CN103873869A - Code rate control method - Google Patents
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- CN103873869A CN103873869A CN201210549518.1A CN201210549518A CN103873869A CN 103873869 A CN103873869 A CN 103873869A CN 201210549518 A CN201210549518 A CN 201210549518A CN 103873869 A CN103873869 A CN 103873869A
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Abstract
The invention discloses a code rate control method. An I frame in an image sequence is partitioned into a plurality of segments for respectively coding transferring. The code rate control method specifically comprises the following steps: (1) carrying out data partitioning: in static transcoding, dynamically determining a next I frame in advance for coding in the image sequence; (2) carrying out parallel transmission: carrying out segment partitioning on the data of the I frame, and carrying out respective transmission; when P frame or B frame of data is transmitted, transmitting subsequent coded parts of segment data of the I frame together according to the size of the P frame or B frame of data, and causing the size of the data which is conveyed by combining the P frame or B frame with the I frame to achieve a stable value; (3) carrying out combining decoding: in the transmission process of receiving the P frame and B frame, continuously collecting a subsequent I frame data segment by a corresponding progressive decoder, decoding after combining, and consistently displaying within a specified I frame time. The code rate control method disclosed by the invention has the advantages that code stream fluctuation brought by the fact that the I frame must be inserted in the image coding/decoding process can be effectively smoothened, and possibility is provided for the stable transmission of the video code stream.
Description
Technical field
The present invention relates to a kind of video encoding method, be specifically related to a kind of first section and cut apart then the bit rate control method of coding transmission respectively.
Background technology
There have been multiple technical standards about coding and decoding video present stage, comprise the MPEG-1 of ISO/IEC motion expert group (MPEG) series, MPEG-2, MPEG-4, and the combination with standard of the joint video team (JVT) of ITU Video coding expert group of International Telecommunications Union (VCEG) H.264/AVC, H.264 be also called MPEG4 part 10, thereby these video compression technology standards are all by compress technique, video data to be compressed and improves efficiency of transmission.In actual telecommunications application, the specified transmission bandwidth of circuit is fixed often, is difficult to adapt to the significantly shake of variable bit rate VBR (Variable Bitrate).For example, the compressed video stream that VBR mode is encoded, the upper and lower fluctuation range of its maximal rate and minimum code rate likely reaches 10 times, and so significantly fluctuation is difficult to carry out adaptation with existing telecommunications network.For the adaptation comparing with existing telecommunications network, need to be fixed code check CBR (Constant Bitrate) coding.
In modern video encoding standard, generally there is Intra (I) frame, P frame, B frame, the efficiency of I frame is minimum, and B frame can carry out two-way reference, it most effective.The data bit bit number that I frame takies can be the hundreds of times of B frame, and the significantly shake that this has just caused code check is fundamentally unfavorable for CBR cbr (constant bit rate) coding very much.H.264 allow each macro block with reference to different images, select different reference pictures can improve compression efficiency.
A typical video compression sequence is made up of above-mentioned I frame P frame B frame exactly.The code efficiency of I frame is lower than P frame and B frame.I frame can independently be decoded, and IDR frame (Ins tananeousDecoding Refresh, the instant refresh frame of decoding) is exactly an entrance or random access point, does not allow follow-up frame to cross over I DR reference frame above, and I frame limits without this.IDR is exactly the starting point of a decoding.In order to allow video sequence of arbitrary access, need in sequence, insert the IDR frame of some.In the time that camera lens switches, because scene changes is very large, the content that can use for reference between frame and frame is few, and now more effective with I frame coding, this I frame can need not to be an IDR frame.The first frame starting in a GOP must be an IDR frame, and a GOP finished before another one IDR.The I frame due to factor insertions such as carry overs between IDR can be crossed over reference to the previous frame of this I frame by following frame.One more the IDR frame density of crypto set be obviously more conducive to video sequence of user's random access.Thereby the I frame inserting due to carry over can be defined as the beginning of a new GOP of IDR guiding, and such IDR can be called nature IDR.Do not having between carry over, because GOP length constraint is forced to the IDR frame inserting, can be called passive IDR frame.Passive IDR frame has redundancy with frame before.Frame after IDR can not be with reference to the frame before IDR, and the frame after I frame can be with reference to the frame before I frame.
Hierarchy has four layers, is followed successively by from top to bottom image layer (picture layer), slice layer (slice, GOB), macroblock layer (MB) and piece layer (block layer).Ribbon structure is a slice header and follow-up strip data.Band is defined as the combination of some macro blocks in an image.Band can absolute coding, and a band can not be with reference to the data of other band.In the transmission environment that has error code, ribbon structure is conducive to mistake and recovers.There are multiple MB each band inside, the luminance pixel data that MB is 16x16 and the chroma data of 8x8.H.264 in standard, the data VCL of video compression is separated with the transport layer NAL that on adaptive particular network that these data are packed, transmission forms.Similitude on image redundancy representation space between neighbor, time redundancy represents between frame and frame, have very large similitude, mutually reference and reference.Spectral redundancy refers to the mutual relation that has between different color compositions.Reference picture is selected, and the reference picture of motion compensation can be selected in reference picture buffering area.H.264 allow each macro block with reference to different images, select different reference pictures can improve compression efficiency.
Progressive decoding device refreshes and relates to " dirty " random access, and picture material is progressive recovery in multiple coded images.The basic idea that progressive decoding refreshes is to be intraframe coding by a part of macroblock coding of frame.When decoder is in the time that a random accessing points starts to decode, for this decoder, the reference frame of motion compensation is unknown.Decoder can be rebuild the macro block of intraframe coding, but motion compensation macro block relates to and correctly do not receive can not being resumed of reference frame.After multiple decoded frames, the intra-coded regions of accumulation increases gradually, finally can obtain a complete reconstruction image.
H.264 in, use loop filtering to weaken boundary effect, may fail to be correctly decoded reconstruction but close on macro block.Half-pix and 1/4 pixel are also rebuild by 6 taps or 4 tap filters.The pixel of failing correctly to rebuild may be used to pixel being positioned within reliable decoding region of interpolation, and this will cause separating code error.
For solving problems, many units and inventor have made more deep research to this, and disclose a series of solutions that have creation.As Nokia Oy once disclosed the patent of invention (number of patent application is 03809615.3) of " random access point in Video coding " by name on April 28th, 2003 application and on May 17th, 2006, it is to carry out on the basis of the potential complexity that realizes at identification progressive decoding device method for refreshing.According to the method, the video sequence being made up of frame of video is encoded, and wherein coding method comprises at least one frame of video is divided into a group coding piece, and the encoding block of encoding described at least one with intraframe coding.Then, the the first reliable region that comprises the encoding block of at least one intraframe coding determined, thereby and in described video sequence the first described reliable region of coding prevent from producing information dependence between the encoding block outside the first described reliable region and described the first reliable region.In the time accessing this video sequence arbitrarily from one, decoder can use described reliable region as a random access point.The advantage of this invention is can be used in provides random access point in encoded video streams, a part for reliably updating image-region, rather than the coverage of the whole intra-frame macro block in this region simultaneously, and stop the space-time of transmission error to be propagated.In addition; thereby it allows different error protections and transmission priority to improve the visual quality of reception and forms the traffic according to the subjective priority of the video data of different piece; and can avoid the whole I frames in conversational applications; so that the delay minimum between terminal-terminal, and improve the visual quality receiving.But the method is good not for the treatment effect of carry over I frame, because the part that the image content of carry over I frame is identical with the picture of front and continued is little, the intraframe coding part of front and continued picture do not have much can to inherit and the content of reference, so can not play very large help to follow-up carry over I frame.In addition, Tsing-Hua University has applied for " a kind of video coding-decoding method of supporting that frame of video reads an at random " patent of invention (number of patent application is 200710062633.5) by name on January 12nd, 2007, its coding method is: frame of video is divided into groups, all frames in group are arranged to I frame, P frame, B frame and read at random frame W frame, and to all frame I frames in group, P frame, B frame carries out tradition coding, first W frame is encoded according to the coded system of P frame, the coding method of recycling distributed video coding is encoded to this W frame with reference to any frame before the nearest I frame of this W frame and this I frame and this W frame, coding/decoding method is: in the time not needing to read at random, the I frame of each group, P frame, B frame are carried out to tradition decoding, W frame is decoded by the method for P frame, in the time that needs read at random, utilize the coding/decoding method of distributed video coding directly W frame to be decoded.The advantage of the method is not only can improve the random reading performance of frame of video, and the code stream generating has certain error resilience energy, but also there is an obvious shortcoming in it, exactly except I frame, P frame, B frame being carried out tradition decoding, also to decode to W frame by the method for P frame, and can not remove the dependence to front I frame, practical effect is poor.
Summary of the invention
The defect existing in order to overcome above-mentioned prior art, the invention provides a kind of bit rate control method, by the fluctuation that has brought code stream itself due to the I frame that must insert in can be the effectively mild image coding and decoding process of the method, for the steady propagation of video code flow provides possible.
To achieve these goals, technical scheme of the present invention is as follows: a kind of bit rate control method, I frame in image sequence is divided into multiple sections, coding transmits respectively, specifically comprise the steps: that (1) carry out Data Segmentation: in static transcoding, in described image sequence, dynamically determine in advance that next I frame encodes; (2) transmission simultaneously: the data of this I frame are cut apart to section, transmit respectively; In the time of transmission P frame or B frame data, according to the size of P frame or B frame data, transmit in the lump the follow-up encoded partially sliced data of I frame that complete, make P frame or B frame be combined the size of data of transmission with I frame and reach a stationary value; (3) merge decoding: corresponding progressive decoding device, receiving in P frame and B frame transmitting procedure, is constantly collected follow-up I frame data section, decoding after merging, and unanimously show at the I frame time of regulation.Next I frame can be a scene switching point, can be also the pressure I frame of fixed position.
Further, in described decoding step, canonical solution coded program receiving merging decoding after slice of data, unanimously shows at the displaying time of the I of standard frame, will obtain a complete I frame.
Further, the I frame in described step (1) shifts to an earlier date absolute coding.
Further, while transmission in described step (2) simultaneously, select the slice of data of the follow-up I frame of transmission in the lump according to the size of P or B frame, P frame and the merging transmission frame of I frame data section composition more level off to target bit rate, make the steadily equilibrium of overall code stream.
For a video encoder for bit rate control method claimed in claim 1, this encoder is arranged to the coded data of follow-up I frame to cut apart.
For a Video Decoder for bit rate control method claimed in claim 1, it is characterized in that, described decoder is progressive decoding device, merges decoding for the multiple data slicers of I frame to collected.
Beneficial effect of the present invention is: (1) is in decoding end, because these displaying times of cutting apart section are consistent, it is all the displaying time that equals the I frame of their representatives, canonical solution coded program is receiving that these slice of datas merge rear decoding, displaying time at the I of standard frame shows, will obtain a complete I frame.By these steps, the fluctuation that just can avoid the big data quantity of I frame to bring, and P frame B interframe, and in a GOP, amount of exercise is not of uniform size causes etc., the coded data that causes is not of uniform size causes the code stream fluctuation bringing.(2) this method is the I frame of the next GOP of coding transmission in this GOP, across GOP global adaptation Bit allocation, so both smoothly GOP was interior because the codec complexity fluctuation that motion and texture etc. cause, also can be across the level and smooth this complexity fluctuation of GOP, for example, when texture and the complicated movement of next GOP, the I frame of next GOP beginning can be carried out to meticulousr coding; When the complexity of this GOP is high, simplify the degree that becomes more meticulous of the I frame coding of next GOP, carry out Rate Control adjustment of overall importance, form the approximate effect that CBR requires.(3) the follow-up I frame of coding is coding transmission after data slicer after coding in advance.(4) because these I frame data are important, be the basis of subsequent frame reference, these data of transmitting in advance can be carried out the transmission of cyclic check coding protection according to importance, in the time having partial data to lose in transmitting procedure, can do data and recover.This method is more suitable for the off-line static coding of program request, because off-line coding can be surveyed next carry over point in advance, can confirm in advance the position of next I frame.Force the live of I frame position for fixing GOP, this method can be used.
Accompanying drawing explanation
Fig. 1 is the design principle block diagram of the embodiment of the present invention.
Embodiment
Be easy to understand understanding in order to make technological means of the present invention, creation characteristic and to reach object, further set forth the present invention below in conjunction with specific embodiment.
Embodiment 1: a kind of bit rate control method, will after the I frame coding in described image sequence, be divided into multiple sections, coding transmits respectively, specifically comprises the steps:
Step 1 for static transcoding process, can find in advance next scene switching point in image sequence, and determines to insert I frame at this scene switching point place.This I frame is owing to being in-line coding, irrelevant with other frame, can shift to an earlier date absolute coding than P frame and B frame before it.
Step 2, cuts apart by section the data that then coding produces and transmits respectively.
Step 3, because the data of P frame and B frame are obviously less than the data of I frame, in the time of transmission P frame or B frame data, along the I frame data of the follow-up encoded section partition encoding completing of band transmission, is conducive to smooth-going code stream.The size of the data fragments of the follow-up I frame transmitting along band, be according to the size of this frame (P or B), the data fragments of the large I frame of this frame is just less, and the data fragments of the little I of this frame frame is just large, main purpose is smooth-going code stream, strives for reaching target bit rate in the timeslice of each frame.For example, for the video of fps=25, the timeslice of a frame is 40ms, if target bit rate is 1Mbps, the desirable amount of every frame is 41943bit.
Step 4, in decoding end, decoder, in P frame and B frame transmitting procedure, is constantly collected follow-up I frame data, waits whole collections to complete, this I frame of can intactly decoding.
Step 5, because existing video standard is not realized the standard syntax of above-mentioned algorithm, realize said process, can, by the method for sideband data transmission, realize by the cooperation of decoding end.
Step 6, in decoding end, because these displaying times of cutting apart band are consistent, it is all the displaying time that equals the I frame of their representatives, canonical solution coded program receiving decoding respectively after these strip data, unanimously shows at the displaying time of the I of standard frame, will obtain a complete I frame.
By these steps, the fluctuation that just can avoid the big data quantity of I frame to bring, and P frame B interframe, and complexity and amount of exercise is not of uniform size causes etc. in a GOP and between GOP, the coded data that causes is not of uniform size causes the code stream fluctuation bringing.
Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention; do not departing under the prerequisite of core idea of the present invention; those of ordinary skill that also can art field; do not departing under the prerequisite of core idea of the present invention; can also make some simple deduction or replace, these changes and improvements all fall in the claimed scope of the invention.
Claims (7)
1. a bit rate control method, it is characterized in that, the I frame in image sequence is divided into multiple sections, coding transmits respectively, specifically comprise the steps: that (1) carry out Data Segmentation: in static transcoding, in described image sequence, dynamically determine in advance that next I frame encodes; (2) transmission simultaneously: the data of this I frame are cut apart to section, transmit respectively; In the time of transmission P frame or B frame data, according to the size of P frame or B frame data, transmit in the lump the follow-up encoded partially sliced data of I frame that complete, make P frame or B frame be combined the size of data of transmission with I frame and reach a stationary value; (3) merge decoding: corresponding progressive decoding device, receiving in P frame and B frame transmitting procedure, is constantly collected follow-up I frame data section, decoding after merging, and unanimously show at the I frame time of regulation.
2. bit rate control method according to claim 1, is characterized in that, in described decoding step, canonical solution coded program is being received after the slice of data of I frame, merges decoding, by obtaining a complete I frame, shows at the displaying time of the I of standard frame.
3. bit rate control method according to claim 1, is characterized in that, the I frame in described step (1) shifts to an earlier date absolute coding.
4. bit rate control method according to claim 1, is characterized in that, while transmission, selects the follow-up I frame of transmission in the lump according to the size of P or B frame in described step (2) simultaneously.
5. bit rate control method according to claim 1, it is characterized in that, Data Segmentation after next I frame coding in described image sequence becomes some parts, its umber of cutting apart and size are according to the size of data after the quantity of P frame or B frame and coding, these data after cutting apart are with P frame or the transmission of B frame of preorder, to level off to target bit rate as object, mate in conjunction with transmitting.
6. bit rate control method according to claim 5; it is characterized in that; in the time that the P frame with preorder or B frame transmit, it accompanies the follow-up I frame data that transmit first to sort according to importance, can use cyclic check coding etc. to have the encoding scheme of protectiveness for significant data.
7. for a Video Decoder for bit rate control method claimed in claim 1, it is characterized in that, merge rear decoding for the P frame to collected, B frame and I frame slice of data.
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| CN105025347A (en) * | 2015-07-21 | 2015-11-04 | 北京暴风科技股份有限公司 | Sending and receiving methods of GOP image groups |
| CN105898373A (en) * | 2015-12-17 | 2016-08-24 | 乐视云计算有限公司 | Video slicing method and device |
| CN105898319A (en) * | 2015-12-22 | 2016-08-24 | 乐视云计算有限公司 | Video transcoding method and device |
| WO2016154888A1 (en) * | 2015-03-31 | 2016-10-06 | 深圳市大疆创新科技有限公司 | Image coding method and coding apparatus |
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| US10715822B2 (en) | 2015-03-31 | 2020-07-14 | SZ DJI Technology Co., Ltd. | Image encoding method and encoder |
| WO2016154888A1 (en) * | 2015-03-31 | 2016-10-06 | 深圳市大疆创新科技有限公司 | Image coding method and coding apparatus |
| US10469855B2 (en) | 2015-03-31 | 2019-11-05 | SZ DJI Technology Co., Ltd. | Image encoding method and encoder |
| CN105025347B (en) * | 2015-07-21 | 2018-10-09 | 暴风集团股份有限公司 | A kind of method of sending and receiving of GOP images group |
| CN105025347A (en) * | 2015-07-21 | 2015-11-04 | 北京暴风科技股份有限公司 | Sending and receiving methods of GOP image groups |
| CN106713913A (en) * | 2015-12-09 | 2017-05-24 | 腾讯科技（深圳）有限公司 | Video picture frame sending method and device and video picture frame receiving method and device |
| CN106713913B (en) * | 2015-12-09 | 2020-01-10 | 腾讯科技（深圳）有限公司 | Video image frame sending method and device and video image frame receiving method and device |
| CN105898373A (en) * | 2015-12-17 | 2016-08-24 | 乐视云计算有限公司 | Video slicing method and device |
| CN105898319A (en) * | 2015-12-22 | 2016-08-24 | 乐视云计算有限公司 | Video transcoding method and device |
| CN109076194A (en) * | 2017-11-21 | 2018-12-21 | 深圳市大疆创新科技有限公司 | A kind of method for processing video frequency, equipment, aircraft, system and storage medium |
| CN109076194B (en) * | 2017-11-21 | 2021-04-16 | 深圳市大疆创新科技有限公司 | Video processing method, device, aircraft, system and storage medium |
| CN110741647A (en) * | 2018-09-29 | 2020-01-31 | 深圳市大疆创新科技有限公司 | image processing method, device, movable platform and storage medium |
| US11444884B2 (en) | 2019-11-29 | 2022-09-13 | Axis Ab | Encoding and transmitting image frames of a video stream |
| CN113316028A (en) * | 2020-02-27 | 2021-08-27 | 华为技术有限公司 | Screen projection method, screen projection equipment and storage medium |
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