Two-pass MPEG-2 variable-bit-rate encoding
IBM Journal of Research and Development
A novel two-pass VBR coding algorithm for fixed-size storage application
IEEE Transactions on Circuits and Systems for Video Technology
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There have been increasing market demands to develop more effective schemes for applying MPEG video coding standard to meet the challenges from the emerging applications. We present a real-time MPEG video coding system with information look-ahead for constant bit rate (CBR) applications, such as video-on-demand (VoD) over ADSL. This scheme employs two MPEG encoders. Both encoders operate at the same CBR. The second encoder has a buffer to delay the input by an amount of time relative to the first encoder to create a look-ahead window. In encoding, the first encoder collects the information of statistics and rate-quality characteristics. An on-line information processor then uses the collected information to derive the best coding strategy for the second encoder to encode the incoming frames in the look-ahead window. The second encoder uses the encoding parameters from the processor as the coding guide to execute the coding strategy and generate the final bitstream. Results on an IBM MPEG-2 encoder testing system with a 15 frame look-ahead window have shown that the scheme can obtain a 0.6 to 1.6 dB improvement in PSNR over the conventional single encoder on MPEG test video sources. Moreover, measured by the Tektronix Inc.'s picture quality analysis (PQA) system, this scheme achieved 0.87 /spl sim/ 1.35 reduction in PQA measurement. The visual quality improvement is also very evident.