摘要:
If the number of frames in a GOP of an input stream is not less than 15, the GOP is determined as a control unit time. If the number of frames in the GOP is less than 15, the following GOP is connected thereto until the number of frames becomes not less than 15 and the connected GOPs are determined as a control unit time. After correcting the control unit time, the average input bit rate Sn in each control unit time is obtained, and by using information on the input stream including the average input bit rate Sn, a quantization step value of an output stream is calculated.
摘要:
If the number of frames in a GOP of an input stream is not less than 15, the GOP is determined as a control unit time. If the number of frames in the GOP is less than 15, the following GOP is connected thereto until the number of frames becomes not less than 15 and the connected GOPs are determined as a control unit time. After correcting the control unit time, the average input bit rate Sn in each control unit time is obtained, and by using information on the input stream including the average input bit rate Sn, a quantization step value of an output stream is calculated.
摘要:
A quantization step determination part inputs an evaluation value (ACT_MB) indicating the dispersion in a macroblock and its average value (ACT_PIC). A subtracter obtains the difference between these values, and a multiplier multiplies the difference by raq ( 1) to obtain a converted quantization step value (Qstep_AVC). This optimizes a bit allocation in accordance with an Activity value of the macroblock, to thereby improve the quality of image.
摘要:
A category setting part sets a type of a decoded image based on characteristics of the decoded image which are fineness of the decoded image and an intensity of movement of the decoded image. A code amount setting part sets a target code amount of an output image based on the type of the decoded image. A quantization step value setting part sets a quantization step value of the output image based on the target code amount of the output image. A transcoder can set the target code amount of the output image depending on fineness of the decoded image. The transcoder can distribute the target code amount of the output image to a reference image and a predicted image depending on the intensity of movement of the decoded image.
摘要:
A reference differential value calculation part calculates a reference differential value by subtracting an accumulated value of the target amounts of codes from an accumulated value of the amounts of generated codes from the first period to the (n−1) period. A comparison part compares a cumulative differential value obtained by subtracting the cumulative amount of generated codes from the cumulative target amount of codes of the first to m-th picture frames in the n period with the reference differential value. If the cumulative differential value is larger than the reference differential value, stuffing bits are added to the m-th picture frame to be processed by the amount of codes obtained by subtracting the reference differential value from the cumulative differential value.
摘要:
A scene change detection part detects a scene change based on a characteristic amount of an input image. A target code amount setting part executes correction by a correction code amount on a target code amount previously set for suppressing variation of an output code amount around the time of scene change. A quantization step value setting part sets a quantization step value based on the target code amount. That is to say, a transcoder 1 does not detect a scene change by previously reading an input image or by detecting variation of the output code amount.
摘要:
In a transcoder, a decoder decodes a stream and an encoder encodes the stream again. The encoder calculates the quantization step value by using an average period bit rate (ASn(M)) of a first stream or an average period bit rate (ACn(M)) of a second stream. Buffers store bit rates (Sn, Cn) of the first and second streams for M periods, respectively. The encoder uses the average period bit rate (ASn(M)) of the first stream or then average period bit rate (ACn(M)) of the second stream in any one of the periods M1, M2 and M3 among M periods.
摘要:
A reference differential value calculation part calculates a reference differential value by subtracting an accumulated value of the target amounts of codes from an accumulated value of the amounts of generated codes from the first period to the (n−1) period. A comparison part compares a cumulative differential value obtained by subtracting the cumulative amount of generated codes from the cumulative target amount of codes of the first to m-th picture frames in the n period with the reference differential value. If the cumulative differential value is larger than the reference differential value, stuffing bits are added to the m-th picture frame to be processed by the amount of codes obtained by subtracting the reference differential value from the cumulative differential value.
摘要:
A category setting part sets a type of a decoded image based on characteristics of the decoded image which are fineness of the decoded image and an intensity of movement of the decoded image. A code amount setting part sets a target code amount of an output image based on the type of the decoded image. A quantization step value setting part sets a quantization step value of the output image based on the target code amount of the output image. A transcoder can set the target code amount of the output image depending on fineness of the decoded image. The transcoder can distribute the target code amount of the output image to a reference image and a predicted image depending on the intensity of movement of the decoded image.
摘要:
A generated code amount accumulation part adds up the amounts of generated codes of pictures in 1 GOP which are encoded up to the current stage. An upper limit code amount accumulation part adds up the upper limit amounts of codes of the pictures in the 1 GOP which are encoded up to the current stage. A transmission load of an image transmission system is taken into consideration in the setting of the upper limit amount of codes. An update ratio setting part outputs an update instruction to lower a target rate when the accumulated amount of generated codes exceeds the accumulated upper limit amount of codes. The update ratio setting part does not output the update instruction for lowering the target rate when the accumulated amount of generated codes does not exceed the accumulated upper limit amount of codes. A transcoder can predict whether or not there is a possibility that the load of transmitting image data will increase while each picture in 1 GOP is encoded.