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• FFmpeg massive data loss when writing large data and swapping segments

  25 avril 2023, par Bohdan Petrenko

  I have an ffmpeg process running which continiously writes audio data to two 30 seconds (for testing, I'm actually planning to use 5 minutes) segments. The problem is that when I write some audio data with length more than size of two segments (60 seconds), 8-17 seconds of audio is lost. Here is how I run FFmpeg and write data :

  


      _ffmpeg = Process.Start(new ProcessStartInfo
    {
        FileName = "ffmpeg",
        Arguments = 
            $"-y -f s16le -ar 48000 -ac {Channels} -i pipe:0 -c:a libmp3lame -f segment -segment_time {BufferDuration} -segment_format mp3 -segment_wrap 2 -reset_timestamps 1 -segment_list \"{_segmentListPath}\" \"{segmentName}\"",
        UseShellExecute = false,
        RedirectStandardInput = true
    })!;
    // Channels is usually 1, BufferDuration is 30


  


  And here is how I write data :

  


  public async Task WriteSilenceAsync(int amount)
{
    if (amount > _size) amount = _size; // _size is 48000 * 1 * 2 * 30 * 2 = 5760000 (size of 1 minute of audio)
    
    var silence = _silenceBuffer.AsMemory(0, amount);
    await _ffmpeg.StandardInput.BaseStream.WriteAsync(silence);
}


  


  I tried to change the ffmpeg parameters and ways I write data. But I haven't found the solution.

  


  I'm sure that the problem is caused by ffmpeg segments, because if I disable segmenting and write audio to a single file, there are no problems with data loss or audio missmatch. I also sure that amount of silence to add in WriteSilenceAsync() method is calculated right. I'm not sure if the problem appears with data length more than 30 seconds but less then 1 minute, but I think it doesn't.

  


  I don't know how to solve this problem and would be glad to see any suggestions or solutions.

  


• How to insert emote-like images among text with ffmpeg ?

  26 janvier 2020, par Vijay Bharadwaj

  I am using FFMPEG to recreate a twitch-like video chat for streaming overlay and wanted a way to insert twitch emotes into the chat that I have. The twitch emotes come in small png/jpg files.

  Currently, I use the drawtext command on several messages to get the text part of the chat, but the emotes are integral to make it look like twitch chat. Any idea how to do this ?

  If it helps, I have a working simulation of the twitch chat on a video in a webpage, using HTML, CSS, and javascript. All I’m trying to do is take what’s simulated and embed it into the video.

• ffmpeg watermark without vhook ?

  12 juin 2015, par felixge

  Since the vhook subsystem has been removed from the latest version of FFMPEG, how can I add a watermark to a video ?

  I need to be able to overlay a PNG with background transparency.