JP4239318B2 - Recording / reproducing method and recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording / reproducing method and a recording / reproducing apparatus, and more particularly, to a technique for compressing a digital signal and performing random access to record it on a recording medium.
[0002]
[Prior art]
A recording / reproducing apparatus for recording a video signal, an audio signal, or the like on a disc-like randomly accessible recording medium such as a DVD-RAM, a hard disk, or a magneto-optical disk that can be arbitrarily recorded / reproduced has been developed.
[0003]
Since data including such an image has a large amount of information, image data or the like is compressed and encoded when recorded on a disk-shaped recording medium. As a method for compressing and encoding image data, various encoding methods such as MPEG (Moving Picture Experts Group) 2 are known.
[0004]
When recording while encoding in real time like a TV signal, the amount of data will be unexpected and will exceed the free capacity of the recording medium, so recording will be stopped halfway or data already recorded will be erased. In many cases, new data is recorded.
[0005]
As a countermeasure for such a case, for example, a method disclosed in Japanese Patent Application Laid-Open No. 11-167770 has been proposed. The technology disclosed here creates a space by recompressing a signal recorded by a compression method such as MPEG2, but at this time, after decompressing the previously recorded stream once and returning it to its original state, Further, a method is employed in which the compression rate is further increased and recompression is performed to re-record the stream.
[0006]
In this case, the compression by MPEG2 is basically performed by DCT (Discrete Cosine Transform) on small blocks in an image, and the higher frequency components are subjected to variable length coding after the bit allocation is reduced.
[0007]
In order to further increase the compression efficiency, the compression in the amplitude direction by quantization, the compression in the time axis direction by motion compensation between fields or frames, and the difference information remaining by motion compensation and the field or frame Only the one with the smaller amount of information is switched and transmitted.
[0008]
[Problems to be solved by the invention]
However, a technique for creating a space by decompressing a data stream that has been compressed based on an operation involving lossy conversion such as MPEG2 and then recompressing the data stream has the following problems.
[0009]
First, in lossy compression by MPEG2, part of the data is erased during the quantization process or inter-frame compression, so the signal is not completely restored when decompressed. S / N deteriorates by repeating.
[0010]
Secondly, when recompression by MPEG2 is performed using the video signal thus deteriorated, motion detection may be erroneously caused by newly generated noise, which causes image quality deterioration.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems, a recording / reproducing method according to the present invention creates a low-rate and high-rate bitstream by compressing a digital signal, and records each of the created low-rate and high-rate bitstreams. When the recording area of the recording medium has run out of space, the recorded high rate bit stream is recorded.This is to newly record a low-rate and high-rate bit stream in an area that is deleted and freed.
[0012]
The digital signal is composed of broadcast program data; the digital signal is composed of a video signal and an audio signal corresponding to the video signal; and the digital signal is only a video signal. The deletion of the recorded high-rate bitstream is a designated high-rate bitstream; the deletion of the recorded high-rate bitstream is based on a preset priority; When deleting a recorded high-rate bitstream, the older recorded date takes precedence; deleting the recorded high-rate bitstream requires that the high-rate bitstream played back at least once Among them, the recording date and time are in chronological order.
[0013]
  A recording / reproducing apparatus includes: a unit that compresses a digital signal to generate a low-rate and a high-rate bit stream; a unit that records each of the generated low-rate and high-rate bit streams on a recording medium; Recording control means for deleting the recorded high-rate bitstream when there is no more room in the recording area.The recording control means deletes the high-rate bit stream by the recording control means and newly records a low-rate and high-rate bit stream in an empty area.
[0014]
The digital signal is composed of broadcast program data; the digital signal is composed of a video signal and an audio signal corresponding to the video signal; and the digital signal is only a video signal. The deletion of the recorded high-rate bitstream is a designated high-rate bitstream; the deletion of the recorded high-rate bitstream is based on a preset priority; When deleting a recorded high-rate bitstream, the older recorded date takes precedence; deleting the recorded high-rate bitstream requires that the high-rate bitstream played back at least once Among them, the recording date and time are in chronological order.
[0015]
With the above configuration, according to the recording / reproducing method or the recording / reproducing apparatus according to the present invention, when there is a space in the recording medium, the space is not left as it is, but both high and low rate bit streams are placed on the recording medium. By ensuring that the high bit rate stream is preferentially reproduced at the time of reproduction, it is possible to effectively use the recording medium and view high quality image quality.
[0016]
In addition, according to the recording / reproducing method or recording / reproducing apparatus of the present invention, when the recording medium runs out of space, many low-rate bitstreams can be left. In the case of a bit stream, since there is less deterioration at the time of compression compared to the conventional technique of recompression, good image quality can be ensured.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a recording / reproducing method and a recording / reproducing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram schematically showing one embodiment of the present invention. In the following description, a case where a color television signal is received and recorded in a recording / reproducing apparatus will be described as an example.
[0018]
A video signal CVS modulated with a carrier in a color television signal is applied to the input terminal 9, and this video signal is demodulated by a demodulator 10 to obtain a baseband signal, that is, a part of an analog TV signal. The resulting video signal AVS is taken out.
[0019]
The video signal AVS is converted into a digital video signal DVS by an analog / digital converter 13 with a conversion timing controlled by a microcomputer 12 to which a user interface 11 is connected.
[0020]
The user interface 11 is composed of, for example, a keyboard and the like, and the user instructs a command to the microcomputer 12 that controls the entire system through the user interface 11.
[0021]
The video signal DVS is input to means for compressing the digital signal to generate a low-rate bit stream and a high-rate bit stream, ie, a high-rate encoder 14 and a low-rate encoder 15, both of which receive the video signal DVS. It is converted into a high-rate video stream HVS that functions as a high-rate bit stream and a low-rate video stream LVS that functions as a low-rate bit stream, respectively, using an irreversible compression method, for example, a compression method such as MPEG2.
[0022]
In this case, the rate is set as the parameter HR1 so that the high-rate encoder 14 is compressed from the microcomputer 12 to a high image quality. Therefore, when recording on the recording medium 16, a high capacity is required with low compression. However, high-quality recording is possible.
[0023]
In addition, since the low-rate encoder 15 is set to the parameter LR1 that is lower than the parameter HR1 so that the microcomputer 12 can compress the image to low image quality, when recording on the recording medium 16, the low-rate encoder 15 has low image quality. However, high compression and low storage capacity are required.
[0024]
An audio signal AOS forming another part of the analog TV signal corresponding to the video signal AVS is applied to the input terminal 17, and the audio signal AOS is converted by the microcomputer 12 by the analog / digital converter 18. It is controlled and converted into a digital audio signal DOS.
[0025]
The audio signal DOS is input to the high-rate encoder 20 and the low-rate encoder 21. Both of these audio signals DOS function as a high bit rate stream by an irreversible compression method, for example, a compression method such as MPEG2. It is converted into a rate audio stream HOS and a low rate audio stream LOS that functions as a low bit rate stream.
[0026]
In this case, the high-rate encoder 20 is set as a parameter HR2 so as to compress the low-rate and high-rate bitstreams onto the recording medium, that is, from the microcomputer 12 to be compressed with high sound quality. When recording on the recording medium 16, since the compression is low, a large storage capacity is required, but recording with high sound quality is possible.
[0027]
Further, since the low-rate encoder 21 is set to the parameter LR2 that is lower than the parameter HR2 so as to be compressed with low sound quality from the microcomputer 12, when recording on the recording medium 16, the low-rate encoder 21 is highly compressed. However, it requires only a small capacity, but can record with low sound quality.
[0028]
If the bit rate of the high-rate video stream HVS or the high-rate audio stream HOS is 10 Mbps, for example, the bit rate of the low-rate video stream LVS or the low-rate audio stream LOS is about 2 Mbps, and the bit rate is about 5 times. Therefore, there is a difference of about 5 times in recording capacity between the high bit rate stream and the low bit rate stream.
[0029]
The interface 22 receives four streams, a high-rate video stream HVS, a low-rate video stream LVS, a high-rate audio stream HOS, and a low-rate audio stream LOS.
[0030]
Since the interface 22 has a buffer memory 23 for input, the high-rate video stream HVS, the low-rate video stream LVS, and the high-rate audio stream HOS are stored in the buffer memory 23 under the control of the microcomputer 12. Four streams of the low rate audio stream LOS are input simultaneously.
[0031]
These four streams are converted into formats that can be recorded as separate files, respectively, and data transfer, that is, writing to the recording medium 16 is executed. The reason why these streams are made separate files is to enable each stream to be reproduced independently.
[0032]
The recording medium 16 may be any medium that compresses and stores data, and can be written and read in a random access manner. For example, a hard disk, a DVD-RAM, or a magneto-optical disk is employed.
[0033]
The interface 24 has a buffer memory 25 for storing a recorded data stream recorded on the recording medium 16, and a format that can be input to the video stream decoder 26 and the audio stream decoder 27 using the buffer memory 25, respectively. Convert to
[0034]
The digital / analog converter 28 receives the video stream read from the recording medium 16 after being converted by the video stream decoder 26, converts it into an analog signal under the timing control of the microcomputer 12, and outputs it to the modulator 29. To do. The modulator 29 modulates the analog signal into a video signal and outputs the video signal as a modulated video signal to the output terminal 30.
[0035]
On the other hand, in the digital / analog converter 31, the audio stream read from the recording medium 16 corresponding to the video signal is converted and input by the audio stream decoder 27 and converted into an analog signal by timing control of the microcomputer 12. The data is converted and output to the output terminal 32 as an audio signal.
[0036]
Next, when there is no room in the recording area of the recording medium, recording control means for deleting the recorded high-rate bit stream, that is, each stream recorded on the recording medium 16 by the interface 22 is configured. As shown in FIG. 2A, a TV signal program is first composed of four streams: a high-rate video stream HVS, a low-rate video stream LVS, a high-rate audio stream HOS, and a low-rate audio stream LOS. It is created as a set 33 of type A stream files.
[0037]
Further, as shown in FIG. 2B, a program constituted by each stream recorded on the recording medium 16 by the interface 22 is sent from a set 33 of type A stream files to a high-rate video stream HVS and a high-rate audio. It is also created as a set 34 of type B stream files excluding the stream HOS.
[0038]
The set 34 of type B stream files is a space-saving version of the set 33 of type A, and when the recordable area of the recording medium 16 runs out, a stream from type A is created for the purpose of creating a new recordable space. The file is deleted and created in the recording medium 16. Therefore, the low-rate video stream LVS and the low-rate audio stream LOS shown in FIG. 2A have the same contents as the low-rate video stream LVS and the low-rate audio stream LOS shown in FIG.
[0039]
Next, a system operation of the recording / reproducing apparatus according to the present invention configured as described above will be described with reference to a flowchart. Although the microcomputer 12 shown in FIG. 1 is not shown in the drawing, a microprocessor, a memory, and the like are mounted therein, and programs for executing the following flows are stored in a built-in memory. According to this program, the microprocessor controls each operation shown in the flow and processes the entire calculation.
[0040]
In the following explanation, for the sake of easy understanding, it is assumed that the operation is simplified and the system has only three states of a power-off state, a recording state, and a reproduction state. It is assumed that the recording is always performed on the medium, and the signal is always reproduced from the recording medium in the reproduction state.
[0041]
As shown in FIG. 3, the main routine starts from step ST1, and first, power is turned on in step ST2 to make each device operable.
[0042]
Next, in step ST3, it is determined whether or not the system is in the power-on continuation and the recording mode is set. If YES, since the system is in the recording mode, the control shifts to the recording routine shown in FIG. After exiting the recording routine shown in FIG. 4, control is transferred to step ST3.
[0043]
If NO is determined in step ST3, the system has either received an instruction to shift to a power-off state or has entered a reproduction mode, and this is determined in step ST5.
[0044]
If it is determined in step ST5 that the playback mode is set, the process returns to the determination in step ST3 shown in FIG. 3 via the playback routine shown in FIG. 5 in step ST6. If it is determined in step ST5 that the playback mode is not set, step ST7 is executed. And the main routine is terminated in the termination process of step ST8.
[0045]
At step ST4 shown in FIG. 3, control is transferred to the recording routine shown in FIG. 4, and the recording operation starts from step ST9 shown in FIG. It is determined whether or not there is a space where a type A program can be recorded.
[0046]
If it is determined in step 10 that “there is space”, the control moves to step ST12 where the input signal (video, audio) is converted into the program format of the set 33 of type A stream files and recorded on the recording medium 16. And returns to step ST3 of the main routine shown in FIG. 3 via step ST13.
[0047]
Next, if it is determined in step 10 that there is no space, the control moves to step ST11, and a new recordable area is recorded from the recorded area on the recording medium 16 in this step ST11 by the deletion routine shown in FIG. After the recording area is secured, the process returns to step ST12 of the recording routine shown in FIG.
[0048]
In step ST12, the input signal (video, audio) is converted into the program format of the set 33 of type A stream files and recorded on the recording medium 16, and step ST3 of the main routine shown in FIG. 3 is performed via step ST13. Return to.
[0049]
Next, the deletion routine shown in FIG. 6 is entered from step ST11. By this deletion routine, the stream of the recorded area is deleted and a new recordable area is created. enter.
[0050]
Shifting from step ST14 to step ST15, in this step ST15, the value of the number of elements N is set to the work variable k. The number of elements N is the set φ of the type A format programs φ existing on the recording medium 16. Indicates the number of elements. After setting the value of the number of elements N, it is determined in step ST16 whether a type A recorded program exists (k> 0).
[0051]
As shown in FIG. 2A, the type A recorded program has two high and low rate streams in the same program, so a part of the program stream recorded in the type A format is erased. By changing to the type B shown in FIG. 2B, a newly recordable area can be formed on the recording medium 16 while the contents of the program remain.
[0052]
If YES is determined in step ST16, a type A program exists on the recording medium 16. Therefore, in step ST17, a predetermined program P is selected from the set φ by a method described later from the set φ.
[0053]
Thereafter, in step ST18, the high-rate video stream HVS and the high-rate audio stream HOS, which are high-bit rate streams of video and audio, are deleted from the constituent elements of the selected program P, and the program P of type A is changed to type B. Change to a program.
[0054]
Next, in step ST19, the program P that is no longer an element of the type A format program set φ is removed from the set φ and added to the recorded type B format program set φ, and in step ST20, the set φ is set. 1 is subtracted from the number k of elements.
[0055]
Thereafter, it is checked in step ST21 whether or not the necessary space has been created. If it is determined that the space has been secured, the process returns to step ST11 of the recording routine shown in FIG. When it is determined that it is not secured, the control is returned to step ST16.
[0056]
If k> 0 cannot be satisfied in step ST23, no more recording space can be secured by the conversion from type A to type B. Therefore, in step ST23, the set ψ can be obtained by the method described later. To select program Q and delete it.
[0057]
In step ST24, the program Q, which is no longer an element of the set ψ, is removed from the set ψ, and it is checked in step ST25 whether a necessary recording space has been created. Returning to step ST11 of the recording routine shown in FIG. 4B, when it is determined that the necessary recording space has not yet been secured, the control is returned to step ST23.
[0058]
Next, returning to FIG. 3, the reproduction operation will be described. If it is determined in step ST5 that the playback mode is set, the playback routine shown in FIG. 5 is entered in step ST6. This playback operation starts from step ST26.
[0059]
In step ST27, it is determined whether the type of the program to be reproduced is type A or type B. If type A, the process proceeds to step ST28 to reproduce a high bit rate stream. Since there is only a low bit rate stream, the process proceeds to step 29 and is reproduced. When these reproductions are completed, this reproduction routine is exited via step ST30.
[0060]
Step ST17 and step ST18 shown in FIG. 6 for selecting a program and converting from type A to type B in order to secure a recording space, or step ST24 shown in FIG. In the case of the above process, there are various methods for selecting a target program as described below.
[0061]
First, the user directly instructs the microcomputer 12 via the user interface 11 to designate and erase the program, and second, the priority order of the program to be erased in advance by the user is registered in the microcomputer 12. There is a method of automatically erasing the microcomputer 12 according to this priority when erasing.
[0062]
Thirdly, there is a method of selecting and erasing a program recorded on the recording medium 16 with the oldest date and time, and a fourth method of erasing from a program with the oldest recording date and time among programs that have been reproduced once by the user.
[0063]
As described above, various recordings and erasures are repeated on the recording medium 16. Here, the state transition of the recording medium 16 at the time of recording will be mainly described with reference to the state transition diagram shown in FIG. It is possible for the user to delete any program regardless of type A or type B. However, in order to facilitate understanding, these deletions are omitted.
[0064]
The state CD10 is an initial state of the recording medium 16, and the data on the recording medium 16 is indefinite x. When type A recording is performed from the state CD10, the state CD10 passes through the path PT10 or the path PT11 to the state CD11 or the state CD12. Transition.
[0065]
State CD11 is a state in which there are many writable areas and recording is possible with type A, and state CD12 is a state in which there are few writable areas and recording is not possible with type A beyond this.
[0066]
Therefore, when recording is further performed with type A in the state CD11, there are a case where the state returns to the state CD11 again through the path PT12 and a case where the state transitions to the state CD12 via the path PT13.
[0067]
From the state CD12, there is no path for transition to another state other than making a space by converting the type A program on the recording medium 16 to the type B. Transition to possible state CD11.
[0068]
In the state CD12, when the path PT15 is passed, even though all the type A programs on the recording medium 16 have been converted to the type B, there is not enough space to record the type A. Transition to state CD13.
[0069]
From this state CD13, by erasing the type B program, it is possible to transit to the state CD11 where the type A can be recorded through the path PT16.
[0070]
In the description so far, when recording a program, as shown in FIG. 1, when encoding a video signal DVS into a high-rate video stream HVS and a low-rate video stream LVS, a high-rate encoder 14 and a low-rate encoder Fifteen two encoders are used, but this can also be combined into one by improving the encoding algorithm.
[0071]
Also, since the audio signal DOS has a smaller recording capacity than the video signal AVS, when creating a high-rate audio stream HOS, it is compressed without increasing the rate setting of the parameter HR2 without compression processing. It is possible to record with linear PCM (pulse code modulation) to further improve the sound quality. For this reason, it is assumed here that the high bit rate stream includes an uncompressed one.
[0072]
【The invention's effect】
  As described above, according to the recording / reproducing apparatus of the present invention, when there is a margin in the recording space of the recording medium, recording is performed with a bit stream of both high and low rates. High-rate bitstreamSince the new low-rate and high-rate bitstreams are recorded in the area that has been deleted and freed up, the high-rate bitstreams are deleted to ensure the capacity and the new digital signal has low image quality. A bit stream and a high-quality bit stream can be recorded.
[0073]
In addition, since the recording medium records a bit stream of both high and low rates using a spare space, the user can preferentially play back the high-rate bit stream during playback, and enjoy high image quality. I can do it. Furthermore, if there is a high-rate bit stream on the recording medium, it is possible to create a new writing space by deleting these, and in this case, the low-rate bit stream remains, so In addition, many low-rate bit streams (programs) can be secured.
[0074]
The low-rate bit stream in the recording / reproducing apparatus according to the present invention has a good image quality because there is no missing bit at the same bit rate compared to the conventional low-rate bit stream to be recompressed. Conversely, if the image quality is comparable to that of a low-rate bit stream by conventional recompression, the compression rate can be further increased.
This is because the low-rate bit stream in the recording / reproducing apparatus according to the present invention uses the same source as that used to create the high-rate bit stream, and therefore there is little deterioration during compression. On the other hand, in the conventional case where MPEG2 is used to recreate a low-rate bitstream by recompression accompanied by decompression, the noise itself generated because MPEG2 is irreversible conversion, and this noise during recompression This is because the image quality is lowered due to the double factor of causing an error in motion detection.
[0074]
In addition, according to the recording / reproducing method of the present invention, when there is a margin in the recording area of the recording medium, recording is performed as a bit stream of both high and low rates, and when the recording medium runs out of space, a predetermined recorded high rate is recorded. Since the bitstream is deleted to create a recording area and a new low-rate bitstream is recorded, if there is space on the recording medium, the space is not opened as it is. A bit stream is secured on a recording medium, and a high-rate bit stream is preferentially reproduced at the time of reproduction, thereby enabling high-quality image quality to be viewed using the recording medium effectively.
[0075]
Furthermore, according to the recording / reproducing method of the present invention, when the recording medium runs out of space, it is possible to leave many low-rate bitstreams. Since there is less deterioration at the time of compression compared to the conventional technique for recompression, it is possible to ensure good image quality.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment according to the present invention.
FIG. 2 is an explanatory diagram showing a configuration of a data format stored in the recording medium shown in FIG.
FIG. 3 is a flowchart of a main routine for explaining the operation of the recording / reproducing apparatus shown in FIG. 1;
4 is a flowchart of a recording routine for explaining the operation of the recording / reproducing apparatus shown in FIG.
FIG. 5 is a flowchart of a playback routine for explaining the operation of the recording / playback apparatus shown in FIG. 1;
FIG. 6 is a flowchart of a deletion routine for explaining the operation of the recording / reproducing apparatus shown in FIG. 1;
7 is a state transition diagram for explaining state transition in the recording medium of the recording / reproducing apparatus shown in FIG.
[Explanation of symbols]
10; demodulator, 11; user interface, 12; microcomputer, 13; analog / digital converter, 14; high-rate encoder, 15; low-rate encoder, 16; recording medium, 18; High-rate encoder, 21; low-rate encoder, 22; interface, 23; buffer memory, 24; interface, 25; buffer memory, 26; video stream decoder, 27; audio stream decoder, 28; digital / analog converter, 29 Modulator, 31; digital / analog converter, DVS; video signal, DOS; audio signal, HVS; high-rate video stream, LVS; low-rate video stream, HOS; high-rate audio stream, LOS; Oh stream, AVS; video signal, AOS; audio signal

Claims (16)

The digital signal is compressed to create a low-rate and high-rate bitstream, and each of the created low-rate and high-rate bitstreams is recorded on a recording medium, and there is no room in the recording area of the recording medium. A recording / reproducing method characterized in that a low-rate and a high-rate bit stream are newly recorded in an empty area by deleting a recorded high-rate bit stream .   The recording / reproducing method according to claim 1, wherein the digital signal is composed of broadcast program data.   2. The recording / reproducing method according to claim 1, wherein the digital signal includes a video signal and an audio signal corresponding to the video signal.   2. The recording / reproducing method according to claim 1, wherein the digital signal is only a video signal.   2. The recording / reproducing method according to claim 1, wherein the deletion of the recorded high-rate bit stream is a designated high-rate bit stream.   The recording / reproducing method according to claim 1, wherein the deletion of the recorded high-rate bitstream is based on a preset priority order.   2. The recording / reproducing method according to claim 1, wherein deletion of the recorded high-rate bitstream gives priority to the older recorded date and time.   2. The recording / reproducing method according to claim 1, wherein the deletion of the recorded high-rate bit stream is in the order of recording date and time among the high-rate bit streams reproduced at least once. Means for compressing the digital signal to generate a low-rate and high-rate bit stream; means for recording each of the generated low-rate and high-rate bit streams on a recording medium; and a margin in the recording area of the recording medium Recording control means for deleting the recorded high-rate bitstream when
The recording / reproducing apparatus is characterized in that the recording means newly records a low-rate and high-rate bitstream in an empty area by deleting the high-rate bitstream by the recording control means .   The recording / reproducing apparatus according to claim 9, wherein the digital signal is composed of broadcast program data.   The recording / reproducing apparatus according to claim 9, wherein the digital signal includes a video signal and an audio signal corresponding to the video signal.   The recording / reproducing apparatus according to claim 9, wherein the digital signal is only a video signal.   10. The recording / reproducing apparatus according to claim 9, wherein the deletion of the recorded high-rate bit stream is a designated high-rate bit stream.   10. The recording / reproducing apparatus according to claim 9, wherein the deletion of the recorded high-rate bitstream is based on a preset priority order.   10. The recording / reproducing apparatus according to claim 9, wherein in the deletion of the recorded high-rate bit stream, priority is given to the older recorded date and time. 10. The recording / reproducing apparatus according to claim 9, wherein the deletion of the recorded high-rate bit stream is in the order of recording date and time in the high-rate bit stream reproduced at least once.

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