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• How can I combine HDR video with a still PNG in FFMPEG without messing up colors ?

  2 juin 2022, par Robert

  I'm trying to add a still image to the end of a video as a title-card. Normally this is simple, but the video is HDR (shot on an iPhone) and for reasons I don't understand that's causing the colors in the PNG to go nuts.

  


  Here's the original png :


  


  Here's a screenshot from the end of the output video :


  


  Clearly something is amiss. I made the PNG image in Photoshop from a photo, and I've tried it with and without embedding the color profile without any noticeable difference.

  


  Here's the command for ffmpeg :

  


  ffmpeg -y\
 -t 5 -i '../inputs/video.MOV'\
 -loop 1 -t 5 -i '../../common/end-youtube.png'\
 -filter_complex '
[1:v] fade=type=in:duration=1:alpha=1, setpts=PTS-STARTPTS+5/TB[end];
[0:v][end] overlay [outV]
'\
 -map [outV] '../test.mp4'


  


  I've tried this with non-HDR videos and the colors look perfectly normal, so clearly the HDRness is somehow involved. I've also tried adding this line to set the colorspace etc of the output. It helps with the PNG (although it's not perfect) but then the video is washed out.

  


   -colorspace bt709 -color_trc bt709 -color_primaries bt709 -color_range mpeg \


  


  I don't really care if the output video is HDR or not, as long as the video and png parts both look visually close to the inputs. This is something I'll need to do to many videos, so if possible a solution that doesn't involve tweaking colors for each one would be ideal.

  


• Is it possible to merge two or more videos in real-time like this ?

  25 février 2015, par Marko

  Is it possible to play video online that’s made of two or more video files ?

  Since my original post wasn’t clear enough, here’s expanded explanation and question.

  My site is hosted on Linux/Apache/PHP server. I have video files in FLV/F4V format. I can also convert them to other available formats if necessary. All videos have same aspect ratio and other parameters.

  What I want is to build (or use if exist) online video player that plays video composed of multiple video files concatenated together in real-time, i.e. when user clicks to see a video.

  For example, visitor comes to my site and sees video titled "Welcome" available to play. When he/she clicks to play that video, I take video files "Opening.f4v", "Welcome.f4v" and "Ending.f4v" and join/merge/concatenate them one after another to create one continuous video on the fly.

  Resulting video looks like one video, with no visual clues, lags or even smallest observable delay between video parts. Basically what is done is some form of on-the-fly editing or pre-editing, and user sees the result. This resulting video is not saved on the server, it’s just composed and played that way real-time.

  Also, if possible, user shouldn’t be made to wait for this merging to be over before he/she sees resulting video, but to be able to get first part of the video playing immediately, while merging is done simultaneously.

  Is this possible with flash/actionscript, ffmpeg, html5 or some other online technology ? I don’t need explanation how it’s possible, just a nod that it’s possible and some links to further investigate.

  Also, if one option is to use flash, what are alternatives for making this work when site is visited from iphone/ipad ?

• ffmpeg.js running extremely slow in iOS cordova (but fine in iOS safari ?)

  14 mai 2019, par PEWify

  I’m trying to create a phonegap app that converts videos into maybe 30 or so jpeg frames..
  This page converts a bigbuckbunny video into 30 frames > https://www.pewify.com/test/ (taken from https://bgrins.github.io/videoconverter.js/demo/)

  It runs fine on an iPhone x running iOS 12 in mobile safari, it takes about 12-15 seconds to complete, but the same code packaged into a iOS cordova app running on the same phone will take almost 160 seconds to complete (both end results the same, but almost 10x as long), it works fine for android browsers or an android cordova app though

  I’m using cordova android 7.0 and cordova ios 4.5.4 (phonegap cli-8.0.0) for the app

  I’ve tried removing all unneeded plugins with just the bare minimum code but to no effect, it still runs just as slow

  From what i understand phonegap is just using a webview similar to safari to render the app but in this case it works but much slower, on top of that the phone starts to get heated up (presumably doing some intensive CPU ?)

  Did read something about using WKWebview being faster in cordova instead but that messes up the app with lots of CORS and ’operation insecure" errors so have decided not to implement that for now (unless that is the solution ?)

  Hopefully someone can point me in the right direction as i’m not exactly sure what is the issue here as it works somewhat flawlessly in android (both chrome and phonegap) but only in iOS safari and not the phonegap app