In Video On Demand Service System, it is not easy to implement FF/R(Fast Forward/Reverse) function with the limited bandwidth of transport channel and limited capacity of storage media of video server. In this paper, we propose a new scheme to provide FF/R fuction to users.
The proposed scheme is to use only I and P pictures obtained by sampling MPEG2 bitstream. New frame_rate for FF/R play is specified with parameters of MPEG2 syntax, frame_rate_value in sequance header and frame_rate_extension_n/d in sequance extension. Bits of I and P pictures are reduced in three steps to provide FF/R function without any additional bandwidth allocation : VLD, inverse quantization and requantization with increased quantization step size, which can be processed in real-time.
The stored scheme requires large storage media in video server to store specific bitstream for FF/R function. Image quality of each picture in the proposed scheme is a little worse than that in the stored scheme. However, we could not perceive the degradation in the image quality during FF/R operations. The proposed scheme is more economical in the sense that it can provide FF/R function without any additional requirement on the bandwidth and on the storage media in video server.
