Naked Science Forum
Non Life Sciences => Technology => Topic started by: theThinker on 11/01/2018 16:27:02
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I made a home 45 min video of myself giving a presentation on a physics topic using my iphone 6. The format is quicktime .MOV - about 2.6 GB. I converted it to .mp4, now down to 600 MB, using a software avidemux.
After that I used a linux utility ffmpeg and used a 'drawtext' feature to add relevant text/equations at relevant portions of my video. This is a .mpeg-4 to .mpeg-4 with little change in size I understand it may be similar to a hard-sub with re-endcoding (I don't understand what is re-encoding). I uploaded it to youtube and China's youku and everything was working find.
I then made a post in China's Weibo (an equivalent to Twitter) with a link to my youku video. I got a surprise! The video plays perfectly, but somehow all the text that I added with 'drawtext' disappeared. I don't understand.
I know that Weibo is heavily censored, but I can't understand if somehow they would go to this extend. They might as well take away my audio track or delete my video link.
I ask a relative of mine who has a B.Sc in computer science and he told me there are ways using AI neural network to remove texts from my video. The text from my video is very clear with blue and a ttf font style.
Can someone confirm this is what Weibo did to my video, censoring all the texts. If it is true, can someone explain how I could redo my video so that no one could just remove the texts added. I have the original video in .MOV and .mp4
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Are you sure that this is what happened and that you did not just upload the wrong version? Ockham's razor and all that...
It seems an extraordinary length for someone to go to over a harmless physics video.
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Are you sure that this is what happened and that you did not just upload the wrong version? Ockham's razor and all that...
It seems an extraordinary length for someone to go to over a harmless physics video.
I am dead sure.
My Weibo post has only a link to my China Youku (China's youtube) video. When I play the video in the Youku site, all the texts are there, just as with youtube.
But at my Weibo mircrobloging post, there is a link to youku and another image of my video. Playing the video by clicking the video will be without text. But clicking the link brings me Youku site; the video there will play complete with text.
The Chinese are great! I don't have another mp4 files over the internet anywhere.
Note: If there was censoring of text, it could only be done using AI automatically. I click on the video just minutes after posting. There was no "waiting for approval".
Also, I don't think my mp4 video has an extra subtitle track.
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The subtitles may just be a overlay which was lost when the video was transcoded by the video-host.
If you burn the subtitles into the video that should solve the problem ... https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo
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The subtitles may just be a overlay which was lost when the video was transcoded by the video-host.
If you burn the subtitles into the video that should solve the problem ... https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo
But I have no subtitle files so cannot do any 'burning'. I did experimented with subtitles but the text has very bad fonts.
I use multiple ffmpeg 'drawtext' in a batch file.
#!/bin/bash
ffmpeg -i input.mp4 -vf "
drawtext=enable='between(t, 28*60, 30*60)': fontfile=/usr/share/fonts/TTF/DejaVuSans.ttf: text=\
'My text here..
Something'\
: fontcolor=blue: fontsize=22: box=0: x=(w-text_w)/20: y=(h-text_h)/20,
drawtext=enable='between(t, 31*60 + 25, 32*60 + 6)': fontfile=/usr/share/fonts/TTF/DejaVuSans.ttf: text=\
'Other text.
'\
: fontcolor=blue: fontsize=22: box=0: x=(w-text_w)/20: y=(h-text_h)/20
" -vcodec libx264 -preset fast -crf 24 -codec:a copy output.mp4
I was told changing from mp4 to avi may solve the problem. The avi file I got is only slightly larger - 650 to 800 MB. I am now uploading to youku and see what I get.
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The subtitles may just be a overlay which was lost when the video was transcoded by the video-host.
If you burn the subtitles into the video that should solve the problem ... https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo
OK. I uploaded an avi version to youku and did a post to weibo linking to this new avi video. The same; text removed in the hosted video.
I read that it is trivial to detect text with OCR ? or something.
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Automatically editing-out any video with on-screen-text would be possible, but displaying the video which had text, with text removed, would be impossible, IMO, if the text was burned into the video.
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Very sorry. My mistake. I am new to Weibo with only 1 post. Weibo gives an image for preview of any video link. I think it is limited to 6 min 30secs. My drawtext starts only after. So there is no text removal by Weibo.