ffmpeg: How to avoid "start: 0.033333" when extraction audio from mp4 When extracting audio and video separately from a mp4 and recombining again 

ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -vn output-audio.mp4
ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -an output-video.mp4
ffmpeg -i output-audio.mp4 -i output-video.mp4 output-combine.mp4


the three mp4-s have different length according to ffprobe:

ffprobe output-video.mp4
Duration: 00:00:10.00, start: 0.000000, ...
ffprobe output-audio.mp4
Duration: 00:00:10.03, start: 0.033333, ...
ffprobe output-combine.mp4
Duration: 00:00:10.08, start: 0.033333, ...


when combining audio and video with -shortest

ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4


the length is

ffprobe output-combine.mp4
Duration: 00:00:10.04, start: 0.033333, ...


How can the start-offset (0.033333) be avoided so that all parts have the same length and the original part can be restored by combining audio and video?
Correction: instead of

ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4


it should be

ffmpeg -i output-audio.mp4 -i output-video.mp4 -shortest output-combine.mp4


Kind of answer:

ffmpeg -i output-video.mp4 -itsoffset 0.033333 -t 9.966666 -i output-audio.mp4  output-combine.mp4


seems to do the job, although the result differs in file-size slightly from an direct extraction (direct is bigger than combine) done with

ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 output-direct.mp4