Network Optimization for Broadcast Contribution Services Under H.264 Hi422 Profile

摘要

This paper addresses the cascaded encoding-decoding cycles involved in broadcast contribution services and production chains and evaluates the performance of the High 422 profile of H.264 in terms of both video quality and bandwidth requirements. Several encoding-decoding concatenation processes are common in the production workflow, involving different format conversions, such as 422 to 420 chroma down-sampling, image resizing, and pixel shifting, which all significantly increase quality losses. Exhaustive simulations using three multigeneration encoding-decoding cycles are herein carried out using the High 422 profile. The results show that close to 1 dB quality losses and a 30% bit rate penalty are obtained for the third generation. With the aim of comparing the performances of the 422 and 420 H.264 profiles, the experiments were repeated for the High profile (420) of H.264. The results show a worse performance for 420 encoding, requiring increasing the bit rate by up to 15%, compared with the High 422 profile in order to achieve the same video quality. Thus, broadcasters and network operators can reduce their bandwidth estimations for contribution links and information technology networks.