Method and system for rate control during video transcoding

• US 10,129,552 B2
• Filed: 04/22/2015
• Issued: 11/13/2018
• Est. Priority Date: 11/21/2001
• Status: Active Grant

• Current Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Original Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Inventors: Laksono, Indra, Zeng, Zhihua
• Primary Examiner(s): Diep, Nhon T
• Application Number:
  US14/692,830
• Publication Number:
  US 20150373351A1
• Time in Patent Office: 1,301 Days
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A local system encodes previously decoded video data using a transcoding quantization value based on a source quantization value provided by a previous encoder as part of the retrieved video data. The transcoding quantization value can be determined additionally based the fullness of the video buffer of a target system, where a measure of the fullness can be obtained directly from the target system or modeled by the local system. The video data is encoded by the local system and then provided to a target system for decoding and subsequent display and/or storage.

Claims

1. A method comprising:

determining a first quantization value associated with a first macroblock; and

modifying the first macroblock using a second quantization value, wherein the second quantization value is based on a ratio of a quantization ratio to the first quantization value, wherein the quantization ratio is based on a first expected characteristic of a video buffer, wherein the quantization ratio is based on a product value of a X scaling value and a Y scaling value, and wherein the product value is raised to a power of Z where Z is less than one.

2. The method of claim 1, wherein the X scaling value includes a horizontal frame scaling value and the Y scaling value includes a vertical frame scaling value.

3. The method of claim 1, wherein Z is 0.75+/−

0.1.

4. The method of claim 1, wherein:

the quantization ratio includes a first constant value when the first expected characteristic is greater than a first indicator;

the quantization ratio includes a second constant value when the first expected characteristic is less than the first indicator and greater than a second buffer indicator; and

the quantization ratio is determined from a non-linear function when the first expected characteristic is less than the second indicator.

5. The method of claim 4, wherein the first indicator is a buffer fullness value of 75%+/−

1% of a maximum buffer fullness.

6. The method of claim 4, wherein the second indicator is a buffer fullness value of 20%+/−

1% of a maximum buffer fullness.

7. The method of claim 4, wherein the non-linear function is represented by an equation:

R=Q*X<sup>(Y−

W)/Z</sup>

where R is the quantization ratio, Q is an initial quantization ratio, X is a first constant value, Y is a second constant, W is a value representing the amount of data, and Z is a third constant value.