• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A video encoding method comprising: determining a first ratio (IPRATIO) based on previously encoded image frames of a video sequence comprising one or more intra (I) encoded images and one or more predicted images. (P), the first ratio (IPRATIO) being calculated on the basis of the ratio between the size of one or more previously coded intra-encoded images and the size of one or more predicted images previously encoded; and determining a quantization parameter (QP) to be applied to a frame to be encoded based on the first report (IPRATIO).
    公开号:FR3024313A1
    申请号:FR1457229
    申请日:2014-07-25
    公开日:2016-01-29
    发明作者:Pascal Eymery；Christophe Chong-Pan
    申请人:ALLEGRO DVT；
    IPC主号:
    专利说明:

    [0001] TECHNICAL FIELD This invention relates to the field of video coding, and in particular to a constant or variable bit rate video encoder and a video coding method.
    [0002] BACKGROUND OF THE PRIOR ART In some applications it is desirable to encode a video sequence so that the compressed video does not exceed a given bit rate. For example, this may be due to the fact that the compressed video has to be transmitted on a transmission interface having a limited transmission bit rate, or that there is an output buffer on the transmit side and / or a buffer entrance on the receiving side of limited sizes. The bit rate of the compressed video can be adjusted by controlling the compression ratio applied by the encoding algorithm. However, existing solutions for controlling the compression ratio tend to be complex, slow and / or unable to achieve the desired bit rate while also maintaining high video quality.
    [0003] There is therefore a need in the art for a video encoder and a video encoding method which can control the compression ratio in a simple and efficient manner, while maintaining a high quality of video. SUMMARY An object of embodiments of the present disclosure is to at least partially meet one or more needs of the prior art. In one aspect, there is provided a video encoding method comprising: determining a first report based on previously encoded picture frames of a video sequence comprising one or more intra-encoded images and one or more predicted images, the first ratio being calculated on the basis of the ratio between the size of one or more previously encoded intra-encoded images and the size of one or more predicted images previously encoded; and determining a quantization parameter to be applied to a frame to be encoded based on the first report. According to one embodiment, the first ratio is determined on the basis of a previous value of the first report and a last ratio between the coded size of the last of the intra coded images to be encoded and that of the last of the predicted images. to code. According to one embodiment, the first ratio is determined on the basis of the following equation: PREVIOUS_IPRATio + LATEST_IPRATIo / PRATIO = COUNT_IPRATIOS where PREVIOUS IP RATIO is the previous value of the first report, W is a weighting applied to the previous value of the first report, LATEST_IP RATIO is the last report, and COUNT IP RATIOS is a value determined on the basis of the following equation: COUNT_IP PREVIOUS_COUNT_IPRATIos + 1 - RATIOS = 147 3024313 'B13072EN 3 where PREVIOUS COUNT IP RATIOS is the previous value of COUNT_IPRATIOS- According to one embodiment, the determination of the quantization parameter comprises: determining the size of a sliding window of N frames of previously encoded images of the video sequence, the sliding window comprising one or more of the intra-encoded images and a or more than one predicted picture, where N is an integer greater than or equal to three; determining a target size of the sliding window based on at least the first report; and determining the quantization parameter to be applied to a frame to be encoded based on the comparison of the size of the sliding window to the target size of the sliding window. According to one embodiment, the sliding window 15 further comprises one or more bi-predicted images; and determining the target size of the sliding window is further based on a second ratio representing the ratio of the size of one or more of the predicted images to the size of one or more of the bi-predicted images.
    [0004] According to one embodiment, the target size of the sliding window is determined on the basis of a target size of a group of successive images comprising the number of images counted from an intra coded image up to , but not inclusive, a next intra coded image.
    [0005] According to one embodiment, the target size of the sliding window is determined on the basis of the following equation: GOPTARGET_SIZE SWTARGET_S1ZE = (N1_SW X 1PRATIO NP_SW) X ne I 11 RATIO ± NPGOP where NI sw is the number of images intra coded in the sliding window, Np sw is the number of predicted images in the sliding window, (2, n1D --- TARGET SIZE is the target size of the successive image group, IPRATIO is the first report and Np Gop is the number of predicted images in the group of successive images.
    [0006] According to one embodiment, the target size of the group of successive images is determined on the basis of the following equation: BITRATETARGET x GOP_LENGTH FRAMERATE 5 where BITRATETARGET is a target bit rate of the encoded video stream, GOP LENGTH is the number of frames in the picture group, and FRAME RATE is the frame rate of the video clip. According to one embodiment, determining a quantization parameter to be applied to a frame to be encoded comprises determining a correction factor to be applied to a preceding quantization parameter by dividing the size of the sliding window by the size. target of the sliding window. According to one embodiment, the quantization parameter has a logarithmic relationship with the bit rate, and the quantization parameter is determined by applying the correction factor to a determined linearized value by linearizing the preceding quantization parameter. According to one embodiment, the quantization parameter is determined based on the following equation: NEWQP = h2p (hs (OLDQP) xCORRECTION_FACTOR) where OLDQP is the previous quantization parameter, FACTOR CORRECTION is the correction factor, fQs is a linearization function for linearizing the preceding quantization parameter and fQp is the inverse of the linearization function. In another aspect, there is provided a video encoder including a rate control circuit adapted to: determine a first ratio based on previously encoded picture frames of a video sequence comprising one or more intra and one or more images. p_rdites, the first ratio being calculated as being the ratio between the size of one or more intra coded pictures previously encoded and the size of one or more previously coded predicted pictures; and determining a quantization parameter to be applied to a frame to be encoded based on the first report. According to one embodiment, the rate control circuit is further adapted to: determine the size of a sliding window of N frames of previously encoded pictures of a video sequence, the sliding window comprising one or more of intra coded images and one or more of the predicted images, where N is an integer greater than or equal to three; determining a target size of the sliding window based on at least the first report; and determining the quantization parameter to be applied to a frame to be encoded based on the comparison of the size of the sliding window to the target size of the sliding window. According to one embodiment, the sliding window 15 further comprises one or more bi-predicted images; and determining the target size of the sliding window is further based on a second ratio representing the ratio of the size of one or more of the predicted images to the size of one or more of the bi-predicted images.
    [0007] According to one embodiment, the rate control circuit is adapted to determine the first ratio based on a previous value of the first ratio and a last ratio between the encoded size of the last of the intra coded images to be encoded. and the last of the predicted images to code.
    [0008] BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other features and advantages will become apparent from the following detailed description of embodiments, given by way of illustration and not limitation, with reference to the accompanying drawings in which: FIG. 1 schematically illustrates a video transmission system according to an exemplary embodiment; Fig. 2 is a diagram showing frames of video forming groups of pictures according to an exemplary embodiment of the present description; and FIG. 3 is a flowchart illustrating steps in a video encoding method according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION Although in the following description the particular encoding standard used to compress the video data has not been described in detail, it will be apparent to those skilled in the art that the embodiments described herein could be to apply to a big one. range of video compression standards, such as the ISO H.264 MPEG4 AVC standard, the MPEG-2 video standard, the VP9 standard, and the MPEG HEVC (High Efficiency Video Coding) standard. Figure 1 schematically illustrates a video transmission system according to an exemplary embodiment. On a TX transmit side, the system includes an encoder (ENCODER) 102, which receives uncompressed frames of a video signal (VIDEO), and encodes the frames based on a quantization parameter QP. As known to those skilled in the art, the quantization parameter determines the compression rate used by the encoder to encode at least some of the video data, and thereby influences the number of data bits encoded for a number given bits of input data. The lower the QP, the greater the number of bits in each compressed frame, and therefore the video signal that will be recovered after decoding will generally be of higher quality. On the contrary, increasing QP will result in a reduction in the number of bits and will often lead to a reduction in the quality of the video. For example, according to ISO H.264, the quantization parameter is a value between 0 and 51 which determines the size of the quantization step. The relationship between QP and the compression ratio is logarithmic. In many cases, it can be considered that there is a general rule that when QP decreases by 6 units, the number of coded data bits doubles.
    [0009] Other encoding standards may use other types of quantization parameters to determine, at least to a certain extent, the amount of compression that must be applied during the coding of the video signal.
    [0010] Referring again to FIG. 1, the quantization parameter supplied to the encoder 102 is for example generated by a RATE CONTROL block 103, based on previously encoded frames. The flow control block 103 is for example implemented by a hardware circuit such as an ASIC 10 (application specific integrated circuit) or an FPGA (field programmable integrated circuit). Alternatively, the functions of the rate control block 103 could be implemented at least partially by software, in other words by a processing device under the control of instructions stored in an instruction memory. The video signal to be encoded by the encoder 102 is for example received from a capture device (CAPTURE DEVICE) 104, for example a camera, on the transmitter side. Alternatively, the video could be stored or stored in a memory (not shown in FIG. 1) on the transmitter side and retrieved from the memory by the encoder 102. The encoder 102, for example, provides a compressed output stream of video to a buffer the output side (0 / P BUFFER) 106 on the transmitter side, which stores the compressed video data packets 25 until they can be transmitted on a transmission interface 107. The transmission interface 107 is for example a wired interface, like a serial interface. Alternatively, in some embodiments, the transmission interface 107 could be a wireless interface. The length of the transmission interface 107, in other words the distance between the transmitter and receiver sides of the system, could be between a few tens of centimeters, for example 50 cm, and tens of meters, or more, depending on the application. In some cases, the transmission interface could include one or more intermediate networks, including the Internet. In addition, the video data stored in the output buffer could be in the form of a file, which could be saved in a memory card before being transmitted. The transmission of the compressed video data is, for example, performed at a constant bit rate determined by the capabilities of the transmission line. On the receiver side RX, the compressed video data is for example received by an input buffer (I / P BUFFER) 108. The video compression data is then read in the input buffer 108 by a decoder ( DECODER) 110, which decodes the video stream to provide a VIDEO uncompressed video signal which will generally be a slightly degraded version of the original VIDEO signal. In some embodiments, the decoded video is displayed on a display (DISPLAY) 112 on the receiver side. Although FIG. 1 illustrates an example of a system comprising a transmission interface 107 between the TX transmitter side and the RX receiver side, in alternative embodiments only the encoder 102 and the flow control block 103 could be provided. , and the encoded video stream could be stored in a memory and / or written on a digital storage medium such as a DVD (Digital Versatile Disc). FIG. 2 is a diagram showing an example of a sequence of frames, each represented by a rectangle 25 with a letter I, P or B respectively corresponding to an intra (I) coded picture, a predicted picture (P) and a bi-predicted picture (B). As is known in the art, an intra coded picture is encoded only on the basis of data from the frame itself, whereas a predicted picture is encoded in general using at most one motion vector to predict each image block, and a bi-predicted image is encoded in general using up to two motion vectors to predict each image block. In some embodiments, the frame sequence may comprise only intra-coded images and predicted images.
    [0011] A group of images (GOP) is for example defined as two or more successive images of the video sequence, comprising at least one intra coded image. In the example of FIG. 2, each group of images comprises an intra-coded picture 5 (I) followed by 9 other predicted (P) and bi-predicted (B) images, after which there is another intra-coded picture ( I). Figure 2 shows four images of a GOPi image group on the right of the figure, a previous GOPi_l group of ten images in the center of the figure, and four images of an earlier GOPi_2 image group on the left. of the figure. A sliding window SW is also defined as being a block of the last N images that have been encoded. In the example of FIG. 2, N is 15. It will be assumed that the third image of group GOPi is the last image to be encoded, and the sliding window SW is therefore shown including this image and 14 other images. previously coded. More generally, the sliding window comprises, for example, at least three images, and in certain embodiments, the sliding window corresponds to a duration of approximately 1 second of video, for example between 0.5 and 2 seconds. As will become clear in the following, the size of the sliding window is a compromise, since the larger it is, the lower the difference in quality between two consecutive images, but the less the flow control will be responsive in the monitoring of the 25 changes of scene. A method for controlling the bit rate during video coding based on the groups of images and the sliding window of FIG. 2 will now be described in more detail with reference to a flowchart in FIG.
    [0012] The method of FIG. 3 is for example applied each time a new image has been coded. Alternatively, it could be applied each time a few images have been encoded, for example, after encoding each group of GOPi images.
    [0013] In an operation 301, coded image size ratios are determined. For example, in the case where the video sequence comprises intra, predicted and bi-divided encoded images, an IP RATIO ratio is determined, for example, which represents the size ratio between intra coded images and predicted images in the coded sequence. , and a ratio -PBRATIO is for example determined, which represents the ratio between predicted images and bi-predicted images in the coded sequence. In the case where there are only intra coded images and predicted images in the sequence, only the RATIO IP ratio is provided. Reports are variables that are periodically recalculated based on one or more previously encoded images of each type. For example, the ratios can be determined in the following manner based on the sizes of the last images of each group that have been encoded: IPratio = last_I_picture size / lastPpicturesize, and PBratio = last_P_picture_size / last_Bpicture size where last I picture size is the Normalized size of the last intra coded picture that was coded, lastPpicture_size is the normalized size of the last coded predicted picture, and last B picture size is the normalized size of the last coded bi-predicted picture. The sizes of the last intra image, the last predicted image and / or the last coded bi-predicted image are, for example, normalized if they have been coded on the basis of different QP values between them. For example, normalization could be done on the assumption that when QP decreases by 6 units, the number of coded data bits doubles.
    [0014] Alternatively, the ratios can be calculated based on more than one previous image of each size. For example, reports are calculated as the average of one or more previous reports, as we will now describe in the case of the RATIO report. The ratio PB RATIO can be calculated in the same way. For example, the RATIO IP ratio is calculated on the basis of the following formula: 1PRATIO = COUNT_IPRATIOS PREVIOUS_IPRAPio + LATEST_IPRATIo 5 where PREVIOUS_IP RATIO is a previous value of the IP RATIO report, W is a weighting applied to the previous report, LATEST IP RATIO is the ratio of the size of the last intra coded picture to the last coded predicted picture, and COUNT IP RATIOS is a value representing the number of reports, which is, for example, determined based on the following formula: PREVIOUS_COUNT_IPRATios COUNT_I- PRATIOS = + 1 where PREVIOUS COUNT IP RATIOS is the previous value of COUNT IP RATIOS. Thus, for each newly encoded I or P picture, a new last LATEST IP RATIO report is computed, the current IPRATIO becomes the previous PREVIOUS_IP RATIO report, and the aforementioned formulas are used to determine the new IP report. In one embodiment, the weighting W is greater than or equal to 2, thus giving greater weight to the last IP ratio compared to previous IP reports. Referring again to Figure 3, in a subsequent operation 302, the current size Ssw of the sliding window is, for example, determined. In particular, this involves, for example, summing the sizes of the last N images. Alternatively, other techniques could be used to determine or estimate the size of the sliding window, such as removing the oldest image from the sliding window, and adding the latest coded images, so that the new size 30 New Ssw of the sliding window is equal to Old Ssw-Sp [cn] + Sp [c], where Old Ssw is the previous size of the sliding window, 3024313 B13072 12 Sp [cn] is the size of the image located with n images before the current image, and Sp [c] is the last coded image. In a next operation 303, a target size T5 of the sliding window is determined, based on the ratios determined in the operation 301. For example, this includes determining a target size of each group of GOP images. For example, in the case where there are only intra coded images and predicted images, the target size of the sliding window (SW TARGET SIZE) is determined based on the following equation: GOPTARGET_SIZE SW TARGET_SIZE - ISW X 1PRATIO NPSW) X ID RATIO + NPGOP where NI _SW is the number of intra-coded images in the sliding window, Np SW is the number of predicted images in the sliding window, nc0 --- TARGET SIZE is the target size of the group 15 and Np Gop is the number of predicted images in each group of images. Alternatively, in the case where there are intra, predicted and bi-predicted encoded images, the target size of the sliding window is determined based on the following equation: SWTARGETSIZE = (NI SW X 1PRATIO NP_SW where NB SW is slippery, and GOPTARGETSIZE 1PRATIO NP_GOP NB_GOP X PBRATIO the number of bi-predicted images in the window NB GOP is the number of bi-predicted images in NB SW X BPRATIO) X 25 each group of images. The target size of the GOP image group is for example determined on the basis of the following equation: BITRATETARGET x GOP_LENGTH GOPTARGETSIZE - FRAME_RATE 3024313 B13072EN 13 where BITRATE TARGET is a target bit rate of the coded video stream, GOP LENGTH is the number in the image group, and FRAME RATE is the frame rate of the video clip. In a subsequent operation 304, the size Ssw of the sliding window is for example compared to the target size Tsw of the sliding window to determine whether the effective size SSW exceeds the target size Tsw or not. On the basis of the comparison, the quantization parameter is adjusted. For example, if in operation 304 the size of the sliding window is not greater than the target size, in a subsequent operation 305, the current quantization parameter QP is maintained, or reduced. For example, if the size of the sliding window is within a given percentage limit relative to the target size, for example, 5 percent, the current QP is maintained. If, however, the size of the sliding window is more than 5 percent smaller than the target size, QP is reduced, in order to increase the bit rate of the video sequence and thereby increase the quality of the video. The process returns to operation 301, where a next frame is processed. In the other case, if in operation 304 we find that the size of the sliding window Ssw is greater than the target size Tsw, in a subsequent operation 306, the quantization parameter is for example increased. The process then returns to operation 301, in which a next frame is processed. In some embodiments, the quantization parameter is adjusted based on a correction factor. For example, the correction factor is determined on the basis of the following equation: CORRECTION FACTOR = Ssw / Tsw The correction factor is, for example, applied linearly to the quantization parameter. Indeed, the quantization parameter generally has a logarithmic relationship with the bit rate of the output video stream.
    [0015] For example, in some cases, when QP increases by 6 units, the number of coded data bits doubles. The correction factor is therefore for example applied to a linearized value of the quantization parameter, and the linearized value 5 and then reconverted to a logarithmic value. For example, a new quantization parameter (NEWQP) is determined based on the following equation: NEWQP = fQp (hs (OLDQP) xCORRECTION_FACTOR) where OLDQP is the previous quantization parameter, 10 FACTOR CORRECTION is the correction factor, for example equal to the size of the sliding window SSW divided by the target size of the sliding window TSW, fQs is a linearization function for linearizing the preceding quantization parameter and fQp is the inverse of the linearization function.
    [0016] The linearization function is for example based on the following equation: fQs (QP) = 0.85 * 2 (QP-12) / 6 The inverse of the linearization function is for example based on the following equation: (QS) = 12 + 6 * log2 (QS / 0.85) In alternative embodiments, the correction factor is used to modify QP by calculating a difference value DIFF based on the following equation: DIFF - (SsW -FOCUS_SIZE) * 100 / FOCUS_SIZE 25 where Ssw 'is the size of the previous sliding window, and FOCUS SIZE is a value between the size of the previous sliding window and the size of the sliding target window TSW. For example, FOCUSSIZE is determined by the following equation: FOCUS SIZE = TARGET SIZE + (TARGET_SIZE x CURRENT _ERROR x FRAME _RATE) (SPEED_COEFF x TARGET _BITRATE) 3024313 'B13072EN 15 where CURRENT ERROR is an error value equal to SswPREDICTED Ssw, where Ssw is the current sliding window size and PREDICTED_Ssw is the predicted sliding window size, and SPEED COEFF is a coefficient determined based on the error value, for example based on the next table applied from the top downwards: CURRENT ERROR SPEED COEFF> = 0,20 x BITRATETARGET 2> = 0,15 x BITRATETARGET 3> = 0,10 x BITRATETARGET 4> -0,10 x BITRATETARGET None> -0,15 x BITRATETARGET 4> - 0.20 x BITRATETARGET 3 Elsewhere 2 Of course, the above chart is just one example, and it will be clear to those skilled in the art that various choices of 10 error thresholds and velocity coefficients correspondents would be possible. The value FOCUS SIZE thus determines the speed with which the size of the sliding window converges to the target size, and is, for example, calculated so as not to converge rapidly to the target size when the error is small, thus avoiding differences. brutal quality between one image and the next. The quantization parameter is then adjusted for example on the basis of the calculated difference DIFF. For example, the quantization parameter is changed by a determined AQP amount using the rules defined in the following table, applied from top to bottom: DIFF AQP> 100% +4> 50% +3> B13072 30% +2> 15% +1> = -24% 0> = -34% -1> = -50% -2 Otherwise -3 Of course, the table above is just an example, and It will be apparent to those skilled in the art that various threshold choices and corresponding changes in the quantization parameter would be possible. In alternative embodiments, other algorithms may be used to determine the updated quantization parameter. An advantage of the embodiments described herein is that the bit rate of the encoded video can be controlled simply and efficiently to stay close to a target bit rate, while maintaining high video quality. In particular, by basing the computation on a sliding window of three or more images, the changes in the quantization parameter will be relatively smooth. With the description thus made of an illustrative embodiment, various variations, modifications and improvements will readily occur to those skilled in the art. For example, it will be clear to those skilled in the art that the changes applied to QP based on the comparison of the size of the sliding window and the target size will depend on the particular application. In addition, it will be clear to those skilled in the art that, rather than being based on a sliding window of images, the new value of QP could be determined using other techniques. In addition, it will be clear to those skilled in the art that the various elements described in connection with the various embodiments could be combined, in alternative embodiments, in any combinations.
    权利要求:
    Claims (15)
    [0001]
    REVENDICATIONS1. A video encoding method comprising: determining a first ratio (IPRATI0) based on previously encoded picture frames of a video sequence comprising one or more intra (I) encoded pictures and one or more predicted pictures (P), the first ratio (IP RATIO) being calculated on the basis of the ratio between the size of one or more previously encoded intra-encoded images and the size of one or more predicted images previously encoded; and determining a quantization parameter (QP) to be applied to a frame to be coded on the basis of the first report (IPRATIO) -
    [0002]
    The method according to claim 1, wherein the first ratio (IP RATIO) is determined based on a previous value of the first report (PREVIOUS IP RATIO) and a last ratio between the coded size of the last one. intra coded images to be encoded and that of the last of the predicted images to be encoded.
    [0003]
    The method of claim 2, wherein the first ratio is determined based on the following equation: PREVIOUS_IP RAT LATEST_IPRATIO COUNT_IP RATIOS where PREVIOUS_IPRATIO is the previous value of the first report, W is a weighting applied to the value Previous of the first report, LATEST IPRATIO is the last report, and COUNT_IPRATIOS is a value determined on the basis of the following equation: COUNT_IPRATIOS PREVIOUS_COUNT_IPRATios +1 where PREVIOUS COUNT IP RATIOS is the previous value of COUNT_IPRATIOS.
    [0004]
    4. A method according to any one of claims 1 to 3, wherein determining the quantization parameter comprises: determining the size (Ssw) of a sliding window of N frames of images; previously encoded of the video sequence, the sliding window comprising one or more of the intra (I) encoded images and one or more of the predicted images (P), where N is an integer greater than or equal to three; determining a target size (Tsw) of the sliding window based on at least the first report (IP RATIO); and determining the quantization parameter (QP) to be applied to a frame to be encoded based on the comparison of the size of the sliding window with the target size of the sliding window.
    [0005]
    The method of claim 4, wherein: the sliding window further comprises one or more bi-predicted images (B); and determining the target size (Tsw) of the sliding window is further based on a second ratio (PB RATIO) representing the ratio between the size of one or more of the predicted images and the size of one or more of the bi-published images. 20
    [0006]
    The method of claim 4 or 5, wherein the target size (Tsw) of the sliding window is determined based on a target size of a group (GOP) of successive images including the number of images counted. from an intra coded image up to, but not inclusive of, an intra-coded intra picture.
    [0007]
    The method of claim 6, wherein the target size of the sliding window (SW TARGET SIZE) is determined based on the following equation: GOPTARGET_SIZE SWTARGET_SIZE = (NUM, X 1RATIO NP_SW) X in it RATIO + NP_GOP 30 where NI sw is the number of intra coded images in the sliding window, Np sw is the number of predicted images in the sliding window, nnP --- TARGET SIZE is the target size of the successive image group, IP RATIO is the first ratio and Np Gop is the number of predicted images in the group of successive images. 3024313 B13072EN 20
    [0008]
    The method of claim 6 or 7, wherein the target size of the successive image group is determined based on the following equation: BITRATETARGET x GOP_LENGTH FRAME_RATE 5 where BITRATETARGET is a target bit rate of the encoded video stream, GOP LENGTH is the number of frames in the picture group, and FRAME RATE is the frame rate of the video clip.
    [0009]
    The method of any one of claims 4 to 8, wherein determining a quantization parameter (QP) to be applied to a frame to be encoded comprises determining a correction factor to be applied to a quantization parameter. preceding by dividing the size of the sliding window by the target size of the sliding window.
    [0010]
    The method of claim 9, wherein the quantization parameter has a logarithmic relationship with the bit rate, and the quantization parameter is determined by applying the correction factor to a linearized value (QS) determined by linearizing the parameter of previous quantification. 20
    [0011]
    The method of claim 9 or 10, wherein the quantization parameter (NEWQP) is determined on the basis of the following equation: NEWQP = fQp (fQs (OLDQP) x FACTOR_CORRECTION) where OLDQP is the previous quantization parameter FACTOR CORRECTION is the correction factor, f, Qs is a linearization function for linearizing the preceding quantization parameter and fQp is the inverse of the linearization function.
    [0012]
    A video encoder comprising a rate control circuit (103) adapted to: determine a first ratio (IP RATIO) based on previously encoded picture frames of a video sequence comprising one or more intra-coded pictures (I) and one or more predicted images (P), the first ratio (IP RATIO) being calculated as being the ratio between the size of one or more previously encoded intra-coded images and the size of a or more predicted images previously encoded; and determining a quantization parameter (QP) to be applied to a frame to be coded on the basis of the first report (IPRATIO) -
    [0013]
    The video encoder of claim 12, wherein the rate control circuit (103) is further adapted to: determine the size (Ssw) of a sliding window of N code frames previously coded from a video sequence, the sliding window comprising one or more of the intra (I) encoded images and one or more of the predicted images (P), where N is an integer greater than or equal to three; determining a target size (Tsw) of the sliding window based on at least the first report (IP RATIO); and determining the quantization parameter (QP) to be applied to a frame to be encoded based on the comparison of the size of the sliding window with the target size of the sliding window.
    [0014]
    The video encoder of claim 13, wherein: the sliding window further comprises one or more bi-predicted images (B); and determining the target size (TSw) of the sliding window is further based on a second ratio (PB RATIO) representing the ratio between the size of one or more of the predicted images and the size of one or more of the images. bi-predicted.
    [0015]
    The video encoder of any one of claims 12 to 14, wherein the debit rate control circuit (103) is adapted to determine the first ratio (IP RATIO) based on a previous value of the first report. 35 (PREVIOUS_IP RATIO) and a last ratio between the coded size of the last of the intra coded images to be coded and the last of the predicted images to be coded.
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    同族专利:
    公开号 | 公开日
    US20160029042A1|2016-01-28|
    EP2978219A1|2016-01-27|
    US10027979B2|2018-07-17|
    EP2978219B1|2021-09-08|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1457229A|FR3024313B1|2014-07-25|2014-07-25|VARIABLE RATE VIDEO ENCODER|FR1457229A| FR3024313B1|2014-07-25|2014-07-25|VARIABLE RATE VIDEO ENCODER|
    EP15177495.7A| EP2978219B1|2014-07-25|2015-07-20|Variable rate video encoder|
    US14/805,152| US10027979B2|2014-07-25|2015-07-21|Variable rate video encoder|
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