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• Processing Video Frames in C# (FFMPEG Slow)

  9 septembre 2020, par julian bechtold

  I am trying to extract frames out of mp4 videos in order to process them.

  


  Namely there is a watermark / timestamp within the video image which I want to use to automatically stitch the videos together. The Video creation date is not sufficient for this task.


  


  Also the part of extracting the text out of the video with AI is fine.

  


  However, FFMPEG seems terribly slow. the source Video is 1080p / 60fps (roughly 1GB per 5 Minutes of video).

  


  I have tried two methods so far using Accord.FFMPEG wrapper :

  


  public void GetVideoFrames(string path)
{
    using (var vFReader = new VideoFileReader())
    {
        // open video file
        vFReader.Open(path);
        // counter is beeing used to extract every xth frame (1 Frame per second)
        int counter = 0;
        for (int i = 0; i < vFReader.FrameCount;i ++)
        {
            counter++;
            if (counter <= 60)
            {
                _ = vFReader.ReadVideoFrame();
                continue;
            }
            else
            {
                Bitmap frame = vFReader.ReadVideoFrame();
                // Process Bitmap
            }
        }
    }
}


  


  The other attempt :

  


  for (int i = 0; i < vFReader.FrameCount;i+= 60)
{
    // notice here, I am specifying which exact frame to extract
    Bitmap frame = vFReader.ReadVideoFrame(i);
    // process frame
}


  


  The second method is what I tried first and it's totally unfeasible. Apparently FFMPEG makes a new seek for each specific frame and thus the operation takes longer and longer for each frame processed.
After 5 frames already, it takes roughly 4 seconds to produce one Frame.

  


  The first method at least does not seem to suffer from that issue as heavily but it still takes roughly 2 seconds to yield a frame. At this rate i'm faster to process the video manually.

  


  Is there anything wrong with my approach ? Also I rather don't want to have a solution where I need to separately install third party libraries on the target machine.
So, if there are any alternatives, I'd be happy to try them out but it seems litterally everyone on stack overflow is either pointing to ffmpeg or opencv.

  


• Low latency rendering pipeline Implementation [closed]

  9 septembre 2024, par Makis Christou

  The goal that I am trying to accomplish is to be able to render small/per-compressed (<5MB) videos based on a given config on demand. The config would tell the renderer what text/icons to overlay on the video for example. Currently I have decided to go with ffmpeg and wrapping it in a flask api using Python (I use the ffmpeg-python module). The api has 2 routes. An upload route and a render route. So some other service first uploads their background video (which will be reused) and then use the render route to choose a different config, on demand, to render on top of their background video.

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  Currently an average video takes 0.4s (on a 7950x 128GB RAM) to be rendered and the whole request including I/O, starting ffmpeg, reading assets from SSD and everything takes around 0.7s. That is when the server is not busy at all. Once we increase the concurrent requests it quickly drops to 4-5s range when handling 10 concurrent requests and increases linearly thereafter. We have a predefined output resolution and its the lowest possible before quality takes a hit so reducing further is not an option.

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  My goal here is 2 fold.

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  1. Reduce latency i.e. keep it under 2s instead of 5 for 10 concurrent renders (the hard part)

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  2. Increase throughput (easier to achieve but looking for cost effectiveness here)

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  Besides vertical scaling (to reduce render time < 0.4s), moving the server closer to the client (to reduce network latency) are there any obvious ways to reduce the latency of a single request ? One inefficiency that I see is that ffmpeg starts/stops as a new process in every request. Also assets are loaded from disk when ffmpeg starts for each request. Not sure if there is a way to solve this by keeping it all in RAM 24/7. Also have not tried GPUs but I assume it will be worse since copying to the GPU back and forth is expensive.

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  For increasing throughput, load balancing on multiple machines is the way to go but then I would need a shared storage solution with caching. Any recommendations that are performance oriented ?

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  Explained above.

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  • use ffmpeg

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  • use a better server

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• Compress video like whatsapp

  10 juillet 2021, par user1079425

  I'm not an expert in Video Editing but what I want to understand the logic of Whatsapp video processing.

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  First of all I have noticed that whatever the file is, Whatsapp sets the limit of Uploaded videos to 16MB, after which whatsapp crops the video to not exceed the limit. is this a convention or it's a personal choice ?

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  Secondly, When a video is recorded using the Camera it's not compressed by default, so whatsapp compresses it using FFMPEG I guess, and it takes no time. (tried for a video of 1min 1920x1080 with 125MB of size, becomes 640x360 with 5MB of size in no time, and the upload starts automatically).. how may they do this ? and why the choice of 640x360, It seems to me very fast for 2 asynchronous tasks : Compression + Upload.

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  When I run the compression command ffmpeg -y -i in.mp4 -codec:v libx264 -crf 23 -preset medium -codec:a libfdk_aac -vbr 4 -vf scale=-1:640,format=yuv420p out.mp4 it takes approximatively 1 min and the video is being rotated !! :D

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  Finally, when we download a video from Youtube it's already compressed (I guess) and whatsapp doesn't even try to compress it. So I think that it automatically detects thats the video is compressed. How can we detect this ?

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  Thank you.

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