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• Web-based video editor

  10 octobre 2014, par Danny

  We have a web-based editor currently that allows users to build animated web apps. The apps are made up of shapes, text, images, and videos. Except for videos, all other elements can also be animated around the screen. The result of building a animated app is basically a big blob of JSON.

  The playback code for the web app is web-based as well. It takes the JSON blob and constructs the HTML, which ends up playing back in some sort of browser environment. The problem is that most of the time this playback occurs on lower-end hardware like televisions and set-top boxes.

  These performance issues go away if there is some way to be able to convert a digital sign to video. Then the STB/smart TV simply plays a video, which is much more performant than playing back animations in a web view.

  Given a blob of JSON describing each layer and how to draw each type of object, its animation points, etc, how could I somehow take that and convert it to video on the server ?

  My first attempt at this was using PhantomJS to load the playback page in a headless browser, take a series of screenshots, and then use ffmpeg to merge those screenshots into a video. That worked great so long as there is no video. But it does not work with video since there is no HTML5 video tag support in PhantomJS, and even if there was, I would lose any audio.

  The other way I was thinking of doing it would be to again load the playback page in PhantomJS, but turn off the video layers and leave them transparent, then take screenshots as a series of PNGs with transparency. I would then combine these with the video layers.

  None of this feels very elegant though. I know there are web-based video editors out there that basically do what I’m trying to accomplish, so how do they do it ?

• ffmpeg encoding sample wanted ?

  24 juin 2015, par Rella

  I found this tutorial about ffmpeg the thing i do not get is how to encode video.

  can any one, please provide a tutorial.. with explanations for that ? (not that i dont get this official one but i’d love to see more comments)

• How to add subtitles to PowerPoint presentation

  5 septembre 2018, par ppdlx

  Okay, to clear things up I will say that I’m posting here because I found the answer and want to help people in future who come upon the same problem. Since PowerPoint is not the right tool to title an presentation I will tell you my way of doing this. If you can do it in PowerPoint alone, super for you but I could not do it in PowerPoint alone, therefore this way. So what I did is the following, I simply recorded the presentation and made subtitles for it and in the final I hardcoded the subtitles into the video. Here is how I did it.

  How to add subtitles to your PowerPoint presentation

  First, I downloaded the latest SnagIt software from their official website. You can have a free trial there. Click here to download SnagIt. Then using SnagIt I recorded my whole screen and played the presentation. I made a video file of the presentation. Let’s call it presentation.mp4.

  Then I downloaded my subtitle making software, an awesome open source program called Subtitle Edit from it’s official website. It’s really simple to use it and it is awesome and user friendly. It doesn’t take too long to subtitle a three minute presentation. When you are satisfied with the subtitles save them as .srt and call them whatever you like. Now we have a video file and corresponding subtitles for it.

  Now we need to hardcode the subtitles into the video file, in other words to burn the subtitles to the video. I did this using another awesome open source software called ffmpeg. See the website and download it from official ffmpeg website. Extract it somewhere and for convinience put subtitle and video file to it’s bin directory. You can put it elsewhere if you like it that way. The first command I used is to transform .srt to .ass.

  ffmpeg -i subtitles.srt subtitles.ass

  Afterwards it’s easy to make a subtitled video file with the following command :

  ffmpeg -i presentation.mp4 -vf ass=subtitles.ass presentation_subtitled.mp4

  I am not sure for the command and can’t get now to see the correct command but if it fails you can seek help on this page.

  Now that we have our presentation_subtitled.mp4 we can now trim the video to our likings.

  ffmpeg -i presentation_subtitled.mp4 -ss 00:01:00 -to 00:02:00 -c copy presentation_final.mp4

  Of course, edit the -ss and -to option, it’s the start time and the end time of your video.

  That’s it ! Now you have your presentation_final.mp4 video file where you have your presentation with subtitles. Ffmpeg is awesome because you can convert it to any format you like.

  You have some help with hardcoding subtitles on Subtitle Edit web page, but one software gave me a virus, one software didn’t work, and after trial and error this is the way that worked for me and it’s really convinied due to great open source software - Subtitle Edit and ffmpeg.