# US 8,542,747 B2 · Low latency cadence detection for frame rate conversion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,747 B2 - Document ID: US8542747B2 - Status: Granted - Kind: B2 - Application number: 11/616,192 - Filed: 2006-12-26 - Published: 2008-06-26 - Granted: 2013-09-24 - Earliest claimed: 2006-12-26 - Assignees: Broadcom Corporation - Applicants: Daniel Doswald - Inventors: Daniel Doswald - Web page: https://patentgrep.com/patent/US8542747B2 ## CPC - H04N 7/0135: {involving interpolation processes (interpolation-based image scaling G06T3/4007; interpolation for video coding H04N19/587, H04N19/59)} - H04N 7/0115: {with details on the detection of a particular field or frame pattern in the incoming video signal, e.g. 3:2 pull-down pattern} - H04N 7/0147: {the interpolation using an indication of film mode or an indication of a specific pattern, e.g. 3:2 pull-down pattern} - H04N 7/0127: {by changing the field or frame frequency of the incoming video signal, e.g. frame rate converter} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A frame rate converter sequentially buffers video frames in a sequence of video frames in a buffer and interpolates at least two of the plurality of video frames in the buffer based on at least one interpolation parameter, to form interpolated output frames. Conveniently, the interpolation parameter is adjusted with each newly buffered frame in dependence on the current value of the cadence of the frame sequence. In this way, delays associated with cadence detection may be reduced. ## Claims ### Claim 1 A method of providing frame rate converted video comprising: sequentially buffering a plurality of video frames in a sequence of said video frames in a buffer; analyzing each newly buffered frame in said buffer to determine a change in a current cadence of the sequence relative to a previously detected cadence; adjusting with each newly buffered frame an interpolation parameter based on detecting the change in the current cadence of said sequence relative to the previously detected cadence, wherein the interpolation parameter corresponds to a plurality of future interpolated output frames; and interpolating at least two of said plurality of video frames in said buffer based on said interpolation parameter and a frequency scaling factor to form a plurality of output frames, wherein the frequency scaling factor corresponds to a rate of the plurality of output frames. ### Claim 2 (depends on 1) The method of claim 1, further comprising receiving an indicator of cadence from an upstream video processor. ### Claim 3 (depends on 1) The method of claim 1, wherein said interpolating is performed prior to completion of said analyzing. ### Claim 4 (depends on 1) The method of claim 1, wherein said at least two of said plurality of video frames are chosen based on said current cadence. ### Claim 5 (depends on 4) The method of claim 4, wherein said buffer is a first-in, first out buffer that stores four of said plurality of video frames. ### Claim 6 (depends on 1) The method of claim 1, wherein said interpolation parameter identifies a position of each of said plurality of output frames relative to two of said plurality of video frames in said buffer. ### Claim 7 (depends on 6) The method of claim 6, wherein said interpolating produces said plurality of output frames at twice the rate at which said plurality of video frames are sequentially buffered. ### Claim 8 (depends on 7) The method of claim 7, wherein said interpolation parameter indicates a position in fractional fifths relative to two of said plurality of video frames in said buffer, when said current cadence comprises a 3:2 pull-down pattern. ### Claim 9 (depends on 7) The method of claim 7, wherein said interpolation parameter indicates motion in fractional halves between said plurality of video frames in said buffer responsive to a change in said current cadence from a 3:2 pull-down pattern. ### Claim 10 (depends on 7) The method of claim 7, wherein said interpolation parameter indicates a position in fractional fourths relative to two of said plurality of video frames in said buffer, when said current cadence comprises a 2:2 pull-down pattern. ### Claim 11 (depends on 1) The method of claim 1, wherein said buffer is a first-in, first out buffer that stores at least four of said plurality of video frames. ### Claim 12 (depends on 1) The method of claim 1, wherein said analyzing comprises comparing said newly buffered frame to an immediately previously buffered frame in said buffer. ### Claim 13 (depends on 1) The method of claim 1, further comprising decoding each of said plurality of video frames prior to storing said plurality of video frames in said buffer. ### Claim 14 (depends on 13) The method of claim 13, wherein said current cadence reflects a 3:2 pull-down pattern in said sequence, and said interpolating introduces a delay of 1.5 of said plurality of video frames that are buffered, between newly buffering a video frame in said sequence, and forming one of said plurality of output frames therefrom. ### Claim 15 A video device comprising: a buffer for buffering a sequence of a plurality of video frames, a cadence detector, in communication with said buffer to analyze each newly buffered frame in said buffer to determine a cadence of said sequence of said plurality of video frames, and responsive thereto form a cadence indicator to reflect the cadence; and a frame rate converter for forming a plurality of interpolated video frames from at least two of said plurality of video frames in said buffer in accordance with an interpolation parameter dependent on a change in the cadence indicated by said cadence indicator, wherein the interpolation parameter specifies a fractional motion between adjacent ones of said video frames that is adjusted according to the cadence. ### Claim 16 (depends on 15) The video device of claim 15, wherein said buffer is a first-in, first out buffer. ### Claim 17 (depends on 15) The video device of claim 15, wherein said buffer stores at least four of said plurality of video frames. ### Claim 18 (depends on 15) The video device of claim 15, wherein said buffer stores four of said plurality of video frames. ### Claim 19 (depends on 15) The video device of claim 15, further comprising a video decoder to decode said sequence of said plurality of video frames. ### Claim 20 (depends on 15) The video device of claim 15, wherein said cadence detector compares each newly buffered video frame in said buffer to an immediately previously buffered video frame in said buffer to determine the cadence. ### Claim 21 (depends on 15) The video device of claim 15, wherein said interpolation parameter identifies a position of each of said plurality of interpolated video frames relative to two of said plurality of video frames in said buffer. ### Claim 22 (depends on 21) The video device of claim 21, wherein said frame rate converter produces said plurality of interpolated video frames at twice the rate at which said sequence of said plurality of video frames is buffered. ### Claim 23 (depends on 22) The video device of claim 22, wherein when said cadence indicator indicates a 2:2 pull-down pattern, and said interpolation parameter indicates a position in fractional fourths relative to two of said plurality of video frames in said buffer. ### Claim 24 (depends on 22) The video device of claim 22, wherein when said cadence indicator indicates a 3:2 pull-down pattern, and said interpolation parameter indicates a position in fractional fifths relative to two of said plurality of video frames in said buffer. ### Claim 25 (depends on 24) The video device of claim 24, wherein when said cadence indicator indicates the change in the cadence from the 3:2 pull-down pattern, and said interpolation parameter indicates motion in fractional halves between said plurality of video frames in said buffer. ### Claim 26 (depends on 15) A display comprising the video device of claim 15. ### Claim 27 A method of providing frame rate converted video comprising: sequentially buffering a plurality of video frames in a sequence of said plurality of video frames in a buffer; analyzing each newly buffered frame in the buffer to determine a change in a cadence of the sequence relative to a previously detected cadence; adjusting a plurality of interpolation parameters for a plurality of future interpolated output frames, wherein adjusting is performed responsive to detecting the change in the cadence of the sequence relative to the previously detected cadence, wherein the plurality of interpolation parameters specify a number of fractional motion units (1/m) between adjacent ones of said plurality of video frames, wherein m is a function of the cadence; interpolating at least two of the plurality of video frames in the buffer based on the plurality of interpolation parameters; and outputting the plurality of future interpolated output frames.