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• Node.js : realtime conversion from jpeg images to video file

  15 mai 2020, par MastErAldo

  I'm using node.js and through the socket.io library I receive chunks of data that are actually jpeg images. These images are frames of a realtime video captured from a remote webcam. I'm forced to stream the video as jpeg frames. I'm looking for a way to convert on the fly these jpeg images in a video file (mpeg 4 or mjpeg file). Does node have a library that can do this ? I already took a look at the Node-fluent-FFMPEG library but the only examples given were about conversions of jpeg files to a video and not a conversion on the fly from a stream of jpeg images. Or alternatively, does ffmpeg for windows support a stream of jpeg images as input ?

  


• Programmatically get non-overlapping images from MP4

  16 novembre 2019, par Carlos F

  My ultimate goal is to get meaningful snapshots from MP4 videos that are either 30 min or 1 hour long. "Meaningful" is a bit ambitious, so I have simplified my requirements.

  The image should be crisp - non-overlapping, and ideally not blurry. Initially, I thought getting a keyframe would work, but I had no idea that keyframes could have overlapping images embedded in them like this :

  Of course, some keyframe images look like this and those are much better :

  

  I was wondering if someone might have source code to :

  Take a sequence of say 10-15 continuous keyframes (jpg or png) and identify the best keyframe from all of them.

  This must happen entirely programmatically. I found this paper : http://research.microsoft.com/pubs/68802/blur_determination_compressed.pdf

  and felt that I could "rank" a few images based on the above paper, but then I was dissuaded by this link : Extracting DCT coefficients from encoded images and video given that my source video is an MP4. Of course, this confuses me because the input into the system is just a sequence of jpg images.

  Another link that is interesting is :

  Detection of Blur in Images/Video sequences

  However, I am not sure if this will work for "overlapping" images.

• Crossfade between images in video using ffmpeg in android

  11 septembre 2015, par vishnus

  I have managed to create a video from a series of images using this ffmpeg library ffmpeg-android-java

  My command to generate the video is

  "-y -r 1/3 -i /path/img%d.jpg  +
  
    "-strict experimental -vcodec libx264 -pix_fmt yuv420p -preset ultrafast -t 21 -crf 30 /path/out.mp4"

  In my case each image is shown for 3 seconds in the video and video is made of total 7 images.

  I want to achieve a crossfade effect when the images change in the video.

  If anyone has done this before then please point me in the right direction.