KR20040078935A - Coding method for moving picture - Google Patents

Abstract

PURPOSE: A moving picture coding method is provided to effectively initiate a reference picture index used for motion compensation in consideration of coding efficiency when an interlaced scanned moving picture is coded into a field picture. CONSTITUTION: An initial reference picture index is allocated to each reference field in a reference buffer when a moving picture coding system using a multiple reference picture codes an interlaced scanning moving picture into a field picture. In the case of P picture, the reference picture index is allocated in a coding order irrespective of the parity of the current field. When the reference picture index of the P picture is allocated, all of short-term reference pictures are arranged in the inverse order of the coding order and the reference picture index is allocated increasing one by one from zero in the order of the arranged fields of the short-term reference pictures irrespective of the parity.

Description

Coding method for moving picture}

The present invention relates to video coding, and more particularly, to a video coding method for coding an interlaced scanning video in a video coding system using multiple reference pictures.

In general video coding system, motion compensation is performed using motion vector information. Especially in video coding system using multiple reference pictures, reference picture index information is required in addition to motion vector for motion compensation. do. In this case, the reference picture index is a value used to distinguish each of the multiple reference pictures. The encoder transmits a reference picture index value used for motion compensation to the decoder, and the decoder performs motion compensation from the reference picture indicated by the value.

When using multiple reference pictures, the reference buffer may be divided into a short term reference buffer storing short-term reference pictures and a long term reference buffer storing long-term reference pictures. The short term reference buffer is a buffer for storing recently coded pictures, and the pictures stored therein are deleted from the buffer in a first-in-first-out (FIFO) manner over time. On the other hand, pictures in the long term reference buffer are stored and deleted by a specific syntax regardless of time.

On the other hand, there are two types of video scanning methods, a progressive scan method and an interlaced scan method. In sequential scanning, images of one frame are all sampled at the same time, whereas in interlaced scanning, the sampling time of odd-numbered and even-numbered lines in the image of one frame is different. Regardless of the sampling time order, the field including the first line of the frame is called a top field, and the remaining fields are called bottom fields.

In an interlaced scan image, one frame is composed of two field images. The top field may be temporally advanced or the bottom field may be temporally temporal among the two fields of a frame. In the present invention, an image is treated as a unit called a picture, and the picture may indicate a frame or a field.

The coding method of interlaced scan image includes a field picture coding method for coding each field as an independent picture at the picture level, a frame picture coding method for coding after combining two fields into one frame at the picture level, and two There are three methods such as a frame picture coding method having a frame / field macroblock that combines a field into one frame and then selects and codes a frame or a field mode at a macroblock level.

In the case of using multiple reference pictures, the reference buffer that stores the reference picture is configured in units of frames. In the case of field picture coding, all reference pictures are regarded as being present in units of fields, and one of these reference field pictures is used for motion compensation. Therefore, the reference picture index is assigned a value in units of fields.

Before coding each field picture, an initial reference index is assigned to each reference field stored in the reference buffer through the reference index initialization process, and the reference buffer is reordered based on the initial reference index. The final reference index for each reference field in is determined. If there is no reordering of the reference index, the initial reference index is used as the final reference index for each reference field in the reference buffer.

An initial reference index allocation method for each field picture of a P frame is as follows.

(1) Perform (2) to (5) below for the short-term reference buffer.

(2) All reference fields in the reference buffer are combined in units of frames, and the frames are arranged in the reverse order of coding order.

(3) An index value incremented by 1 is alternately assigned to a reference field having the same parity as the current picture, alternately visiting the reference fields having different parities, starting with the index value 0 and sequentially visiting the reference frames.

(4) If the field of the parity to which the reference picture index is to be allocated does not exist in the reference buffer, the index value is assigned to the field of the same parity in the next frame aligned.

(5) If the parity to be allocated no longer exists in the reference buffer, the index is allocated according to the order of the frames arranged in the remaining field regardless of the parity type.

(6) If a picture exists in the long term reference buffer, the pictures are sorted in increasing order of the long term reference frame index.

(7) Assign a reference index in the same way as (3) ~ (5). However, the index value starts from a number larger than the maximum index value allocated for the short term reference.

1 shows an example of an initial reference picture index for a top field picture of a P frame and an initial reference picture index for a bottom field picture when the reference buffer size is 5 and only a short reference picture is present. 2 shows an example of an initial reference picture index allocated when one reference field does not exist in the middle.

On the other hand, since the B frame has motion compensation using up to two reference pictures, there are two reference index lists. The two index lists are represented as 'List 0' and 'List 1', respectively.

In this case, an initial reference index allocation method for field picture coding on the reference picture index list 0 is as follows.

(1) Perform (2) to (5) below for the short-term reference buffer.

(2) All reference fields in the reference buffer are combined in units of frames, and all reference frames whose display order precedes the current picture are arranged in the reverse order of the display order.

(3) The reference picture index is allocated in the same manner as in (3) to (5) of the above P frame.

(4) Next, arrange all reference frames whose display order is later than the current picture in display order.

(5) The reference picture index is allocated in the same manner as in (3) to (5) of the above P frame. However, the index value starts from the number one larger than the maximum index value allocated in (3).

(6) If a picture exists in the long term reference buffer, the pictures are combined in units of frames, and the long term reference frame indexes are arranged in increasing order.

(7) Allocate a reference index in the same manner as in (3) to (5) above P frame. However, the index value starts from a number that is one greater than the maximum index value allocated for the short-term reference picture.

The initial reference index allocation method for field picture coding for reference picture index list 1 is as follows.

(1) Perform (2) to (5) below for the short-term reference buffer.

(2) All reference fields in the reference buffer are combined in units of frames, and all reference frames whose display order is later than the current picture are arranged in display order.

(3) The reference picture index is allocated in the same manner as in (3) to (5) of the above P frame.

(4) Next, all the reference frames whose display order precedes the current picture are arranged in the reverse order of the display order.

(5) The reference picture index is allocated in the same manner as in (3) to (5) of the above P frame. However, the index value starts from the number one larger than the maximum index value allocated in (3).

(6) If a picture exists in the long term reference buffer, the pictures are combined in units of frames, and the long term reference frame indexes are arranged in increasing order.

(7) Allocate a reference index in the same manner as in (3) to (5) above P frame. However, the index value starts from a number that is one greater than the maximum index value allocated for the short-term reference picture.

3 is an initial reference picture index list 0 and a list 1 and a bottom field picture for the top field picture of a B frame when the reference buffer size is 5 and only a short reference picture exists. An example of 0 and list 1 is shown.

However, in the case of setting the reference picture index through such a method, a portion in which video coding efficiency decreases due to an increase in the number of bits used to transmit reference picture index information is generated. For more efficient video coding, a reference picture is generated. Research into how to set up an index is being sought.

The present invention provides a video coding method capable of efficiently initializing a reference picture index used for motion compensation in consideration of coding efficiency when coding interlaced video as a field picture in a video coding system using multiple reference pictures. The purpose is to provide.

The present invention also provides a video coding method for determining a field picture to be deleted from a reference buffer in a process of storing a current field in a reference buffer when coding a video of an interlaced scan method as a field picture in a video coding system using multiple reference pictures. There is another purpose in providing.

1 is a diagram for explaining an initial reference picture index for a Top field and a Bottom field of a P frame in a conventional video coding system.

FIG. 2 is a diagram for explaining an initial reference picture index for a Top field of a P frame when there is an empty field in the middle of reference pictures in the conventional video coding system. FIG.

FIG. 3 is a diagram for explaining an initial reference picture index list 0 and a list 1 for a top field and a bottom field of a B frame in a conventional video coding system. FIG.

4 is a diagram illustrating an initial reference picture index when a Top field is temporally advanced and a current field is a Top field of a P frame in the video coding system according to the present invention.

5 is a diagram illustrating an initial reference picture index when a top field is temporally advanced and a current field is a bottom field of a P frame in a video coding system according to the present invention.

FIG. 6 is a diagram illustrating an initial reference picture index when a bottom field is temporally advanced and a current field is a bottom field of a P frame in a video coding system according to the present invention. FIG.

7 is a diagram illustrating an initial reference picture index when a bottom field is temporally advanced and a current field is a top field of a P frame in a video coding system according to the present invention.

8 is an initial reference picture when a top field is temporally advanced, a current field is a top field of a P frame, and there is an empty field in the middle of reference pictures in the video coding system according to the present invention. Figure showing the index.

9 illustrates a short-term reference picture and a long-term reference picture in a video coding system according to the present invention, a top field is temporally advanced, and a current field is a P-frame. A diagram showing an initial reference picture index in the case of a top field.

FIG. 10 is an initial reference when a short-term reference picture and a long-term reference picture exist, a top field advances in time, and a current field is a bottom field of a P frame in a video coding system according to the present invention. Figure showing a picture index.

FIG. 11 is a diagram illustrating an initial reference picture index when a top field is temporally advanced and a current field is a top field of a B frame to be used as a reference in the video coding system according to the present invention. FIG.

12 is a diagram illustrating an initial reference picture index when a top field is temporally advanced and a current field is a bottom field of a B frame to be used as a reference in the video coding system according to the present invention.

FIG. 13 is a diagram illustrating an initial reference picture index when a top field is temporally advanced and a bottom field of a B frame is not used as a reference in the video coding system according to the present invention. FIG.

14 is a video coding system according to the present invention, in which a short-term reference picture and a long-term reference picture exist, a top field is temporally advanced, and a current field is a top field of a B frame to be used as a reference. Diagram showing an initial reference picture index of a symbol;

FIG. 15 illustrates that a short-term reference picture and a long-term reference picture exist, a top field advances in time, and a current field is a bottom field of a B frame to be used as a reference in the video coding system according to the present invention. Diagram showing an initial reference picture index of a symbol;

FIG. 16 illustrates that a short-term reference picture and a long-term reference picture exist in a video coding system according to the present invention, and some of the long-term reference pictures are earlier in display order than the current picture, and others are later in display order than the current picture. A diagram showing an initial reference picture index when the current field is a top field of a B frame to be used as a reference.

In order to achieve the above object, a video coding method according to the present invention, when coding a video of the interlaced scan method as a field picture in a video coding system using a multiple reference picture,

In assigning an initial reference picture index to each reference field in the reference buffer, in the case of a P picture, the reference picture index is assigned in a coding order regardless of the parity of the current field. There is a characteristic.

According to the present invention, in allocating the reference picture index of the P picture, all the short-term reference pictures are arranged in the reverse order of coding order by field unit, and the ordered field order is from 0 regardless of parity. The feature is that the reference picture index is assigned in increments of one.

According to the present invention, when allocating a reference picture index of the P picture, when a short-term reference picture and a long-term reference picture exist, all the short-term reference pictures are coded in field units. Sorting in reverse order, then sorting all long-term reference pictures in field-by-field coding order, and then assigning reference picture indices in increasing order from 0 to 1, regardless of parity, in sorted field order. .

In addition, another example of a video coding method according to the present invention in order to achieve the above object, when coding a video of the interlaced scan method as a field picture in a video coding system using a multiple reference picture (multiple reference picture),

In assigning an initial reference picture index to each reference field in the reference buffer, in the case of a B picture, the reference picture index is assigned according to the display order regardless of the parity of the current field. There is a characteristic.

According to the present invention, in allocating the reference picture index of the B picture, in assigning the initial reference picture index of the list 0, all the short-term reference pictures whose display order precedes the current picture are reversed in the display order. Then sort all the short-term reference pictures whose display order is later than the current picture, in field-by-field order, and then increase the reference pictures in incremental order from 0 to 1 for all sorted reference fields, regardless of parity. The distinction is in assigning indexes.

According to the present invention, in allocating the reference picture index of the B picture, in the case of assigning the initial reference picture index of the list 0, when there are short-term reference pictures and long-term reference pictures, the display order is earlier than the current picture. Sort short-term reference pictures in field order in reverse display order, then sort all short-term reference pictures later in field display order than the current picture, and then display all the long-term reference pictures in display order ahead of the current picture. Sorts by field in reverse display order, finally sorts all long-term reference pictures that are later than the current picture in display order by field, and then returns parity for all sorted reference fields, regardless of parity. Aligned in order, increasing from zero one by one is that characterized by assigning a reference picture index.

According to the present invention, in allocating the reference picture index of the B picture, in assigning the initial reference picture index of List 1, all the short-term reference pictures whose display order is later than the current picture are arranged in the display order. Then, sort all the short-term reference pictures whose display order precedes the current picture in the reverse order of the display order by field, and then increase the reference pictures by increasing the values from 0 to 1 in the sorted order regardless of parity for all sorted reference fields. The distinction is in assigning indexes.

According to the present invention, when allocating the reference picture index of the B picture, in the case of assigning the initial reference picture index of List 1, when there are short-term reference pictures and long-term reference pictures, the display order is lower than that of the current picture. Sort short-term reference pictures in field-by-field display order, then sort all short-term reference pictures in display order that precede the current picture in field order, and then display all long-term reference pictures that are later in display order than current picture. Sorts by display order by field, and finally sorts all long-term reference pictures whose display order precedes the current picture in the reverse order of display order by field, and then returns parity for all sorted reference fields, regardless of parity. Aligned in order, increasing from zero one by one is that characterized by assigning a reference picture index.

In addition, the video coding method according to the present invention for achieving the above another object,

When coding interlaced video as a field picture in a video coding system using multiple reference pictures, each field picture is previously stored in a reference buffer to be stored in a reference buffer after coding / decoding each field picture. In determining the field picture to be deleted among the existing field pictures, the P picture is characterized in that the field picture in the coding order among the field pictures in the short-term reference buffer is deleted.

In addition, another example of a video coding method according to the present invention for achieving the above object,

When coding interlaced video as a field picture in a video coding system using multiple reference pictures, each field picture is previously stored in a reference buffer to be stored in a reference buffer after coding / decoding each field picture. In determining the field picture to be deleted among the existing field pictures, the B picture has a feature of deleting the field picture having the earliest display order among the field pictures in the short-term reference buffer.

According to the present invention, when coding interlaced video as a field picture in a video coding system using multiple reference pictures, reference is made to each reference field in an order close to the current field regardless of parity. There is an advantage in that coding efficiency can be improved by allocating a picture index.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the case of frame picture coding, since the reference picture index is allocated in units of frames, both fields in one frame have the same reference picture index. In the case of field picture coding, the reference picture indices are allocated in units of fields, so that two fields in one frame are allocated. Different reference picture indices are assigned to the fields.

In the prior art, since a lower index is assigned to a reference field that is far from time than a reference field that is temporally close to the current field, coding efficiency may be reduced in the case of an image having a lot of motion. In particular, when a field having the same parity is empty in the middle of the reference field pictures as shown in FIG. 2, a decrease in coding efficiency may appear more large.

In order to solve the problem of the initial reference picture index allocation method in the field picture coding, the present invention provides the following methods for the P picture and the B picture, respectively.

In the case of a P picture, a reference picture index is allocated through the following process.

(1) All short-term reference pictures are arranged in field order in the reverse order of coding order.

(2) Then, all the long term reference pictures are arranged in the reverse order of coding order in field units.

(3) The reference picture indexes are allocated in increasing order of 0 from 1 regardless of parity in the order of the sorted fields.

4 to 8 show an example of an initial reference picture index allocated to a P picture according to the present invention for a P picture when only a short reference picture exists. 9 and 10 show an example of an initial reference picture index assigned to a P picture according to the present invention by the video coding method when the short-term reference picture and the long-term reference picture exist.

In addition, in the case of the B picture, a method of allocating the initial reference picture index of the list 0 is as follows.

(1) All short-term reference pictures whose display order precedes the current picture are arranged in the reverse order of the display order in field units.

(2) Subsequently, all short-term reference pictures whose display order is later than the current picture are arranged in the display order on a field basis.

(3) Subsequently, all long-term reference pictures whose display order precedes the current picture are arranged in the reverse order of the display order in units of fields.

(4) Then, all the long term reference pictures whose display order is later than the current picture are arranged in display order on a field basis.

(5) The reference picture indexes are allocated to all the sorted reference fields in incremental order from 0 to 1, regardless of parity.

In addition, in the case of a B picture, a method of allocating an initial reference picture index of List 1 is as follows.

(1) All short-term reference pictures whose display order is later than the current picture are arranged in display order on a field basis.

(2) Next, all short-term reference pictures whose display order is preceded by the current picture are arranged in the reverse order of the display order in field units.

(3) Then, all the long term reference pictures whose display order is later than the current picture are arranged in display order on a field basis.

(4) Next, all long-term reference pictures whose display order precedes the current picture are arranged in the reverse order of the display order in units of fields.

(5) The reference picture indexes are allocated to all the sorted reference fields in incremental order from 0 to 1, regardless of parity.

11 and 12 show examples of an initial reference picture index assigned to a B picture stored as a picture as a reference when there is only a short reference in the video coding method according to the present invention. FIG. 13 shows an example of an initial reference picture index assigned to a B picture that is not stored as a picture as a reference when only a short term reference exists, by the video coding method according to the present invention.

14 and 15 show that a short reference picture and a long term reference picture exist, and the display order of the long term reference pictures is earlier than the current picture, the B picture stored as the reference picture is allocated to the video coding method according to the present invention. An example of an initial reference picture index is shown. FIG. 16 illustrates a B picture stored as a reference picture when a short reference picture and a long term reference picture exist, and some of the long term reference pictures display a display order earlier than a current picture and others display a later order than the current picture. An example of an initial reference picture index allocated by the video coding method according to the present invention is shown.

On the other hand, in the case of a P picture or a B picture to be used as a reference, each field picture must be stored in a reference buffer to be used as a reference of another picture after coding / decoding. Since the size of the reference buffer is limited in units of frames, in order to store the current field, one of the field pictures stored in the reference buffer must be deleted. The field picture to be deleted can be determined as follows.

(1) In the case of the P picture, the field picture having the earliest coding order among the field pictures in the short-term reference buffer is deleted and the current field is stored.

(2) In the case of the B picture, the field picture having the earliest display order among the field pictures in the short-term reference buffer is deleted and the current field is stored.

According to the video coding method according to the present invention as described above, when coding interlaced video as a field picture in a video coding system using a multi-reference picture, according to the order close to the current field regardless of parity By assigning a reference picture index to each reference field, it is possible to increase coding efficiency.

Claims (10)

When coding interlaced video as a field picture in a video coding system using multiple reference pictures, In assigning an initial reference picture index to each reference field in the reference buffer, in the case of a P picture, the reference picture index is assigned in a coding order regardless of the parity of the current field. How to code a video. The method of claim 1, In assigning the reference picture index of the P picture, all short-term reference pictures are arranged in the reverse order of coding order in field units, and the reference pictures are incremented by 0 from 1 regardless of parity in the sorted field order. A video coding method comprising assigning an index. The method of claim 1, In assigning the reference picture index of the P picture, if there is a short-term reference picture and a long-term reference picture, all the short-term reference pictures are arranged in the reverse order of coding order in field units, and then And arranging all the long-term reference pictures in field order in the reverse order of coding order, and then assigning reference picture indices while increasing the order of zero by one regardless of parity in the sorted field order. When coding interlaced video as a field picture in a video coding system using multiple reference pictures, In assigning an initial reference picture index to each reference field in the reference buffer, in the case of the B picture, the reference picture index is assigned according to the display order regardless of the parity of the current field. How to code a video. The method of claim 4, wherein In allocating the reference picture index of the B picture, in allocating the initial reference picture index of the list 0, Sort all the short-term reference pictures with display order earlier than the current picture in field order, and then sort all the short-term reference pictures with display order later than the current picture in field order, then display all sorted references. And a reference picture index is assigned to the field in incremental order of 0 from 1 regardless of parity. The method of claim 4, wherein In allocating the reference picture index of the B picture, in allocating the initial reference picture index of the list 0, If short-term reference pictures and long-term reference pictures are present, all short-term reference pictures that have a display order that precedes the current picture are arranged in field order, and then all short-term reference pictures that have a later display order than the current picture are in field units. Sorting by display order, and then sorting all long-term reference pictures with display order prior to the current picture in field order, and finally displaying all long-term reference pictures with display order later than the current picture in field order. And then assigning reference picture indices to all sorted reference fields in increasing order from 0 to 1 in the sorted order regardless of parity. The method of claim 4, wherein In allocating the reference picture index of the B picture, in allocating the initial reference picture index of List 1, Sort all the short-term reference pictures with display order later than the current picture in field order, then sort all the short-term reference pictures with display order prior to the current picture in field order, and then reverse all sorted references. And a reference picture index is assigned to the field in incremental order of 0 from 1 regardless of parity. The method of claim 4, wherein In allocating the reference picture index of the B picture, in allocating the initial reference picture index of List 1, If short-term reference pictures and long-term reference pictures are present, all short-term reference pictures with a display order that is later than the current picture are arranged in field order, and then all short-term reference pictures whose display order precedes the current picture are displayed in field order. Sort in reverse display order, followed by all the long-term reference pictures with display order later than the current picture, in field order, and finally, all the long-term reference pictures with display order prior to the current picture in field order. And then assigning reference picture indices to all sorted reference fields in increasing order from 0 to 1 in the sorted order regardless of parity. When coding interlaced video as a field picture in a video coding system using multiple reference pictures, each field picture is previously stored in a reference buffer to be stored in a reference buffer after coding / decoding each field picture. In determining the field picture to be deleted among the existing field pictures, In the case of a P picture, the video coding method of the field pictures in the short-term reference buffer is deleted. When coding interlaced video as a field picture in a video coding system using multiple reference pictures, each field picture is previously stored in a reference buffer to be stored in a reference buffer after coding / decoding each field picture. In determining the field picture to be deleted among the existing field pictures, In the case of the B picture, the video coding method of the field pictures in the short-term reference buffer is deleted.