x265使用方法与命令行解析

将编译好的x265可以通过命令直接调用。为了调试，要先准备一个未编码的YUV文件，并且知道其分辨率，然后直接输入命令即可，例如：
/x265 --input BQMall_832x480_60.yuv --fps 20 --input-res 832x480 -o basket.265
这个是最简洁的X265命令了。
上面的input 后指定了输入文件名，fps指定了输出帧率，input-res 指定了输入文件的分辨率，-o是输出的文件。

1.X265参数分类

X265的其他参数比较多，可以通过x265 --hep来查看。
整体而言，其命令分为以下几类：

1. 执行选项；2. 日志选项； 3. 性能选项； 4. 层次档次和级别；5. 模式选择和分析
   ； 6. 时间和运动搜索选项；7. 空间和帧内选项；8. 心理与视觉选项；9. 片决策选项；10. 质量，码率控制和率失真选项；11. 量化选项；12. 环路滤波选型；13. VUI选项；14. 比特流选项；15. DCT近似值；16. Debug选项

下面整理各个参数，为了便于阅读，功能一样的选项只保留一个，例如-o和–output一样，就只保留-o。
有些指标说是CLI only，就是只能用在命令行窗口的意思 。
1. 执行选项

• –help, -h： 显示帮助信息
• –version, -V：显示版本信息

2. 日志和输出选项

• -o 编码后的输出文件
• -D 8|10|12 输出文件的颜色深度，默认为 8
• –log-level 日志的级别有 none error warning info debug full几个。默认是 full
• –no-progress 不输出编码的进度信息，只在编码完成之后打印一条。
• –csv 逗号分割的日志文件,如果 csv-log-level > 0 就每编码一帧，统计一条，否则x265执行一次就输出一行。如果将输出文件的后缀写为.csv文件，就生成一个csv文件，如果是.txt就以一个文本文件来记录。
• –csv-log-level csv 日志的级别, 如果 csv-log-level > 0 就编码每一帧输出一条记录,否则执行一次x265就生成一个文件。取值范围为0～2，数值越大，打印的信息越多。0表示编码完成后的总结信息，1表示帧级统计信息。2表示帧级统计信息和性能统计信息。具体选项含义见下一个博客。

3. 输入选项

• –input 原始的YUV 或者 Y4M 输入的文件. - 表示从标准输入中读。

• –y4m 忽略输入文件的后缀，强制解析为YUV4MPEG2。

• –fps 原始文件帧率,如果是Y4M的话就自动识别

• –input-res WxH 原始文件大小，格式为 [w x h],

• –input-depth 输入文件的比特深度.默认为 8

• –input-csp 色度抽样
  0 - i400 (4:0:0 单色的，也就是灰度图像)
  1 - i420 (4:2:0 默认)
  2 - i422 (4:2:2)
  3 - i444 (4:4:4)

• –nalu-file 输入一个包含SEI的文本文件。

• -f/–frames 编码的最大帧率

• –seek 编码第一帧的位置，也就是要跳跃几帧。

• –[no-]interlace 表示输入图片是按时间顺序的交错场。 0. 逐行图像（缺省） 1. 先顶场 2. 先底场。HEVC将交错的内容作为一场进行编码。提供正确的场的顺序给编码器。源尺寸必须是场的尺寸，FPS必须是每秒以场为单位。解码器必须要根据场的定向重新组合以用于显示。

• –dither 如果下采样到8位像素，则启用抖动。默认禁用

• –[no-]copy-pic 将输入图像的缓存保存到帧中，默认是可以。
  4. 性能和指标选项

• –[no-]ssim 允许输出SSIM 统计结果. 默认为禁止

• –[no-]psnr 允许输出PSNR 统计结果. 默认为禁止

• –pools 每 NUMA 个节点有一个逗号分隔的线程列表。如果是 “none”，就没有工作池创建，只有可能有帧的并行化。如果是 NULL 或 “ ”（缺省），x265 所有的线程都用在每 NUMA 个节点上。

• -F/–frame-threads 并行编码的帧数. 0:自动决策

• –[no-]wpp 允许波前并行处理.默认为允许。波前编码。编码器可能开始编码一行只要当前行上方至少有个 CTU（编码树单元）处于编码过程中。这会带来3-5倍的并行化和提高大约1%的压缩率。如果线程池不可用，这个特性会被隐式地关闭掉。缺省：开启

• –[no-]slices 启用多个片的功能. Default 1

• –[no-]pmode 并行模式预测. 默认禁止。并行模式或分布式模式。如果开启，编码器会将每个CU（merge、inter、intra）的分析工作部署到多个工作线程。只有当x265没有使得CPU核饱和才推荐使用该模式。如果-rect开启，RD level处于3或4，此时是最有效的。RD level处于5或6时，通常会部署足够多的工作来保证CPU过头，假定你的CPU还没有饱和。
  –pmode 会增加利用率而不会降低压缩效果。事实上，因为这个模式是在并行模式下测量，这使得一些不切实际的模式过早退出，从而使得你通常会得到稍微好一点的压缩率当开启的时候（是以不跳过不太可能的模式为代价）。pmode绕过提前退出会降低编码速度，尤其是preset为faster的时候。
  当不存在线程池的时候，这个特征被隐式地关闭了。

• –[no-]pme 并行运动预测，默认禁止。并行运动估计。当开启的时候，如果对于一个给定的CU有多余两个的参考需要运动搜索，编码器会将运动估计部署到多个工作线程进行工作。只有当x265没有使得CPU核饱和才推荐使用该模式。–pmode比这个选项更有效，因为它所分发的工作量更高。开启–pme选项，分发的工作过量超过并行带来的好处一般不常见。
  当不存在线程池的时候，这个特征被隐式地关闭了。

• –[no-]asm cpu检测，默认自动，x265缺省地会使用所有检测到的CPU SIMD架构。你也可以试用 –no-asm 来禁止使用任何 SIMD 架构，或指定一个以逗号分隔的 SIMD 架构使用列表，匹配以下字符串： MMX2, SSE, SSE2, SSE3, SSSE3, SSE4, SSE4.1, SSE4.2, AVX, XOP, FMA4, AVX2, FMA3， 一些高的架构就隐含了低架构可用；你也可以直接提供一个CPU能力图。

• -p/–preset 编码的级别。提供了几个预设的值，在编码效率和编码速度之间做一个折中。该参数需在其他输入参数应用之前启用，因此可以覆盖任何这些值所控制的参数值。预设的参数值如下： 0 – ultrafast； 1 – superfast；2 – veryfast； 3 – faster； 4 - fast；5 - medium（缺省）；6 – slow； 7 – slower； 8 – veryslow； 9 – placebo.

• -t/–tune 设置特定的视频源或情景，这个参数设置的应用是在preset之后，但在其他所有参数之前。缺省：none，值：psnr、ssim、grain、zero-latency、fast-decode。
  4. 层次档次和级别

• -P/–profile 强制指定档次的需求，确保解码器的输出流可修饰以支持指定的档次。如果指定的档次不被编码器的编译选项所支持（高比特位深度的编码器不能输出与Main或MainStillPicture兼容的比特流），则有可能放弃该编码器。

• –level-idc 最低的解码需求级别。缺省值0，意味着由编码器自动检测。如果指定了值，编码器就会在指定级别内赋予编码一些指定规则。如果编码器不能达到这个级别，就会给出警告并放弃这个编码器。如果所要求的级别比实际级别高，则发送实际的需求级别。
  注意，指定解码界别会强制编码器开启 VBV 用于常码率因子编码，可能会导致不确定性。 值被指定为浮点数或一个整数（级别乘以10），例如：级别 5.1 可以被指定为 “5.1” 或 “51”，级别 5.0 被指定为 “5.0”或“50”。

• –[no-]high-tier 如果 --level-idc 被指定，–high-tier允许支持那个级别的高等级。编码器首先会在指定的级别和主等级下编码，仅当有必要且那个级别的高等级可用的情况下才开启高等级。如果你所要求的级别不支持高等级，那么高等级不会被支持。如果 --no-high-tier 被指定，则编码器只会在主等级下编码。
  缺省：开启

• –uhd-bd 允许支持HD蓝光碟格式，如果指定了与编码选项不兼容，则编码器会尝试着去修正或设置正确的编码配置。如果编码器不能这么做，则这个选项就会被关闭。

• –[no-]allow-non-conformance ，允许libx265指定profile和无级别的情况下生成比特流。如果不满足严格的级别条件，缺省是放弃任何编码。两种最有可能的原因就是：–ctu太小，–ref太大，或者码率或者分辨率超出了指定条件。
  5. 模式选择和分析

• –rd <1…6> 模式决策中RDO水平。这个值越大，模式分析越耗时，使用更多的率失真优化。值越小编码速度越快，通常值越大比特流越小。缺省：3

• –[no-]psy-rd <0…5.0> 心理视率失真优化的强度，0表示禁止，默认为2。

• –[no-]rdoq-level <0|1|2> 量化中的RDO水平， 0:none, 1:levels, 2:levels & coding groups. Default 0

• –[no-]psy-rdoq <0…50.0> Strength of psycho-visual optimization in RDO quantization, 0 to disable. Default 0.0

• –dynamic-rd <0…4.0> Strength of dynamic RD, 0 to disable. Default 0.00

• –[no-]ssim-rd Enable ssim rate distortion optimization, 0 to disable. Default disabled

• –[no-]rd-refine Enable QP based RD refinement for rd levels 5 and 6. Default disabled

• –[no-]early-skip Enable early SKIP detection. Default disabled

• –[no-]rskip Enable early exit from recursion. Default enabled

• –[no-]tskip-fast Enable fast intra transform skipping. Default disabled

• –[no-]splitrd-skip Enable skipping split RD analysis when sum of split CU rdCost larger than one split CU rdCost for Intra CU. Default disabled

• –nr-intra An integer value in range of 0 to 2000, which denotes strength of noise reduction in intra CUs. Default 0

• –nr-inter An integer value in range of 0 to 2000, which denotes strength of noise reduction in inter CUs. Default 0

• –ctu-info Enable receiving ctu information asynchronously and determine reaction to the CTU information (0, 1, 2, 4, 6) Default 0
  - 1: force the partitions if CTU information is present
  - 2: functionality of (1) and reduce qp if CTU information has changed
  - 4: functionality of (1) and force Inter modes when CTU Information has changed, merge/skip otherwise
  Enable this option only when planning to invoke the API function x265_encoder_ctu_info to copy ctu-info asynchronously

• -w/–[no-]weightp Enable weighted prediction in P slices. Default enabled

• –[no-]weightb Enable weighted prediction in B slices. Default disabled

• –[no-]cu-lossless Consider lossless mode in CU RDO decisions. Default disabled

• –[no-]signhide Hide sign bit of one coeff per TU (rdo). Default enabled

• –[no-]tskip Enable intra 4x4 transform skipping. Default disabled

6. 时间和运动搜索选项

• –max-merge <1…5> Maximum number of merge candidates. Default 2

• –ref max number of L0 references to be allowed (1 … 16) Default 3

• –limit-refs <0|1|2|3> Limit references per depth (1) or CU (2) or both (3). Default 3

• –me Motion search method dia hex umh star full. Default 1

• -m/–subme Amount of subpel refinement to perform (0:least … 7:most). Default 2

• –merange Motion search range. Default 57

• –[no-]rect Enable rectangular motion partitions Nx2N and 2NxN. Default disabled

• –[no-]amp Enable asymmetric motion partitions, requires --rect. Default disabled

• –[no-]limit-modes Limit rectangular and asymmetric motion predictions. Default 0

• –[no-]temporal-mvp Enable temporal MV predictors. Default enabled
  7. 空间和帧内选项

• –[no-]strong-intra-smoothing Enable strong intra smoothing for 32x32 blocks. Default enabled

• –[no-]constrained-intra Constrained intra prediction (use only intra coded reference pixels) Default disabled

• –[no-]b-intra Enable intra in B frames in veryslow presets. Default disabled

• –[no-]fast-intra Enable faster search method for angular intra predictions. Default disabled

• –rdpenalty <0…2> penalty for 32x32 intra TU in non-I slices. 0:disabled 1:RD-penalty 2:maximum. Default 0
  8. 心理与视觉选项
  9. 片决策选项

• –[no-]open-gop Enable open-GOP, allows I slices to be non-IDR. Default enabled

• -I/–keyint Max IDR period in frames. -1 for infinite-gop. Default 250

• -i/–min-keyint Scenecuts closer together than this are coded as I, not IDR. Default: auto

• –gop-lookahead Extends gop boundary if a scenecut is found within this from keyint boundary. Default 0

• –no-scenecut Disable adaptive I-frame decision

• –scenecut How aggressively to insert extra I-frames. Default 40

• –scenecut-bias <0…100.0> Bias for scenecut detection. Default 5.00

• –radl Number of RADL pictures allowed in front of IDR. Default 0

• –intra-refresh Use Periodic Intra Refresh instead of IDR frames

• –rc-lookahead Number of frames for frame-type lookahead (determines encoder latency) Default 20

• –lookahead-slices <0…16> Number of slices to use per lookahead cost estimate. Default 8

• –lookahead-threads Number of threads to be dedicated to perform lookahead only. Default 0

• -b/–bframes <0…16> Maximum number of consecutive b-frames. Default 4

• –bframe-bias Bias towards B frame decisions. Default 0

• –b-adapt <0…2> 0 - none, 1 - fast, 2 - full (trellis) adaptive B frame scheduling. Default 2

• –[no-]b-pyramid Use B-frames as references. Default enabled

• –qpfile Force frametypes and QPs for some or all frames
  Format of each line: framenumber frametype QP
  QP is optional (none lets x265 choose). Frametypes: I,i,K,P,B,b.
  QPs are restricted by qpmin/qpmax.

• –force-flush Force the encoder to flush frames. Default 0
  0 - flush the encoder only when all the input pictures are over.
  1 - flush all the frames even when the input is not over. Slicetype decision may change with this option.
  2 - flush the slicetype decided frames only.
  10. 质量，码率控制和率失真选项

• –bitrate Target bitrate (kbps) for ABR (implied). Default 0

• -q/–qp QP for P slices in CQP mode (implied). --ipratio and --pbration determine other slice QPs

  • –crf Quality-based VBR (0-51). Default 28.0
  • –[no-]lossless Enable lossless: bypass transform, quant and loop filters globally. Default disabled
  • –crf-max With CRF+VBV, limit RF to this value. Default 0.000000
    May cause VBV underflows!
  • –crf-min With CRF+VBV, limit RF to this value. Default 0.000000
    this specifies a minimum rate factor value for encode!
  • –vbv-maxrate Max local bitrate (kbit/s). Default 0
  • –vbv-bufsize Set size of the VBV buffer (kbit). Default 0
  • –vbv-init Initial VBV buffer occupancy (fraction of bufsize or in kbits). Default 0.90
  • –vbv-end Final VBV buffer emptiness (fraction of bufsize or in kbits). Default 0 (disabled)
  • –vbv-end-fr-adj Frame from which qp has to be adjusted to achieve final decode buffer emptiness. Default 0
  • –chunk-start First frame of the chunk. Default 0 (disabled)
  • –chunk-end Last frame of the chunk. Default 0 (disabled)
  • –pass Multi pass rate control.
    - 1 : First pass, creates stats file
    - 2 : Last pass, does not overwrite stats file
    - 3 : Nth pass, overwrites stats file
  • –[no-]multi-pass-opt-analysis Refine analysis in 2 pass based on analysis information from pass 1
  • –[no-]multi-pass-opt-distortion Use distortion of CTU from pass 1 to refine qp in 2 pass
  • –stats Filename for stats file in multipass pass rate control. Default x265_2pass.log
  • –[no-]analyze-src-pics Motion estimation uses source frame planes. Default disable
  • –[no-]slow-firstpass Enable a slow first pass in a multipass rate control mode. Default enabled
  • –[no-]strict-cbr Enable stricter conditions and tolerance for bitrate deviations in CBR mode. Default disabled
  • –analysis-save Dump analysis info into the specified file. Default Disabled
  • –analysis-load Load analysis buffers from the file specified. Default Disabled
  • –analysis-reuse-file Specify file name used for either dumping or reading analysis data. Deault x265_analysis.dat
  • –analysis-reuse-level <1…10> Level of analysis reuse indicates amount of info stored/reused in save/load mode, 1:least…10:most. Default 5
  • –refine-mv-type Reuse MV information received through API call. Supported option is avc. Default disabled - 0
  • –scale-factor Specify factor by which input video is scaled down for analysis save mode. Default 0
  • –refine-intra <0…4> Enable intra refinement for encode that uses analysis-load.
    - 0 : Forces both mode and depth from the save encode.
    - 1 : Functionality of (0) + evaluate all intra modes at min-cu-size’s depth when current depth is one smaller than min-cu-size’s depth.
    - 2 : Functionality of (1) + irrespective of size evaluate all angular modes when the save encode decides the best mode as angular.
    - 3 : Functionality of (1) + irrespective of size evaluate all intra modes.
    - 4 : Re-evaluate all intra blocks, does not reuse data from save encode.
    Default:0
  • –refine-inter <0…3> Enable inter refinement for encode that uses analysis-load.
    - 0 : Forces both mode and depth from the save encode.
    - 1 : Functionality of (0) + evaluate all inter modes at min-cu-size’s depth when current depth is one smaller than
    min-cu-size’s depth. When save encode decides the current block as skip(for all sizes) evaluate skip/merge.
    - 2 : Functionality of (1) + irrespective of size restrict the modes evaluated when specific modes are decided as the best mode by the save encode.
    - 3 : Functionality of (1) + irrespective of size evaluate all inter modes.
    Default:0

• –[no-]dynamic-refine Dynamically changes refine-inter level for each CU. Default disabled

• –[no-]refine-mv Enable mv refinement for load mode. Default disabled

• –aq-mode Mode for Adaptive Quantization - 0:none 1:uniform AQ 2:auto variance 3:auto variance with bias to dark scenes. Default 1

• –aq-strength Reduces blocking and blurring in flat and textured areas (0 to 3.0). Default 1.00

• –[no-]aq-motion Adaptive Quantization based on the relative motion of each CU w.r.t., frame. Default disabled

• –qg-size Specifies the size of the quantization group (64, 32, 16, 8). Default 32

• –[no-]cutree Enable cutree for Adaptive Quantization. Default enabled

• –[no-]rc-grain Enable ratecontrol mode to handle grains specifically. turned on with tune grain. Default disabled

• –ipratio QP factor between I and P. Default 1.40

• –pbratio QP factor between P and B. Default 1.30

• –qcomp Weight given to predicted complexity. Default 0.60

• –qpstep The maximum single adjustment in QP allowed to rate control. Default 4

• –qpmin sets a hard lower limit on QP allowed to ratecontrol. Default 0

• –qpmax sets a hard upper limit on QP allowed to ratecontrol. Default 69

• –[no-]const-vbv Enable consistent vbv. turned on with tune grain. Default disabled

• –cbqpoffs Chroma Cb QP Offset [-12…12]. Default 0

• –crqpoffs Chroma Cr QP Offset [-12…12]. Default 0

• –scaling-list Specify a file containing HM style quant scaling lists or ‘default’ or ‘off’. Default: off

• –zones //… Tweak the bitrate of regions of the video
  Each zone is of the form
  ,,
  where is either
  q= (force QP)
  or b= (bitrate multiplier)

• –lambda-file Specify a file containing replacement values for the lambda tables
  MAX_MAX_QP+1 floats for lambda table, then again for lambda2 table
  Blank lines and lines starting with hash(#) are ignored
  Comma is considered to be white-space

• –max-ausize-factor This value controls the maximum AU size defined in specification.
  It represents the percentage of maximum AU size used. Default 1.0

• –[no-]deblock Enable Deblocking Loop Filter, optionally specify tC:Beta offsets Default enabled

• –[no-]sao Enable Sample Adaptive Offset. Default enabled

• –[no-]sao-non-deblock Use non-deblocked pixels, else right/bottom boundary areas skipped. Default disabled

• –[no-]limit-sao Limit Sample Adaptive Offset types. Default disabled
  11. 量化和深度选项

• -s/–ctu <64|32|16> 最大CU尺寸（宽和高）。该值越大，x265编码图像平坦区域的效率就越高，码流降低的就越厉害。然而这会带来并行化的损失，更少的CU行并行编码，同样更少的帧并行编码。因为这个原因，preset选择faster的话，CU的尺寸就设置为32。缺省：64

• –min-cu-size <64|32|16|8> 最小Cu大小.默认为8

• –max-tu-size <32|16|8|4> Maximum TU size (WxH). Default 32

• –tu-intra-depth Max TU recursive depth for intra CUs. Default 1

• –tu-inter-depth Max TU recursive depth for inter CUs. Default 1

• –limit-tu <0…4> Enable early exit from TU recursion for inter coded blocks. Default 0**
  12. 环路滤波

• –[no-]deblock Enable Deblocking Loop Filter, optionally specify tC:Beta offsets Default enabled

• –[no-]sao Enable Sample Adaptive Offset. Default enabled

• –[no-]sao-non-deblock Use non-deblocked pixels, else right/bottom boundary areas skipped. Default disabled
  –[no-]limit-sao Limit Sample Adaptive Offset types. Default disabled
  13. VUI选项

• –sar width:height|int Sample Aspect Ratio, the ratio of width to height of an individual pixel.
  Choose from 0=undef, 1=1:1(“square”), 2=12:11, 3=10:11, 4=16:11,
  5=40:33, 6=24:11, 7=20:11, 8=32:11, 9=80:33, 10=18:11, 11=15:11,
  12=64:33, 13=160:99, 14=4:3, 15=3:2, 16=2:1 or custom ratio of int:int. Default 0

• –display-window Describe overscan cropping region as ‘left,top,right,bottom’ in pixels

• –overscan Specify whether it is appropriate for decoder to show cropped region: undef, show or crop. Default undef

• –videoformat Specify video format from undef, component, pal, ntsc, secam, mac. Default undef

• –range Specify black level and range of luma and chroma signals as full or limited Default limited

• –colorprim Specify color primaries from bt709, unknown, reserved, bt470m, bt470bg, smpte170m,
  smpte240m, film, bt2020, smpte428, smpte431, smpte432. Default undef

• –transfer Specify transfer characteristics from bt709, unknown, reserved, bt470m, bt470bg, smpte170m,
  smpte240m, linear, log100, log316, iec61966-2-4, bt1361e, iec61966-2-1,
  bt2020-10, bt2020-12, smpte2084, smpte428, arib-std-b67. Default undef

• –colormatrix Specify color matrix setting from undef, bt709, fcc, bt470bg, smpte170m,
  smpte240m, GBR, YCgCo, bt2020nc, bt2020c, smpte2085, chroma-derived-nc, chroma-derived-c, ictcp. Default undef

• –chromaloc Specify chroma sample location (0 to 5). Default of 0

• –master-display SMPTE ST 2086 master display color volume info SEI (HDR)
  format: G(x,y)B(x,y)R(x,y)WP(x,y)L(max,min)

• –max-cll Emit content light level info SEI as “cll,fall” (HDR)

• –[no-]hdr Control dumping of HDR SEI packet. If max-cll or master-display has non-zero values, this is enabled. Default disabled

• –[no-]hdr-opt Add luma and chroma offsets for HDR/WCG content. Default disabled

• –min-luma Minimum luma plane value of input source picture

• –max-luma Maximum luma plane value of input source picture
  14. 比特流选项

• –[no-]repeat-headers Emit SPS and PPS headers at each keyframe. Default disabled

• –[no-]info Emit SEI identifying encoder and parameters. Default enabled

• –[no-]hrd Enable HRD parameters signaling. Default disabled

• –[no-]idr-recovery-sei Emit recovery point infor SEI at each IDR frame

• –[no-]temporal-layers Enable a temporal sublayer for unreferenced B frames. Default disabled

• –[no-]aud Emit access unit delimiters at the start of each access unit. Default disabled

• –hash Decoded Picture Hash SEI 0: disabled, 1: MD5, 2: CRC, 3: Checksum. Default 0

• –atc-sei Emit the alternative transfer characteristics SEI message where the integer is the preferred transfer characteristics. Default disabled

• –pic-struct Set the picture structure and emits it in the picture timing SEI message. Values in the range 0…12. See D.3.3 of the HEVC spec. for a detailed explanation.

• –log2-max-poc-lsb Maximum of the picture order count

• –[no-]vui-timing-info Emit VUI timing information in the bistream. Default enabled

• –[no-]vui-hrd-info Emit VUI HRD information in the bistream. Default enabled

• –[no-]opt-qp-pps Dynamically optimize QP in PPS (instead of default 26) based on QPs in previous GOP. Default disabled

• –[no-]opt-ref-list-length-pps Dynamically set L0 and L1 ref list length in PPS (instead of default 0) based on values in last GOP. Default disabled

• –[no-]multi-pass-opt-rps Enable storing commonly used RPS in SPS in multi pass mode. Default disabled

• –[no-]opt-cu-delta-qp Optimize to signal consistent CU level delta QPs in frame. Default disabled
  15. DCT近似值
  **16. Debug选项 **

• -r/–recon Reconstructed raw image YUV or Y4M output file name

• –recon-depth Bit-depth of reconstructed raw image file. Defaults to input bit depth, or 8 if Y4M

• –recon-y4m-exec pipe reconstructed frames to Y4M viewer, ex:“ffplay -i pipe:0 -autoexit”

• –lowpass-dct Use low-pass subband dct approximation. Default disabled