CN1972451A - Macro-block loop filtering method based on AVS standard video decoding - Google Patents

Abstract

This invention relates to macro block ring path filter method based on AVS standard visual frequency codes, which comprises the following steps: cutting one frame of image into several blocks and after decoding each macro block and then filtering each block; for new filtered macro blocks are sent to outer memory covering the extensive macro data onto left and top surface of block of other block boundary values.

Description

Macro-block loop filtering method based on the AVS standard video decoding

Technical field

The present invention is a kind of loop circuit filtering method that is applied to the AVS standard video decoding of embedded system, promptly each macro block is carried out Filtering Processing in advance specifically in decode procedure.

Background technology

In AVS standard video decoding process, generally adopt at present based on the macroblock encoding framework.Be about to input video and be divided into several macro blocks, to each macro block predict, estimation, conversion, quantification and decode operation.Handle because video data is carried out piecemeal, so just cause occurring block effect inevitably, therefore existing video decode is all introduced the loop filtering technology.

Because adopt loop filtering, except that the border of general image border and band, all block boundaries of each macro block all should carry out filtering.At this moment, the block boundary of macro block is defined as each border of 4 * 4 of interior macroblocks, and the coboundary of current macro and adjacent macroblocks and left margin.

Loop filtering is to handle unit with the macro block, and the filtering of each macro block carries out loop filtering respectively to the brightness and the colourity of each macro block: at first, from left to right vertical boundary is carried out filtering as shown in Figure 1 in the image; Then, from top to bottom horizontal boundary is carried out filtering.

In carrying out the loop filtering processing procedure, for the macro block when pre-treatment, the input data of its loop filtering are the sample value that image does not carry out filtering, and the current macro loop filtering can be revised these sample values.In the current macro vertical boundary filtering, the sample value of being revised will be as the input of horizontal boundary filtering.Infra-frame prediction uses the reconstructed image sample value before the loop filtering.

As mentioned above, existing loop circuit filtering method is after frame complete image decoding, carries out filtering one by one at each macro block again.Because the frame data amount is very big, and internal memory is limited in the sheet of embedded system decoder, common way is that the data that will produce in the macro-block decoding process are kept at chip external memory, handle at the data on the outer internal memory of sheet one by one again during pending loop filtering, therefore existing loop filtering action need is in the inside and outside data of transferring repeatedly of sheet, filtering consuming time long, cause whole decode procedure to take too much system time.

Summary of the invention

Macro-block loop filtering method based on the AVS standard video decoding of the present invention, its purpose is to address the above problem and at the AVS standard video decoding on the embedded system, carry out loop filtering in advance at each macro block, rather than etc. frame data all carry out filtering again after the decoding, thereby reduced in the decoder sheet and the number of times and the data volume of the outer buffer-stored of sheet.

For achieving the above object, described macro-block loop filtering method based on the AVS standard video decoding is that a two field picture is divided into several macro blocks, and each macro block after decoding finishes, is promptly carried out boundary filtering at the macro block after the expansion.

For filtered new macro block, be sent to chip external memory, the macro block data of expansion is covered the boundary value of this macro block left side and top other macro blocks.

Because the macro block data before the loop filtering need use in next macro block of decoding.Therefore, before a macro block is carried out loop filtering, this macro block data is sent to sheet cushions backup outward.

As above-mentioned method content, described method is that each macro block is carried out loop filtering, passes to the sheet external memory again.After so whole macro block decoding finishes, just need not again these frame data all to have been carried out loop filtering.

Even, and increased backup procedure in next macro block of decoding to macro block data before the filtering owing to the macro block data before the filtering needs use.But because only need the low volume data at macroblock boundaries place is backed up, so transfer rate is very fast, with respect in the sheet, sheet is outer transmits the spent time of macro block data mutually, this processing mode is still comparatively time saving.

For effectively shortening the processing time at each macro block, above-mentioned process with the transmission of the macro block data before filtering backup can be carried out simultaneously with the loop filtering process of this macro block.

And further improvement project is, carry out sheet and back up outward for preventing to transmit macro block data before the filtering, to sheet, preserve and clash with transmitting the filtered macro block data of loop, enable 2 DMA (Direct Memory Access) passage in the method for the invention.And it is consuming time also can to reduce system effectively in conjunction with 2 DMA passages simultaneously.

From the angle of whole Filtering Processing time spent, a frame image data of existing AVS normal video is that each decoded macro block is sent to the sheet external memory, treats to carry out loop filtering at frame data again after all macro blocks transmission finish.Owing to directly do not carry out filtering operation at chip external memory, so just needs return the data-moving of sheet external memory in the sheet earlier, carry out filtering again, and filtered data are sent once more in the sheet external memory.Total like this calculation comes, and the number of times of transmission is that interior the arriving outward to outer (1 time)+sheet of sheet of sheet arrived sheet outer (1 time) in (1 time)+sheet in the sheet, needs to carry out moving of 3 macro block datas altogether.

And use the macro-block loop filtering method based on the AVS standard video decoding of the present invention, and each decoded macro block data directly carries out border extension, carries out loop filtering with adjacent macroblocks in sheet again, and filtering finishes the back macro block data and delivers to the sheet external memory again.

Because the transmission backup of the macro block data before the filtering can be carried out simultaneously with the loop filtering process of this macro block, the time that therefore in fact only need take a data-moving gets final product.

The structure of contrast is to use filtering method of the present invention and can save about 2/3rds handling time mutually.

And as mentioned above, enable 2 DMA passages simultaneously, the efficient that carry out in the sheet, the outer data of sheet transmits can be higher.

Described macro-block loop filtering method based on the AVS standard video decoding, its realization flow is:

The first step is divided into several macro blocks with a two field picture, and each macro block is decoded;

Second step, expand for a decoded macro block, carry out boundary filtering at the macro block after the expansion, obtain new macro block;

The 3rd step, adopt the DMA passage that filtered macro block is sent to outside the sheet, the macro block data of expansion is covered the boundary value that is in this macro block left side and top macro block;

With the loop filtering process of above-mentioned macro block simultaneously, enable the macro block data of another DMA passage before and be sent to sheet and back up outward filtering;

Finish until the used macro-block loop filtering of cutting apart.

Content to sum up, the advantage of described macro-block loop filtering method based on the AVS standard video decoding is: according to macro block filtering only at the characteristics of the left side and top macro block, changed the problem that existing filtering method must carry out whole filtering to a two field picture, both reduced in the decoder sheet and the number of times of the outer buffer-stored of sheet, adopt 2 DMA passages to carry out data passes, also guaranteed loop filtering quality, improved speed.

Description of drawings

Fig. 1 is the border schematic diagram that needs filtering in the macro block;

The border schematic diagram that Fig. 2 need expand when being single macro block filtering.

As shown in Figure 1, black solid line wherein is a vertical boundary, and black dotted line is a horizontal boundary.

As shown in Figure 2, dash area wherein is for expanding part.

Embodiment

Embodiment 1, in conjunction with Fig. 1 and Fig. 2, and described macro-block loop filtering method based on the AVS standard video decoding, the performing step that a frame brightness is partly carried out loop filtering is:

The first step is divided into 16 * 16 macro blocks with the present frame luminance pixel;

In second step, should expand to (18 * 18) macro block by (16 * 16) macro block; Carry out boundary filtering at the macro block after the expansion, obtain the macro block of new (18 * 18);

In the 3rd step, new (18 * 18) macro block that adopts 1 DMA passage to obtain is sent to outside the sheet, and two row, two row of expansion cover the boundary value of the left side and top macro block;

Simultaneously, enabling the macro block data of another DMA passage before with filtering is sent to sheet and backs up outward.

Claims (4)

1, a kind of macro-block loop filtering method based on the AVS standard video decoding is characterized in that: a two field picture is divided into several macro blocks, and each macro block after decoding finishes, is promptly carried out boundary filtering at the macro block after the expansion;

For filtered new macro block, be sent to chip external memory, the macro block data of expansion is covered the boundary value of this macro block left side and top other macro blocks;

Before a macro block is carried out loop filtering, this macro block data is sent to sheet cushions backup outward.

2, the macro-block loop filtering method based on the AVS standard video decoding according to claim 1 is characterized in that: the macro block data before the filtering is transmitted the process of backup, can carry out simultaneously with the loop filtering process of this macro block.

3, the macro-block loop filtering method based on the AVS standard video decoding according to claim 2, it is characterized in that: the macro block data before transmitting filtering carries out backing up outside the sheet, and transmits in the process that the filtered macro block data of loop preserves to sheet and enable 2 DMA passages respectively.

4, the macro-block loop filtering method based on the AVS standard video decoding according to claim 3 is characterized in that: its realization flow is,

The first step is divided into several macro blocks with a two field picture, and each macro block is decoded;

Second step, expand for a decoded macro block, carry out boundary filtering at the macro block after the expansion, obtain new macro block;

The 3rd step, adopt the DMA passage that filtered macro block is sent to outside the sheet, the macro block data of expansion is covered the boundary value that is in this macro block left side and top macro block;

With the loop filtering process of above-mentioned macro block simultaneously, enable the macro block data of another DMA passage before and be sent to sheet and back up outward filtering;

Finish until the used macro-block loop filtering of cutting apart.