1.X264码率控制之VBV
2.求大师分享，码解告诉我这个红绿背景主图是码解什么指标公式源码。那里可以下载？
3.x264的码解码率控制总结
X264码率控制之VBV
视频数据的庞大给存储和传输带来挑战，为此诞生了众多编码标准，码解其中h.因其广泛使用而备受关注。码解H的码解锤子矿场源码开源编码器中，JM主要用于研究，码解OpenH性能优良且支持SVC编码，码解而x以其高效性能常被商业软件如OBS、码解VLC、码解ffmpeg采用，码解尤其在实时场景如视频会议中，码解码率控制至关重要。码解
在实时视频中，码解码率控制需考虑网络状况，码解dw怎么用做代源码编码后的码流大小由图像复杂度、帧间相似度和量化程度决定。x通过调整量化程度实现码率控制，提供了CQP、CRF和ABR三种方式。CQP侧重保证质量，CRF在保证质量的同时控制码率，ABR则更侧重码率稳定，牺牲一定图像质量以保持稳定。
在编码过程中，x计算出帧级量化值（QP），CRF和ABR会计算出qscale值，而CQP则是固定的。CRF采用固定码率因子，溯源码如何查真假确保编码质量稳定，而ABR通过动态调整，使实际比特数与目标比特数同步，保证码率稳定。
然而，帧级码控并不够，x引入了VBV，即视频缓冲区校验器，作为第二道码率调控关卡。VBV模拟一个有容量限制的管道，通过控制注入和流出的水量来维持编码码率在设定范围内。它并非必须，但开启后能更好地稳定码率。VBV调控涉及设置注水和出水的梦幻西游师门源码警戒线，以避免水位过高或过低，从而调整当前帧的QP。
尽管本文仅触及了x码率控制的表面，实际过程更为复杂，涉及图像复杂度计算、行级码控等技术。深入理解还需参考x源码。实践是检验真理的唯一标准，理论学习后，实践操作才能揭示更多奥秘。
求大师分享，告诉我这个红绿背景主图是什么指标公式源码。那里可以下载？
NA:=STRCAT(CON2STR(YEAR,0),' 年 ');
YA:=STRCAT(CON2STR(MONTH,0),' 月 ');
RA:=STRCAT(CON2STR(DAY,0),' 日 ');
SJ:=STRCAT(STRCAT(NA,YA), RA);
DRAWTEXT_FIX(C>0,0.,0,0,SJ);
{ 布林+宝塔+蓝灰操盘}
{ 蓝灰底}
买线:=EMA(C,2);
卖线:=EMA(SLOPE(C,)*+C,);
STICKLINE(买线>=卖线,HHV(H,),LLV(L,),5,0),COLOR;
STICKLINE(买线<卖线,HHV(H,),LLV(L,),5,0),COLOR;
{ 红轨道}
红轨道:=MA(MA(CLOSE,3),1),LINETHICK1,COLORYELLOW;
轨道:MA(MA(CLOSE,3),3),COLORCD,LINETHICK2;
SHENG:=IF(红轨道>=轨道,轨道,DRAWNULL);
升:SHENG,COLORMAGENTA,LINETHICK2;
{ 变色K线}
N1:=;
M:=6;
TR1:=EXPMEMA(MAX(MAX(HIGH-LOW,ABS(HIGH-REF(CLOSE,1))),ABS(REF(CLOSE,1)-LOW)),N1);
HD :=HIGH-REF(HIGH,1);
LD :=REF(LOW,1)-LOW;
DMP:=EXPMEMA(IF(HD>0&&HD>LD,HD,0),N1);
DMM:=EXPMEMA(IF(LD>0&&LD>HD,LD,0),N1);
PDI:=DMP*/TR1,LINETHICK2;
MDI:=DMM*/TR1;
ADX:=EXPMEMA(ABS(MDI-PDI)/(MDI+PDI)*,M);
ADXR:=EXPMEMA(ADX,M);
VAR1:=CLOSE>REF(CLOSE,1) AND CLOSE>REF(CLOSE,2);
VAR2:=REF(VAR1,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR3:=REF(VAR2,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR4:=REF(VAR3,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR5:=REF(VAR4,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR6:=REF(VAR5,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR7:=REF(VAR6,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR8:=REF(VAR7,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR9:=REF(VAR8,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VARA:=REF(VAR9,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VARB:=REF(VARA,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VARC:=REF(VARB,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
STICKLINE(VAR1 OR VAR2 OR VAR3 OR VAR4 OR VAR5 OR VAR6 OR VAR7 OR VAR8 OR VAR9 OR VARA OR VARB OR VARC,CLOSE,REF(CLOSE,1),3,1),COLORFF;
VARD:=CLOSE<REF(CLOSE,1) AND CLOSE<REF(CLOSE,2);
VARE:=REF(VARD,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VARF:=REF(VARE,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR:=REF(VARF,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE<=REF(CLOSE,1) AND CLOSE>=REF(CLOSE,2);
VAR:=REF(VAR,1) AND CLOSE>=REF(CLOSE,1) AND CLOSE<=REF(CLOSE,2);
STICKLINE(VARD OR VARE OR VARF OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR,CLOSE,REF(CLOSE,1),3,0),COLORC;
VAR:=REF(VARD OR VARE OR VARF OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR OR VAR,1) AND VAR1;
STICKLINE(VAR,REF(CLOSE,1),REF(CLOSE,2),3,0),COLORMAGENTA ;
VAR1A:=REF(VAR1 OR VAR2 OR VAR3 OR VAR4 OR VAR5 OR VAR6 OR VAR7 OR VAR8 OR VAR9 OR VARA OR VARB OR VARC,1) AND VARD;
STICKLINE(VAR1A,REF(CLOSE,1),REF(CLOSE,2),3,0) ,COLORFF; }
{ 箱体线}
N:=7;
T1:=CONST(LLVBARS(LOW,N));
T1HIGH:=CONST(REF(HIGH,T1));
CC:=CONST(CURRBARSCOUNT);
T2:=CONST(BARSLAST((CURRBARSCOUNT >(CC+T1)) AND (HIGH>T1HIGH)));
T2HIGH:=CONST(REF(HIGH,T2));
T3:=CONST(BARSLAST((CURRBARSCOUNT >(CC+T2)) AND (HIGH>T2HIGH)));
T3HIGH:=CONST(REF(HIGH,T3));
突破杀入线:DRAWLINE(CURRBARSCOUNT=T3+1, T3HIGH, ISLASTBAR, T3HIGH, 1),LINETHICK1,COLORYELLOW;
DRAWTEXT(ISLASTBAR, T3HIGH, '杀入线!'),LINETHICK1,COLORYELLOW;
AB:=EMA(((2*C+H+L)/4-LLV(LOW,))/(HHV(HIGH,)-LLV(LOW,))*,8);
BA:=EMA(AB,5);
A1{ 高}:=REFDATE(REF(HHV(H,),5),DATE);
B1{ 低}:=REFDATE(REF(LLV(L,),5),DATE);
DY{ 中}:=((A1)+(B1))/2;
箱顶:IF(AB>0 AND AB-BA<=0,A1,A1),COLORGREEN,DOTLINE;
箱腰:IF(AB>0 AND AB-BA<=0,DY,DY),COLORYELLOW,DOTLINE;
箱低:IF(AB>0 AND AB-BA<=0,B1,B1),COLORRED,DOTLINE;
DRAWTEXT(ISLASTBAR,箱顶,'箱顶'),COLORYELLOW;
DRAWTEXT(ISLASTBAR,箱腰,'箱腰'),COLORYELLOW;
DRAWTEXT(ISLASTBAR,箱低,'箱低'),COLORYELLOW;
VARAA:=IF(CLOSE>,.3,0.);
{ 突破:INTPART(CLOSE/VARAA )*VARAA,POINTDOT,LINETHICK4,COLORRED;
再突破:突破+VARAA,POINTDOT,LINETHICK4,COLORFF ;
回踩:(突破+再突破)/2,POINTDOT,COLORWHITE,LINETHICK4;}
STICKLINE(CROSS(ZIG(3,5),REF(ZIG(3,5),1)),箱低,箱腰,0.1,-1),COLORRED;
STICKLINE(CROSS(REF(ZIG(3,5),1),ZIG(3,5)),箱顶,箱腰,0.1,-1),COLORGREEN;
DRAWICON(CROSS(ZIG(3,5),REF(ZIG(3,5),1)),箱腰,1);
DRAWICON(CROSS(REF(ZIG(3,5),1),ZIG(3,5)),箱腰,2);
DRAWTEXT_FIX(CURRBARSCOUNT=1,0.,0.,0,'K线底部出红色或粉色，可低吸建仓！vc6 mfc源码'),COLORRED;
DRAWTEXT_FIX(CURRBARSCOUNT=1,0.,0.,0,'绿点表示长期的压力点！'),COLORGREEN;
DRAWTEXT_FIX(CURRBARSCOUNT=1,0.,0.,0,'白点表示中短期的压力和支撑点，'),COLORGREEN;
DRAWTEXT_FIX(CURRBARSCOUNT=1,0.,0.,0,'红点表示有效支撑或突破长中短期压力点！股价向下跌破，原则清仓！'),COLORGREEN;
EE:=(H+L+O+2*C)/5;
CRTP:=EE+(H-L);
CRZL:=2*EE-L;
CRZC:=2*EE-H;
CRFZ:=EE-(H-L);
高:CONST(CRTP),COLORRED;
阻:CONST(CRZL),COLORC7C9FF;
支:CONST(CRZC),COLOR7C9CFF;
反:CONST(CRFZ),COLORDDDD;
DRAWTEXT(ISLASTBAR, 反, '反转价'),LINETHICK1,COLORDDDD;
DRAWTEXT(ISLASTBAR, 支, '支撑'),LINETHICK1,COLOR7C9CFF;
DRAWTEXT(ISLASTBAR, 阻, '阻力'),LINETHICK1,COLORC7C9FF;
DRAWTEXT(ISLASTBAR, 高, ' 高破线'),LINETHICK1,COLORGREEN;
均线:=EXPMA(C,),COLORGRAY,LINETHICK2;
日:=;
昨前:=3;
高2:=REF(HHV(H,日),昨前);
低2:=REF(LLV(L,日),昨前);
H4:=高2-(高2-低2)*0.;
H5:=高2-(高2-低2)*0.;
支撑.9%:REFDATE(H5,DATE),COLORRED;
支撑.8%:REFDATE(H4,DATE),COLORGREEN,;
STICKLINE(CURRBARSCOUNT=1,支撑.9%,支撑.9%,,-1),COLORGREEN;
STICKLINE(CURRBARSCOUNT=1,支撑.8%,支撑.8%,,-1),COLORRED;
DRAWTEXT(CURRBARSCOUNT=1 AND 支撑.9%,支撑.9%,'备钱'),COLORGREEN;
DRAWTEXT(CURRBARSCOUNT=1 AND 支撑.8%,支撑.8%,'转运'),COLORRED;
WH1:=IF(L=LLV(L,9),L,0);
WH2:=CONST(BARSLAST(WH1!=0));
WH3:=CONST(IF(WH2=0,H,REF(H,WH2)));
WH4:=CONST(REF(BARSLAST(H>WH3),WH2+1)+WH2+1);
WH5:=CONST(IF(WH4=0,H,REF(H,WH4)));
WH6:=CONST(REF(BARSLAST(H>WH5),WH4+1)+WH4+1);
WH7:IF(CURRBARSCOUNT<=WH2+,CONST(IF(WH6=0,H,REF(H,WH6))),DRAWNULL),COLORRED,DOTLINE;
STICKLINE(CURRBARSCOUNT<=WH2+1 AND L=LLV(L,9),O,C,3,0),COLORRED;
DRAWTEXT(CURRBARSCOUNT=WH2+,WH7,'LINE'),COLORRED;
DRAWTEXT(ISLASTBAR,WH7,'进场'),COLORRED;
WH8:IF(CURRBARSCOUNT<=WH2+1,IF(L=LLV(L,9),L,DRAWNULL),DRAWNULL),CIRCLEDOT;
H:=IF(H=HHV(H,9),H,DRAWNULL);
H:=CONST(BARSLAST(H!=DRAWNULL));
H:=CONST(IF(H=0,L,REF(L,H)));
H:=CONST(REF(BARSLAST(L<H),H+1)+H+1);
H:=CONST(IF(H=0,L,REF(L,H)));
H:=CONST(REF(BARSLAST(L<H),H+1)+H+1);
H:=IF(CURRBARSCOUNT<=H+,CONST(IF(H=0,L,REF(L,H))),DRAWNULL),DOTLINE;
H:=IF(CURRBARSCOUNT<=H+1,IF(H=HHV(H,9),H,DRAWNULL),DRAWNULL),CIRCLEDOT;
DRAWTEXT(CURRBARSCOUNT=H+,H,'LINE'),COLORYELLOW;
DRAWTEXT(ISLASTBAR,H,'止损'),COLORYELLOW;
DIF:=EMA(DCLOSE,)-EMA(DCLOSE,);
DEA:=EMA(DIF,9);
AAA:=(DIF-DEA)*2*;
起爆:=CROSS(AAA-REF(AAA,1),);
DRAWTEXT(起爆,MA(L,3),'↖暴张'),COLORYELLOW,LINETHICK2;
LC:=REF((O+H+L+2*C)/5,1);
{ 短线擒黑码}
RSI:=SMA(MAX(C-LC,0),7,1)/SMA(ABS(C-LC),7,1)*;
TYP:=(HIGH+LOW+CLOSE)/3;
CCI:=(TYP-MA(TYP,))/(0.*AVEDEV(TYP,));
买:=CROSS(RSI,7.1) AND MA(V,5)>MA(V,),COLORRED;
DRAWTEXT(CROSS(RSI,7.1) AND MA(V,5)>MA(V,),MA(L,3),'↖◆短线擒黑码◆'),COLORWHITE;
DRAWICON(买,MA(L,3),);
卖:=CROSS(7.1,RSI) AND MA(V,)>MA(V,5),COLORGREEN;
DRAWTEXT(CROSS(7.1,RSI) AND MA(V,)>MA(V,5),箱顶,'■■逃跑■■'),COLORGREEN;
DRAWICON(卖,MA(H,3),);
{ 绝密买点}
A:=EMA(C,3),COLORWHITE;
A:=EMA(C,5),COLORYELLOW;
A:=EMA(C,7),COLORMAGENTA;
A:=EMA(C,),COLORGREEN;
A:=EMA(C,),COLORRED;
A:=EMA(C,),COLORBLUE,LINETHICK2;
SS8:=CROSS(A,A) AND C>O AND C>REF(C,1) AND C/REF(C,1)>=1. ;
SSS8:=CROSS(A,A) AND C>O AND C>REF(C,1) AND C/REF(C,1)>=1.;
DRAWICON(SS8 ,MA(L,3),5);
DRAWTEXT(SS8,MA(L,3),'↖绝密买点'),COLORYELLOW;
ZYX1:="DMI.PDI"(,6);
ZYX2:="DMI.MDI"(,6);
ZYX3:=ZYX1> AND ZYX1>REF(ZYX1,1);
ZYX4:=LLV(ZYX1,0);
ZYX5:=BARSLAST(ZYX4=ZYX1);
ZYX6:=(0-REF(ZYX2,4))/(ZYX4-REF(ZYX2,ZYX5))>2;
ZYX7:=ZYX1>REF(ZYX1,1);
ZYX8:=VOL>2*MA(VOL,);
ZYX9:="DMI.ADX"(,6);
ZYXA:="DMI.ADXR"(,6);
ZYXB:=CLOSE>MA(CLOSE,) AND CLOSE<MA(CLOSE,)*1.;
ZYXC:=MA(CLOSE,)>REF(MA(CLOSE,),1);
ZYXD:=BARSLAST(CROSS(MA(CLOSE,5),MA(CLOSE,)))<BARSLAST(CROSS(MA(CLOSE,),MA(CLOSE,5)));
{ ZYXE:=0-"MACD.DIFF"(7,,3);}
ZYXF:=TROUGHBARS(3,,1)<4;
ZYX:=EMA(CLOSE,)>REF(EMA(CLOSE,),2);
ZYX:=IF(ZYXF=1,,0);
ZYX:=CROSS(ZYX2,ZYX1) AND CROSS(ZYXA,ZYX9);
ZYX:=CROSS(ZYX2,ZYX1) AND CROSS(ZYX9,ZYXA);
ZYX:=ZYXB AND ZYXC AND ZYXD AND ZYX AND ZYX6 AND ZYX7 AND ZYX8*;
ZYX:=BARSLAST(CROSS(ZYX2,ZYX1)=1);
ZYX:=BARSLAST(CROSS(ZYX1,ZYX2)=1);
ZYX:=HHV(ZYX1,ZYX);
ZYX:=BARSLAST(ZYX1=ZYX);
{ STICKLINE(FILTER(ZYXF=1,5),,0,,0),COLORRED;}
ZYX:=ZYX3 OR ZYX OR ZYX*;
ZYX1A:=ZYX*;
DRAWICON(FILTER(ZYXF=1,3),MA(L,3),);
DRAWTEXT(FILTER(ZYXF=1,3),箱低,'■■铁底■■'),COLORGREEN;
{ 量能平台}
ND:=;
PTD:=CONST(LLVBARS(V,ND));
TDPX:IF(CURRBARSCOUNT<=ND,CONST(IF(PTD=0,O,REF(O,PTD))),DRAWNULL),COLORFF;
IF(CURRBARSCOUNT=PTD+1,TDPX,DRAWNULL),CIRCLEDOT,COLORFF,LINETHICK2;
DRAWTEXT(ISLASTBAR,TDPX,' 地平线'),COLORFF;
G:=;
T:=CONST(HHVBARS(V,G));
T:=IF(CURRBARSCOUNT<=G+7,CONST(IF(T=0,H,REF(H,T))),DRAWNULL);
TA:=IF(CURRBARSCOUNT=T+1,T,DRAWNULL),CIRCLEDOT,COLORWHITE;
DRAWTEXT(ISLASTBAR,T,'天量能平台'),COLORWHITE;
W:=;
TW1:=CONST(HHVBARS(V,W));
TW0:=IF(CURRBARSCOUNT<=W+7,CONST(IF(TW1=0,C,REF(C,TW1))),DRAWNULL);
TW0A:=IF(CURRBARSCOUNT=TW1+1,TW0,DRAWNULL),CIRCLEDOT,COLORWHITE;
DRAWTEXT(ISLASTBAR,TW0,'量能平台'),COLORWHITE;
W:=;
TW:=CONST(HHVBARS(V,W));
TW:=IF(CURRBARSCOUNT<=W+7,CONST(IF(TW=0,C,REF(C,TW))),DRAWNULL);
TWA:=IF(CURRBARSCOUNT=TW+1,TW,DRAWNULL),COLORWHITE;
DRAWTEXT(ISLASTBAR,TW,'量能平台'),COLORWHITE;
MW:=;
MW1:=CONST(LLVBARS(V,MW));
MW0:=IF(CURRBARSCOUNT<=MW+7,CONST(IF(MW1=0,O,REF(O,MW1))),DRAWNULL);
MW0A:=IF(CURRBARSCOUNT=MW1+1,MW0,DRAWNULL),CIRCLEDOT,COLORWHITE;
DRAWTEXT(ISLASTBAR,MW0,'地量反弹量能平台'),COLORWHITE;
{ N1:=;N2:=;N3:=;}
EM1:=EMA(C,),NODRAW;
EM2:=EMA(C,),COLORRED;
EM3:=EMA(C,),COLORGREEN;
TJ8:=BETWEEN(EM2,EM1,EM3);
{ DRAWICON(TJ8=0,L,);}
B:='<-----------------财富平台';
DRAWTEXT(VOL=HHV(VOL,),C ,B),COLORRED;
{ 超跌反弹}
RSV:=(CLOSE-LLV(LOW,))/(HHV(HIGH,)-LLV(LOW,))*;
短期底部:=LLV(OPEN,);
K:=SMA(RSV,3,1);
D:=SMA(K,3,1);
J:=(3*K-2*D),LINETHICK2;
D2:=SMA(J,3,1)*0.;
x的码率控制总结
编码器中的码率控制模块，通过选择一系列编码参数，来确保输出视频的码率满足需求并保持失真最小。尽管码率控制不属于视频编码标准，但它属于率失真优化领域。X支持的码率控制方法有ABR（平均比特率）、CQP（恒定量化参数）和CRF（恒定质量因子）。
在X中，码率控制有三种主要方式：X_RC_CQP、X_RC_CRF、X_RC_ABR。默认设置使用CRF方式，此设置在x_param_default函数中进行。
网上有说法表示优先级为ABR > CQP > CRF，但根据X源码分析，并无明确优先级顺序。设置码率控制方法的代码示例如下：在bitrate或QP设置时，表示使用相应的方法进行编码。如无设置，CRF缺省值为，表示使用此值进行编码。
在X中，QP值的默认设置为P帧QP，通过命令行传递的qp_qp_constant实际设置的是P帧的QP值。I帧和B帧的QP值基于特定因子计算得出。
在编码算法评估时，通常采用CQP方法，设置QP值（如、、、、等，常选4个QP值）进行比较。CQP编码输出的文件通常比CRF模式大，但CQP因不依赖预测而运行更快。
视频帧的重要性排序为：IDR帧 > I帧 > P帧 > 做参考的B帧 > 不做参考的B帧。QP值可以依次增大。
X中的默认设置包括QPmin、QPmax、QPstep。QPmin为0，定义X可使用的最小量化值，量化值越小，输出视频质量越好。QPmax为，为H.规格中最大的量化值，默认值适用于控制最低品质。QPstep为4，设置不同帧间量化值的最大变化幅度。
在X中，CRF方法提供与QP相似的视觉质量，但文件更小。CRF通过降低某些“不那么重要”帧的质量来实现，这些帧通常难以察觉，如复杂或高速运动场景。节省的码率将分配给更有效的帧。
CRF和bitrate在内部采用相同的调整策略，但不遵循特定输出码率。通过改变不同重要级别帧（I、P、B类型）以及帧内不同宏块类型的QP值，来调整输出视觉质量。
CRF的范围为[0, ]，其中0表示无损模式，为缺省值，表示质量最差。与QP值类似，CRF值增加6，输出码率减少约一半；减少6，码率翻倍。至的CRF值通常被认为是合理的，常被认为接近无损。
三种码率控制方式之间的比较包括：视觉质量稳定性、即时输出码率以及输出视频文件大小的控制。这有助于在传输和存储方面优化视频。
