关于amix

inputs

The number of inputs. If unspecified, it defaults to 2.//输入的数量，如果没有指明，默认为2.

duration

How to determine the end-of-stream.//决定了流的结束

longest

The duration of the longest input. (default)//最长输入的持续时间

shortest

The duration of the shortest input.//最短输入的持续时间

first

The duration of the first input.//第一个输入的持续时间

dropout_transition

The transition time, in seconds, for volume renormalization when an input stream ends. The default value is 2 seconds.

//输入流结束时（音频）容量重整化的转换时间（以秒为单位）。 默认值为2秒。

Video

// 黑色背景视频
time ./bin/ffmpeg-cli -v level+error \
-filter_complex "color=s=1280x720:c=black,trim=0:100[blankV]" -map "[blankV]" -vcodec libx264 -y bg.mp4
 
// overlay logo
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp4 \
-i "image-1280x720.jpeg" \
-filter_complex "[1:v]scale=480:360[logo1];[0:v][logo1]overlay=x='if(between(t,0,5),10,NAN)':10[videologo1]" \
-map "[videologo1]" \
-vcodec libx264 -pix_fmt yuv420p -an -y resultblank.mp4
 
 
// overlay logo + set show start time
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp4 \
-ss 10 -t 10 -i 1080p.mp4 \
-filter_complex "[1:v]scale=480:360,setpts=PTS+10/TB[logo1];[0:v][logo1]overlay=x='if(between(t,10,20),10,NAN)':10[videologo1]" \
-map "[videologo1]" \
-vcodec libx264 -pix_fmt yuv420p -an -y resultblank.mp4

Audio

// 静音帧 STEP 01
time ./bin/ffmpeg-cli -f lavfi -t 60 -i anullsrc -acodec mp3 -y bg.mp3
time ./bin/ffmpeg-cli -re -f lavfi -i abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo -acodec aac -y bg1.aac
 
// test STEP 02
// Summer [---30----]play---> -f lavfi -t 30 -i anullsrc=channel_layout=stereo:sample_rate=44100
// -f lavfi -t 1 -i anullsrc=channel_layout=stereo:sample_rate=44100 \
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp3 \
-i "summer.mp3" \
-i "drum.mp3" \
-filter_complex "[1:a]volume=1,atrim=0:10[audio1];[2:a]volume=1,atrim=0:10[audio2];[audio1][0:a][audio2]concat=n=3:v=0:a=1,atrim=0:30[result]" \
-map "[result]" -acodec aac -ar 44100 -y tmp.aac
real    0m0.973s
user    0m0.567s
sys 0m0.050s
 
// 重要
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp3 \
-i "summer.mp3" \
-i "drum.mp3" \
-filter_complex "[0:a]volume=1,aloop=loop=-1:size=2e+09,atrim=0:10[bgm];[1:a]volume=1,atrim=0:10[audio1];[2:a]volume=1,atrim=0:10[audio2];[audio1][bgm][audio2]concat=n=3:v=0:a=1,atrim=0:30[result]" \
-map "[result]" -acodec mp3 -y tmp.mp3
real    0m2.996s
user    0m2.287s
sys 0m0.054s

Audio 2

// 静音帧 STEP 01
time ./bin/ffmpeg-cli -f lavfi -t 60 -i anullsrc -acodec mp3 -y bg.mp3
time ./bin/ffmpeg-cli -re -f lavfi -i abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo -acodec aac -y bg1.aac
 
// test STEP 02
// Summer [---30----]play---> -f lavfi -t 30 -i anullsrc=channel_layout=stereo:sample_rate=44100
// -f lavfi -t 1 -i anullsrc=channel_layout=stereo:sample_rate=44100 \
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp3 \
-i "summer.mp3" \
-i "drum.mp3" \
-filter_complex "[1:a]volume=1,atrim=0:10[audio1];[2:a]volume=1,atrim=0:10[audio2];[audio1][0:a][audio2]concat=n=3:v=0:a=1,atrim=0:30[result]" \
-map "[result]" -acodec aac -ar 44100 -y tmp.aac
real    0m0.973s
user    0m0.567s
sys 0m0.050s
 
// 重要
time ./bin/ffmpeg-cli -v level+error \
-i bg.mp3 \
-i "summer.mp3" \
-i "drum.mp3" \
-filter_complex "[0:a]volume=1,aloop=loop=-1:size=2e+09,atrim=0:10[bgm];[1:a]volume=1,atrim=0:10[audio1];[2:a]volume=1,atrim=0:10[audio2];[audio1][bgm][audio2]concat=n=3:v=0:a=1,atrim=0:30[result]" \
-map "[result]" -acodec mp3 -y tmp.mp3
real    0m2.996s
user    0m2.287s
sys 0m0.054s
 
,aloop=loop=-1:size=2e+09,atrim=0:30
 
> time ./bin/ffmpeg-cli -v level+error \
> -i "summer.mp3" \
> -i "drum.mp3" \
> -i bg.aac \
> -filter_complex "[0:0][1:0]concat=n=2:v=0:a=1,volume=1dB,aformat=fltp,pan=stereo|c0=c0|c1=c1[a0];[2]volume=0.5dB,aformat=fltp,pan=stereo|c0=c0|c1=c1[a1];[a0][a1]amerge,aformat=fltp[a]" \
> -map "[a]" \
> -acodec aac -strict -2 -y final.aac
// ,afade=t=out:st=38.000000:d=2
 
// overlay aac
time ./bin/ffmpeg-cli -v level+error \
-i bg.aac \
-i "summer.mp3" \f

-i drum.mp3 \
-filter_complex "[0:a]volume=1[BG1];[1:a]volume=0.8,atrim=0:10[Speech];[2:a]volume=1,atrim=0:10,afade=t=in:st=0:d=3[Bgm];[BG1][Bgm][Speech]amix=inputs=3:duration=first[Audio]" \
-map "[Audio]" \
-acodec aac \
-strict experimental \
-y resultblank.aac
 
// overlay test2 aac mp4
time ./bin/ffmpeg-cli -v level+error \
-i bgaac.mp4 \
-i "summer.mp3" \
-i drum.mp3 \
-filter_complex "[0:a]volume=1[BG1];[1:a]volume=0.8,atrim=0:10[Speech];[2:a]volume=1,atrim=0:10,afade=t=in:st=0:d=3[Bgm];[BG1][Bgm][Speech]amix=inputs=3:duration=first[Audio]" \
-map "[Audio]" \
-acodec aac \
-strict experimental \
-y resultblank.aac

time ./bin/ffmpeg-cli -v level+error \
-i bg.mp4 -t 30 \
-i tmp.mp3 \
-map 0:v -map 1:a -vcodec copy -acodec copy \
-y result.mp4