Sadaf Ahamed

3G/4G Cellular Telephony Figure 1.Typical situation on 3G/4G cellular telephony [8]

Goal of Error Control: Overcome the effect of errors, during the transmission of the video frames in the wireless medium, e.g. packet loss on a packet network on a wireless network. Method used for Error Control : Error Concealment

Purpose of H.264 Higher coding efficiency than previous standards, MPEG- 1,2,4 part 2, H.261, H.263 More error robustness Various applications like video broadcasting, video streaming, video conferencing, D-Cinema, HDTV Network friendliness Simple syntax specifications

Block Diagram of H.264 Encoder Figure 2. Encoder [9]

Block Diagram of H.264 Decoder Figure 3. Decoder [3]

Error Concealment Problem: Transmission errors may result in lost information Goal: Estimate the lost information in order to conceal the fact that an error has occurred Error concealment is performed at the decoder Basic approach: Perform some form of spatial/temporal Concealment to estimate the lost information from correctly received data

Error Concealment(cont.): Spatial Error Concealment: 1.Estimate missing pixels by smoothly extrapolating surrounding pixels. 2.Correctly recovering missing pixels is extremely difficult. Temporal Error Concealment: 1. Copy the pixels at the same spatial location in the previous frame. 2.Effective when there is no motion, potential problems when there is motion.

Compare results of the recovered frames by error concealment technique from MSE: It calculates the “difference” between two images. It can be applied to digital video by averaging the results for each frame. PSNR: The most commonly used objective quality metric is the Peak Signal to Noise Ratio (PSNR). For a video sequence of frames. SSIM: This approach emphasizes that the Human Visual System (HVS) is highly adapted to extract structural information from visual scenes. Therefore, a measurement of structural similarity (or difference) should provide a good approximation to perceptual image quality.

References: [1] H.Zhi-hua and Y.Ben-shun, “A new temporal error concealment algorithm for H.264 using motion strength of neighboring area”, Conference on Education Technology and Computer Science, Vol. 1, pp , Mar [2] X.Xiu., L. Zhuo and L.Shen, “A hybrid error concealment method based on H.264 standard”,International conference on signal processing, Vol 2, Apr [3] S. K. Bandyopadhyay, Z. Wu, P. Pandit and J. M. Boyce, “An error concealment scheme for entire frame losses for H.264/AVC”, Proc. IEEE Sarnoff Symposium, Mar [4] L. Liu, S. Zhang, X. Ye and Y. Zhang, “Error resilience schemes of H.264/AVC for 3G conversational video”, Proc. IEEE CIT, pp , Sept [5] S.Kumar, L.Xu, M. K. Mandal, and S. Panchanathan, ” Error resiliency schemes in H.264/AVC standard,” J. Visual Communication and Image Representation, vol. 17, pp , April [6] S. Wenger, “H.264/AVC over IP” IEEE Trans. Circuits and Systems for Video Technology, vol. 13, pp , July [7] J.Panyavarapom and S.Aramvith, “An error resilient framework using one-pass explicit FMO map generation and error concealment for H.264/AVC wireless video communication”, Journal of electronic imaging. [8] L. Liu, S. Zhang, X. Ye and Y. Zhang, “Error Resilience Schemes of H.264/AVC for 3G Conversational Video”, Proc. IEEE Conf. Computer and Information Technology, pp , Sept [9] Soon-kak Kwon, A. Tamhankar and K.R. Rao, ”Overview of H.264 / MPEG-4 Part 10”, J. Visual Communication and Image Representation, vol. 17, pp , April 2006.