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• How to deal ffplay bein too slow playing iPhone's videos ?

  21 janvier 2019, par Mikhail T.

  Trying to play a 3840x2160 video recorded by an iPhone 7 (@30fps), I get frequent pauses — in the video, music keeps playing.

  This happens both in firefox and when ffplay is invoked to play the file directly — from command-line. The CPU is a dual E6700 @3.20GHz — not super fast, but it should be able to play smoothly, shouldn’t it ? Video is Intel’s "series 4" integrated chipset — again, not a speed-daemon, but it should be adequate... Support for Intel’s VA API is included.

  I build ffmpeg-4.1 from source using FreeBSD port. As you can see, the port has a maddening amount of options — including several different ones for the 264-codec.

  Any suggestions for improving the decoding speed to the point, where it is watchable by a human ? Thank you !

• 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.

• FFMPEG h.264 stream to VLC from raw YUV444 produces black screen

  30 novembre 2018, par GerbGerb

  Not sure if this fits better here or over on Super User, so please redirect if here is the wrong place.

  I am piping raw YUV444 640x480 frames to ffmpeg from inside a C++ program using stdout. ffmpeg encodes them using h.264 and streams the video via UDP to an IP of my choice.

  When I am not streaming and saving the video as -mp4 file, everything works - But when I stream over the network and try to receive in VLC, the stream is received and the playing timer under the video screen runs, but the image is black, none of the video is displayed. Also I have some crackling sounds on my audio output.

  My FFMPEG settings are as follows :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 -f mpegts udp://192.168.150.1:20001

  in VLC, I just use "open network stream" with udp ://@:20001. The port is open, I tested it with a simple dummy sender/receiver.
  Almost the same cli arguments for the video recording lead to a perfectly playable video when writing to a file and downloading it :

  ffmpeg -y -loglevel info -f rawvideo -r 25 -c:v rawvideo -pix_fmt yuv444p -s 640x480 -i - -c:v libx264 -preset superfast -framerate 25 video.mp4

  If I try to stream the same video using

  ffmpeg -i video.mp4 -v 0 -vcodec mpeg4 -f mpegts udp://192.168.150:20001

  the screen remains black.

  VLC debug output changes between different runs, because other modules are selected, so I assume stream type recognition goes haywire. But why ?

  What am I doing wrong ?

  Here the ffmpeg log
  and the VLC log