US 7,397,855 B2Granted

Rate controlling method and apparatus for use in a transcoder

AssigneeCorel TW Corp.

InventorYi-Kai Chen

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Abstract

A rate controlling method for computing a reference quantization parameter is provided, for use in a transcoder having a variable length decoder, an inverse quantizer, a quantizer and a variable length encoder. The rate controlling method comprising: receiving an input quantization parameter and motion information for each of the macroblocks from the variable length decoder; analyzing the similarity of motion information between a current macroblock and its neighboring macroblocks to compute a scaling factor for the current macroblock when allocated within P- and B-pictures; computing a bit difference between a target outputting bit stream and a real outputting bit stream; estimating the fullness of a virtual buffer to encode the current macroblock in view of the scaling factor; and computing the reference parameter based on a target bit rate, the first quantization parameter and the bit difference.

Claims2

Dependent claims

A rate controlling method for computing a reference quantization parameter, used in a transcoder having a variable length decoder, an inverse quantizer, a quantizer and a variable length encoder, the rate controlling method comprising:

receiving an input quantization parameter and motion information for each of the macroblocks from the variable length decoder;
analyzing the similarity of motion information between a current macroblock and its neighboring macroblocks to compute a scaling factor for the current macroblock when allocated within P- and B-pictures;
computing a bit difference between a target outputting bit stream and a real outputting bit stream from the variable length encoder;
estimating the fullness of a virtual buffer to encode the current macroblock in view of the scaling factor;
and
computing the reference parameter based on a target bit rate, the first quantization parameter and the bit difference;
wherein said motion information is a motion vector, and said scaling factor is defined as the following:
d
factor
=
1
+
sign
⁡
(
MV
⁡
(
j
)
·
MV
median
)
·
(
MV
⁡
(
j
)
·
MV
median
)
(

MV
⁡
(
j
)

·

MV
median

)
sign
⁡
(
a
)
=
{
1
if
⁢
⁢
a
≥
0
-
1
if
⁢
⁢
a
<
0
where “·” is operator for inner product, MV is the motion vector of the current macroblock, and MVmedian is the median of the motion vectors of its neighboring macroblocks.

69 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/823,576Filed 14 Apr 2004
Published: US 2005/0232354 A120 Oct 2005
Granted: 8 Jul 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

H04N 19/40
Methods or arrangements for coding, decoding, compressing or decompressing digital video signals: using video transcoding, i.e. partial or full…
H04N 19/126
Quantisation: details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
H04N 19/139
Motion inside a coding unit, e.g. average field, frame or block difference: analysis of motion vectors, e.g. their magnitude, direction, variance…
H04N 19/149
Data rate or code amount at the encoder output: by estimating the code amount by means of a model, e.g. mathematical model or statistical model