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• Concatenate multiple video files alongside delayed audio files

  28 mars 2022, par Spartan 117

  I am currently working on a utility that is responsible for pulling audio and video files from the cloud and merging them together via FFMPEG. As I am new to FFMPEG, I am going to split the question into an FFMPEG part and a C# part just so people can answer either 1 part or the other (or both !).

  


  FFMPEG Part

  


  Currently, I have a working FFMPEG arg if there is only 1 video file present and it needs to be merged with multiple files.

  


  ffmpeg -i input1.mkv -i input1.mka -i input2.mka -i input3.mka -i input4.mka -filter_complex "[1:a]adelay=0s:all=1[a1pad];[2:a]adelay=20s:all=1[a2pad];[3:a]adelay=30s:all=1[a3pad];[4:a]adelay=40s:all=1[a4pad];[a1pad][a2pad][a3pad][a4pad]amix=inputs=4:weights=1|1|1|1[aout]" -map [aout] -map 0:0 output4.mkv


  


  The delays you see in there are determined by subtracting the start time of each file from the start time of the earliest created audio or video file. I know that if I wanted to create a horizontal stack of multiple videos, i could just do

  


  ffmpeg -i input1.mkv -i input1.mka -i input2.mkv -i input2.mka -i input3.mka -i input4.mka
-filter_complex 
"[2:v]tpad=start_duration=120:color=black[vpad]; 
 [3:a]adelay=120000:all=1[a2pad]; 
 [4:a]adelay=180000:all=1[a3pad];
 [5:a]adelay=200000:all=1[a4pad]; 
 [0:v][vpad]hstack=inputs=2[vout]; 
 [1:a][a2pad][a3pad][a4pad]amix=inputs=4:weights=1|1|1|1[aout]" 
 -map [vout] -map [aout] 
 output.mkv


  


  but what I want to do is both keep those delays for the audio and video files AND concatenate (not stack) those videos, how would i go about doing that ?

  


  C# Part

  


  You see that giant arg up there ? The utility is supposed to generate that based on a List of recordings. Here is the model.

  


  List<filemodel> _records;&#xA;public class FileModel {&#xA;  public string Id { get; set; }&#xA;  public string FileType { get; set; }&#xA;  public string StartTime { get; set; }&#xA;}&#xA;</filemodel>

  


  The utility has to then go through that list and create the arg (as seen in the FFMPEG part) to be executed by the Xabe.FFMPEG package. The way i was thinking to approach this is to basically create 2 string builders. 1 string builder will be responsible for dealing with the inputs, the other string builder. Here is what i have so far

  


  private async Task CombineAsync()
    {
        var minTime = _records.Min(y => Convert.ToDateTime(y.StartTime));
        var frontBuilder = new StringBuilder("-y ");
        var middleBuilder = new StringBuilder("-filter_complex \"");
        var endString = $" -map [vout] -map [aout] {_folderPath}\\CombinedOutput.mkv";

        for (var i = 0; i < _records.Count; i++)
        {
            var type = _records[i].FileType.ToLower();
            var delay = (Convert.ToDateTime(_records[i].StartTime).Subtract(minTime)).TotalSeconds;
            frontBuilder.Append($"-i {_folderPath + "\\" + _records[i].Id} ");
            var addColon = i != _records.Count - 1 ? ";" : "";
            middleBuilder.Append(type.Equals("video") ? $"[{i}:v]tpad=start_duration={delay}:color=black[v{i}pad]{addColon} " : $"[{i}:a]adelay={delay}s:all=1[a{i}pad]{addColon} ");
        }
        middleBuilder.Append("\"");
        Console.WriteLine(frontBuilder.ToString() + middleBuilder.ToString() + endString);
        // var args = frontBuilder + middleBuilder + endString;
        // try
        // {
        //     var conversionResult = await FFmpeg.Conversions.New().Start(args);
        //     Console.WriteLine(JsonConvert.SerializeObject(conversionResult));
        // }
        // catch (Exception e)
        // {
        //     Console.WriteLine(e);
        // }
    }


  


  


  1. Is this the correct way to go about building the argument out ?

     


  


  2. How in god's name do i get something like this in there, since it relies on naming and total count for the piping and inputs=

     


       [0:v][vpad]hstack=inputs=2[vout]; // This part will change for video concatenation depending on what gets answered above
  [1:a][a2pad][a3pad][a4pad]amix=inputs=4:weights=1|1|1|1[aout]


     


  


  


• Scroll seamless image with FFMPEG

  22 septembre 2022, par Rob

  I want to create a video from a single image. The image should scroll vertically and the output needs to be seamless so it can be looped (the image itself is seamless).

  


  Example of what I want to create :
GIF example
and the texture from the example : seamless texture.

  


  Length of the video is not that important since if the scrolling is seamless I should be able to just loop it with ffmpeg -stream_loop 3 -i input.mp4 -c copy output.mp4 afterwards.

  


  I have tried :

  


  ffmpeg -loop 1 -i input.png -framerate 30 -vf "scroll=vertical=0.002,crop=iw:600:0:0,format=yuv420p" -t 10 -y output.mp4


  


  which creates a video with the desired scrolling effect but its not seamless due to Issues matching the video length with the height of the image/scrolling speed and it looks something like this : Example output (exaggerated) Also ignore it scrolls the other way.

  


  I'm not sure how to proceed, maybe its just a simple math that needs to be done to add to
-t X by looking at the scroll speed & image height ? . Any ideas welcome how to solve this with either ffmpeg/python/powershell under windows.

  


• Gradient is bad in video [closed]

  1er juillet 2023, par Andres Miguel Campos

  I'm trying to capture a css animation with gradient. But when capturing the video I get a bad quality

  


  I have used the following css for the screen

  


  


  


  &#xA;&#xA;&#xA;&#xA;  &#xA;  &#xA;&#xA;&#xA;&#xA;&#xA;  <div class="horizontal-gradient">&#xA;&#xA;  </div>&#xA;&#xA;&#xA;&#xA;

  


  


  



  I have also used the following libraries or frameworks

  


  


  puppeteer-screen-recorder(NodeJS)

  


  


  


  Canvas(JavaScript)

  


  


  


  remotion.dev(Reac and Nodejs)

  


  


  


  Obs

  


  


  But it still shows me poor video quality

  


  

  


  Any support is welcome