ffmpeg

[szcf-weiya]

second way to speed up

https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video

ffmpeg -i VID_20220623_183559.mp4 -map 0:v -c:v copy -bsf:v h264_mp4toannexb VID_20220623_183559_raw.h264
ffmpeg -fflags +genpts -r 120 -i VID_20220623_183559_raw.h264 -c:v copy VID_20220623_183559_r120.mp4

However, it might throw the following error,

not enough frames to estimate rate; consider increasing probesize

refer to https://stackoverflow.com/questions/57903639/why-getting-and-how-to-fix-the-warning-error-on-ffmpeg-not-enough-frames-to-es

try

ffmpeg -fflags +genpts -probesize 2G -r 120 -i VID_20220623_183559_raw.h264 -c:v copy VID_20220623_183559_r120.mp4

otherwise, it might behave like

but note that in this method, the size of the video would not decrease, i.e., no loss.

see also: https://zhuanlan.zhihu.com/p/142593316

[szcf-weiya]

add mosaic at a static position via crop and overlay

1. create a snapshot and then open with geeqie, which can show the pixel coordinate of the cursor, determine the start position (left corner) and the width and height of the region to be blur

ffmpeg -i test.mp4 -filter_complex "[0:v]crop=210:20:47:233,avgblur=20[fg];[0:v][fg]overlay=47:233[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy -movflags +faststart test2.mp4

where

• 210:20:47:233 indicates the start position is at (47, 233), and the (width, height) are 210x20
• overlay means that we crop the region and blur it and finally overlay on the original figure

see also: https://superuser.com/questions/901099/ffmpeg-apply-blur-over-face

similarly, we add another mosaic region,

ffmpeg -i test2.mp4 -filter_complex "[0:v]crop=142:20:372:212,avgblur=20[fg];[0:v][fg]overlay=372:212[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy -movflags +faststart test3.mp4

since the right corner is empty, so crop them out

ffmpg -i test3.mp4 -filter:v "crop=680:630:1:1" -c:a copy test4.mp4

the resulting video is here

https://user-images.githubusercontent.com/13688320/196267281-a4e4780d-513a-4a47-9149-169e7aac2093.mp4