording / reproducing device. Still another object of the present invention is to provide
An object of the present invention is to improve the reproduction quality of reproduced data in a data stream recording / reproducing apparatus.

[0006]

A data stream recording / reproducing apparatus according to the present invention comprises: a stream capturing section for capturing stream data from a signal source; and a buffer memory for receiving the stream data from the stream capturing section and temporarily storing the stream data. And a random access storage device for receiving and storing stream data from the buffer memory, a stream reproducing unit for receiving and reproducing the stream data from the buffer memory or storage device, and managing and controlling the buffer memory. A memory management unit. As one feature, the apparatus of the present invention includes, while the stream capture unit is capturing stream data, the memory management unit based on the stream playback position based on the stream data of the captured stream data. The data to be held in the buffer memory until the data is transferred to the reproducing unit is determined.

According to another feature of the above-described device of the present invention,
While the stream capture unit is capturing stream data, the buffer memory transfers at least a part of the data from the stream capture position to the stream playback position of the stream data to the stream playback unit. Hold until transferred. Further, the part of the data is selected in a regular arrangement (periodically) at a certain ratio from the stream data from the stream capturing position to the stream reproducing position.

[0008] According to still another feature of the above-described apparatus of the present invention, while the stream capture unit is capturing stream data, the memory management unit is based on the stream playback position and the stream playback rate. Of the fetched stream data to be held in the buffer memory until the stream data is transferred to the stream reproducing unit.

According to still another feature of the above-described apparatus of the present invention, the above-described data stream recording / reproducing apparatus further includes a plurality of stream reproducing sections, and the stream capturing section transmits stream data. While capturing, the memory management unit may determine at least one of the plurality of stream playback units of the captured stream data based on the evaluation function for the plurality of stream playback units.
The data to be held in the buffer memory is dynamically determined until the data is transferred.

According to the above-mentioned feature of the present invention, when recording and reproduction are simultaneously performed in the data stream recording / reproducing apparatus, the buffer memory can be used in an efficient manner, and the data stream recording / reproducing apparatus can reproduce the data from the storage medium. The load on data transfer can be reduced, and the reproduction quality of reproduced data in the data stream recording / reproducing device can be improved.

[0011]

FIG. 1 shows a basic configuration of a data stream recording / reproducing apparatus having a time shift function (hereinafter, referred to as a time shift apparatus) according to a first embodiment of the present invention. In the following description, the term time shift device should be understood to mean an information processing device having a time shift function. In FIG.
The time shift device can be a receiving tuner or digital
From a data stream signal source such as a network
A stream capturing unit 11 for capturing a PEG2-type data stream; for example, an MPEG2-type decoder and DA
It comprises a stream reproducing unit 14 including a converter and the like, a buffer unit 12, and a random access large-capacity storage device 13 such as a hard disk device. The storage device 13 includes a random access type large-capacity storage medium such as a hard disk, a recording head and a pickup, a disk drive unit, and other components necessary for recording and reproducing data. Buffer unit 1
2 basically manages and controls the buffer memories (30, 31 and 32) coupled to the capture unit 11, the reproduction unit 14 and the storage device 13 and the operation of the buffer memory, and writes the data to the storage device. And a memory management unit (also called a buffer management unit) that controls reading from a storage device
35. The capturing unit 11 and the reproducing unit 14
It may be configured to be controlled by a processor or a controller. The memory management unit may be configured as a part of the function of the processor or the controller.
The buffer unit 12, the capturing unit 11, and the reproducing unit 14 may be connected via an internal bus (not shown). In the drawings, components having the same function and the same components are denoted by the same reference numerals.

In the time shift device of FIG. 1, the memory management unit 35, as will be described in detail later, stores a difference between a data stream fetch position and a reproduction position, that is, a shift amount Cs and a storage capacity Cb of the entire buffer memory. , The allocation of the buffer memory to the data storage buffer 30 for recording and reproduction, the capture temporary buffer 31 for recording, and the reproduction temporary buffer 32 for reproduction is dynamically determined. The data fetched into the data storage buffer 30 is retained in the data storage buffer 30 until the time for reproduction is reached even after the data has been written to the storage device 13, and at the time of reproduction, the data is read out from the buffer 30 and read from the reproduction unit. 14. Data storage buffer 30
The amount of data to be read from the storage device 13 having a low read transfer rate (speed) is reduced as much as possible by increasing the amount of data taken in and stored in the storage device.

FIG. 3 shows stream data written in the buffer unit 12 and the storage device 13 shown in FIG.
The current stream capture position 20 and the current stream playback position 21 and the shift amount Cs, which is the difference between the two positions.
22 is shown. The memory management unit 35 manages the recording module and the reproduction module, and calculates a shift amount Cs22 that is a difference between the stream capturing position 20 and the stream reproduction position 21. This shift amount Cs
From the data and the buffer memory capacity Cb, the amount of data that can be stored in the buffer 30 until reproduction or the data storage ratio in the buffer 30 is calculated. As much or as much as possible all of the data required for reproduction is stored in the data storage buffer 30, and the amount of data read from the storage device 13 is reduced as much as possible, or no data is read from the storage device 13. As a result, the load for reading from the storage device 13 can be reduced or eliminated as much as possible, and the loss of data necessary for stream reproduction due to a low read data rate from the storage device 13 can be reduced or eliminated.

FIG. 1 shows the configuration of the buffer unit 12 dynamically determined by the memory management unit 35 of the time shift device when the shift amount Cs is larger than the buffer memory capacity Cb and Cs> Cb. . First, a case where the data stream capture rate (speed) and the data stream reproduction rate are the same will be described. When Cs> Cb, it is not possible to hold all of the fetched data in the buffer memory until reproduction. Therefore, the memory management unit 35 divides the buffer memory into the data storage buffer 30, the capture temporary buffer 31, and the reproduction temporary buffer 32 having the capacity Cd, and stores a part of the captured data stream in the data storage buffer 30. The buffer memory is read out at the time of reproduction, and the rest of the fetched data stream is stored in the temporary buffer 31 and written to the storage device 13, while the remaining reproduction data required for reproduction is read out from the storage device 13, thereby saving the buffer memory. Operate to use efficiently. Data storage buffer 3
0 indicates a plurality of buffer pages logically connected in a ring by the memory management unit 35, for example, the BFP 40
... 44. Capture temporary buffer 31
The reproduction temporary buffer 32 is for absorbing the time required for accessing the storage device 13. The minimum buffers required for the access are allocated, and as many buffers as possible are allocated to the data storage buffer 30.

With respect to the shift amount Cs, data corresponding to the capacity Cd of the data storage buffer 30 can be stored.
That is, data of the ratio of Cd / Cs in the shift data amount can be left in the buffer. Therefore, the fetched data amount is represented by the ratio of Cd per Cs, that is, the transfer count (page) Cd.
One time (page) per s / Cd times (page),
Data storage buffer 3 for fetched stream data
0 to each of the buffer pages BFP44 to BFP40. The stream data of the remaining times (pages) is sequentially captured in buffer pages of the capture temporary buffer 31, for example, alternately in the BFPs 50 and 51. In each data capture, at each point in time when capture into a buffer page, eg, BFP 40 or 50, is completed, the page data is sequentially written to storage device 13, while the subsequent stream data is stored in the next free buffer buffer. Pages, for example, BFP 44 or 51, are sequentially loaded. The buffer page in the data storage buffer 30, for example, the data of the BFP 40 is held until the reproduction is performed. After the data is written to the storage device 13, the buffer page used in the capture temporary buffer 31, for example, the BFP 50, is reused for the next or later writing of new data to the storage device 13.

After allocating the buffer memory to the data storage buffer 30, the capture temporary buffer 31, and the reproduction temporary buffer 32, the memory management unit 35 stores the data to be reproduced after a time shift from the present time in the data storage buffer 30. Check and determine if it exists.
When data to be reproduced in the stream exists in the data storage buffer 30, the memory management unit 35 reads out the data and transfers it to the reproduction unit 14. If the data to be reproduced is not in the data storage buffer 30, the data is written from the storage device 13 to the reproduction temporary buffer 32 in advance and transferred to the stream reproduction unit 14. In this way, while the data writing from the capture unit 11 to the buffers 30 and 31 and the data reading from the buffers 31 and 32 to the reproduction unit 14 are continued, meanwhile, the data is transferred from the buffers 30 and 31 to the storage device 13. The writing of data to the storage device and the reading of data from the storage device 13 to the buffer 32 are performed in a time-division manner, and the storage device
3 and the supply of the data stream to the reproducing unit 14 can be simultaneously performed in a time shift mode. In the data storage buffer 30, the buffer page to which the data has been transferred to the reproducing unit 14, for example, the BFP 44, is reused for the next or later data capture. In the playback temporary buffer 32, the buffer page, for example, the BFP 61, to which the data has been transferred to the playback unit 14, is reused for reading data from the storage device 13 next or later.

FIG. 2 shows the configuration of the buffer memory of the buffer unit 12 determined by the memory management unit 35 in FIG. 1 when the shift amount Cs is equal to or smaller than the buffer memory capacity Cb and Cs ≦ Cb. When Cs ≦ Cb,
Since the amount of data to be stored until the reproduction is within the range of the capacity of the buffer memory, all the reproduction data can be read from the buffer memory. Therefore, the memory management unit 35 sets the page allocation to the capture temporary buffer 31 and the reproduction temporary buffer 32 to 0 (zero). Data corresponding to the buffer capture position 20 in FIG. 3 is sent from the stream capture unit 11 to the data storage buffer 30. The stream data sent to the data storage buffer 30 is stored in a buffer page in the data storage buffer 30, for example, B
The data is taken into the FP40. Buffer page BFP40
Becomes full, the buffer unit 12 transfers and writes the stream data from the buffer page BFP 40 to the storage device 13 while writing the subsequent data stream to the next free buffer page in the buffer 30, for example, the BFP 45. . Even after the writing is completed, the data in the buffer page 40 is retained. On the other hand, data is transferred from the buffer page holding the data corresponding to the buffer playback position 21, for example, the BFP 44 to the stream data playback unit 14. As in the case of FIG. 1, in the data storage buffer 30, the buffer page whose data has been transferred to the reproducing unit 14, for example, the BFP 44, is reused for the next or later data capture.

Next, with reference to FIG. 4, a description will be given of a case where the stream capture rate and the stream reproduction rate are different, for example, a case where fast forward (high speed) reproduction or slow (low speed) reproduction is performed. FIG. 4 shows changes in the stream capturing position, the stream reproducing position, and the shift amount when the stream capturing rate and the stream reproducing rate are different. The stream reproduction rate is represented by Rp, and the stream capture rate, that is, the stream recording rate is represented by Rr. In FIG. 4A, the time until the data captured when the shift amount is Cs is actually reproduced is Cs
/ Rp. In FIG. 4B, the time Cs / R
The data to be stored at the time point after the elapse of p is Rr × Cs / Rp corresponding to the moving amount of the stream capturing position. Of this data, an amount equal to or less than the capacity Cb of the buffer memory can be stored in the buffer memory. Therefore, when Cb ≧ Rr × Cs / Rp at the time point after the elapse of the time Cs / Rp, recording and reproduction can be performed using only the storage buffer 30 as in the case of Cb ≧ Cs in FIG. On the other hand, time Cs / R
If Cb <Rr × Cs / Rp at the time point after the passage of p, the buffer memory is used efficiently in the same manner as in the case of Cs> Cb in FIG. 1, and the storage in the data storage buffer is (Rr × 1 per Cs / Rp) / Cd times (page)
Times (page), and Rp × Cd / (Rr ×
Cs) data can be stored in the buffer. Ratio Cd / Cs or Rp × Cd / (Rr × Cs) of data that can be stored in the buffer in the reproduced data of this shift amount
Is hereinafter also referred to as buffer storage efficiency. As described above, even when the stream reproduction rate and the recording rate are different, the data transfer load from the storage device 13 to the buffer unit 12 can be reduced by efficiently using the buffer memory. In particular, as the reproduction rate becomes higher than the normal reproduction rate, the amount of data to be supplied to the reproduction unit 14 becomes larger than in the case of the normal reproduction rate. Therefore, the effect of reducing the data transfer amount from the storage device 13 to the buffer unit 12 is obtained. large.

When the shift amount Cs changes due to the difference between the reproduction rate and the capture rate, the memory management unit 35 dynamically calculates an optimal data storage ratio in the data storage buffer 30 and changes the buffer storage ratio. Control to the optimal state. Also, when the stream reproduction rate Rp or the shift amount Cs changes due to a user's operation or the like, the memory management unit 35 determines whether the data storage amount and the data storage amount to be stored in the data storage buffer 30 according to the reproduction rate Rp or the shift amount Cs. The new data storage ratio is recalculated, and the data storage buffer 30 is used at the current data storage ratio.
If it is determined that the required data cannot be stored, the data storage ratio is reduced to the new ratio, and as a result, unnecessary data in buffer pages that are no longer used are discarded to free buffer pages. And prepares to write another data. Conversely, when it is determined that there are a plurality of free buffer pages that are not used in the buffer 30 at the current data storage ratio, the data storage ratio is raised to a new ratio. Try to write another data to a free buffer page that is not being used. Some of these free buffer pages may be temporarily allocated to the playback temporary buffer 32 until it is time for use by the buffer 30.

FIG. 5 illustrates writing from the data storage buffer 30 and the fetch temporary buffer 31 to the storage device 13 and dynamic reading from the storage device 13 to the reproduction temporary buffer 32 in the embodiment of the present invention. FIG. The period between the end of the writing to the storage device 13 and the start of the next writing, that is, the scheduled free time is one of the data streams to the buffer 31 or 30.
The calculation is performed based on the amount of data to be taken, the bit rate of the data stream to be taken, and the time required to write one data from the buffer 31 or 30 to the storage device 13. Since it is necessary to perform writing to the storage device 13 with priority and surely, as shown by the hatched frame in FIG. 13 is written, that is, recorded. As the time required for writing to the storage device 13, the latest time required for writing this time may be used. Therefore, the next scheduled idle time is represented by the following equation.

[Equation 1] Free time = (amount of data captured at one time) / (bit rate of stream) − (time required for writing to storage device) (1)

The free time and the reproduction temporary buffer 32 from the storage device 13 predicted from the reproduction operation up to that time.
, The amount of data to be read is calculated from the storage device 13, the average read bit rate from the storage device 13, and the amount of buffer that can be read into the buffer 32, and the data is read from the storage device 13. However, in the steady state, since the reproduction data is also supplied from the buffer 30 to the reproduction unit 14, as shown in FIG. 5, between the end of the writing to the storage device 13 and the start of the next writing. The reproduction data is not always read from the storage device 13 to the buffer 32 every time. Also, the operation of reading data from the storage device 13 to the buffer 32 on the reproduction side does not need to be performed in a fixed manner according to the reproduction timing.
If there is room in the allocated temporary playback buffer 32 and the processing time, and there is playback data to be pre-read from the storage device 13, the playback data is stored in the buffer 32 from the storage device 13 regardless of the playback timing. May be read first. For that purpose, a time margin usable for pre-reading the reproduction data is calculated from the read bit rate of the reproduction data read from the storage device 13 to the buffer 32 according to the reproduction operation. If there is an empty area in the data storage buffer 30, a buffer area temporarily available for pre-reading of the reproduction data is calculated from the time until the empty area is used in the buffer 30, and the calculated buffer area is used as a reproduction temporary buffer. 32 may be dynamically allocated and used for pre-reading the reproduction data from the storage device 13. FIG. 6 shows changes in the used area and the free area of the data storage buffer 30 after a predetermined time t. For example, time t
When trying to prefetch data to be reproduced later, the time t
The free space available at a later time can be calculated from the following equation. If the amount of data from the point of time of prefetching to after the time t falls within the range of the free area, it is determined that prefetching is possible and prefetching is performed.

[Equation 2] Free area = Cd− (Amount of buffer used at that time) − (Capture rate) × (Data storage ratio) × t (2)

On the other hand, if the buffer capacity Cd is very small compared to the shift amount Cs, the effect obtained as compared with the load of the buffer management operation becomes small. Therefore, when the data storage ratio becomes lower than a certain threshold value. , The buffer allocation amount to the data storage buffer 30 may be set to 0 (zero), and only the capture temporary buffer 31 and the reproduction temporary buffer 32 may be used to shift to a normal time-shift reproduction mode as shown in FIG. .

In the above embodiment, the case where there is one stream reproducing unit has been described. However, for example, as shown in FIG. 7, reproduction may be performed using a plurality of reproducing units at the same time. For example, in a multi-screen, PIP (picture-in-picture) or POP (picture outside picture) display mode, when displaying an image several seconds ago and a real-time image simultaneously on one display, a plurality of playback units At each point in time. In this case, the data storage buffer 30 is allocated to the reproduction units such that the sum of the data storage ratios Cd / Cs or Rp × Cd / (Rr × Cs) of the buffer 30 with respect to the plurality of reproduction units increases.

FIG. 7 shows an apparatus according to an embodiment of the present invention having two playback units, a stream playback unit 101 and a stream playback unit 102. First, the stream reproducing unit 10
The buffer storage efficiency of the stream reproduction unit 101 with respect to the reproduction data and the buffer storage efficiency of the stream reproduction unit 102 with respect to the reproduction data when the buffering is performed according to 1 are obtained. Next, the buffer storage efficiency for the reproduced data of the stream reproducing unit 101 and the buffer storage efficiency for the reproduced data of the stream reproducing unit 102 when the buffering is performed in accordance with the stream reproducing unit 102 are obtained.

Next, this will be described with reference to FIG. For example, the shift amount Cs ₁₀₁ for the reproduction data of the stream reproduction unit 101 is Cd × 2, and the stream reproduction unit 102
The shift amount _{Cs 102} and Cd × 3 for the reproduction data. Here, when buffering is performed in accordance with the stream reproducing unit 101, the buffer 30 can be used with a buffer storage efficiency of 1/2 in the stream reproducing unit 101 as shown in the left part of FIG. FIG. 8 (a)
As shown on the right, the stream reproduction unit 102 cannot use the buffer 30 (buffer storage efficiency =
0). This is because the stream reproducing unit 10 has a small shift amount.
This is because the data is discarded after the reproduction by the reproduction unit 101 in accordance with the reproduction of No. 1. On the other hand, when buffering is performed in accordance with the stream reproducing unit 102 as shown in FIG. 8B, the buffer storage efficiency of each of the stream reproducing units 101 and 102 is 1/3, and the stream reproducing unit 102
Since the data is held until playback is performed, and the stream playback unit 101 having a small shift amount performs playback prior to the stream playback unit 102, the stream playback unit 101 also uses the buffer 30 stored in accordance with the stream playback unit 102. It is possible to Accordingly, in this example, the total (2/3) of the buffer storage efficiency is larger when the buffering is adjusted based on the stream reproducing unit 102 as a reference, so that the buffer 30 is operated in accordance with the stream reproducing unit 102.

As another method, an evaluation function g (priority, buffer storage efficiency) determined by the priority and the buffer storage efficiency is introduced into each of the plurality of playback units, and based on the evaluation function g. A method for determining the page allocation of the data storage buffer 30 will be described. This evaluation function is compared for a plurality of playback units, and a buffer is preferentially assigned to a playback unit having the highest evaluation function value, or a buffer is assigned such that the sum of evaluation functions for all playback units is maximized. Is also good. The evaluation function g can be arbitrarily determined,
For example, it is represented by any of the following equations.

G (priority, buffer storage efficiency) = priority × buffer storage efficiency (3)

G (priority, buffer storage efficiency) = priority (4)

G (priority, buffer storage efficiency) = buffer storage efficiency (5)

Next, a specific example of the above embodiment will be described. The description will be made mainly with reference to the block diagram of the apparatus shown in FIG. The buffer memory capacity Cb is 32 MB, and the bit rate of the data stream is 1 MB / s. Also, 1
Assume that the capacity of one buffer page, which is a unit of processing for writing or reading, is 500 KB.

First, a description will be given of a case where the user views and listens in real time while recording image and audio data streams. In this case, the shift amount is 0 and C
Since s (0) <Cb (32 MB), all data is transferred from the buffer 30 and reproduced as shown in FIG. Next, as shown in FIGS. 3 and 9, when the reproduction position is changed by the user operation and the time shift amount becomes 60 seconds, that is, when the reproduction is performed from the position 60 seconds before (past) at the normal reproduction rate. I do. The buffer 32 stores the reproduction data that does not exist in the buffer 30 of the storage device 13 in 6 bytes.
The data is read from the position 0 seconds before and supplied to the reproducing unit 14. On the other hand, when the playback position changes, the memory management unit immediately recalculates the buffer usage and the buffer storage efficiency. Here, the shift amount for 60 seconds is a bit rate of 1
60 MB because MB / s, Cs (60 MB)> C
Since it is b (32 MB), the stream data is separately loaded into the temporary buffer 31 and the storage buffer 30 as shown in FIG. Also, 1 MB for two pages is stored in the capture temporary buffer 31, 1 MB for two pages is stored in the reproduction temporary buffer 31, and three MB for 60 pages are stored in the data storage buffer 30.
Allocate 0 MB. In this case, both the capture temporary buffer 31 and the reproduction temporary buffer 32 are processed in the double buffer format. After dividing the buffer memory,
The ratio of the data stored in the buffer 30 is determined. 60
Since there is a buffer of 30 MB for the shift amount of MB, the storage ratio of data that can be stored in the buffer 30 = Cd
Based on / Cs = 30/60, data having a ratio of 1/2 of the stream data can be stored in the buffer 30. Therefore, the memory management unit 35 operates to take in the storage buffer 30 once every two times and take in the remaining times into the temporary buffer 31.

When the shift amount changes as described above, the memory management unit 35 checks whether the data existing in the buffer memory at that time is valid. When the shift amount changes, all data up to 30 seconds before is held in the buffer memory, and 30 MB is used. This 30 MB data cannot be used at the time of reproduction unless it is held for at least 30 seconds. The buffer amount corresponding to 30 seconds after the shift amount is changed is 15
Since it is MB, it is necessary to create a free area for 15 MB. Therefore, the memory management unit 35 determines that one of the 30 MB
Discard 5 MB of data. FIG. 9 shows the state of the data storage buffer 30 at that time. Of the buffers stored in the buffer 30, a buffer of 15 MB is stored.
Page data, for example, BFP 41, 4 every other page
The data in 3, 45 ... is discarded and its buffer
The page will be reusable. Here, a part of the buffer page that can be reused, for example, the BFP 41, is reused for capturing a new data stream. On the other hand, a reusable buffer page that is not necessary for capturing for a while, for example, the BFP 43, 45, is used as much as possible until the timing used for capturing the data stream in the buffer 30 is reached.
2 temporarily used for pre-reading the reproduction data from the storage device 13.

In the read-ahead operation of the reproduced data, first, at the time when the next writing of the data stream to the storage device 13 is completed (see FIG. 5), the buffer 32 is read from the storage device 13.
To determine whether stream data can be read into For example, it is assumed that it takes 200 ms from the time when the fetch of one data stream to the buffer 31 or 30 is completed (that is, from the time when the writing to the storage device 13 is started) to the time when the writing to the storage device 13 is completed. At this time, the bit rate of the data stream is 1 MB / s
Therefore, it takes 500 ms to finish taking in the 500 KB buffer page. Therefore, the reproduction data can be read from the storage device 13 to the buffer 32 and prefetched in a period of 300 ms after the writing to the storage device 13 is completed. For example, if it takes an average of 200 ms to read the reproduction data from the storage device 13 to the buffer 32 during a transitional period from the shift operation to the steady state, the remaining 100 ms
Can be used for look-ahead.

Next, the buffer management unit 35 checks whether there is enough free buffer space. Time t after shift
(S) The free buffer when the time has elapsed is the total buffer capacity =
30 MB, already used buffer amount = 15 MB,
Since the capture bit rate = 1 MB / s and the storage ratio = 1/2, the free space = 30−15 according to the equation (2).
1 × １ ／ × t (s). For example, after t = 20 seconds, a buffer of 30−15−20 × 1/2 = 25 MB becomes a used area. Therefore, whether to pre-read data to be reproduced 20 seconds after the shift point is determined by whether or not the pre-read data fits in the remaining 5 MB. For example,
At 10 seconds after the shift, to pre-read data up to the data reproduced at 20 seconds after the shift, (20-1
0) × 1 (bit rate) = 10 MB is required at the maximum, and at 10 seconds after the shift, it is not possible to read ahead up to the reproduced data 20 seconds after the shift. On the other hand, at the time of 15 seconds after the shift, (20-15) ×
1 (bit rate) = 5 MB, which fits in the free space.
, And the reproduction data is pre-read from the current position in the storage device 13 and read into the 5-MB buffer page. After the pre-read reproduction data written to the buffer page temporarily allocated to the reproduction temporary buffer 32 is transferred to the reproduction unit 14, the buffer page is sequentially re-stored in the data storage buffer 30.
And used to capture a new data stream.

On the other hand, as shown in FIG. 10, the stream capture unit performs the data storage buffer 30 once every two times.
To the storage device 13 at the same time, and the remaining time, the data is fetched to the fetch temporary buffer 31 and written to the storage device 13. 30 in this state
When the reproduction is performed for a second and 30 MB is used for the reproduction as the capacity of the buffer 30, a steady state is reached. In the steady state, the stream playback unit 14 transfers and plays the data from the data storage buffer 30 once every two times because the data exists in the data storage buffer 30, and the stream playback unit 32
The corresponding data is read from the storage device 13 and reproduced.

Next, referring to FIG.
A case where the reproduction rate is changed from a state where the time is shifted by 0 seconds will be described. It is assumed that the reproduction rate is changed to, for example, 1.2 times. At this time, the buffering is changed according to the reproduction rate. First, Cd = 30MB, R
r = 1 MB / s, Rp = 1.2 MB / s, Cs = 60
Since it is MB, Cd <(Rr × Cs / Rp). 30
Since × 1.2 / 60 = 6/10, the operation is changed so that the stream data is fetched into the data storage buffer at a rate of three out of five times as shown in FIG. Since there is no unnecessary buffer data due to the change in the reproduction rate, the data is not discarded.

In this case, since the reproduction rate is higher than the recording rate, if the reproduction is continued as it is, the shift amount Cs gradually decreases. Therefore, according to the change in the shift amount,
The ratio of data to be taken into the storage buffer 30 is gradually increased. For example, at the point of time 60 seconds after the rate change, the reproduction rate = 1.2 × recording rate, so that data 72 seconds after the constant-speed conversion from the reproduction position at the time of the rate change is reproduced. On the other hand, the capture position is 60
Since the movement from the second reproduction position is further advanced by 60 seconds, the shift amount at this time is 120-72 = 48 MB. At that time, the data storage ratio in the data storage buffer is 30 × 1.2 / 48 = 3/4, so
The stream data is taken into the data storage buffer 30 at a rate of three times at a time. As described above, the ratio of storing the captured data is dynamically changed according to the change of the shift position.

Next, the reproduction position is further changed to 18
Suppose that an attempt is made to reproduce data that is 00 seconds ago (past).
At this time, the ratio that can be stored in the data storage buffer 30 is:
30 × 1.2 / 1800 = 0.02, and the reading reduction effect is only 2%. In such a case, the load on the management unit 35 may be larger than the effect of reducing the load of the data transfer from the storage device 13 to the buffer 32. In consideration of such a case, the data storage ratio is, for example, a threshold 5
%, The operation of storing the data until the reproduction may be stopped. Therefore, the buffer allocation to the data storage buffer 30 is set to 0 in the form shown in FIG. Buffer 32
May be allocated, that is, to shift to general time shift reproduction.

Next, a case where two reproducing units are used at the same time in FIG. 7 will be described with reference to a specific example. For example, as shown in FIG.
It is assumed that data is reproduced in a form shifted by 0 seconds, and that the stream reproduction unit 102 reproduces data shifted by 80 seconds. The playback rate is the normal playback rate (1x speed).
And

The total sum of the buffer storage efficiencies on the basis of the respective reproducing units 101 and 102 is calculated. Stream playback unit 101 based on stream playback unit 101
Is Cd × Rp
/(Cs×Rr)=30×1/120×1×1=0.2
5 In this case, since the data to be stored in the buffer is to be held for 120 seconds after the capturing, the data remains in the buffer even when the stream reproducing unit 102 that performs the reproduction 80 seconds after the capturing performs the reproduction. Accordingly, the stream reproduction unit 102 can use the same buffer as the stream reproduction unit 101, and the overall buffer storage efficiency is 0.25 × 2 = 0.
5 On the other hand, the buffer storage efficiency for the reproduction data of the stream reproduction unit 102 based on the stream reproduction unit 102 is Cd × Rp / (Cs × Rr) = 30 × 1 /
80 × 1 × 1 = 0.375, and the stream reproduction unit 1
However, if the data is fetched based on the stream playback unit 102 and discarded after 80 seconds, the buffer cannot be used in the stream playback unit 101 that plays back after 120 seconds. Therefore, the overall buffer storage efficiency is 0.375. Therefore, it is determined that the buffer allocation based on the stream reproduction unit 101 is more efficient, and the stream reproduction unit 1
Buffer allocation is performed based on 01.

As another embodiment, when the stream reproducing unit 101 and the stream reproducing unit 102 have different priorities, evaluation is performed using an evaluation function based on the priority and the buffer storage efficiency, and the allocation of the buffer memory is determined. May be. For example, if the priority of the stream reproduction unit 101 is 1
0, the priority of the stream reproduction unit 102 is 20, and the evaluation function g is represented by g (priority, buffer storage efficiency) = priority × buffer storage efficiency in Expression (3). The value of the evaluation function g in the stream reproducing unit 101 is 10 × 0.25
= 2.5, and the value of the evaluation function g in the stream reproduction unit 102 is 20 × 0.375 = 7.5. In this case, since the evaluation function of the stream reproduction unit 102 is larger than the evaluation function of the stream reproduction unit 101, the buffer allocation based on the stream reproduction unit 102 is performed.

The embodiments described above are given only as typical examples, and modifications and variations thereof will be apparent to those skilled in the art, and those skilled in the art will appreciate the principles of the present invention and the scope of the invention described in the claims. Obviously, various modifications of the above-described embodiment can be made without departing from the invention.

[0040]

According to the present invention, when recording and reproduction are simultaneously performed in the data stream recording / reproducing apparatus, the buffer memory can be used in an efficient form,
It is possible to reduce the load on the data stream recording / reproducing apparatus for transferring the reproduced data from the storage medium and to improve the reproduction quality of the reproduced data in the data stream recording / reproducing apparatus. (Supplementary Note 1) A stream capturing unit that captures stream data from a signal source, a buffer memory that temporarily receives and stores the stream data from the stream capturing unit, and receives and stores the stream data from the buffer memory. A data stream recording device comprising: a random access storage device, a stream reproduction unit that receives and reproduces the stream data from the buffer memory or the storage device, and a memory management unit that manages and controls the buffer memory. The playback device, wherein, while the stream capturing unit captures the stream data, the memory management unit transmits the stream data of the captured stream data to the stream reproducing unit based on a stream playback position. Stored in the buffer memory until transferred A data stream recording / reproducing device for determining data to be held. (Supplementary Note 2) The buffer memory has an area for holding data until the data is written to the storage device, an area for holding data until the data is written to the storage device, and is transferred to the stream playback unit. 2. The recording / reproducing apparatus according to claim 1, wherein the data read from the device is divided into an area for holding the data until the data is transferred to the reproducing unit. (Supplementary Note 3) The memory management unit stores the captured stream data in the buffer memory until it is transferred to the stream reproduction unit based on the capacity of the buffer memory, the stream capture position, and the stream reproduction position. 3. The data stream recording / reproducing apparatus according to claim 1, wherein data to be determined is determined. (Supplementary Note 4) A stream capture unit that captures stream data from a signal source, a buffer memory that temporarily receives and stores the stream data from the stream capture unit, and receives and stores the stream data from the buffer memory. A data stream recording device comprising: a random access storage device, a stream reproduction unit that receives and reproduces the stream data from the buffer memory or the storage device, and a memory management unit that manages and controls the buffer memory. A playback device, wherein the buffer memory stores at least one of data of the stream data from a stream capture position to a stream playback position while the stream capture unit captures the stream data. Part of the stream The data is held until transferred to the raw part, and the partial data is selected from the stream data from the stream capturing position to the stream reproduction position in a regular arrangement at a certain ratio. , A data stream recording / reproducing device. (Supplementary Note 5) A stream capturing unit that captures stream data from a signal source, a buffer memory that temporarily receives and stores the stream data from the stream capturing unit, and receives and stores the stream data from the buffer memory. A data stream recording device comprising: a random access storage device, a stream reproduction unit that receives and reproduces the stream data from the buffer memory or the storage device, and a memory management unit that manages and controls the buffer memory. The playback device, wherein, while the stream capture unit captures the stream data, the memory management unit, based on the stream playback position and the stream playback rate, the memory of the captured stream data Transferred to stream playback unit A data stream recording / reproducing apparatus, wherein data to be held in the buffer memory is dynamically determined until the data stream. (Supplementary Note 6) The memory management unit may be configured to change a difference between a future stream capturing position and a stream reproducing position based on the capacity of the buffer, a current stream capturing position, a current stream reproducing position, a stream capturing rate, and a stream reproducing rate. Wherein the ratio of data of the captured stream data to be held in the buffer memory until the stream data is transferred to the stream reproducing unit is dynamically determined. Data stream recording and playback device. (Supplementary note 7) The data stream recording / reproducing apparatus according to supplementary note 5, wherein the stream reproduction position and the stream reproduction rate can be determined or changed by a user. (Supplementary Note 8) When the stream reproduction position and / or the stream reproduction rate is changed by a user, a ratio of data to be held in the buffer memory is recalculated, and the ratio is stored in the buffer memory according to the recalculated ratio. 6. The data stream recording / reproducing device according to appendix 5, wherein retention of retained data is maintained. (Supplementary note 9) The data stream recording / reproducing apparatus according to supplementary note 5, wherein unnecessary data in the data held in the buffer memory is discarded. (Supplementary Note 10) The free space after a predetermined time based on the current free space in the buffer memory, the reproduction timing of the data stored in the buffer memory, and the bit rate of the stream data to be captured, 6. The data stream recording according to claim 5, wherein a time that can be read from the device is calculated, and data to be reproduced from the storage device after a predetermined time is prefetched within a free space range after the predetermined time. Playback device. (Supplementary Note 11) The memory management unit stores the buffer memory in a first area for holding data until the data is written to the storage device, and stores the data in the buffer memory until the data is written to the storage device and transferred to the stream reproduction unit. And a third area for holding data read from the storage device until the data is transferred to the playback unit; and a third area for holding data until the data is transferred to the playback unit; The data stream recording / reproducing apparatus according to claim 5, wherein the data to be held in the buffer memory until the data is stored is held in the second area of the buffer memory. (Supplementary Note 12) By setting a threshold for the data storage ratio,
When the calculated data storage ratio is equal to or less than the threshold, the allocated capacity of the second area is set to 0.
6. The data stream recording / reproducing apparatus according to supplementary note 5. (Supplementary Note 13) A stream capturing unit that captures stream data from a signal source, a buffer memory that temporarily receives and stores the stream data from the stream capturing unit, and receives and stores the stream data from the buffer memory. Data comprising: a randomly accessible storage device, a plurality of stream reproduction units for receiving and reproducing the stream data from the buffer memory or the storage device, and a memory management unit for managing and controlling the buffer memory. A stream recording / reproducing apparatus, wherein the stream capturing unit is configured to output the stream
While capturing data, the memory management unit is transferred to at least one of the plurality of stream playback units of the captured stream data based on an evaluation function for the plurality of stream playback units. A data stream recording / reproducing apparatus for determining data to be held in the buffer memory until the data stream is recorded. (Supplementary note 14) The data stream recording / reproducing apparatus according to supplementary note 13, wherein the evaluation function is determined based on a priority and / or a data storage ratio. (Supplementary Note 15) The evaluation function is a data storage ratio,
The memory management unit calculates a sum of data storage ratios based on each playback unit of the plurality of stream playback units, and determines data to be held in the buffer memory in a form in which the sum of the data storage ratios is high. 14. The data stream recording / reproducing apparatus according to supplementary note 13, wherein:

[Brief description of the drawings]

FIG. 1 shows a basic configuration of a device having a time shift function according to a first embodiment of the present invention.

FIG. 2 shows a configuration of a buffer memory of a buffer unit 12 determined by a memory management unit 35 in FIG. 1 when Cs ≦ Cb.

FIG. 3 is a diagram showing a relationship between a current stream capture position, a stream reproduction position, and a shift amount Cs, which is a difference between the two positions, in the stream data written in the buffer unit and the storage device in FIG. Is shown.

FIG. 4 shows changes in a stream capturing position, a stream reproducing position, and a shift amount when the stream capturing rate and the stream reproducing rate are different.

FIG. 5 is a diagram for explaining writing from a data storage buffer and a capture temporary buffer to a storage device, and dynamic reading from the storage device to a reproduction temporary buffer.

FIG. 6 shows a change in a used area and a free area of the data storage buffer after a predetermined time.

FIG. 7 shows two reproduction units, a stream reproduction unit 10;
1 shows an embodiment of a system having a stream playback unit 102 and a stream playback unit 102.

FIG. 8 illustrates a data storage ratio of a data storage buffer by two stream reproducing units.

FIG. 9 shows a change in buffer memory allocation when a reproduction position changes.

FIG. 10 is a diagram illustrating a case where the ratio of the stream data taken in is held in a data storage buffer;
2 shows the operation of the device of the embodiment shown in FIG.

FIG. 11 is a diagram illustrating a case where a ratio 3/5 of captured stream data is stored in a data storage buffer;
2 shows the operation of the device of the embodiment shown in FIG.

FIG. 12 shows the operation of the apparatus of the embodiment shown in FIG. 1 when the captured stream data is not held in the data storage buffer.

FIG. 13 illustrates the relationship between two playback positions in recorded stream data when two stream playback units in FIG. 7 are used.

FIG. 14 shows a schematic configuration of a normal time shift device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Stream acquisition part 12 Memory part 30 Data storage buffer 31 Capture temporary buffer 32 Reproduction temporary buffer 35 Memory management part 13 Randomly accessible storage device 14 Stream reproduction part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/92 H04N 5/92 H (72) Inventor Kiyomi Shibata 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited F-term (reference) 5C053 FA23 GB21 HA21 HA33 KA01 KA24 KA25 5D044 AB07 BC01 CC04 EF03 FG10 GK04 HL11

Claims (5)

[Claims] 1. A stream capturing unit for capturing stream data from a signal source, a buffer memory for receiving and temporarily storing the stream data from the stream capturing unit, and a buffer memory for receiving the stream data from the buffer memory. A data stream comprising: a randomly accessible storage device for storing; a stream reproduction unit for receiving and reproducing the stream data from the buffer memory or the storage device; and a memory management unit for managing and controlling the buffer memory. A recording / reproducing apparatus, wherein the stream management unit is configured to capture the stream data, and the memory management unit is configured to perform the stream playback unit of the captured stream data based on a stream playback position. Buffer memory until transferred to And determining the data to be held, the data stream recording and reproducing apparatus. 2. An area for holding data until the buffer memory is written to the storage device, an area for holding data until the data is written to the storage device and until the data is transferred to the stream reproduction unit, 2. The recording / reproducing apparatus according to claim 1, wherein the data read from the apparatus is divided into an area for holding data until the data is transferred to the reproducing unit. 3. A stream capturing unit that captures stream data from a signal source, a buffer memory that receives the stream data from the stream capturing unit and temporarily stores the stream data, and receives the stream data from the buffer memory. A data stream comprising: a randomly accessible storage device for storing; a stream reproduction unit for receiving and reproducing the stream data from the buffer memory or the storage device; and a memory management unit for managing and controlling the buffer memory. In the recording / reproducing apparatus, while the stream capturing unit captures the stream data, the buffer memory stores at least data of data from the stream capturing position to the stream reproducing position of the stream data. Part of the story The data is held until transferred to a playback unit, and the partial data is selected from the stream data from the stream capture position to the stream playback position in a regular arrangement at a certain ratio. , A data stream recording / reproducing device. 4. A stream capturing unit for capturing stream data from a signal source, a buffer memory for receiving the stream data from the stream capturing unit and temporarily storing the stream data, and receiving the stream data from the buffer memory. A data stream comprising: a randomly accessible storage device for storing; a stream reproduction unit for receiving and reproducing the stream data from the buffer memory or the storage device; and a memory management unit for managing and controlling the buffer memory. A recording / reproducing apparatus, wherein, while the stream capturing unit is capturing the stream data, the memory management unit is configured to output the stream data based on a stream playback position and a stream playback rate. Transferred to the stream playback unit. Characterized in that it dynamically determines the data to be held in the buffer memory until the data stream recording and reproducing apparatus. 5. A stream capturing unit for capturing stream data from a signal source, a buffer memory for receiving and temporarily storing the stream data from the stream capturing unit, and receiving the stream data from the buffer memory. A random access storage device for storing, a plurality of stream reproduction units for receiving and reproducing the stream data from the buffer memory or the storage device, and a memory management unit for managing and controlling the buffer memory. A data stream recording / reproducing device, wherein, while the stream capturing unit is capturing the stream data, the memory management unit is configured to perform the capturing of the captured stream based on an evaluation function for the plurality of stream reproducing units. Playing the plurality of streams of data Characterized in that it dynamically determines the data to be held in the buffer memory until they are transferred to at least one data stream recording and reproducing apparatus.