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Rate control system of MPEG code converter under condition that picture type is not understood in advance

A transcoder and picture technology, applied in TV, selective content distribution, electrical components, etc., can solve problems such as not being able to know the picture type and difficulties in advance

Inactive Publication Date: 2006-08-09
GOOGLE TECHNOLOGY HOLDINGS LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In contrast, a transcoder cannot know the picture type in advance before actually processing the picture
Difficulty arises when the transcoder allocates the appropriate number of bits to encode the picture

Method used

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  • Rate control system of MPEG code converter under condition that picture type is not understood in advance
  • Rate control system of MPEG code converter under condition that picture type is not understood in advance
  • Rate control system of MPEG code converter under condition that picture type is not understood in advance

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Experimental program
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Embodiment Construction

[0061] The present invention relates to a digital video transcoder and method for allocating bits for coding successive pictures in a group of pictures (GOP) without prior knowledge of the picture types in the GOP.

[0062] A novel rate control scheme and apparatus is shown for a digital video transcoder, eg, compliant with the MPEG standard, requiring no prior (advance) knowledge of picture type. The research done shows that the target ratio of the frames determined using the proposed ratio control system is very close with and without prior knowledge of the frame types.

[0063] MPEG defines three picture types according to time processing. These are intra-coded pictures (I-pictures), forward temporally predictively coded pictures (P-pictures), and bidirectional temporally predictively coded pictures (B-pictures). In MPEG video coding, pictures of an input video sequence are often grouped into groups of pictures (GOPs), where each GOP may contain an I-picture, multiple P-pi...

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Abstract

A rate control system suitable for use with a digital video transcoder, such as one conforming to the MPEG standard. The proposed rate control system starts coding without a priori knowledge of the Group of Pictures (GOP) parameters, thereby avoiding a processing delay of about one GOP which would otherwise be incurred to extract the complete GOP structure information. In addition, the system avoids the need to store the data corresponding to the GOP, thereby reducing the memory required for transcoding. An initially allocated bit budget is gradually corrected as successive pictures are coded according to their picture types. Changes in the GOP structure of pre-compressed bitstreams can be addressed, for example, when switching channels or inserting commercials. Target rates with incorrect starting GOP parameters will converge within a few GOPs.

Description

technical field [0001] The present invention relates to a digital video transcoder and method for allocating bits for coding successive pictures in a group of pictures (GOP) without prior knowledge of the picture types in the GOP. Background technique [0002] Using a digital video encoding method such as MPEG, an input picture can be encoded into three picture types, ie, I, P, and B. These three pictures require completely different numbers of coding bits due to their different temporal processing characteristics. Therefore, an intelligent bit allocation strategy should specify the number of bits used for encoding according to the picture type. This requires prior knowledge of the picture type for a given bit budget. This requirement does not pose a problem for an independent encoder, since the encoder is able to determine the type of each input picture. [0003] In fact, the encoder is able to plan ahead for the type of input picture. In contrast, a transcoder cannot k...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N7/26H04N7/46H04N7/50H04N21/2365H04N21/434
CPCH04N19/00781H04N19/00472H04N19/00721H04N19/00054H04N21/2365H04N7/506H04N19/00284H04N19/00212H04N19/00193H04N19/00218H04N21/23655H04N7/5026H04N7/26191H04N21/4347H04N7/5033H04N19/00266H04N19/159H04N19/172H04N19/61H04N19/114H04N19/152H04N19/157H04N19/177H04N19/40H04N19/577
Inventor 王利民阿贾伊·卢特拉罗伯特·O·艾弗瑞格
Owner GOOGLE TECHNOLOGY HOLDINGS LLC