Caption processing for MPEG video in MC-DCT compressed domain

  • Authors:

  • Jongho Nang;Ohyeong Kwon;Seungwook Hong

  • Affiliations:

  • Dept. of Computer Science and Engineering, Sogang University, 1 Shinsoo-Dong, Mapo-Ku, Seoul 121-742, Korea;Dept. of Computer Science and Engineering, Sogang University, 1 Shinsoo-Dong, Mapo-Ku, Seoul 121-742, Korea;Dept. of Computer Science and Engineering, Sogang University, 1 Shinsoo-Dong, Mapo-Ku, Seoul 121-742, Korea

  • Venue:
  • MULTIMEDIA '00 Proceedings of the eighth ACM international conference on Multimedia
  • Year:
  • 2000

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Abstract

The (cinema) caption processing that adds descriptive texts on the sequence of frames is an important video manipulation function that video editor should support. This paper proposes an efficient MC-DCT compressed domain approach to insert the caption into the MPEG-compressed video stream. It basically adds the DCT blocks of the caption image to the corresponding DCT blocks of the input frames one by one in MC-DCT domain as in [5]. However, the strength of the caption image is adjusted in the DCT domain to prevent the resulting DCT coefficients from exceeding the maximum value that is allowed in MPEG. In order to adjust the strength of caption image adaptively, we should know the exact pixel values of input image that is a difficult task in DCT domain. We propose an approximation scheme for the pixel values in which the DC value of a block is used as the expected pixel value for all pixels in that block. Although this approximation may lead some errors in the caption area, it still provides a relatively high image quality in the non-caption area, while the processing time is about 4.9 times faster than the decode-captioning-reencode approach.