Patent ID: 8413197

Claim:
A key frame delivery method of selecting key frames of a video file by a video delivery server connected over a network to a client device, where the video file is stored on a storage device, the key frame delivery method comprising the steps of: a) storing on the storage device, for each of the respective key frames included in the video file, key frame information including a key frame number that identifies the respective key frame, offset from the beginning of the video file, a relative delivery time of the key frame from the beginning of the video file in a case of delivering the video file at normal play and a size of the key frame; b) determining a cycle delivery time t k , where t k =T 0 +N×k×T and T 0 is the relative start time of a trick play from the beginning of the video file, k is a cycle number of the trick play and N is a reproduction speed of the trick play; c) acquiring a key frame relative delivery time i j of a key frame l j prior and closest to the relative delivery time t k ; d) acquiring a key frame relative delivery time i j+1 of a key frame l j+1 subsequent and closest to the relative delivery time t k ; e) selecting, at the video delivery server, a key frame l k having the delivery time closest to the cycle delivery time t k , where l k is selected from among key frames l j and the l j+1 by comparing |t k −i j | with |i j+1 −t k |; f) transmitting the selected key frame l k to the client device; g) incrementing the cycle number k; and h) repeating steps b) through g), wherein said |t k −i j | is an absolute difference between the relative delivery time t k and the key frame relative delivery time i j of the key frame l j prior and closest to the relative delivery time t k , and wherein said |i j+i −t k | is an absolute difference between the key frame relative delivery time i j+1 of the key frame l j+1 subsequent and closest to the relative delivery time t k .