Method and system for transcoding video data

• US 20040179597A1
• Filed: 02/24/2003
• Published: 09/16/2004
• Est. Priority Date: 02/24/2003
• Status: Active Grant

• Current Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Original Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Inventors: Rault, Patrick
• Granted Patent: US 7,327,784 B2
• Time in Patent Office: Days
• US Class Current: 375/240.08
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/134 characterised by the element, parameter or criterion affecting or controlling the adaptive coding
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• 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

Abstract

A first method of transcoding video data is disclosed that generates a motion vector for a macroblock encoded as a dual prime macro block that has a direct motion vector, and differential motion vector for its two fields respectively. Another method of transcoding includes replacing a skipped P-macroblock that has been used to backward predict a B-Frame with a P-macroblock having a motion vector of zero. Another method of transcoding includes replacing a skipped B-Macroblock with a macroblock having a motion vector from a macroblock of the same frame of the skipped B-Macroblock that is not co-located.

Claims

1. A method comprising the steps of:

receiving a first MPEG (Motion Pictures Expert Group) data of a first type, wherein the first MPEG data comprises compressed data that has been quantified;

determining if the first MPEG data meets a predetermined criteria;

scaling the compressed data when the first MPEG data meets the predetermined criteria.

2. The method of claim 1, wherein receiving the first MPEG data comprises the first MPEG data being MPEG2 data.

3. The method of claim 1, wherein scaling comprises scaling the compressed data when the first MPEG data meets the predetermined criteria to generate a second MPEG data of a second type.

4. The method of claim 3, wherein receiving the first MPEG data comprises the first MPEG data being MPEG2 data.

5. The method of claim 4, wherein receiving the second MPEG data comprises the second MPEG data being MPEG4 data.

6. The method of claim 5, wherein determining comprises the predetermined criteria being a MPEG2 data DC quatization scalar equal to 8.

7. The method of claim 6, wherein scaling comprises scaling the compressed data by 4.

8. The method of claim 6, wherein scaling comprises scaling the compressed data by 3.

9. The method of claim 6, wherein scaling comprises scaling the compressed data by 2.

10. The method of claim 6, wherein scaling comprises scaling the compressed data by 1.

11. The method of claim 6, wherein scaling comprises determining a scale factor being a positive integer of 4 or less.

12. The method of claim 1, wherein determining comprises the predetermined criteria being a MPEG2 data DC quantization scalar equal to 8.

13. The method of claim 12, wherein scaling comprises:

determining a scale factor being a positive integer of 4 or less.

14. The method of claim 13, wherein scaling comprises:

dequantifying the first MPEG data to obtain the compressed data.

15. The method of claim 14, wherein scaling comprises:

scaling the compressed data by the scale factor to obtain a scaled data.

16. The method of claim 15, wherein scaling comprises:

encoding the scaled data using a MPEG AC quantization scalar of the second type.

17. The method of claim 16, wherein encoding comprises a MPEG AC quantization scalar of the first type, associated with the first MPEG data, divided by the MPEG AC quantization scalar is equal to the quantization factor.

18. A method comprising the steps of:

determining an AC quantization factor for a first MPEG data comprising compressed data that has been quantified;

determining an AC quantization factor for a second MPEG data wherein the AC quantization factor for the first MPEG data divided by the AC quantization factor for the second MPEG data is an integer less than or equal to 4.

19. The method of claim 18 comprising:

scaling the compressed data by the integer to obtain a scaled compressed data.

20. The method of claim 19 comprising:

encoding the scaled compressed data based upon the AC quantization factor for the second MPEG data.