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• Replacing I-frame in MP4 video

  19 janvier 2013, par Ryfeus

  I'd like to replace I-frame with another picture in order to achieve ghost-effect. (So P- and B-frames remain the same)

  How can I do this via ffmpeg (or any other soft) ?

• How to convert a Stream on the fly with FFMpegCore ?

  18 octobre 2023, par Adrian

  For a school project, I need to stream videos that I get from torrents while they are downloading on the server.
When the video is a .mp4 file, there's no problem, but I must also be able to stream .mkv files, and for that I need to convert them into .mp4 before sending them to the client, and I can't find a way to convert my Stream that I get from MonoTorrents with FFMpegCore into a Stream that I can send to my client.

  


  Here is the code I wrote to simply download and stream my torrent :

  


  var cEngine = new ClientEngine();

var manager = await cEngine.AddStreamingAsync(GenerateMagnet(torrent), ) ?? throw new Exception("An error occurred while creating the torrent manager");

await manager.StartAsync();
await manager.WaitForMetadataAsync();

var videoFile = manager.Files.OrderByDescending(f => f.Length).FirstOrDefault();
if (videoFile == null)
    return Results.NotFound();

var stream = await manager.StreamProvider!.CreateStreamAsync(videoFile, true);
return Results.File(stream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);


  


  I saw that the most common way to convert videos is by using ffmpeg. .NET has a package called FFMpefCore that is a wrapper for ffmpeg.

  


  To my previous code, I would add right before the return :

  


  if (!videoFile.Path.EndsWith(".mp4"))
{
    var outputStream = new MemoryStream();
    FFMpegArguments
        .FromPipeInput(new StreamPipeSource(stream), options =>
        {
            options.ForceFormat("mp4");
        })
        .OutputToPipe(new StreamPipeSink(outputStream))
        .ProcessAsynchronously();
    return Results.File(outputStream, contentType: "video/mp4", fileDownloadName: manager.Name, enableRangeProcessing: true);
}


  


  I unfortunately can't get a "live" Stream to send to my client.

  


• Next drawtext clears the previous one ffmpeg

  27 août 2021, par Макс Шульдинер

  ffmpeg.exe -i ffmpeg_inputs/zheltiy_chelik.mp4  -vf "[in]drawtext=fonts/Temporarium.otf:text='r':fontcolor=orange:fontsize=100:x=(w-text_w)/2+0:y=0:enable='between(t,0, 11)', drawtext =fonts/Temporarium.otf:text = 'r':fontcolor=orange:fontsize=100:x=(w-text_w)/2+20:y=0:enable='between(t,11, 22)', drawtext =fonts/Temporarium.otf:text = 'r':fontcolor=orange:fontsize=100:x=(w-text_w)/2+40:y=0:enable='between(t,22, 33)'[out]" ffmpeg_outputs/test2.mp4 -y 


  


  There is such a ffmpeg line. Its meaning is to draw a letter 20 pixels to the right of the current position of the word every 11 seconds, and in this way "write the word". But here's the problem - when the second letter starts to render, it overwrites the first, and the third, respectively, overwrites the second. The string seems to have prescribed [in] and [out] but does not help, maybe someone has ideas