초록 ▼

Methods and apparatus for performing synchronization and DC-offset compensation in FM transmission systems significantly reduce the overhead associated with transmitting a conventional digital preamble at the start of each of a succession of transmitted digital data packets. According to exemplary e

Methods and apparatus for performing synchronization and DC-offset compensation in FM transmission systems significantly reduce the overhead associated with transmitting a conventional digital preamble at the start of each of a succession of transmitted digital data packets. According to exemplary embodiments, a multi-part digital preamble includes a short, substantially DC-free leading part followed by a code-protected synchronization part which is not necessarily substantially DC-free. The leading part provides for coarse DC offset estimation and synchronization, while the coded synchronization part carries timing and/or other useful information which can be unique for each packet. One or more substantially DC-free trailing parts follow the synchronization part, or are included in the synchronization part itself, and provide for fine tuning of the DC-offset estimate. Since the substantially DC-free leading and trailing parts are extremely short, and since the synchronization part carries useful information, the overhead associated with a preamble according to the invention is significantly reduced as compared to a conventional, entirely DC-free, preamble.

대표청구항 ▼

Methods and apparatus for performing synchronization and DC-offset compensation in FM transmission systems significantly reduce the overhead associated with transmitting a conventional digital preamble at the start of each of a succession of transmitted digital data packets. According to exemplary e

Methods and apparatus for performing synchronization and DC-offset compensation in FM transmission systems significantly reduce the overhead associated with transmitting a conventional digital preamble at the start of each of a succession of transmitted digital data packets. According to exemplary embodiments, a multi-part digital preamble includes a short, substantially DC-free leading part followed by a code-protected synchronization part which is not necessarily substantially DC-free. The leading part provides for coarse DC offset estimation and synchronization, while the coded synchronization part carries timing and/or other useful information which can be unique for each packet. One or more substantially DC-free trailing parts follow the synchronization part, or are included in the synchronization part itself, and provide for fine tuning of the DC-offset estimate. Since the substantially DC-free leading and trailing parts are extremely short, and since the synchronization part carries useful information, the overhead associated with a preamble according to the invention is significantly reduced as compared to a conventional, entirely DC-free, preamble. it in the memory bank. 13. The article of claim 8 in which the first and second images are images in a sequence of video images. 14. The article of claim 8 in which the matches approximate the motion of the pixel blocks in the second image from the first image to the second image or in the first image from the second image to the first image. 15. A method comprising: receiving a succession of related images containing pixels; and estimating the motion of two first and second, different, current pixel blocks in a first image in the succession of related images from a second image that is temporally adjacent to the first image in the succession of related images by comparing both of the two current pixel blocks with the same stored pixel blocks from the second image, stored in internal memory. 16. The method of claim 15 further comprising estimating the motion of one or more pixel blocks in the first image that are contiguous to the current pixel blocks with the pixel blocks from the second image stored in internal memory. 17. The method of claim 15 further comprising storing the pixel blocks in the second image in memory banks included in internal memory. 18. The method of claim 15 further comprising dividing the second image into X rows of Y rows each. 19. The method of claim 18 further comprising storing single columns of Y pixel blocks in each row in the memory banks starting with the first of the X rows and moving from left to right. ed feature points calculated as a percentage, where the percentage of initiated feature points is the number of new feature points divided by the total number of feature points in the current frame, and the percentage of terminated feature points is the number of removed feature points divided by the total number of feature points in the previous frame. 9. A method according to claim 7, wherein feature points in the frames of the video signal are extracted using both kinematic components and photometric components. 10. A method according to claim 7, wherein when the video signal is a compressed video signal comprising I-frames, only the I-frames are decoded and used as input frames for determining shot boundaries and selecting key frames. 11. An apparatus for extracting key frames from a video signal, comprising: means for measuring the number of new or lost feature points between consecutive frames, means for determining shot boundaries in the video signal when the number of new or lost feature points is above a certain threshold value, and means for selecting as a key frame, a frame located between two shot boundaries when the number of new or lost feature points matches a predetermined criteria. 12. An apparatus according to claim 11, wherein the threshold value is defined as a maximum between terminated and initiated feature points calculated as a percentage, where the percentage of initiated feature points is the number of new feature points divided by the total number of feature points in the current frame, and the percentage of terminated feature points is the number of removed feature points divided by the total number of feature points in the previous frame. 13. An apparatus according to claim 11, further comprising: means for selecting the key frame as a frame for which the number of new or lost feature points is constant for a number of consecutive frames in the video signal. 14. An apparatus according to claim 11, further comprising: means for selecting the key frame as a frame for which the number of new or lost feature points corresponds to a local minima between two shot boundaries or for which the number is below a certain pre-set threshold value. 15. An apparatus according to claim 11, wherein when the video signal is a compressed video signal comprising I-frames, the apparatus further comprises: means for only decoding the I-frames and using the I-frames as input frames for determining shot boundaries and selecting key frames. 16. An apparatus according to claim 11, further comprising: means for extracting feature points in the frames of the video signal using both kinematic components and photometric components of the video signal. 17. An apparatus for shot boundary detection in a video signal, comprising: means for measuring the number of new or lost feature points between consecutive frames, and means for determining shot boundaries in the video signal when the number of new or lost feature points is above a certain threshold value. 18. An apparatus according to claim 17, wherein the threshold value is defined as a maximum between terminated and initiated feature points calculated as a percentage, where the percentage of initiated feature points is the number of new feature points divided by the total number of feature points in the current frame, and the percentage of terminated feature points is the number of removed feature points divided by the total number of feature points in the previous frame. 19. An apparatus according to claim 17, further comprising: means for extracting feature points in the frames of the video signal using both kinematic components and photometric components of the video signal. 20. An apparatus according to claim 17, wherein when the video signal is a compressed video signal comprising I-frames, the apparatus further comprising: means for only decoding the I-frames and using the decoded I-frames as input frames for determining shot boun daries. 21. A system for video summarization comprising an apparatus according to claim 11.