New DCT-domain transcoding using split and merge technique

For the conventional downscaling video transcoder, the video server would be to first decompress the video, perform the downscaling operation in the pixel domain, and then recompress it. This is computational intensive. However, it is difficult to perform video downscaling in the DCT-domain since the prediction errors of each frame are computed from its immediate past higher resolution frames. Besides, the motion vector need to resample due to the size of the video is changed. Due to the mismatch of the resampled motion vector with the incoming DCT coefficients, the video transcoder need to recalculate the new DCT coefficient with lower resolution in pixel domain; this can create undesirable complexity as well as introduce re-encoding error. In this paper, we propose a new architecture to obtain the new DCT coefficients and the new motion vector by reuse the incoming motion vector and DCT coefficients. Since our proposed transcoder is mainly performing in DCT domain, low computational complexity can be achieved as well as the re-encoding can be reduced. Experimental result show that our proposed video downscaling transcoder can lead to significant computational savings as well as provide a high video quality compared to the conventional approach.