Patent ID: 8107530

Claim:
A video transcoder comprising: a decoding unit decoding compressed video to generate a video header, a motion vector, and a DCT (discrete cosine transform) coefficient for each frame of the compressed video; a single description/multiple description determining unit determining whether to perform transcoding into a single description or multiple descriptions based on the possibility of errors occurring in a transmission channel of the compressed video; and a transcoding unit performing transcoding into the single description by coding the DCT coefficient together with the video header and the motion vector when the single description/multiple description determining unit determines to perform transcoding into the single description and performing transcoding into the multiple descriptions by dividing the DCT coefficient into a plurality of DCT coefficients and coding each of the DCT coefficients together with the video header and the motion vector when the single description/multiple description determining unit determines to perform transcoding into the multiple descriptions; wherein the transcoding unit comprises: a single description transcoding unit performing transcoding into the single description; and a multiple description transcoding unit performing transcoding into the multiple descriptions, wherein the multiple description transcoding unit includes: a start position determining unit determining a start position of division of the DCT coefficient in a predetermined or desired scanning order according to a frequency characteristic of the DCT coefficient; a DCT coefficient dividing unit causing all data of the DCT coefficient preceding the start position to be included in each of the plurality of divided DCT coefficients and causing data of the DCT coefficient following the start position to be alternatively included in each of the plurality of divided DCT coefficients, thereby generating the plurality of divided DCT coefficients; and a compression coding unit coding each of the plurality of divided DCT coefficients together with the video header and the motion vector, and wherein the start position determining unit determines the start position as follows: Start position= a log 10 ( PLR )+ b where a is the number of pixels included in a macroblock for which the DCT coefficient is calculated, b=2a, 0<Start position<(a−1), and PLR is a packet loss rate in the transmission channel.