To eliminate XY problem, here is what's my situation. I have source YouTube videos in MP4 container. I create voiceovers for them using Sony Vegas on Windows machine and then export them as WAV file, which I then use as new audio track for original video with ffmpeg. If I want to translate on-screen captions (e.g. public service announcements, signs, intro titles or anything like that), then Sony Vegas transcoding goes like forever and creates enormous files. And my kind of solution for this would be to split original video into pieces and only transcode the altered part, and then just concatenate them: unaltered-start.mp4 + altered.mp4 + unaltered-end.mp4 using intermediate files method in Concat protocol

So my question here is how can I convert altered.mp4 into exact same format as unaltered-start.mp4 (resolution, encoding, bitrate, etc.)? Is there any ffmpeg flag to use in the meaning "use encoding format exactly from this media file"?

  • Or, maybe there's a good way to encode video in Sony Vegas really fast and make it relatively small (e.g. under 200Mb for 15 min. 1080p@30fps)? – Eduard Sukharev Jul 16 '18 at 16:02
  • If you want to do voice-overs for on-screen captions, why do you need to transcode the video? Or is the voice-over part not related to your question? If so (i.e. your question is about how to reduce encoding time), why don't you write your captions as standalone subtitle files, which can later be merged with the original video, if needed? Or do the captions have to be hardcoded? Even if you went for splitting up the video (which I don't recommend), how would you figure out which parts have been changed? – slhck Jul 16 '18 at 20:02
  • Sorry for confusion, voiceover part is not really related to the reason I want to transcode. It's the whole viewer experience, rather: not only you want to hear translated speech, but also some on-screen captions, titles, Public service announcements and so on. That's why I want to actually edit the video to place translated text over the original. – Eduard Sukharev Jul 17 '18 at 7:51

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