Enhanced Video Stream Switching Schemes for H.264
Two enhanced video stream switching schemes for H.264 are proposed aiming at prompt switching among compressed video streams coded at different quality levels and bit rates. The stream switching scheme using primary and secondary SP/SI pictures in H.264 is effective in switching, but degrades the compression efficiency of the transmitted stream even if the switching operation does not take place. In the two proposed schemes, no modification is made to the original compressed streams (namely, no primary SP picture is adopted) so that compression efficiency is maintained at switching points. As a result, switching points can be assigned flexibly in our enhanced schemes according to the need of applications and network conditions without worrying about the bit rate overhead. When switching occurs, the proposed schemes use a new picture type-DIFF (difference picture) in different ways to compensate the mismatch of reference frames. The first proposed scheme is designed to simplify the implementation while the second scheme is designed to further reduce the bit rate overhead. It is shown by experimental results that both of the proposed schemes outperform the switching scheme defined in H.264 and they are able to realize prompt stream switching without noticeable quality degradation and have a small bit rate overhead only when the actual switching operation occurs