The input will be parsed using keyframes, which is very fast. If the -ss comes before -i, it will also produce one image frame (yosemite.png) somewhere around the 18 seconds from the beginning of the movie. The command will seek to the position of 0h:0m:18sec:123msec into the movie and extract one frame (-vframes 1) from that position into a yosemite.png file: When we extract just one frame, we can opt out "-f image2" from the command above:įfmpeg -i yosemiteA.mp4 -ss 00:00:18.123 -frames:v 1 yosemite.png image2: to extract the frames in separate png files, we need to force the image2 muxer.vframes: set the number of video frames to record.Expected to be true of most phone/cam/web videos.If we want to extract just a single frame (-vframes 1) from the video ( Yosemite) into an image file, we do:įfmpeg -i yosemiteA.mp4 -ss 00:00:18.123 -f image2 -vframes 1 yosemite.png It's a safe assumption for 95% of videos.įinally, I assume the full video has AAC-LC as its audio codec. I also assume, tacitly, that the full video does not use more reference frames than produced by preset medium of x264. Which should be fine as this is the only pixel format supported by web players and smartphone cameras, consumer camcorders.etc. My first step assumes that the video stream has the most common pixel format yuv420p. Then run ffmpeg -f concat -i list.txt -c copy merged.mp4 ffmpeg -i fullvideo.mp4 -c copy -video_track_timescale 600 full600.mp4
If not done, the combined video will likely run at the wrong speed. Have to do one bookkeeping step for the full video. This device requires that the files being joined share certain properties, like codec, framerate, video dimensions, timebase.etcįirst step is to create the blank segment, which may be used both at the head and tail. The basic method to join videos without re-encoding is to use the concat demuxer.
0 kommentar(er)
