如何使用ffmpeg精确快速地从视频中提取多帧

Question

i want extract frame from video with ffmpeg

for example

ffmpeg.exe -an -r 21 -ss 00:17:50 -i "K:\\test.mkv" -t 00:00:30 -s 560x314 -q:v 1 "T:\\GIF\\test_%05d.png"

the command what i intend is

extract frame from K:\\test.mkv(O)

start at 00:00:30 (O)

extracted image size is 560x314 (o)

output path and file name format T:\\GIF\\test_%05d.png (O)

extract 30seconds from start point -t 00:00:30 (X)

with frame rate 21(so if video's original fps is 24fps, then it reduced to fps22)(maybe? X)

anyway this is not collect

i got 660 images, image number is collect but this is not 30seconds video data only 15seconds data. this is too large error, so i can't ignore it

i think i can fix it by -ss move to after -i , but this need really a lot of time..

how can i solve this problem little error is ok but error is too large

i just want time x to time y, and capture picture every 1000/22 seconds captured

Answer 1

Use

ffmpeg -ss 00:17:50 -i "K:\test.mkv"
       -vf trim=duration=30,scale=560:314,setsar=1,setpts=N/22/TB
       -r 22 -q:v 1 "T:\GIF\test_%05d.png"

If your video isn't constant frame rate in the extracted portion, then total no. of output frames won't be 660.