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• How can I convert the first frame of a video to an I-frame and the rest to P-frames with FFMPEG ?

  18 juin 2015, par Blankasaurus

  I’d like to try to do some datamoshing like this tutorial. But I’d like to be able to do it programatically, so instead of vdub and avidemux, I’d like to figure out how to do as many parts of this process as I can with ffmpeg and/or other command-line tools.

  The first problem I am having is that when I use the ffdshow codec rev 3556 with VDub it just outputs a broken video. I feel like I got close to getting what I want, which is frame 0 as an I-frame and all the rest as P-frames with the following command

  ffmpeg -i input.mp4 -force_key_frames 00:00:00.000 output.avi

  There are a couple of problems with this...

  1) I get B-frames too, which don’t work with that type of data-moshing

  2) There’s still I-frames every 10 or so frames

  I feel like the problem is that I need to use a certain codec to encode the video in and also that -force_key_frames probably just enforces the addition of extra keyframe(I-frames) but doesn’t prevent other I-frames from being created.

• Videos storage and streaming [closed]

  12 juillet 2021, par Tomer

  I'll do my best to describe my thought here.

  


  We came across a need to receive videos from users, store them and later on present those videos to different users upon request.
The argument is based on the idea that we can't serve one single file of the same size and quality to all clients. There must be consideration of the client's network quality.
One side claims that the best way to overcome this issue is by storing multiple versions of one file (360p, 480p, 720p etc..) and then based on the client's network quality we will estimate which file is best suited for his conditions. We shall estimate the client's network quality by testing the connection quality to the s3 servers storing our files.

  


  Second party claims that storing one file of high quality is enough. Then, upon request by client we shall stream the file to the client in the suitable encoding and quality using a third party framework (from brief research, ffmpeg, Gstreamer. Its not established yet which and how, only consider the idea.).

  


  Which is more acceptable in modern ways ? Are there any other ideas we haven't thought of ?

  


  Couple of notes. Our backend is written in node, using aws-sdk for s3 and nest for api.

  


  Thanks

  


• Image scaling boundaries in FFMEG

  6 mars 2018, par Pedro Pereira

  I am implementing my own version of the bilinear and bicubic scaling algorithms to understand how ffmpeg does the scaling. So, I compare the results I get with the results of the ffmpeg. A couple days agora I had trouble implementing the bilinear version because my bilinear scaled images were different from the ffmpeg ones. With the help of people in the IRC chat I understood that the ffmpeg duplicates the nearest original pixel when the index of the neighboring pixels to interpolate is out of the original image bounds.

  In the same perspective, what does the bicubic version in ffmpeg does to out of the original bounds pixels ? I tried duplicating the nearest original pixel (like in bilinear) and my scaled image is not the same as the ffmpeg one.

  Do I have to something like this ? Fill the boundaries of a matrix using Bicubic interpolation