Patent ID: 7844168

Claim:
A video decoding apparatus capable of controlling presentation of sub-pictures, which is for decoding a digital audio/video signal and outputting an output picture through a video output device, wherein the digital audio/video signal includes a video bit stream and a sub-picture bit stream, the video decoding apparatus comprising: a first decoder which receives the video bit stream and decodes the video bit stream to generate a decoded video; a second decoder which receives the sub-picture bit stream and decodes the sub-picture bit stream to generate at least one decoded sub-picture; a first scaler which captures the size of the decoded video and generates a first scaling factor according to the size of the output picture and the size of the decoded video; a second scaler which captures the size and the position of the decoded sub-picture and generates a second scaling factor according to the size of the output picture, the size of the decoded sub-picture, and a sub-picture aspect ratio; and a combiner which sets the size of the decoded video according to the first scaling factor, sets the size and the position of the decoded sub-picture according to the second scaling factor, combines the decoded video and the decoded sub-picture, and outputs the combined picture to the video output device.