I’m currently working on a video editor and there is a feature where you can select a gif from Giphy and overlay it on top of your video after a header transition.
With FFmpeg you can manipulate, combine, add effects with filters. There is a filter called overlay - that we can use.
This did not work as I expected:
To apply a filter after a certain amount of time we’ll use the option enable (this option allows for timeline editing).
The below script overlays the gif.mp4 on top of main_video.mp4 during the 1 - 3 seconds duration.
ffmpeg -i main_video.mp4 -i gif.mp4 -filter_complex
“[0:v][1:v]overlay=enable=‘between(t,1,3)’[out]”
-map [out] complete.mp4
** [0:v] --> first video (main_video.mp4)
** [1:v] --> the second video (gif.mp4)
** [out] --> first and second video combined into one after the overlay.
Problem: gif.mp4 will start playing from the beginning so after 1 second has passed the gif video will be 1 second in already.
Solution:
Use the setpts filter to delay the overlay video (gif.mp4) start with x seconds.
ffmpeg -i main_video.mp4 -i gif.mp4 -filter_complex
“[1:v]setpts=PTS-STARTPTS+1/TB[delayedGif];
[0:v][delayedGif]overlay=enable=‘between(t,1,3)’[out]”
-map [out] complete.mp4
The setpts filter evaluates its expression and assigns the value as the timestamp for the current frame it is processing. For a detailed explanation check out this awesome post.
For setpts=PTS-STARTPTS+1/TB:
** +1 is the time in seconds we want to delay our offset
** TB is the timebase.
Too see the gif-overlay in action check out Glitterly - a web based video editor I’ve been working on.
import ffmpeg # 输入文件
main_video = 'main_video.mp4'
gif_video = 'gif.mp4' # 注意：这里假设gif.mp4是一个有效的视频文件，尽管其扩展名可能误导人认为是GIF图像
output_video = 'complete.mp4' # 创建ffmpeg流
# 加载两个输入文件
stream_main = ffmpeg.input(main_video)
stream_gif = ffmpeg.input(gif_video) # 应用filter_complex
# 设置gif视频的时间戳，使其相对于自身起始点延迟
# 注意：ffmpeg-python中不需要显式地指定流索引（如[1:v]），因为你可以直接通过ffmpeg.input()返回的流对象来引用 delayed_gif = ffmpeg.filter_(stream_gif.video, 'setpts', 'PTS-STARTPTS+1/TB') # 将主视频和延迟后的gif视频进行叠加
# 只在时间1秒到3秒之间启用overlay overlay_filter = ffmpeg.filter_([stream_main.video, delayed_gif], 'overlay', enable='between(t,1,3)', x='(main_w-overlay_w)/2', # 可选：居中gif y='(main_h-overlay_h)/2') # 可选：居中gif # 创建输出流，仅包含处理后的视频
output_stream = ffmpeg.output(overlay_filter, output_video) # 运行ffmpeg命令
ffmpeg.run(output_stream)
