Title :
Motion estimation with entropy coding considerations in H.264/AVC
Author :
Li, Zhen ; Tourapis, A.M.
Author_Institution :
Image Technol. Res., Dolby Labs., Burbank, CA
Abstract :
In many modern video encoders, motion estimation is usually formulated as a Lagrangian cost function that balances motion prediction accuracy and the rate to transmit motion vectors. In H.264/AVC video encoders, including the H.264 reference software, in an effort to reduce computational complexity, the motion vector rate is often estimated using a look-up table based on universal variable length coding regardless of the entropy coding method used. However, the estimated rate could be different from the actual rate used for encoding. In this paper we present an empirical study on the motion vector rate estimation mismatch caused by different entropy coding assumptions and discuss its impact on motion estimation and coding efficiency. We also present a more accurate motion vector rate estimation method for encoding with the context adaptive binary arithmetic coding (CABAC) method while still maintaining low computational complexity. The proposed motion vector rate estimation can provide up to 2.26% in rate savings for low bit rate applications when all modes are considered for the encoding. Results for single mode encoding, which can be useful for fast encoding applications, show that we can achieve benefits of up to 27.15% and 7.39% in rate savings for low and medium to high bit rate applications respectively.
Keywords :
adaptive codes; arithmetic codes; binary codes; computational complexity; entropy codes; motion estimation; optimisation; rate distortion theory; table lookup; variable length codes; video coding; H.264/AVC video encoder; Lagrangian cost function; computational complexity; context adaptive binary arithmetic coding; entropy coding; look-up table; motion estimation; motion prediction accuracy; motion vector rate estimation mismatch; rate distortion optimisation; universal variable length coding; Accuracy; Automatic voltage control; Bit rate; Computational complexity; Cost function; Encoding; Entropy coding; Lagrangian functions; Motion estimation; Table lookup; Motion estimation; entropy coding; motion vector rate estimation; rate-distortion optimization;
Conference_Titel :
Image Processing, 2008. ICIP 2008. 15th IEEE International Conference on
Conference_Location :
San Diego, CA
Print_ISBN :
978-1-4244-1765-0
Electronic_ISBN :
1522-4880
DOI :
10.1109/ICIP.2008.4712211