JP3750846B2 - Video signal recording method and video signal recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a video signal for recording a supplied video signal on a recording medium such as a hard disk as a signal compressed and encoded at a variable bit rate.IssueThe present invention relates to a recording method and a video signal recording apparatus.
[0002]
[Prior art]
A video signal recording apparatus using a randomly accessible recording medium such as a hard disk as a recording medium can record a plurality of TV broadcast video software at the same time because it has a short access time for recording. It has functions such as being able to perform at the same time.
[0003]
A video signal recording apparatus having such a simultaneous recording / playback function is capable of viewing and playing back video software that is being broadcast while continuously shifting time from the present to the past, and video software that has started recording in the past. It has a convenient recording function such as chasing playback that catches up with the currently recorded video software, and will be introduced into the home with VTRs used as conventional time shift machines in the future. It is considered.
[0004]
Also, the recording signal in the conventional VTR is recorded on the video tape by FM modulation of the supplied analog video signal. In the case of the compression encoded signal, the signal compressed and encoded at a fixed rate is recorded on the video tape. However, in a video signal recording apparatus using a random-access recording medium such as a hard disk, a signal compressed and encoded at a variable rate is recorded, and a limited recording capacity is used effectively. It is necessary to.
[0005]
According to the variable-rate compression encoding, a video signal with a small amount of information is encoded with a small bit rate and a video signal with a large amount of information is encoded as a signal with a large bit rate according to the information amount of the supplied video signal. Thus, the encoded and decoded video signal can provide visually comparable video quality to the signal encoded at a fixed rate, and can record a video signal for a predetermined time with a small code amount as a whole. is there.
[0006]
As a method of encoding a video signal at a variable rate, there is a method based on MPEG (moving picture experts group). The MPEG encoding method is a variable in which the bit rate of the encoded signal is variable according to the information amount of the video signal. Bit rate encoding, which is also used in DVDs (Digital versatile discs).
[0007]
In addition, since the video signal authoring for recording the encoded signal on the DVD does not need to encode and record the supplied video signal in real time, the video signal is encoded in advance, and the amount of code necessary for encoding is reduced. After measuring the time change, set the appropriate bit rate change characteristic according to the obtained code amount information, and perform encoding according to the set change characteristic, so-called measurement path and encoding Thus, a variable-rate encoded signal is generated and recorded by a so-called “two-pass method” having two paths for the signal.
[0008]
However, in the case of a video signal recording apparatus used for home use, for example, when a received broadcast signal is recorded in real time, it cannot be encoded by the two-pass method, and a path for code amount measurement is provided. However, an encoding method based on a so-called “one-pass” method is used.
[0009]
FIG. 6 shows the configuration of an encoder that uses the one-pass method.
This encoder includes an encoding difficulty calculator 31, an allocated bit amount calculator 32, and a moving image encoder 33.
[0010]
The moving image information input signal (video signal) is supplied to the moving image encoder 33 and also to the encoding difficulty calculator 31, and the encoding difficulty calculator 31 determines the encoding difficulty. As a result, the encoding difficulty level information d is generated, and the generated encoding difficulty level information d is supplied to the allocated bit amount calculator 32 for each unit time.
[0011]
The allocated bit amount calculator 32 for each unit time is supplied with predetermined desired average bit rate (SQBR) information and encoding difficulty level information d, and is allocated based on the supplied information. Code amount information b is generated, and the assigned code amount information b is supplied to the video encoder 33.
[0012]
In this way, the moving image encoder 33 uses the moving image information input signal supplied as an input signal based on the supplied allocated code amount information b as an encoded signal output encoded at a predetermined average bit rate. To supply.
[0013]
FIG. 7 shows the relationship between the assigned code amount b and the encoding difficulty level d for giving the average bit rate. In variable-length coding using a normal one-pass method, the relationship between the encoding difficulty level d and the allocated code amount b as shown in the figure is obtained in advance, and based on the obtained figure, table, or mathematical expression. Encoding is performed using the allocated bit amount b.
[0014]
That is, the moving image encoder 33 sets a parameter such as a quantization scale of a DCT (Discrete Fourier Transform) coefficient according to the allocated code amount b, thereby encoding according to the allocated code amount b. The details of the encoding method used in the MPEG-2 method and the like are described in Japanese Patent Laid-Open No. 9-23423 “Signal Encoding Method, Signal Encoding Device and Signal Recording Medium”, and No. 10-312396, “Signal encoding method, signal encoding device, signal recording medium, and signal transmission method”.
[0015]
When a signal subjected to variable bit rate encoding in this way is recorded on a recording medium capable of random access such as a hard disk, the capacity of the medium for recording the information content is limited in advance, The total code amount recorded in this area needs to be encoded within a range not exceeding this, and as an encoding method performed by limiting such total code amount to a predetermined range, the above-mentioned Japanese Patent Laid-Open No. 10-133609 is disclosed. No. -30396, “Signal encoding method, signal encoding device, signal recording medium and signal transmission method”, and Japanese Patent Laid-Open No. 2000-156857 “Video encoding method and apparatus with variable bit rate” are disclosed. Yes.
[0016]
[Problems to be solved by the invention]
By the way, when recording video software for a predetermined time broadcast using a video signal recording apparatus using a hard disk or the like as a recording medium as a signal compressed and encoded at a variable rate, the time change characteristic of the amount of information that the video signal has, Or when information on the total data capacity when compressed by a predetermined method is obtained in advance, a predetermined program software can be stored in a predetermined area by performing variable-length compression coding based on the information and recording it. Can be recorded.
[0017]
However, in general, no information about the amount of information of such a video signal is obtained, and the amount of code necessary for recording, that is, the used capacity of the recording medium can be obtained only after the recording of the video software is finished. Thus, it is difficult to record such a signal whose code amount information is unknown in a predetermined area of the recording medium while maintaining little deterioration in image quality.
[0018]
Even when information about the video of the broadcast program is obtained, the quality of the received video signal is deteriorated due to the difference in the reception environment, that is, the S / N (signal to noise ratio) of the video signal. ) Has deteriorated, the amount of code at the time of encoding increases according to the deterioration of the signal.
[0019]
This is, for example, granular noise mixed in the video signal. Snow noise that appears to fall snow increases the amount of information even if it is an image of one frame by including the noise, and the snow noise component is Since the signal has no inter-frame correlation, the code amount increases in both intra-frame coding and inter-frame coding.
[0020]
In this way, when a video signal is supplied and the supplied video signal is encoded, the total amount of codes obtained by encoding cannot be uniquely determined. It is necessary to set the code amount as the target code amount and perform the encoding with the target code amount.
[0021]
In addition, in normal encoding, even if a video with a large amount of information is supplied during encoding, the reproduced video does not break down. It is possible to perform encoding while maintaining a margin for the total code amount in consideration of the fact that a complicated image that requires a large number of bits for encoding is supplied. It is common.
[0022]
However, encoding performed with a reduced total code amount has a problem in that image quality deterioration is included in the decoded video as compared with encoding with an appropriate total code amount, and is more difficult with a one-pass technique. There is a need for a method for performing variable-length coding with an appropriate total code amount and less image quality degradation, and to realize an apparatus configuration therefor.
[0023]
  In view of this, the present invention provides a video signal recording apparatus using a recording medium with excellent random accessibility such as a hard disk, which is a code having an appropriate total code amount obtained by performing variable-length encoding on a predetermined recording area of the recording medium. A video that generates an encoded signal, records the generated encoded signal on the medium, and reduces the impression of image quality deterioration given to the viewer when the recorded program is reproduced, decoded and viewed TrustIssueIt is intended to provide a recording method and a configuration of a video signal recording apparatus.
[0024]
[Means for Solving the Problems]
  Video signal of the present inventionIssueIn order to solve the above problems, the recording method and the video signal recording apparatus are as follows:And 2).
  That is,
[0025]
1)Includes received noiseVideo signalCompressed with an encoder and recorded on a recording mediumVideoIssueRecording methodsmellAnd
  The bit rate of the video signal compressed by the encoder is detected by a stream analyzer (54),
The noise is included when the bit rate detected by the stream analyzer at the start of compression of the video signal is lower than a first target bit rate for compressing the video signal including the predetermined noise. A control signal is output to the encoder so as to compress the video signal at a second target bit rate higher than the first target bit rate for compressing the video signal not yet received (57);
When a bit rate exceeding the first target bit rate is detected after a predetermined time has elapsed since the compression start time, the second target bit is gradually increased so as to approach the first target bit rate. A control signal for lowering the rate is output (57) to the encoder.A video signal characterized byIssueRecording method.
[0026]
2)Includes received noiseVideo signalCompressed with an encoder and recorded on a recording mediumVideo signal recording devicesmellAnd
  A stream analyzer (54) for detecting a bit rate of the video signal compressed by the encoder;
The noise is included when the bit rate detected by the stream analyzer at the start of compression of the video signal is lower than a first target bit rate for compressing the video signal including the predetermined noise. A control signal is output to the encoder so as to compress the video signal at a second target bit rate higher than the first target bit rate for compressing a video signal that has not been compressed. When a bit rate exceeding the first target bit rate is detected after a lapse of time, the second target bit rate is lowered stepwise so as to approach the first target bit rate. A bit rate control unit (57) for outputting a control signal to the encoder;
HaveVideo signal recording characterized byRegenerationapparatus.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
  The video signal of the present invention will be described below.IssueAn embodiment of a recording method and a video signal recording apparatus will be described with reference to a preferred embodiment including a video signal reproducing apparatus for reproducing the recorded signal.
[0034]
FIG. 1 shows a schematic block diagram of a video signal recording / reproducing apparatus for recording a video signal that has been variable-length encoded in a predetermined recording area of the hard disk, and reproducing and decoding the recorded signal to obtain a video signal. The configuration and the operation during normal recording and playback will be outlined.
[0035]
The video signal recording / reproducing apparatus 40 shown in FIG. 1 includes a recording unit 50, a medium unit 60, and a reproducing unit 70, and a monitor TV 90 is connected to the reproducing unit 70 by wire, and to the recording unit 50 and the reproducing unit 70. The remote control 95 is coupled to the playback unit 70 by infrared rays.
[0036]
First, the recording unit 50 includes a TV tuner 51, an A / D converter 52a, an external video input terminal 52b, a changeover switch 52c, an MPEG-2 encoder 53, a stream analyzer 54, a REC-FIFO 55, a microcomputer 57, and a rate setting terminal 59. Composed.
[0037]
The medium unit 60 includes a hard disk recording / reproducing device 61, a hard disk 63, and a writing / reading controller 65. The reproducing unit 70 includes a buffer memory 71, an MPEG-2 decoder 72, a D / A converter 74, a microcomputer 76, and a remote controller. The interface 79 is configured.
[0038]
Next, the operation of the video signal recording / reproducing apparatus 40 configured as described above will be outlined.
First, the TV tuner 51 receives a video signal of a reception channel set by a remote controller 95 among broadcast radio waves coming from an antenna, and a video signal obtained by receiving the video signal is supplied to an A / D converter 52a. It is converted into a digital signal, and the converted signal is supplied to the changeover switch 52c.
[0039]
The changeover switch 52c is supplied with the video signal supplied to the external video input terminal 52b, one of the supplied video signals is selected by a switch operation, and the signal obtained by the selection is MPEG- 2 is supplied to the encoder 53.
[0040]
In the MPEG-2 encoder 53, the supplied video signal is compressed by a variable length method in accordance with the MPEG-2 (moving picture experts group-2) standard defined by ISO / IEC (International Organization for Standardization / International Electrotechnical Commission). The encoded and compressed and encoded signal is supplied to the stream analyzer 54.
[0041]
In the stream analyzer 54, the code amount and the like of the compression-coded signal are analyzed, and the code amount information obtained by the analysis is supplied to the microcomputer 57 described later, and the supplied encoded information signal is the REC-FIFO 55. To be supplied.
[0042]
The REC-FIFO 55 is a FIFO (first in first out) operation of a recording (REC) signal, that is, a circuit that temporarily stores input signals to be supplied and supplies the signals as output signals in the order of input. The signal supplied from the circuit is supplied to the hard disk recording / reproducing device 61.
[0043]
In the hard disk recording / reproducing device 61, the supplied signal is a signal divided for each sector size for recording in a predetermined recording area of the hard disk 63, and the divided signal is subjected to operation control by the writing / reading controller 65. Supplied to the hard disk 63 and recorded in a recording area of a predetermined capacity of the hard disk 63.
[0044]
In this way, the video signal of the received channel or the video signal supplied to the external video input terminal 52b is selected as a signal to be recorded, and the recording time of the selected video signal and the signal to be recorded are selected. The video signal supplied based on the set condition is variable-length encoded and recorded in a recording area having a predetermined recording capacity of the hard disk 63, but has a predetermined recording time. Is set, and the video signal supplied during the recording time is subjected to variable-length coding with the highest possible quality, and the total data amount of the coded signal obtained by the coding is recorded in a predetermined recording area. Is preferred.
[0045]
Next, the reproduction operation of the recording signal of the hard disk 63 recorded in this way will be outlined.
First, when the reproduction button is operated by the remote controller 95, the operation content is transmitted to the remote control interface 79 by the modulated infrared ray, and the operation content of the remote control key is supplied to the microcomputer 76.
[0046]
From the microcomputer 76, a control signal generated according to the operation content is supplied to the write / read control circuit 65, and a video signal recorded in a predetermined recording area of the hard disk designated by the operation is read and read. The obtained signal is supplied to the hard disk recording / reproducing device 61.
[0047]
The hard disk recording / reproducing device 61 amplifies the signal read from the hard disk 63, corrects the characteristic, and detects the reproduced error signal. The signal subjected to such signal processing is supplied to the buffer memory 71. Is done.
[0048]
In the buffer memory 71, the compression-coded signal is temporarily stored, and the temporarily stored signal is read in response to a request from the MPEG-2 decoder and supplied to the MPEG-2 decoder 72.
[0049]
In the MPEG-2 decoder 72, the supplied signal is decoded by a method complementary to the method compressed and encoded by the encoder 53 in accordance with the MPEG-2 standard, and the digital video signal obtained by decoding is D / A converted. The analog video signal is supplied to the monitor 74 and converted into an analog video signal, and the converted analog video signal is supplied to the monitor TV 90 and displayed.
[0050]
In this way, the supplied video signal is converted into an inter-frame compressed signal that is encoded by using the MPEG-2 system and is encoded using intra-frame compression and motion compensation, and these signals are recorded on the hard disk 63. . The signal recorded on the hard disk 63 is read out and decoded by the MPEG-2 decoder. Next, a video signal encoded by the MPEG-2 system, which is performed as described above, will be described.
[0051]
FIG. 2 shows a video signal handled by the MPEG-2 system as a signal for each image unit, and shows the type of the image unit.
In the same figure, I, B, and P are named and arranged in the time direction on the frame images (pictures) constituting the video signal. The I is I (Intra-coded) which is subjected to intra-frame coding. ) A frame image (picture).
[0052]
P is a P (Predictive-coded) frame image that is predictively encoded in one direction as indicated by an arrow at the bottom of the figure, and B is a motion prediction vector obtained from both past and future directions. It is a B (Bidirectionally predictive-coded) frame image to be encoded.
[0053]
As described above, an image encoded by MPEG-2 is composed of frame images having three kinds of properties. For example, I frames are arranged every 15 frames. A group of 15 frame images before the start of the operation is called GOP (Group of Picture).
[0054]
The ratio of the data amount that the I frame occupies in the GOP is about 30% when the number of GOP frames is set to 15, and the remaining 14 frames are composed of the data amount of 70%. 14 × 30% data is encoded as 70% data, and 6 times the ratio is obtained as a result of the increase in encoding efficiency due to motion prediction.
[0055]
By the way, the improvement of the encoding efficiency by the motion prediction differs depending on the supplied video signal. In the case of a still image, the I frame is encoded first, and the next 14 frames are the same. Since the information transmitted for motion prediction can be almost zero, the amount of encoded data becomes very small.
[0056]
On the other hand, even if the video signal is a signal with little still image-like motion, if the noise component included in the signal is large, the MPEG-2 encoder 53 also encodes the noise signal included in the video signal. In order to transmit, the amount of encoded data for motion prediction increases according to the level of the noise signal.
[0057]
The noise level corresponds to the video signal from a video camera (not shown) supplied from the external video input terminal 52b in the video signal recording / reproducing apparatus 40 shown in FIG. In particular, when the electric field strength of the received signal supplied from the antenna is weak, a large difference occurs in the noise component included in the video signal.
[0058]
Therefore, the result of encoding a video signal when the electric field strength is weak requires a large amount of code, whereas a video signal with good S / N encodes a high-quality video signal with a small amount of code. I can do it.
[0059]
Therefore, if the S / N of the supplied video signal can be measured in order to encode a high-quality video signal, the amount of code to be allocated at the time of encoding is determined based on the measured result, and the noise signal is encoded. Therefore, a large amount of code can be avoided.
[0060]
The code amount is set by specifying an appropriate data amount in accordance with the quality of the video signal supplied when the channel of the TV tuner 51 is switched or the video signal is switched by the switch 52c. .
[0061]
  Next, its proper data rate(bit rate)A method for performing the above setting using the data code amount obtained by encoding with the MPEG-2 encoder 53 will be further described with reference to FIG.
[0062]
This method is preferable not only for the above-mentioned means for S / N measurement but also for controlling the amount of code while directly monitoring the encoded signal, and is preferable for processing of the encoded signal. Is.
[0063]
That is, in the video signal recording / reproducing apparatus 40 shown in the figure, when a program recording is reserved using the remote controller 95 or the like, the recording time of the program, or a scheduled encoding time that is a scheduled time from the start of encoding to the end thereof , And one of a plurality of encoding rates is selected as a recording mode, and a total average bit rate during recording time (hereinafter also referred to as an average rate) is determined based on the selected time and the encoding rate. It is done.
[0064]
The encoded signal obtained by encoding at the determined total average bit rate is recorded in a predetermined recording area secured in the hard disk 63.
[0065]
Furthermore, during recording for a relatively long time such as 1 to 10 minutes, for example, the predicted total bit amount at the end of recording temporarily exceeds a predetermined recording area. By allowing the operation, it is also intended to obtain an encoded signal with higher image quality.
[0066]
The configuration of the video signal recording / reproducing apparatus 40 for obtaining the high-quality encoded signal will be further described.
The MPEG-2 encoder 53 used in this apparatus may have the same configuration as the moving picture encoder 33 shown in FIG. 6 described above, and the allocated bit amount calculator for each unit time is performed by the microcomputer 57. .
[0067]
The microcomputer 57 is supplied with a signal relating to the average bit rate (SQBR) from the rate setting terminal 59, and the microcomputer 57 generates an assigned code amount signal based on the code amount information of the encoded signal supplied from the stream analyzer 54. Then, the generated signal is supplied to the MPEG-2 encoder 53.
[0068]
In this way, the MPEG-2 encoder 53 encodes the supplied video signal based on the supplied allocated code amount signal, that is, the target rate, and the encoded signal obtained by the encoding is the stream analyzer 54, The data is recorded in a predetermined recording area of the hard disk 63 via the REC-FIFO 55 and the hard disk recording / reproducing device 61.
[0069]
The transfer rate of the encoded signal to be recorded is supplied from the rate setting terminal and is set at an average rate set by the microcomputer 57. The average rate is obtained by a plurality of different image quality modes such as 1.5 Mbps, 2 Mbps, and 4 Mbps. The transfer rate selected from these modes is set as a desired average bit rate, and the MPEG-2 encoder 53 can obtain an encoded signal encoded at the set average rate. To work.
[0070]
In the encoded signal supplied from the MPEG-2 encoder 53, the bit amount of the encoded signal supplied from the stream analyzer 54 is counted, and the counted value BS is supplied to the microcomputer 57.
[0071]
  FIG. 3 shows the bit rate controlled by the microcomputer 57.(Hereinafter sometimes referred to as data rate)An example of the elapsed state is shown and described.
  In the same figure, the vertical axis is the bit rate, the horizontal axis is the time, and the break of the horizontal axis indicates, for example, the time interval interval of 1 minute, and the numbers shown in parentheses such as (1) are these intervals This is for explaining the above.
[0072]
The amount of information contained in the video signal encoded at this time is less than normal in the sections (1) to (5), and the information amount is large in the sections (6) to (9). , (10) is the case where the amount of information in the section after the latter half is slightly smaller than usual.
[0073]
Here, the state of an encoded signal obtained by encoding such a video signal when a bit rate B0 of 2 Mbps, for example, is set by a user's operation is indicated by a one-dot chain line.
[0074]
First, the transition of the bit rate indicated by the thin line a1 was encoded by the encoder when the bit rate B0 was given as SQBR (average bit rate) in the conventional encoder shown in FIG. 6 illustrates an example of a change in bit rate of an encoded signal.
[0075]
The curve indicated by the thin line a2 encodes the same video signal as described above when the value of SQBR is B0 + A that is larger than B0, for example, B0 = 2, A = 0.5, and SQBR is 2.5 Mbps. The transition of the bit rate of the encoded signal obtained in this way is shown.
[0076]
The thick line a3 shown in the figure shows the transition of the bit rate of the encoded signal obtained by supplying the same moving image signal to the encoding apparatus of the present embodiment.Then, a1, a2, Each operation of a3 is described.
[0077]
First, a1 is encoded with an average bit rate B0 as a target, but in the section (1) to (5), it is encoded at an average bit rate of about 1.5 Mbps for B0 = 2 Mbps, which is considerably lower than B0. It has become.
[0078]
As described above, this is also the case for the increase in the code amount when a video with a large amount of information that requires a large number of bits for encoding in the future, for example, an image with a fine and complicated motion of the picture arrives. This is because encoding is performed so that the code amount does not exceed a predetermined capacity.
[0079]
In the sections (7), (8), and (9), a complicated video signal is supplied and encoding is performed with a bit rate slightly higher than B0, but the code amount of the encoded signal performed so far is This is a case where the amount is less than the planned amount and the average bit rate has a margin with respect to B0.
[0080]
Next, the operation of a2 will be described.
This example is a case where encoding is performed by setting the average bit rate to about 2.5 Mbps which is slightly larger than 2 Mbps with respect to the conventional encoder, but the target of 1.9 Mbps in the section (1) to (5) Encoding is performed at a desired average bit rate slightly lower than the rate of 2 Mbps.
[0081]
However, when video signals with a large amount of information, such as sections (7), (8), (9), are supplied, the rate will greatly exceed the average rate of 2 Mbps. When a moderately complex pattern arrives in (5) and (7) to (9), the bit rate is smaller than (7) to (9) but exceeds 2 Mbps. It is output as a signal.
[0082]
In this way, the section (1) to (5) is encoded as a signal with a bit rate close to the desired average bit rate of 2 Mbps, but if a slightly complicated video is supplied, the target rate will be exceeded. The average bit rate over the entire recording time becomes larger than 2 Mbps, and it is impossible to record all the signals encoded in this way in a recording area of a predetermined capacity.
[0083]
Next, the operation of a3 relating to the present embodiment will be described.
In the figure, a3 indicated by a thick line is encoded at 1.9 Mbps, which is close to the desired average bit rate in the section (1) to (5) where the amount of information of the video signal is small, which is the same as a2, and the code of this section It can be said that the image quality of the converted signal is in a good state close to the target recording bit rate.
[0084]
Next, in the sections (6) and (7) where the information amount of the video signal increases, the coding rate increases in the same way as a2, but after the section (8), the coding rate gradually decreases to a lower value. Change to generate an encoded signal.
[0085]
In other words, when the target rate is determined at the time point (2) shown in the figure, the bit rate in the section (7), that is, the period T1, for example 1 minute, and the period T2, which is longer than the preceding T1, for example, 3 minutes Are determined based on the relationship between the average bit rates of the encoded signals generated in (1).
[0086]
When the bit amount obtained by analyzing in the period T2 analyzed by the stream analyzer at this time is BST2, the average bit rate in period T2 is BST2 / T2, but T2 in this apparatus is constant. BST2 itself is used as a measure of the average bit rate.
[0087]
FIG. 4 shows the relationship of the target rate given to this BST2 value.
In the figure, when the generated bit amount in the period of T2 is small, that is, when the average bit rate is small, the value of B0 + A is set as the target rate value, and the MPEG-2 decoder 53 sets the average bit rate B0 + A as the target rate. Encoding is performed.
[0088]
When the amount of generated bits in the period of T2 is large, that is, when the average bit rate is large, the target rate value is set to B0, so that the average bit rate is encoded targeting B0, and the generated bit amount is If it is in the middle, the intermediate value is taken.
[0089]
In this way, the value of the target rate is determined by monitoring the generated code amount in the period T2, and the generated code amount in the period T2 is as small as B0 or less in the sections (1) to (6) in FIG. Therefore, the target rate value is B0 + A, and the bit rate of the encoded signal made by the target rate is the same as a2.
[0090]
In section (7), the amount of generated code in the immediately preceding section (6) has increased, so a generated code amount slightly smaller than a2 is given as the target rate, and the generated codes in section (7) and later are given. Since the amount is large, the target rate is set so that the amount of generated code is small.
[0091]
Further, since the amount of code generated in the previous sections (7) to (9) is large in the section (10), the target rate value is set to a small value close to B0.
In addition, in the sections (11) and (12), since the code amount of the previous period T2 gradually decreases, the target rate value also gradually increases, and the bold line is close to a2 between a1 and a2. The value of
[0092]
However, if encoding is continued at a target rate close to a2, the target total bit rate may be exceeded, so the following rate processing is further performed to prevent the total bit rate from being exceeded.
[0093]
The rate processing is performed by analyzing the generated code amount at a constant interval T3 longer than the sections T1 and T2, for example, every 10 minutes, in the method for obtaining the target rate from the BST2.
[0094]
In this example, it is assumed that the total code amount is analyzed at time point {circle over (3)}, and if the bit amount generated during the period TX from the beginning of the moving image starting recording to {circle around (1)} is BSTX, the average bit rate during this period RX is RX = BSTX / TX.
[0095]
Then, FT3 is defined as a parameter for defining the relationship between the target rate and BST2, and the value of the target rate when BST2 is small is B0 + FT3, and the target rate is c1, c2 shown in FIG. 4 according to the value of FT3. , Change as shown in the graph of c3.
[0096]
The relationship between RX and FT3 is stored in advance as a mathematical expression or numerical table in a memory (not shown) connected to the microcomputer 57. The relationship between the average bit rate RX and the parameter FT3 is shown as an example.
[0097]
  FIG. 5 illustrates the relationship between the average bit rate RX and the parameter FT3.
  In this example,period TX Average bitrate at When RX is less than a certain value, eg average rate(Total average bit rate)Is 2MbpsThe RX ButWhen the value is 1.74Mbps or less, which is 0.26Mbps smaller than that, or the ratio between RX and average rate is the differenceBitrate ( 0.26Mbps )0.87 of the ratio given byDouble ( 1.74Mbps The 2Mbps Multiple divided byWhen FT3 = A when BST2NewThe target rate should be the relationship of c1 in FIG.To generate an encoded signal.RX is its certain value( 1.74Mbps )If larger, set FT3 = 0 and BST3(period T3 Bit amount generated)Regardless of the value ofIn FIG. c3 RelationshipThe same operation as the generation of the encoded signal performed with the target rate = B0, that is, with SQBR = B0 in the conventional encoder is performed.
[0098]
This operation is determined by analyzing the size of the total code amount predicted from the code amount up to the present with respect to the desired total recording code amount every T3, and at the same time, the encoding parameter control means (microcomputer 57) of the MPEG-2 encoder 53. ) Is set so that the total code amount of the bit stream supplied from the MPEG-2 encoder 53 becomes a more appropriate value.
[0099]
As a result of performing the total code amount control of the bitstream in this way, since the amount of generated code is large in the section T3 before (13) shown in FIG. 3, the encoding after (13) sets the target rate. Encoding is performed in a state where SQBR = B0 in the case of using a conventional encoder without increasing it.
[0100]
Therefore, after (13), the characteristic of the present embodiment indicated by a thick line and the characteristic due to a1 when performed by a conventional encoder coincide.
[0101]
The relationship between RX and FT3 is not limited to that shown in FIG. 4, and when RX is an intermediate value, FT3 takes an intermediate value between 0 and A, and the characteristic c2 shown in FIG. May be used as the target rate signal, and the value of FT3 may be continuously changed between A and 0 when RX is an intermediate value.
[0102]
In the method of the embodiment shown here, depending on the supplied video signal, the total recording bit amount may slightly exceed that in the case of recording at a desired average bit rate. It is possible to set a limit on the degree to which the coding is performed at the average bit rate.
[0103]
In addition, if a recording area corresponding to the limit of the excess is secured separately, all encoded bits including the excess code can be recorded reliably, so that image quality deterioration during recording is reduced. In addition, even when a video signal having a large amount of information is supplied at the end of recording, all bit streams can be recorded.
[0104]
As described above, the encoding method of the video signal in which the code amount of the generated bit stream is increased as much as possible to improve the quality of the encoded signal has been described, and the method for recording the entire bit stream has also been described. The time intervals T1, T2, and T3 illustrated here are merely examples, and these time intervals are arbitrarily set according to the set recording time or the like.
[0105]
Here, the reason why the video signal is analyzed at such a time interval and the target rate is set will be further described.
As described above, the bit amount for encoding varies greatly depending on the noise component included in the video signal.
[0106]
In the case of a video signal with a small noise signal, the ratio between the minimum value and the maximum value of the bit rate obtained by encoding is large. Therefore, even when a large amount of code is allocated to a video signal portion with a large amount of information, Since a high-quality video can be obtained with a small code amount in a small video portion, an encoded signal in which the total code amount of the high-quality video signal falls within a predetermined range can be obtained as a result.
[0107]
However, in the case of a video signal with a deteriorated S / N due to a bad reception state, a predetermined code amount is required to encode a noise signal even if the information amount of the video signal itself is small. Therefore, the bit rate of the encoded signal is always a large value, and there is no portion that gives a small bit rate.
[0108]
In this way, when a smaller value is obtained as the bit rate, the microcomputer 57 detects the minimum value of the bit rate because the total code amount is often suppressed to a predetermined value even when the average rate is set large. The quality of the overall encoded video signal is improved by setting the average rate.
[0109]
On the other hand, when a small bit rate cannot be obtained, the quality of the supplied video signal is often poor. In this case, encoding is performed at a given average rate as much as possible, and noise and other unnecessary signals are used. The total code amount that increases to a minimum is kept as small as possible.
[0110]
Further, the encoding shown in this example relates to the distribution of the total code amount within the recording time, and the first part of the recording is started at a high data rate.
[0111]
The allocation of a high code amount at the start of recording is often started from an attractive video called “eye catch” at the beginning of the program software, and the amount of information in the eye catch video is often large. This is because it is necessary to increase the attractiveness of the video software to be started by encoding the video portion while minimizing the image quality degradation of the video portion.
[0112]
On the other hand, when starting from a title screen with a small amount of motion such as a movie, encoding is often started because a small amount of code is allocated due to a small amount of motion. Noise due to quantization bit truncation error after DCT (Discrete Cosine Transform), which appears as mosquitoes flying over the horizontal bar of characters, called Mosquito noise in high-contrast image parts such as information The noise generated can aggravate the viewer's impression.
[0113]
Especially in program software such as movies, image quality deterioration before viewers are drawn into the story is notable and undesirable, but some image quality deterioration after that is acceptable, and recorded video software Since the total code amount can be adjusted while recording as described above, the bit rate of the recording start portion can be set large.
[0114]
The noise component included in the video signal necessary for adjusting the total code amount can be detected by specifying a large average rate at the recording start time to obtain a large ratio between the maximum value and the minimum value of the bit rate. Thus, the target rate thereafter can be specified more accurately by the detected ratio.
[0115]
In addition, regarding the designation of the target rate, when the supplied video signal is a signal encoded in advance by a method such as MPEG-2, such as BS digital broadcasting and digital terrestrial broadcasting, the encoded signal Is directly supplied to the stream analyzer 54 without going through the MPEG-2 encoder 53 and recorded on the hard disk 63.
[0116]
At this time, when the total data to be broadcast is recorded in the predetermined recording area of the hard disk 63, the supplied digital signal can be recorded as it is. The encoded digital signal is decoded to obtain a digital video signal, and then recorded again by converting it into an encoded digital signal.
[0117]
In this case, it is considered that the quality of the video signal is kept good, but even in that case, recording can be performed with high image quality suitable for the total code amount by the above-described method.
[0118]
The method for encoding and recording a video signal with appropriate image quality in a preset recording area and the recording apparatus therefor have been described in detail together with the embodiments.
In addition to the method of changing the target code amount signal supplied to the encoder as shown in this example, the method of encoding the video signal with such an appropriate image quality includes such a code in the encoder itself. For example, a microcode for controlling the code amount built in the encoder may be provided with a function for performing the amount control, and parameter information relating to recording is supplied by the microcode, and the encoding rate is managed.
[0119]
The recording methods and recording apparatuses shown in these examples have the following effects and are listed.
[0120]
  First, a video signal whose amount of information changes with time is supplied, and the supplied video signal is set with a predetermined data rate relating to recording time and recording image quality as a target value, and the set target data rate A video signal recording method in which an encoded bit stream signal is obtained by variable length encoding using an MPEG-2 encoder or the like, and the obtained signal is recorded in a predetermined area of a recording medium such as a hard disk. First, an encoded signal that is variable-length encoded at a target rate higher than the average rate set by the operation is generated and recording on the medium is started, and then the first of the variable-length encoded signal is The first data rate in the second time interval and the second data in the second time interval that is shorter than the first time interval and close to the encoding time point. Determined rate, the first data rate that is the determined data rate of the difference between the second data rate(Difference bit rate)When the variable length coding is performed while changing the target rate set in advance according to the data rate of the obtained difference or the ratio between the first data rate and the second data rate, supply The video signal part that is not easily affected by the noise signal included in the received video signal and has a large amount of information is encoded at a high bit rate, and the video signal part that has a small amount of information is encoded at an appropriate bit rate with a higher decoded video quality. Therefore, the total code amount can be recorded in a recording area of a predetermined size, and a video signal recording method that effectively uses the recording area can be realized.
[0121]
When the data rate of the difference is smaller than the first predetermined value, it is sufficiently predicted that the video signal to be supplied is not a good video signal such as a large amount of noise components included in the supplied video signal. By changing the target rate set in the value to a small value and continuing the variable length coding of the video signal, the video signal is set to a predetermined value so that no extra code amount is allocated for the noise component. It is possible to realize a video signal recording method in which encoding is performed while suppressing the total code amount and the encoded signal is stored in a predetermined recording area.
[0122]
Further, when the data rate of the difference is larger than the second predetermined value and the second data rate is smaller than the average rate for recording on the medium, the noise component included in the supplied video signal is Since it is considered that the signal is of good quality, such as a small number, the target rate set in advance to a large value is changed to a larger value. By performing variable-length encoding with sufficiently high compression, the total code amount can be obtained as an encoded signal to be recorded in a predetermined recording area, and high-quality video signals can be recorded at an appropriate encoding rate. A method can be realized.
[0123]
In the case of program software in which the amount of information of a supplied video signal is larger than that of a normal video signal, the ratio between the maximum value and the minimum value of the bit rate is large as described above, and the quality of the video signal is good. However, if the average encoding rate from the recording start point to the current point is larger than the target rate and the total data amount is very large, the preset target rate is changed to a larger value by detecting it. Therefore, it is possible to obtain a coded signal for recording the total code amount in a predetermined recording area and to realize a recording method of a high-quality video coded signal at an appropriate coding rate.
[0124]
In an apparatus equipped with this method, a video signal whose amount of information changes with time is supplied, and the supplied video signal is set with a predetermined data rate relating to recording time and recording image quality as an average rate, and the setting is performed. A video signal that obtains an encoded bitstream signal by variable length encoding using an MPEG-2 encoder or the like according to the average rate and records the obtained signal in a predetermined area of a recording medium such as a hard disk A recording apparatus, a target rate setting means for setting a target rate larger than the average rate, and an encoding means for generating the encoded signal variable-length encoded at the target rate set by the target rate setting means; A first data rate in a first time interval of the variable length encoded signal encoded by the encoding means, and the code A code rate detecting means for detecting a second data rate in a second time interval that is close to the time point and is smaller than the first time interval; a first data rate detected by the code rate detecting means; The target rate set by the target rate setting means according to the difference or the ratio of the data rates obtained by obtaining the data rate of the difference between the two data rates or the ratio of the data rates. And a target rate changing means for changing the set value of the rate to constitute a video signal recording device, which is not easily influenced by unnecessary signals such as noise signals included in the supplied video signal and has a large amount of information The video signal part is recorded at a high bit rate, and the video signal part with a small amount of information is encoded at an appropriate bit rate with a higher decoded video quality so that the total code amount is recorded to a predetermined size. Because that can be recorded in range, it is possible to realize a recording apparatus of a video signal to effectively use the recording area.
[0125]
Furthermore, when the data rate of the difference is smaller than the first predetermined value, it is sufficiently expected that the video signal is not good due to a large amount of noise components included in the supplied video signal. By changing the target rate set to a large value in advance to a small value and continuing variable-length coding of the video signal, the video signal is stored in a predetermined total amount without allocating an extra code amount for the noise component. Since the encoded signal can be recorded in a recording area of a predetermined capacity while suppressing the code amount, it is possible to realize a video signal recording apparatus for decoding and obtaining a high-quality video signal that effectively uses the recording area. it can.
[0126]
In an apparatus equipped with this method, a video signal whose amount of information changes with time is supplied, and the supplied video signal is set with a predetermined data rate relating to recording time and recording image quality as an average rate, According to the set average rate, an encoded bit stream signal is obtained by performing variable length coding using an MPEG-2 encoder or the like, and the obtained signal is stored in a predetermined area and an auxiliary area of a recording medium such as a hard disk. A video signal recording apparatus for recording, a target rate setting means for setting a target rate larger than a predetermined average rate, and the encoded signal that is variable-length encoded at a target rate set by the target rate setting means Encoding means for generating a first signal in a first time interval of a variable-length encoded signal encoded by the encoding means A data rate and a code rate detecting means for detecting a second data rate in a second time interval that is close to the encoding point and smaller than the first time interval, and a first detected by the code rate detecting means The target rate set by the target rate setting means is changed according to the data rate of the difference between the data rate and the second data rate. And a target rate changing means configured to constitute a video signal recording device, and are less susceptible to unnecessary signals such as noise signals included in the supplied video signal, and a video signal portion having a large amount of information has a high bit The video signal portion with a small amount of information is encoded at an appropriate bit rate with a higher decoded video quality, and a large amount of information is projected near the end of the recording time. Even when a signal is supplied, when an encoded signal having a size exceeding a predetermined area is generated for a video signal having a large amount of information, the excess encoded signal is used as an auxiliary area. By encoding so that the total code amount of the video signal is stored in a recording area of a predetermined size without causing a problem such that the last part of the recording signal cannot be recorded because it can be recorded. Therefore, it is possible to realize a video signal recording apparatus capable of recording a high-quality video signal with an increased overall coding rate.
[0127]
Further, the target rate changing means described above prohibits the target rate changing operation to change the target rate to a larger value when the recordable area of the auxiliary area is less than or equal to a predetermined value, so that the recording time is temporarily reduced. Even when a video signal with a large amount of information is supplied to a portion near the end, when an encoded signal having a size exceeding a predetermined area is supplied for the video signal with a large amount of information It is not necessary to increase the size of the auxiliary area to prevent a problem such that the last part of the recording signal for recording the encoded signal exceeding that in the auxiliary area cannot be recorded, and for the video signal. It is possible to realize a video signal recording apparatus capable of recording a high-quality video signal in which the total coding amount is stored in a recording area of a predetermined size and the overall coding rate is increased. .
[0128]
As described above, for a video signal recording / reproducing apparatus that records and reproduces a bit stream obtained by compression encoding with MPEG-2 using a hard disk, a video signal for recording a high-quality video signal in a predetermined recording area is recorded. The recording method and the configuration of the video signal recording / reproducing apparatus have been described.
[0129]
The video signal recording / reproducing apparatus 40 that integrates the recording and reproducing functions in which these problems are solved is a video signal recording apparatus comprising a recording unit 50 and a medium unit 60, and the reproducing unit 70 is a video signal reproducing apparatus. There are ways to configure.
[0130]
Further, the video signal recording device and the video signal reproduction device can be installed in different places, and the devices installed in those remote places can be connected and operated by a home network or the like.
[0131]
The video signal recording device at that time is installed in the home as a home server, the video signal playback device is connected to the home server via a home network, and the video signal playback device is installed in each room where the monitor TV is installed. It is installed as multiple set-top boxes.
[0132]
In this case, the home server is configured as a bit stream transmission device, and the set top box is configured as a bit stream receiving terminal, and both are coupled by a high-speed wireless LAN or a home LAN and recorded on the hard disk while performing bidirectional communication. The video signal information is recorded and played back through a set-top box operated by the user in accordance with an operation command from each room, and the supplied video signal is viewed on the monitor TV. .
[0133]
In this way, when a transmission device and a recording device as a reception terminal and a playback unit are installed at remote locations and are operated by communication means, a plurality of transmission terminals and a plurality of reception terminals are connected by a network. It is also possible to configure a network type video system to be operated.
[0134]
The recording medium used for the medium section of the recording apparatus is described as an example of a hard disk. However, the recording medium is not limited to this, and a medium that can be accessed at high speed, such as a magneto-optical disk, a RAM type, or a RW type DVD. It is obvious that the present invention can also be applied to a recording apparatus using a recording medium capable of other random access such as a semiconductor memory type recording medium.
[0135]
Furthermore, the encoding method of the video signal has been described by taking the MPEG-2 method as an example, but the compression encoding method is not limited to this, and a method of applying intra-frame encoding called motion JPEG, or MPEG-4 Bits to which the code amount is allocated by analyzing the bit rate of the signal encoded by compression encoding, such as the MPEG-21 method, the MPEG-21 method to be standardized from now on, and those using other fractal compression methods When recording an encoded signal generated by a stream generation device, a video signal recording device to which the above-described technology is applied can be configured.
[0136]
【The invention's effect】
  According to the first aspect of the present invention, a video signal portion that is not easily affected by a noise signal included in the supplied video signal and that has a large amount of information has a high bit rate, and a video signal portion that has a small amount of information is more decoded. Since video can be encoded at an appropriate bit rate with high video quality, the video signal can be recorded in a predetermined recording area with a high-quality image and a total code amount of a predetermined size.IssueThis has the effect of providing a recording method.
[0137]
  Claims2According to the described invention, a video signal portion that is not easily affected by a noise signal included in the supplied video signal and that has a large amount of information has a high bit rate, and a video signal portion that has a small amount of information has a higher decoded video quality. Since the total code amount can be recorded in a recording area of a predetermined size, such as encoding at a high appropriate bit rate, there is an effect that it is possible to provide a configuration of a video signal recording apparatus that effectively uses the recording area.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a video signal recording / reproducing apparatus according to an embodiment of a video signal recording apparatus of the present invention.
FIG. 2 is a diagram illustrating a structure of a frame signal that is encoded with motion compensation by the MPEG-2 method.
FIG. 3 is a diagram illustrating a progress state of bit rate control with respect to an average rate according to an embodiment of the present invention.
FIG. 4 is a diagram showing a relationship between a target rate given to a value of a T2 interval bit rate according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a relationship of an encoding parameter with respect to an average bit rate according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a schematic configuration of a one-pass encoder that performs encoding by designating an average rate according to a conventional embodiment.
FIG. 7 is a diagram illustrating a relationship of an assigned code amount with respect to an encoding difficulty level according to a conventional example.
[Explanation of symbols]
31 Coding difficulty calculator
32 Allocated bit amount calculator per unit time
33 Video encoder
40 Video signal recording / reproducing device
50 recording section
51 TV tuner
52a A / D converter
52b External video input terminal
52c selector switch
53 MPEG-2 Encoder
54 Stream Analyzer
55 REC-FIFO
57 Microcomputer
59 Rate setting terminal
60 Media section
61 Hard disk recorder / player
63 hard disk
65 Write / read controller
70 Playback unit
71 Buffer memory
72 MPEG-2 decoder
74 D / A converter
76 microcomputer
79 Remote control interface
90 Monitor TV
95 remote control

Claims (2)

A video signal including the received noise Te video signal Goki recording method odor to be recorded on the recording medium by performing a compression by an encoder,
The bit rate of the video signal compressed by the encoder is detected by a stream analyzer,
The noise is included when the bit rate detected by the stream analyzer at the start of compression of the video signal is lower than a first target bit rate for compressing the video signal including the predetermined noise. Outputting a control signal to the encoder to compress the video signal at a second target bit rate that is higher than the first target bit rate for compressing the uncompressed video signal;
When a bit rate exceeding the first target bit rate is detected after a predetermined time has elapsed since the compression start time, the second target bit is gradually increased so as to approach the first target bit rate. video signal Goki recording method comprising also be output from the control signal for lowering the rate to the encoder. A video signal including the received noise Te video signal recording apparatus odor to be recorded on the recording medium by performing a compression by an encoder,
A stream analyzer for detecting the bit rate of the video signal compressed by the encoder;
The noise is included when the bit rate detected by the stream analyzer at the start of compression of the video signal is lower than a first target bit rate for compressing the video signal including the predetermined noise. A control signal is output to the encoder so as to compress the video signal at a second target bit rate higher than the first target bit rate for compressing a video signal that has not been compressed. When a bit rate exceeding the first target bit rate is detected after a lapse of time, the second target bit rate is lowered stepwise so as to approach the first target bit rate. A bit rate control unit for outputting a control signal to the encoder;
Video signal recording apparatus according to claim Rukoto to have a.

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