JP3309601B2 - Image encoding device and image decoding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding apparatus for encoding a video signal using variable-length encoding, and an image decoding apparatus for decoding a video signal encoded using variable-length encoding. It concerns the device.

[0002]

2. Description of the Related Art With the development of digital storage media,
A method of compressing and recording a long-time video signal on these recording media has been studied. International Organization for Standardization (IS
O) also includes the International Electrotechnical Commission (IEC) Moo-Huo-Kuo-Icture Image Coating Aiharts Proof (MPEG)
(Moving Picture Image Cod
ing Experts Group)) is working on standardization of video coding schemes.

There are two types of video signal sources that can be roughly classified as follows. One is 30 frames /
This is a video taken by a television camera of a second (NTSC system), and the other is a film image of 24 frames / second. As a method for creating a video signal (telecine video signal) from the film image, a 2-3 pull-down method has been conventionally known.

In the 2-3 pull-down method, a video signal for three fields is created from a film image of a 2n (n is a positive integer) frame, and a video signal for two fields is created from a film image of a (2n-1) th frame. Create a video signal of For example,
In the example shown in FIG. 1, No. 2
No. from the second frame. 3, No. 4, N
o. No. 5 from the third frame. 6, no.
No. 7 from the 4th frame in the No. 7 field. 8, no. 9,
No. Ten fields have been created. In the 2-3 pull-down method, one cycle is provided for these ten fields. In the period of these 10 fields, No. 3 and N
o. The fields of No. 5 are exactly the same, 8
And No. The ten fields are exactly the same.

Therefore, encoding a telecine video signal created by the 2-3 pull-down method as it is results in encoding a redundant signal. Therefore, when an input video signal to be coded is a telecine video signal, a technique of deleting redundant fields before coding and deleting a redundant signal before coding is used.

The problem here is that when a signal is input in which the duplicated fields are deleted from the telecine video signal, the input signal is 24 frames / second, which is different from the normal video signal of 30 frames / second. This means that the frame frequency must be converted in some way at the input of the encoding means.

As a conventional method for solving this problem, 2
There is a method in which a clock having two frequencies, 4 Hz and 30 Hz, is operated by changing the operating frequency of the entire encoding means according to the frame frequency of an input signal.

On the other hand, in an image decoding apparatus for decoding a signal coded using variable length coding, if the frame frequency of the input signal is different from the operating frequency of the decoding processing unit, decoding is performed correctly. Since it is not possible, like the above-described encoding device, according to the frame frequency of the input signal,
Conventionally, a method of changing the frequency of the entire decoding process has been performed.

[0009]

However, in the method of changing the operation clock of the entire encoding process according to the frame frequency of the input signal as described above, the method of removing overlapping fields from the telecine video signal is not sufficient. When no duplicate field is detected due to the influence of noise or the like, or when the telecine signal is created by an irregular 2-3 pull-down scheme, the frame frequency of the input signal after the duplicate field is removed is necessarily 24 Hz. However, unlike the frequency of the encoding process, there is a problem that a problem occurs in the encoding process.

Similarly, in the decoding process, if the frame frequency of the input signal changes variously and differs from the frequency of the decoding process, decoding cannot be performed correctly. Further, in order to change the frequency of the decoding process according to the frame frequency of the input signal, clocks of various frequencies and the frame frequency of the input signal are detected, and according to the result, the entire decoding process is performed. An additional circuit for changing the frequency is required.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and performs correct encoding processing when deleting a duplicated field from a telecine video signal, even if the duplicated field cannot be detected and the frame frequency is different from 24 Hz. It is an object of the present invention to provide an image coding apparatus capable of performing the above.

Also, the decoding apparatus can cope with various changes in the frame frequency of the input signal.
It is another object of the present invention to provide an image decoding apparatus which does not require an additional circuit for frequency conversion as in the related art.

[0013]

In order to solve the above-mentioned problems, an image encoding apparatus according to the present invention determines whether or not an input video signal is a telecine video signal created from a film image by a 2-3 pull-down method. A signal discriminating means for discriminating, a 3-2 converting means for converting three fields of the telecine video signal into two fields according to the discrimination result of the signal discriminating means, and an encoding means for performing variable length coding. . With this configuration, when it is determined that the input video signal is a telecine image, the 3-2 conversion unit deletes the duplicated field, creates a data valid signal in accordance with this, and sets the position of the deleted field to The validity signal is used to indicate to the encoding means that the data is invalid. While the data is invalid, the operation of the encoding means is interrupted, and only valid data is encoded.

The image decoding apparatus according to the present invention has a configuration including decoding means for decoding a variable length code, and 2-3 conversion means for converting data of two fields into data of three fields. Similarly to the above-described image encoding apparatus, a data valid signal is input together with input data, decoding processing is performed only when data is valid, and decoding processing is interrupted when data is invalid. Further, the 2-3 conversion means creates a duplicated field according to the information read from the data, and outputs a telecine video signal.

[0015]

[0016]

[0017]

Further, in order to reduce the memory for data storage, a time difference from writing to reading of the memory is determined according to the data valid signal.

[0019]

With the above arrangement, even when the input signal cannot be correctly converted to data having a frame frequency of 24 Hz as a telecine video signal, the encoding processing means always operates at a frequency of 30 Hz, and the data is invalid according to the data valid signal. If there is, the encoding process is interrupted. Thus, even if the frame frequency of the input signal changes, the encoding processing means can always operate at the same operating frequency, and does not require an additional circuit for frequency conversion as in the related art.

Also, the image decoding apparatus uses a data valid signal corresponding to the input signal, as in the image encoding apparatus, and
By suspending the decoding process, it is possible to always operate at the same frequency, and does not require an additional circuit for frequency conversion.

Further, by changing the time difference from writing to reading of the memory according to the valid signal,
It is possible to convert a sequence of data that can be subjected to 2-3 conversion processing with a small memory, and to correctly decode a telecine video signal.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as a first embodiment, an image coding apparatus according to the present invention will be described with reference to FIGS. FIG. 2 is a block diagram, and FIG. 3 is a detailed diagram.

In FIG. 3, an input signal 301 first enters a signal discriminating means 309, and two field memories 303
Is delayed by one frame. In the difference means 304, the input signal 301 and the field memory 30
The difference from the one-frame delay signal 302, which is the output of No. 3, is obtained. The difference value 305 is integrated by the sum-of-products unit 306 after taking the absolute value. The sum-of-products unit 306 is reset by the pulse VD for each field, latches the sum-of-products result immediately before the reset, and sends the result to the comparator 307 in the next stage. The product-sum result in the field unit is compared with the set threshold value 317 in the comparator 307, and outputs “1” when the result is equal to or smaller than the threshold value. That is, this comparator 3
When the field coincidence signal 308, which is the output of 07, is "1", it is a duplicate field.

Next, the one-frame delay signal 302 becomes 3-2.
It enters the conversion means 310 and the two field memories 303
Is further delayed by one frame. Selector 31
In 2, the one-frame delay signal 302 and the two-frame delay signal 311 are input, and one of the two inputs is selected and output according to the selection signal 313. The selection signal creation circuit 314 creates the selection signal 313 from the field match signal 308 and, at the same time, creates the data valid signal 3
15 is also created and input to the encoding means 316 at the next stage.

FIG. 4 shows the timing of the signal discriminating means and the 3-2 converting means. The numbers in FIG. No. is shown in this example. 3 and No.
5, no. 8 and no. Each of the ten fields is the same field. The one-frame delay signal and the two-frame delay signal are selected by the selection signal, and a 3-2 converted output signal is obtained. However, when the data valid signal is "0", that is, when the data is invalid, invalid data is output, and otherwise, a signal from which duplicate fields are deleted is output. The output of the 3-2 conversion means normally outputs one frame of invalid data every five frames, and simultaneously sets the data valid signal to "0". The output signal and the data valid signal are input to the encoding means 216, and a variable length encoding process is performed. The output of the variable length encoding process is output after data rearrangement is performed in accordance with the encoding as shown in the figure. However, when the data valid signal is “0”, the entire variable length coding process is interrupted, and invalid data is output during that time.

As described above, it is possible to prevent the redundant signal from being encoded by deleting the duplicated field by the 3-2 conversion means. Furthermore, by interrupting the encoding processing operation in response to the data valid signal, it is not necessary to change the encoding processing operation frequency according to the frame frequency, which is required conventionally, and the circuit for changing the frequency is not required. Therefore, the circuit scale can be reduced. Also, by using the data valid signal, it is possible to easily cope with various frame frequencies.

Further, in this embodiment, after the duplication in the first field and the duplication in the second field are detected, the deletion position is adjusted, and this is set as invalid data of one frame, and the data valid signal is set in one frame unit. Is changing. Thus, when the encoding unit operates in units of frames, it is easier to interrupt the operation if the data valid signal changes in units of frames.

In the present embodiment, the data valid signal is changed on a frame basis. However, if the encoding processing means is processing on a field basis, the data valid signal is changed on a field basis to operate similarly. It goes without saying that it is possible.

In this embodiment, the one-frame delay is configured by using two field memories. However, it is needless to say that the same operation can be performed by using one frame memory.

Next, as a second embodiment, an image decoding apparatus according to the present invention will be described with reference to FIGS. FIG. 5 is a block diagram of the image decoding apparatus, and FIG. 6 is a diagram showing the 2-3 conversion means in detail.

The input signal 601 is decoded by a decoding means 602 into a variable length code, and a decoded image 603 is obtained. In accordance with the input signal 601, the data valid signal 604
Is input to the decoding means 602, and the operation of the decoding means is suspended during the period of invalid data. Therefore, invalid data is output as the output of the decoding means during the data invalid period.

The decoded image 603 is input to the 2-3 conversion means 604 and enters the selector 607 together with the one-frame delayed decoded image 606 delayed by one frame by the two field memories 612. The selector 607 outputs the selection signal 60
8, one of the two inputs is selected and output. In the selection signal creation circuit 609, the decoding means 602
TFF which is information for 2-3 conversion sent from
A selection signal 608 is created by 610 and RFF 611.

TFF is equal to Top_Filed_Firs
This is a signal indicating which of two fields constituting one frame is abbreviated to t and which is output first. On the other hand, RF
F is an abbreviation for Repeat_First_Field,
This is a signal indicating that the field output first in the frame is repeatedly output. This TFF, RFF
A selection signal is created. Selection signal 608 to be created
Is as shown in FIG. The selection signal 608 is "
In the case of "H", a signal delayed by one frame is output. By performing this processing, a three-field image is created from a two-field image, and a telecine video signal is obtained.

FIG. 7 shows the timing of the image decoding apparatus. It is assumed that the input signal is the same as the output of the image encoding device shown in FIG. The decoded image is output in the same order as before the encoding after a delay required for decoding. When the data valid signal is "0", invalid data is output from the decoding means. According to this decoded image,
The information of TFF and RFF is read. This TFF, R
A selection signal is generated according to the FF, and when the selection signal is “1”, a one-frame-delay decoded image is selected. In this manner, the 2-3 converted output image is the same as the telecine video signal which is the first input signal in FIG.

By interrupting the operation of the decoding means in accordance with the data valid signal, it is not necessary to change the operating frequency of the decoding means even if the frame frequency of the input signal changes. No additional circuit is required, and the circuit scale can be reduced. Further, it is possible to easily cope with the input of various frame frequencies only by changing the data valid signal.

In this embodiment, the case where the data valid signal is changed on a frame basis has been described as an example. However, it is needless to say that the same operation can be performed even if the data valid signal is changed on a field basis.

In this embodiment, TFF, RFF
Has been described as an example in which the signal is recorded as a part of the input signal and is read out from the decoding means. However, it goes without saying that the same operation can be performed even if these signals are input separately from the input signal. .

Although the case where the data valid signal is input separately from the input signal has been described, the same operation can be performed even if a circuit for reading the data valid signal from the input signal is added at the preceding stage of the decoding processing. Needless to say,

In this embodiment, one frame delay is configured by using two field memories. However, it is needless to say that the same operation can be performed by using one frame memory.

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

As described above, the image encoding apparatus of the present invention comprises a signal discriminating means for discriminating whether or not an input video signal is a telecine video signal created from a film image by a 2-3 pull-down method, According to the judgment result of the signal judgment means,
The configuration includes 3-2 conversion means for converting three fields of a telecine video signal into two fields, and coding means for performing variable length coding. With this configuration, when it is determined that the input video signal is a telecine image, the 3-2 conversion unit deletes the duplicated field, creates a data valid signal in accordance with this, and sets the position of the deleted field to The validity signal is used to indicate to the encoding means that the data is invalid. While the data is invalid, the operation of the encoding means is interrupted, and only valid data is encoded.

The image decoding apparatus according to the present invention has a configuration including decoding means for decoding a variable-length code and 2-3 conversion means for converting two-field data into three-field data. Similarly to the above-described image encoding apparatus, a data valid signal is input together with input data, decoding processing is performed only when data is valid, and decoding processing is interrupted when data is invalid. Further, the 2-3 conversion means creates a duplicated field according to the information read from the data, and outputs a telecine video signal.

According to the above configuration, even if the input signal cannot be correctly converted to data having a frame frequency of 24 Hz as a telecine video signal, the encoding processing means always operates at a frequency of 30 Hz, and the data is invalid according to the data valid signal. If it is, the encoding process is interrupted. Thus, even if the frame frequency of the input signal changes, the encoding processing means can always operate at the same operating frequency, and does not require an additional circuit for frequency conversion as in the related art.

Also, the image decoding apparatus uses a data valid signal according to the input signal, similarly to the image encoding apparatus, and
By suspending the decoding process, it is possible to always operate at the same frequency, and does not require an additional circuit for frequency conversion.

Further, in the image encoding device and the image decoding device of the present invention, if the input signal is invalid in accordance with the data valid signal, the encoding and decoding processes are interrupted.
(2) The arrangement of data input from the conversion unit to the encoding unit does not become equal to the arrangement of data output from the decoding unit after performing the encoding and decoding processes and input to the 2-3 conversion unit. Things can happen.

In order to absorb such a difference in the arrangement of data, the image coding apparatus of the present invention includes a memory for storing the output of the 3-2 conversion means.
In this configuration, only valid data is written to the memory, and after encoding and decoding processes are performed, the data is read out from the memory and input in an arrangement of data so that the 2-3 conversion can be performed correctly.

Further, the image coding apparatus of the present invention includes a memory for storing the output of the decoding process, and writes only valid data into the memory in accordance with the data valid signal.
In this configuration, data is read out from the memory and input in a data sequence that can be correctly converted.

Further, in order to reduce the memory for data storage, a time difference from writing to reading of the memory is determined according to the data valid signal. This allows
It is possible to convert a sequence of data that can be subjected to 2-3 conversion processing with a small memory, and to correctly decode a telecine video signal.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a conventional 2-3 pull-down method.

FIG. 2 is a block diagram of an image encoding device according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a signal discriminating unit and a 3-2 converting unit of the image encoding device according to the first embodiment of the present invention.

FIG. 4 is a timing chart of the image encoding apparatus according to the first embodiment of the present invention.

FIG. 5 is a block diagram of an image decoding apparatus according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a 2-3 conversion unit of the image decoding apparatus according to the second embodiment of the present invention.

FIG. 7 is a timing chart of an image decoding apparatus according to a second embodiment of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-328317 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N ^7/ 24-7/68

Claims (2)

(57) [Claims] An image encoding apparatus for performing compression encoding of a moving image using variable length encoding, wherein an input video signal is a telecine video signal created by a 2-3 pull-down method from a film image. Signal discriminating means for discriminating whether or not the input video signal is 3 according to the discrimination result of the signal discriminating means.
3-2 conversion means for converting a field into two fields, and a 3-2 conversion output signal converted by the 3-2 conversion means
And a coding means for performing variable length coding of the case where the input video signal is determined to the a telecine video signal, it removes the field duplicate by the 3-2 converting means, deleted field period and simultaneously enter invalid data to said encoding means to send a data valid signal indicating whether or not the data is valid in the encoding means, to interrupt the operation of said encoding means if the data is not valid An image encoding device, characterized in that: 2. An image decoding apparatus for decoding an image coded using variable length coding, comprising: decoding means for decoding a variable length code; and decoding means for decoding the variable length code .
And 2-3 conversion means for converting two fields of data into three-field data, wherein when the input data is invalid according to a data valid signal input to the decoding means, the operation of the decoding means is performed. Interrupt and invalid data
At the same time as inputting to the 2-3 conversion means,
The signal indicating whether or not to output repeatedly is output from the 2-3 conversion means.
Duplicate field when sending to column and invalid data
An image decoding apparatus characterized by generating: