JPH06292136A - Picture reproduction device - Google Patents

Abstract

PURPOSE:To fetch only reproduction data to a memory when tracing is executed in a best state when a signal of the same track is traced for many number of times in the case of slow reproduction. CONSTITUTION:A demodulator 3 compares an envelope of reproduction data from a reproduction head 2 with two threshold levels and two dropout signals DOS are stored in a write control discrimination section 5a at each tracing. Then the current DOS and the past DOS are mutually compared and reproduction data with high reliability are controlled to be written in a memory 7. Thus, data clearing a higher threshold level in two threshold levels are selected with high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reproducing device such as a digital VTR for recording and reproducing image data.

[0002]

2. Description of the Related Art In recent years, a digital VT for consumer use, which encodes an image signal with high efficiency and records and reproduces it on a medium such as a magnetic tape.
R is proposed. In this method, an image signal is grouped into blocks each having a predetermined number of pixels, orthogonal transform such as discrete cosine transform is performed, and the transformed coefficients are quantized / entropy coded and recorded.

When configuring a VTR using a variable length code, it is desirable to keep the code amount constant in a predetermined block unit in consideration of special reproduction and error propagation. Therefore, there is known a method of adjusting the code amount by adjusting the quantization parameter of the data to be variable-length coded.

FIG. 6 shows an example of a data format of a sync block whose code amount is adjusted by the above method using discrete cosine transform. Here, it is assumed that the code amount is fixed in units of M (for example, 3) sync blocks, and a sync signal (SYNC) and additional information (ID) are recorded at the head of each sync block. A plurality of blocks each having the predetermined number of pixels are inserted into the three sync blocks. In this way, the data converted into sync blocks is shown in FIG.
Error correction code (here, product code structure RS code)
Is recorded on the magnetic tape.

Here, the decoding operation during slow reproduction will be described.

At the time of slow reproduction, the reproducing head performs overlapping tracing on the recording track as shown in FIG. FIG. 8 is a diagram showing the relationship between the recording track and the trace when the reproducing head has one opposite channel, and the same target track is obtained by tracing three times by the A channel head with respect to the fourth target track in the figure. It shows that the data of is detected. The slow reproduction data detected by the reproduction head separates the ID information and the image data. At the same time, as shown in FIG. 9, the amplitude level of reproduced data (hereinafter referred to as envelope level) is determined in sync block units by a certain threshold value, and a dropout signal (hereinafter referred to as DOS) is generated in sync block units. To do. DOS is a signal indicating the reliability of the reproduction state of the data, and detects the deterioration of the envelope due to a defect of the magnetic tape during normal reproduction. Since the trace shown in FIG. 8 is performed during the slow reproduction, the same sync block data is detected by a plurality of traces. The envelope of each trace is different and lower than the envelope of normal playback. Therefore, the threshold value for DOS generation during slow reproduction is set to a value lower than the threshold value during normal reproduction so that the same detected sync block data is written in the memory at least once. .

The reproduced image data is corrected by the inner code. Then, the corrected image data and CIF, which is flag information for determining whether the image data includes error data or not, is generated. CI
Writing of F, image data and ID information to the memory is controlled according to the control of the DOS. If the DOS signal is an OK signal indicating that the reliability of the data is recognized, the writing to the memory is performed. If the NG signal indicating that the reliability of the data is not recognized is written, the writing to the memory is prohibited. The memory mentioned here is a RAM, and addressing is performed by ID information having screen display position information. Therefore, the same sync block data that is repeatedly detected and is DOS OK is overwritten in the memory in trace units. The image data stored in the memory is also read out and subjected to error correction processing using an outer code similar to the inner code correction, and the corrected data is stored again in the memory. When all the error correction decoding is completed, the corrected data is stored in the memory, and the error correction decoding operation is completed by outputting this data.

[0008]

However, in the above-mentioned conventional example, the threshold value for generating DOS during slow reproduction is lower than that during normal reproduction, and the reliability of data is lowered. Then, since all sync block data satisfying the DOS is permitted to be written in the memory, there is a problem as described below.

That is, of the same sync block data repeatedly detected by a plurality of traces, the data satisfying the DOS condition is overwritten in the memory in trace units, and as a result, the envelope of each trace is good or bad. The data of the trace detected at the end of the sync block will be fixed as the data stored in the memory. Therefore, the data in a good reproduction state is not always held in the memory.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide an image reproducing apparatus in which data reproduced when good tracing is performed is stored in a memory. Has an aim.

[0011]

The essence of the above problem is that a threshold value for detecting a good reproduction state is set during slow reproduction, and the reproduction state of the same sync block data previously stored in the memory and the current reproduction state are set. Considering that there is no comparison with the reproduction state of the data, in the first invention, a reproduction means for reproducing the pixel data recorded on the track of the recording medium by the reproduction head tracing the track. , A data storage unit for storing reproduction data obtained from the reproduction unit and a dropout signal indicating the quality of the reproduction data obtained from the reproduction unit in a reproduction mode for tracing the same track on the recording medium in an overlapping manner. Generating dropout signal generating means and a plurality of dropouts of the same track generated by the dropout signal generating means Comparing means for comparing the item, and a write control means for controlling the writing of the reproduced data into the data storing means according to the comparison result of the comparing means.

According to the second aspect of the invention, the reproducing means reproduces the pixel data recorded on the track of the recording medium by the reproducing head tracing the track, and the error of the reproduced data obtained from the reproducing means is corrected. An error correction means for generating a flag when uncorrectable, a data storage means for storing the reproduction data corrected by the error correction means, and a reproduction mode for tracing the same track on the recording medium in duplicate. Dropout signal generating means for generating a dropout signal indicating the quality of reproduced data obtained from the reproducing means, and first comparing means for comparing a plurality of dropout signals of the same track generated by the dropout signal generating means. And a plurality of the above-mentioned flags of the same track obtained from the error correction means in the above-mentioned reproduction mode And a write control means for controlling the writing of the reproduction data to the data storage means according to each comparison result of the first and second comparison means.

[0013]

According to the above invention, the current trace DOS
And the DOS of the previous trace are compared, and when the current trace is in a better reproduction state than the previous trace, the data is overwritten to the memory.

Alternatively, the DOS of the current trace and the flag information at the time of error correction decoding are compared with the DOS of the previous trace and the flag information at the time of error correction decoding, and the present trace is better than the past trace. In the reproducing state, since the data is overwritten in the memory, the data with the best trace is reproduced.

[0015]

1 shows an image reproducing apparatus according to a first embodiment of the present invention.

In FIG. 1, 1 is a magnetic tape, 2 is a reproducing head, 3 is a demodulator which demodulates band-compressed data so as to adapt to the transmission characteristics of the magnetic tape 1, and restores the data before recording. An inner code decoder in the error correction unit, 5 is a write control determination unit that determines write control to the memory 7 by a plurality of DOS generated in the demodulator 3, and 6 is data write by a dropout signal DOS from the demodulator 3. Is a memory for storing data, and 8 is an outer code decoder for correcting the outer code.

The decoding operation during slow reproduction of this embodiment will be described below with reference to FIG. The reproducing head 2 traces the recording tracks in an overlapping manner as described with reference to FIG.
The demodulator 3 converts the band-limited data detected by the reproducing head by Viterbi decoding into normal digital data and separates it into ID information and image data. Then, the image data is output to the inner code decoder 4, and the ID information is output to the write control unit 6. At the same time, the envelope detected by the reproducing head 2 is determined in sync block units by a plurality of threshold values, a plurality of DOS is generated according to each threshold value, and is output as a control signal of the write control unit 6.

FIG. 2 shows an example of DOS generation in this embodiment.
FIG. 2B shows that the envelope detected in one trace is judged by the first and second threshold values to determine the first and second envelopes.
2A is an example of generating DOS of FIG.
FIG. 9 is a diagram showing the envelope and DOS state for each trace by paying attention to one sync block data in the track when the determination as in (b) is performed. That is, FIG.
As shown in (a), a certain sync block data is detected over three times of traces, and the detected envelopes are 10%, 60%, and 30%, respectively. In this example, the first threshold value is set to 50% and the second threshold value is set to 20%. Therefore, the envelope at the first trace is unsatisfactory for the first and second DOS, the envelope at the second trace is satisfied for both the first and second DOS, and the envelope at the third trace is for the second DOS. Only will be satisfied.

The write control determination section 5 has a built-in past memory for storing ID information and first and second DOS. The capacity is the capacity corresponding to the total number of sync block data detected during the period in which the same sync block data is traced redundantly. The write control determination unit 5 determines this write control according to the flowchart shown in FIG.

First, in step S1, ID information and DOS are input to the write control determination unit 5 in sync block units. Next, in step S2, the ID information already stored in the past memory is sequentially read. Then step S
It is checked whether or not there is past ID information that matches the current ID information of the current sync block input in 3. If the past ID information and the current ID information do not match, it is determined in step S4 that the trace is the first trace in which the current sync block data is detected, and the process proceeds to step S7, where it is stored in the memory 7 regardless of the contents of the DOS. Is permitted to write the ID and image data. Then, the DOS and ID of the data for which writing is permitted in step 8 are stored in the past memory. On the other hand, if the past ID information and the current ID information match in step S3, the past DOS of the sync block stored by the past trace is read from the past memory in step S5. Then, in step S3, the current DOS input in the current trace is compared,
Which of the current DOS and the past DOS is the highly reliable data is determined. The reliability of past DOS is now DOS
If it is equal to or higher than the reliability of, the sync block data is not written to the memory 7 and the process proceeds to the next sync block process of step 9. If the reliability of the current DOS is higher than the reliability of the past DOS, writing the sync block data to the memory 7 in steps S7 and S8,
And after writing ID and DOS to the past memory,
Go to step S9.

Next, the above operation will be described with reference to FIG. First, the first trace does not satisfy the conditions of the first and second DOS, but since the sync block is not detected in the traces before that, data writing to the memory 7 is permitted, and Secure the data of.
The second trace satisfies the conditions of the first and second DOS. Also, as the DOS information of the same sync block written in the past memory, the DOS of the first trace is used here.
Call information and compare each DOS information. As a result, it is determined that the reliability of the data detected by the second trace is high, so writing of the second trace data to the memory 7 is permitted. And the DO of the second trace data
Store S and ID in past memory. The data of the third trace satisfies only the condition of the second DOS. However, when compared with the DOS information of the second trace data previously written in the memory 7, since the third trace data is determined to have low reliability, data writing to the memory 7 and writing of DOS and ID to the past memory are performed. Is prohibited.

The write control determination unit 5 performs the above-described processing.
On the other hand, the inner code decoder 4 corrects the inner code of the image data. Then, the corrected image data and CIF, which is flag information indicating whether the image data contains error data or not, are output to the write control unit 6.

The writing control unit 6 controls writing of CIF, image data, and ID information to the memory 7 in accordance with the control signal from the above-mentioned writing control determination unit 5. If the control signal is an OK signal indicating that the reliability of the data is recognized, the memory 7 is written, and if an NG signal indicating that the reliability of the data is not recognized is written, the memory 7 is written. Absent. The memory 7 is a RAM, and addressing is performed by ID information having screen display position information.

The image data stored in the memory 7 is rearranged in the order of the outer code and input to the outer code decoder 8. Here, the same processing as the inner code correction is performed, and the corrected data is stored in the memory 7. After the outer code correction by the outer code decoder 8 is completed, the ID information of the memory 7, the flag information CIF and the corrected image information are output to a high efficiency decoder (not shown) in the subsequent stage.

According to the above, even if the same sync block such as slow reproduction is repeatedly detected for each trace, and even if the state of the envelope is different due to the trace, the reproduced data at the time of good tracing is always stored in the memory 7. Can be secured.

In the present embodiment, the DOS determination threshold value is set to two levels, but a plurality of threshold values higher than that may be set.

[Second Embodiment] FIG. 4 shows an image reproducing apparatus according to a second embodiment of the present invention, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals.

The feature of the second embodiment is that the flag output CIF of the inner code decoder 4 is given to the past memory of the write control judgment unit 5 and data having no error is preferentially held in the memory 7. That is what I did.

FIG. 5 is a flow chart showing the operation of the write control judgment unit 5 according to this embodiment. The same numbers are assigned to the processing steps which are substantially the same as those in FIG. 3, and duplicate explanations are omitted. In FIG. 5, steps S10, S11, and S12 are added after step S3.

In step S3, past ID information that matches the current ID information is searched. If they match, the process proceeds to step S10, and the past CIF is read from the past memory. Then, if the past CIF indicates that there is no error in the data written in the memory 7 in step S11, the process for the sync block is ended, and the process for the next sync block in step S9 is performed. If there is an error, step S
12, the current CIF checks whether the current data contains an error or not. If there is no error in the current data, the process proceeds to step S7 to permit data writing in the memory 7, and in step S8 the data in the past memory is updated to the current DOS and CIF. If it is indicated that an error is included, the determination by DOS is performed in steps S5 and S6 as in the first embodiment.

According to the above, for example, the envelope detected in the first trace is set to 25% of the whole and the envelope detected in the second trace is set to 35%, and the DOS threshold is set to 40%.
%, The second threshold value is set to 20%, and when the first trace has an error and the second trace has no error in the inner code decoding result due to the difference in the envelope, the data of the second trace is written in the memory 7. It will be. That is, in the above case, in the first embodiment, writing to the memory 7 is not performed, and the process proceeds to the next sync block processing. However, according to the second embodiment, it is more difficult than the first embodiment. You can make detailed decisions.

[0032]

As described above, according to the present invention, 2
By obtaining DOS with one or more thresholds, comparing it with the DOS of the trace before the current trace DOS, and leaving the data of a better reproduction state in the memory, a high-quality image can be obtained during slow reproduction. It is effective. Further, the DOS of the current trace and the flag information of the inner code decoding are compared with the flag information of the DOS of the previous trace and the flag information at the time of the error correction decoding, and data in a good reproduction state is left in the memory to make a more detailed judgment. Based on the above, there is an effect that better data can be left in the memory and a high quality image can be obtained during slow reproduction.

[Brief description of drawings]

FIG. 1 is a block diagram showing an image reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram and a waveform diagram for explaining the operation of the above embodiment.

FIG. 3 is a flowchart showing a slow playback operation of the first embodiment.

FIG. 4 is a block diagram showing an image reproducing apparatus of a second embodiment according to the present invention.

FIG. 5 is a flowchart showing a slow playback operation of the second embodiment.

FIG. 6 is a configuration diagram showing a data format of a sync block.

[Fig. 7] Fig. 7 is a configuration diagram illustrating that a sync block is used to make a fixed length.

FIG. 8 is a configuration diagram showing a trace of a head during slow reproduction.

FIG. 9 is a waveform diagram showing a method of obtaining a dropout signal.

[Explanation of symbols]

 1 magnetic tape 2 reproducing head 3 demodulator 4 inner code decoder 5 write control determination unit 6 write control unit 7 memory DOS dropout signal CIF flag

Claims (2)

[Claims] 1. A reproducing means for reproducing pixel data recorded on a track of a recording medium by a reproducing head tracing the track, a data storing means for storing reproduced data obtained from the reproducing means, and the recording method. In a reproducing mode in which the same track on the medium is traced redundantly, a dropout signal generating means for generating a dropout signal indicating the quality of reproduction data obtained from the reproducing means, and a dropout signal generating means for generating the dropout signal An image reproducing apparatus comprising a comparing means for comparing a plurality of dropout signals on the same track, and a writing control means for controlling writing of reproduction data into the data storing means according to a comparison result of the comparing means. 2. A reproducing means for reproducing pixel data recorded on a track of a recording medium by a reproducing head tracing the track, and correcting an error of the reproduced data obtained from the reproducing means.
Error correction means for generating a flag when uncorrectable, data storage means for storing the reproduction data corrected by the error correction means, and reproduction in the reproduction mode for tracing the same track on the recording medium in duplicate. Dropout signal generating means for generating a dropout signal indicating the quality of reproduction data obtained from the means, and first comparing means for comparing a plurality of dropout signals of the same track generated by the dropout signal generating means. A second comparing means for comparing the plurality of flags of the same track obtained from the error correcting means in the reproduction mode, and to the data storing means in accordance with each comparison result of the first and second comparing means. And an image reproduction device for controlling writing of reproduction data of the image reproduction device.