Video coding questions?need answers

Hi anyone,
I have some questions concerning video coding as follow, I hope you will give me a hint
1. What is mathematical relationship between bit rate and quantization?
2. If make comparision between MPEG1,2,4 and H.261, H.263, H.264, what could we say?
3. Why we just do motion estimation on luma frame?
Thanks in advance

Hi
About your first question:
If device quantization level is 2^q and image size is axb pixels, so bit rate for this image or frame in video is axbxq. so bit rate and quantization level is related linearly.

First of all H.262,H.263,H.263+,H.264 are ITU-T standards
whereas MPEG 1,2,4 are MPEG standards Motion Picture Experts Group

In MPEG video only the new parts of the video sequence is included together with information of the moving parts. MPEG-1 is focused on bit-streams of about 1, 5 Mbps and originally for storage of digital VCDs. The focus is on compression ratio rather than picture quality. It can be considered as traditional VCR quality but digital instead.
The MPEG-2 project focused on extending the compression technique of MPEG-1 to cover larger pictures and higher quality at the expense of a lower compression ratio and therefore also higher bandwidth usage.


H.264 video coding standard has the same basic functional elements as previous standards (MPEG-1, MPEG-2, MPEG-4 part 2, H.261, H.263) , i.e., transform for reduction of spatial correlation, quantization for bitrate control, motion compensated prediction for reduction of temporal correlation, entropy encoding for reduction of statistical correlation. However, in order to fulfill better coding performance, the important changes in H.264 occur in the details of each functional element by including intra-picture prediction, a new 4x4 integer transform, multiple reference pictures, variable block sizes and a quarter pel precision for motion compensation, a deblocking filter, and improved entropy coding. Improved coding efficiency comes at the expense of added complexity to the coder/decoder. H.264 utilizes some methods to reduce the implementation complexity. Multiplier-free integer transform is introduced. Multiplication operation for the exact transform is combined with the multiplication of quantization.

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