Video decoding apparatus, video decoding method, and digital audio/video playback system capable of controlling presentation of sub-pictures

Abstract

A video decoding apparatus capable of controlling presentation of sub-pictures includes a first decoder, a second decoder, a first scaler, a second scaler and a combiner. The first decoder and the second decoder respectively decode a digital audio/video signal to generate a decoded video and a decoded sub-picture. In accordance with an output picture size, the decoded video size, the decoded sub-picture size and a sub-picture aspect ratio, the first scaler and the second scaler generate a first scaling factor and a second scaling factor. The combiner combines the decoded video and the decoded sub-picture according to the first scaling factor and the second scaling factor and outputs the combination thereof. A video decoding method and a digital audio/video playback system capable of controlling presentation of sub-pictures are also disclosed.

What is claimed is: 
     
       1. 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. 
 
     
     
       2. The video decoding apparatus as specified in  claim 1 , wherein:
 the first scaling factor comprises a first horizontal scaling factor and a first vertical scaling factor, in which the first horizontal scaling factor is equal to the horizontal width of the output picture divided by the horizontal width of the decoded video, and the first vertical scaling factor is equal to the vertical height of the output picture divided by the vertical height of the decoded video; and 
 the second scaling factor comprises a second horizontal scaling factor and a second vertical scaling factor while the sub-picture aspect ratio includes a horizontal aspect ratio and a vertical aspect ratio, in which the second horizontal scaling factor is equal to the first horizontal scaling factor divided by the horizontal aspect ratio of the sub-picture aspect ratio, and the second scaling factor is equal to the first vertical scaling factor divided by the vertical aspect ratio of the sub-picture aspect ratio. 
 
     
     
       3. The video decoding apparatus as specified in  claim 2 , wherein the horizontal width of the output picture is the product of the horizontal width of the active display area of the video output device and a horizontal aspect ratio of a video aspect ratio, and the vertical height of the output picture is the product of the vertical height of the active display of the video output device and a vertical aspect ratio of the video aspect ratio. 
     
     
       4. The video decoding apparatus as specified in  claim 1 , wherein if the decoded sub-picture is for the purpose of visual effect, the combiner only sets the size of the decoded video and the size of the decoded sub-picture when combining the decoded video and the decoded sub-picture. 
     
     
       5. The video decoding apparatus as specified in  claim 1 , wherein when the decoding of the sub-picture bit stream generates a plurality of decoded sub-pictures, the combiner further sets the positions of the plurality of decoded sub-pictures so as to avoid overlay among the plurality of decoded sub-pictures. 
     
     
       6. The video decoding apparatus as specified in  claim 1 , wherein the first decoder is an MPEG decoder and the second decoder is a run-length decoder. 
     
     
       7. A digital audio/video playback system capable of controlling presentation of sub-pictures, which is for decoding a digital audio/video signal, outputting an output picture through a video output device, and outputting a decoded audio through an audio output device, the digital audio/video playback system comprising:
 a signal loader which receives the digital audio/video signal; 
 a signal parser which divides the digital audio/video signal into a video bit stream, a sub-picture bit stream, and an audio bit stream; 
 an audio decoder which receives the audio bit stream, decodes the audio bit stream to a decoded audio, and outputs the decoded audio to the audio output device; and 
 a video decoding apparatus, including:
 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 sub-picture according the second scaling factor, combines the decoded video and the decoded sub-picture, and outputs the combined picture to the video output device. 
 
 
     
     
       8. The digital audio/video playback system as specified in  claim 7 , wherein:
 the first scaling factor comprises a first horizontal scaling factor and a first vertical scaling factor, in which the first horizontal scaling factor is equal to the horizontal width of the output picture divided by the horizontal width of the decoded video, the first vertical scaling factor is equal to the vertical height of the output picture divided by the vertical height of the decoded video; and 
 the second scaling factor comprises a second horizontal scaling factor and a second vertical scaling factor while the sub-picture aspect ratio includes a horizontal aspect ratio and a vertical aspect ratio, in which the second horizontal scaling factor is equal to the first horizontal scaling factor divided by the vertical aspect ratio of the sub-picture aspect ratio, and the second vertical scaling factor is equal to the first vertical scaling factor divided by the vertical aspect ratio of the sub-picture aspect ratio. 
 
     
     
       9. The digital audio/video playback system as specified in  claim 8 , wherein the horizontal width of the output picture is the product of the horizontal width of the active display area of the video output device and a horizontal aspect ratio of a video aspect ratio, and the vertical height of the output picture is the product of the height of the active display area of the video output device and a vertical aspect ratio of the video aspect ratio. 
     
     
       10. The digital audio/video playback system as specified in  claim 7 , wherein if the decoded sub-picture is for the purpose of visual effect, the combiner only sets the size of the decoded video and the size of the decoded sub-picture when combining the decoded video and the decoded sub-picture. 
     
     
       11. The digital audio/video playback system as specified in  claim 7 , wherein when the decoding of the sub-picture bit stream generates a plurality of decoded sub-pictures, the combiner further sets the positions of the plurality of decoded sub-pictures so as to avoid overlay among the plurality of decoded sub-pictures. 
     
     
       12. The digital audio/video playback system as specified in  claim 7 , wherein the first decoder is an MPEG decoder, and the second decoder is a run-length decoder. 
     
     
       13. The digital audio/video playback system as specified in  claim 7 , wherein the digital audio/video playback system is a DVD playback system or a digital video broadcasting playback system. 
     
     
       14. A video decoding method capable of controlling presentation of sub-pictures, which is for decoding a digital audio/video signal, 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 method comprising the steps of:
 receiving the video bit stream and decoding the video bit stream to generate a decoded video; 
 receiving the sub-picture bit stream and decoding the sub-picture bit stream to generate at least one decoded sub-picture; 
 capturing the size of the decoded video, and generating a first scaling factor according to the size of the output picture and the size of the decoded video; 
 capturing the size and the position of the decoded sub-picture, and generating 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 
 setting the size of the decoded video according to the first scaling factor, setting the size and the position of the decoded sub-picture according to the second scaling factor, combining the decoded video and the decoded sub-picture, and outputting the combined picture to the video output device. 
 
     
     
       15. The video decoding method as specified in  claim 14 , wherein:
 the first scaling factor comprises a first horizontal scaling factor and a first vertical scaling factor, in which the first horizontal scaling factor is equal to the horizontal width of the output picture divided by the horizontal width of the decoded video, and the first vertical scaling factor is equal to the vertical height of the output picture divided by the vertical height of the decoded video; and 
 the second scaling factor comprises a second horizontal scaling factor and a second vertical scaling factor while the sub-picture aspect ratio includes a horizontal aspect ratio and a vertical aspect ratio, in which the second horizontal scaling factor is equal to the first horizontal scaling factor divided by the horizontal aspect ratio of the sub-picture aspect ratio, and the second scaling factor is equal to the first vertical scaling factor divided by the vertical aspect ratio of the sub-picture aspect ratio. 
 
     
     
       16. The video decoding method as specified in  claim 15 , wherein the horizontal width of the output picture is the product of the horizontal width of the active display area of the video output device and a horizontal aspect ratio of a video aspect ratio, and the vertical height of the output picture is the product of the vertical height of the active display of the video output device and a vertical aspect ratio of the video aspect ratio. 
     
     
       17. The video decoding method as specified in  claim 14 , wherein if the decoded sub-picture is for the purpose of visual effect, only the size of the decoded video and the size of the decoded sub-picture are set when combining the decoded video and the decoded sub-picture. 
     
     
       18. The video decoding method as specified in  claim 14 , wherein the decoded sub-picture is prevented from exceeding the border of the output picture and covering the main region of the decoded video when combining the decoded video and the decoded sub-picture. 
     
     
       19. A video decoding method as specified in  claim 14 , wherein when the decoding of the sub-picture bit stream generates a plurality of decoded sub-pictures, overlay among the plurality of decoded sub-pictures is prevented when combining the decoded video and the decoded sub-pictures. 
     
     
       20. The video decoding method as specified in  claim 14 , wherein the first decoder is an MPEG decoder, and the second decoder is a run-length decoder. 
     
     
       21. 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 a decoded sub-picture;   a first scaler which generates a first scaling factor according to the size of the output picture and the size of the decoded video;   a second scaler which generates a second scaling factor according to a ratio of the first scaling factor and a sub-picture aspect ratio; and   a combiner which sets a displayed size of the decoded video according to the first scaling factor, sets a displayed size and a 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.    
     
     
       22. The video decoding apparatus as specified in claim 21, wherein:
 the first scaling factor comprises a first horizontal scaling factor and a first vertical scaling factor, in which the first horizontal scaling factor is equal to the horizontal width of the output picture divided by the horizontal width of the decoded video, and the first vertical scaling factor is equal to the vertical height of the output picture divided by the vertical height of the decoded video.    
     
     
       23. The video decoding apparatus as specified in claim 22, wherein the second scaling factor comprises a second horizontal scaling factor and a second vertical scaling factor while the sub-picture aspect ratio includes a horizontal ratio and a vertical ratio, in which the second horizontal scaling factor is equal to the first horizontal scaling factor divided by the horizontal ratio of the sub-picture aspect ratio, and the second vertical scaling factor is equal to the first vertical scaling factor divided by the vertical ratio of the sub-picture aspect ratio.  
     
     
       24. The video decoding apparatus as specified in claim 22, wherein the horizontal width of the output picture is the product of the horizontal width of the active display area of the video output device and a horizontal ratio of a video aspect ratio, and the vertical height of the output picture is the product of the vertical height of the active display area of the video output device and a vertical ratio of the video aspect ratio.  
     
     
       25. The video decoding apparatus as specified in claim 21, wherein if the decoded sub-picture is for the purpose of visual effect, the combiner sets the displayed size of the decoded sub-picture according to the first scaling factor when combining the decoded video and the decoded sub-picture.  
     
     
       26. The video decoding apparatus as specified in claim 21, wherein when the decoding of the sub-picture bit stream generates a plurality of decoded sub-pictures, the combiner further sets the positions of the plurality of decoded sub-pictures so as to avoid overlay among the plurality of decoded sub-pictures.  
     
     
       27. A digital audio/video playback system capable of controlling presentation of sub-pictures, which is for decoding a digital audio/video signal, outputting an output picture through a video output device, and outputting a decoded audio through an audio output device, the digital audio/video playback system comprising:
 a signal loader which receives the digital audio/video signal;   a signal parser which divides the digital audio/video signal into a video bit stream, a sub-picture bit stream, and an audio bit stream;   an audio decoder which receives the audio bit stream, decodes the audio bit stream to a decoded audio, and outputs the decoded audio to the audio output device; and   a video decoding apparatus of claim 21.    
     
     
       28. A video decoding method capable of controlling presentation of sub-pictures, which is for decoding a digital audio/video signal, 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 method comprising the steps of:
 receiving the video bit stream and decoding the video bit stream to generate a decoded video;   receiving the sub-picture bit stream and decoding the sub-picture bit stream to generate a decoded sub-picture;   generating a first scaling factor according to the size of the output picture and the size of the decoded video;   generating a second scaling factor according to a ratio of the first scaling factor and a sub-picture aspect ratio; and   setting a displayed size of the decoded video according to the first scaling factor, setting a displayed size and a position of the decoded sub-picture according to the second scaling factor, combining the decoded video and the decoded sub-picture, and outputting the combined picture to the video output device.    
     
     
       29. The video decoding method as specified in claim 28, wherein:
 the first scaling factor comprises a first horizontal scaling factor and a first vertical scaling factor, in which the first horizontal scaling factor is equal to the horizontal width of the output picture divided by the horizontal width of the decoded video, and the first vertical scaling factor is equal to the vertical height of the output picture divided by the vertical height of the decoded video.    
     
     
       30. The video decoding method as specified in claim 29, wherein the second scaling factor comprises a second horizontal scaling factor and a second vertical scaling factor while the sub-picture aspect ratio includes a horizontal ratio and a vertical ratio, in which the second horizontal scaling factor is equal to the first horizontal scaling factor divided by the horizontal ratio of the sub-picture aspect ratio, and the second vertical scaling factor is equal to the first vertical scaling factor divided by the vertical ratio of the sub-picture aspect ratio.  
     
     
       31. The video decoding method as specified in claim 29, wherein the horizontal width of the output picture is the product of the horizontal width of the active display area of the video output device and a horizontal ratio of a video aspect ratio, and the vertical height of the output picture is the product of the vertical height of the active display area of the video output device and a vertical ratio of the video aspect ratio.  
     
     
       32. The video decoding method as specified in claim 28, wherein if the decoded sub-picture is for the purpose of visual effect, the displayed size of the decoded sub-picture is set according to the first scaling factor when combining the decoded video and the decoded sub-picture.  
     
     
       33. The video decoding method as specified in claim 28, wherein the decoded sub-picture is prevented from exceeding the border of the output picture and covering the main region of the decoded video when combining the decoded video and the decoded sub-picture.  
     
     
       34. The video decoding method as specified in claim 28, wherein when the decoding of the sub-picture bit stream generates a plurality of decoded sub-pictures, overlay among the plurality of decoded sub-pictures is prevented when combining the decoded video and the decoded sub-pictures.  
     
     
       35. 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 generates a first scaling factor for scaling the decoded video;   a second scaler which generates a second scaling factor for scaling the decoded sub-picture, wherein the generation of the second scaling factor comprises determining the second scaling factor at least via a calculation that uses the first scaling factor; and   a combiner which sets a displayed size of the decoded video according to the first scaling factor, sets a displayed size and a 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.    
     
     
       36. The video decoding apparatus as specified in claim 21, wherein the combiner sets the displayed size and the position of the decoded sub-picture further according to a relative position relationship between at least two of the decoded video and the at least one decoded sub-picture.  
     
     
       37. The video decoding method as specified in claim 28, wherein in the step of setting the displayed size and the position of the decoded sub-picture according to the second scaling factor, the displayed size and the position of the at least one decoded sub-picture are set further according to a relative position relationship between at least two of the decoded video and the at least one decoded sub-picture.