JP2903577B2 - Image data processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data processing apparatus, and more specifically, to an image data processing apparatus capable of preventing deterioration during digital dubbing.

[Prior art] In recent years, digitalization of video equipment has been advanced, and image transmission by digital video communication and digital signal-based dubbing / editing using a digital VTR have been proposed. Signal transmission without signal quality degradation is realized. In such a case, a baseband digital signal is often used in consideration of the use of a heterogeneous connection or a digital switching device.

In a recording / transmission device that compresses and encodes image information, a signal that is once encoded and then decoded into a baseband digital signal, such as DPCM encoding by a mid-tread type quantizer, can be encoded again. An encoding method that can obtain the same code as the previous time is known. If such an encoding method is used, degradation due to encoding will only occur at the time of the first encoding, and the degradation will not be accumulated even if encoding / decoding is repeated on a digital signal basis. Dubbing / editing with a signal can be performed without deterioration.

[Problems to be Solved by the Invention] However, in the case of image information, an uncorrectable error that occurs during recording and reproduction (in a broad sense, transmission) may be corrected by interpolation. When the image information subjected to is re-encoded, an encoding error occurs at that time. There is a problem in that the deterioration due to the modification and the newly added coding deterioration cause the deterioration to accumulate due to repeated coding and decoding.

Therefore, an object of the present invention is to provide an image data processing apparatus in which such deterioration does not accumulate.

[Means for Solving the Problems] An image data processing apparatus according to the present invention provides a data group including compression-encoded image data and a modification flag indicating whether or not the image data has been modified, and an error correction for the data group. Input means for inputting a check code of the data group, and an error in the data group is corrected using the check code input by the input means. An error correction unit for generating a flag, and a modification unit for modifying the image data according to the error flag and the modification flag.

[Operation] With the above-described configuration, even when encoding and decoding are repeatedly performed, the number of locations to be modified may increase, but the situation in which errors are accumulated due to the modification operation does not occur. Further, the modification means can prevent an expansion of the modification range.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an encoding circuit of an encoding / decoding system according to an embodiment of the present invention. Below,
The source of the digital video signal is called a master, and the destination is called a slave. The digital video signal dv input to the input terminal is subjected to data compression by the compression encoding circuit 12 and applied to the modification information adding circuit 14.

The modification information adding circuit 14 is supplied with the modification information cf from the encoding / decoding device at the preceding stage via the input terminal 16.
The modification information adding circuit 14 adds the modification information cf to the output of the compression encoding circuit 12 and outputs the result. When the encoding circuit shown in FIG. 1 is used not in the slave device but in the first stage, or when used as a slave device in which a device of another encoding system is used as a master device, an input terminal
Modification information cf is not supplied to 16. In such a case,
The modification information adding circuit 14 adds information indicating a non-modification mode (an operation mode in which the modification operation is not performed) instead of the modification information. If a variable-length code is used as the data format, the modification information cf may be added only when the modification information cf is required.

The output of the modification information adding circuit 14 is supplied to an error correction encoding circuit 18, where information for error correction is added, and then modulation adapted to the transmission path is performed by a modulation circuit 20. It is sent to the transmission path. What is a transmission line?
In addition to the communication line, a recording medium such as a magnetic disk and a magnetic tape is included.

FIG. 2 is a block diagram showing a configuration of a decoding circuit of the encoding / decoding system according to one embodiment of the present invention. The coded data is input to the input terminal 30 from the transmission line, the demodulation circuit 32 demodulates it, and the error correction decoding circuit 34 detects the transmission line error.
correct. The error correction decoding circuit outputs the error-corrected data to the modification information separation circuit, and outputs an uncorrectable flag ef for the uncorrectable data to the modification flag generation circuit. The modification information separating circuit 36 separates the modification information added on the master side (for example, the modification information adding circuit 14 in FIG. 1) from the compression-encoded image data,
The former is applied to the modification flag generation circuit 38, and the latter is applied to the decompression decoding circuit.
Supply 40. The expansion decoding circuit 40 expands the compression-encoded image data.

It should be noted that the encoding method is a method that is reproducible even after the first encoding and decoding for the second and subsequent iterations (for example, a DPCM encoding method using a mid-tread type quantization characteristic). In this case, the output of the expansion decoding circuit 40 of the slave device is the same as the output of the expansion decoding circuit of the master device corresponding to the expansion decoding circuit 40.

The modification flag generation circuit 38 includes an error flag ef from the error correction circuit 34 and a modification flag cf from the modification information separation circuit 36.
Thus, a modification flag cf _e representing both flags ef and cf is generated. The image retouching circuit 42 retouches the output of the decompression decoding circuit 40 in accordance with the retouching flag cf _e and outputs the digital video signal dv.
Output to the output terminal 44 as _e . Moreover, modification flag cf _e is outputted from the output terminal 46 to the subsequent coding and decoding apparatus.

Next, a connection example when applied to a digital image recording / reproducing device and a digital image transmitting device will be described. FIG. 3 (a) shows an example of connection when two master / slave recording / reproducing devices are connected and dubbing is performed based on a digital video signal. The modification flag cf from the master side is also recorded on the slave side, and if no error occurs on the slave side, the modification operation on the master side is reproduced on the slave side. The master output and the slave output become the same without any deterioration at the time of encoding on the slave side.

FIG. 3 (b) shows a connection example in which image data received from a transmission medium is recorded in a recording / reproducing apparatus. As in the previous example, modified data on the master side, that is, modified by the decoding unit of the transmission apparatus. The recorded data can be recorded and reproduced without deterioration due to encoding. FIG. 3 (c) shows a connection example in which the digital output of the recording / reproducing apparatus is encoded by the transmission apparatus and transmitted to the transmission path. Also in this case, the data modified by the recording / reproducing device does not deteriorate due to the encoding of the transmission device. These are merely examples of the configuration of use, and the actual connection may of course be made via a digital signal switch or the like.

Next, the modification operation using the modification flag cf will be specifically described. In the present invention, any modification method can be adopted depending on the encoding method and the nature of the transmission error. Here, a line interpolation method for DPCM encoding will be described as an example. In the case of DPCM encoding, if an error occurs, this also affects the decoded value later and propagates in the line direction. Reset values are provided at predetermined intervals to suppress propagation. A group of continuous data between the reset values is called a line block. As the above-mentioned correction method, a method of interpolating a line block in which an error has occurred with data of line blocks above and below the line block is a visual method. It is known that the above improvement effect is large. In this case, the modification flag cf is added in units of line blocks.

FIG. 4A shows the output of the decompression decoding circuit 40 on the master side. An error has occurred in line block B,
Error flag ef is set. FIG. 4B shows the output of the image modification circuit 42 on the master side. The data of the line block B is changed to B ₁ = (A + C) / 2 by the modification flag cf _e.
By replacing (interpolation) interpolation data B ₁ by, it is performed gets. FIG. 4 (c) shows the output of the decompression decoding circuit 40 on the slave side of the conventional system. Line block B _2, since the error is added by the coding decoding the slave to B _1, which is modification on the master side, not equal to B _1. In the prior art slave output is the B _2. 4th
FIG. 7D shows the output of the image modification circuit 42 on the slave side. The cf transmitted from the master side with the line block B _1, the error line block A required to retouch line block B _1, the C in the slave side
Since the flag ef is not set, B ₁ = (A +
C) / 2 interpolation is performed, and the same result as the master output is obtained.

In the case of FIGS. 4 (c) and (d), the line is
When the error flag ef is detected in the block C, the line blocks B and C are modified from the line blocks A and D using the data of the line block D below the line block C. Deterioration is large. Therefore, in this embodiment, processing is performed as shown in FIG. Fig. 5 (a)
Then, the error flag ef is set for the line block C,
It is a line block that needs to be modified. But,
Line block B required to modify line block C,
Of D, the line block B has been modified in the previous stage, so that the data is B ₂ = f (B ₁ ) = f ((A + C) /
2), the modification flag cf is passed.

In the present embodiment, as described above, when the flag cf is set for a certain line block, and when the other flag ef is set for another line block necessary for the correction operation of this line block, Ignoring the former flag cf. For example, as shown in FIG. 5 (b), ignoring the flag cf for the line block B, and modification with encoded decoded line block B ₂ in the modification by the master device slave device Do, C ₁ = (B ₂ + D) / 2
Is the modified output. As a result, even if errors continue in the master / slave, the adjustment range can be suppressed to be narrow.

[Effects of the Invention] As can be easily understood from the above description, according to the present invention, even if encoding / decoding is repeatedly performed, deterioration due to modification in the middle can be prevented from propagating. Further, by performing the superimposition determination of the modification processing, expansion of the modification area is prevented. Therefore, it is very useful for devices such as dubbing, editing, and transmission.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an encoding circuit according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a decoding circuit according to an embodiment of the present invention, FIG.
FIG. 4 and FIG. 5 are explanatory diagrams of the effect of the present invention. 14: modification information adding circuit, 18: error correction encoding circuit, 34: error correction decoding circuit, 36: modification information separation, 38: modification flag generation circuit, 40: decompression decoding circuit, 42: image modification circuit

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 5/91-5/956 H04N 7/24-7/68 H04B 14/04

Claims (2)

(57) [Claims] An input unit for inputting a data group including compression-encoded image data and a modification flag indicating whether or not the image data is modified, and an error correction check code for the data group; Error correcting means for correcting an error in the data group using the check code input by the input unit, and generating an error flag indicating the presence of uncorrectable data in the data group, if the data group has error-correctable data; and Modifying means for modifying the image data according to a modifying flag. 2. The image processing apparatus according to claim 1, wherein the modifying unit does not modify the image data having the modifying flag when the error flag exists with respect to the image data necessary for the modifying process, and modifies the image data otherwise. The image data processing device according to claim 1.