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• Pass individual frames as BGRA byte array and set the timestamps via pipe to FFmpeg

  30 juillet 2023, par Nicke Manarin

  I have a set of images (as BGRA byte[]) with their respective timestamps in milliseconds and I want to pass it to FFmpeg to build an animation.

  


  I'm using FFmpeg v6 right now and in this example I'm expecting a GIF as output, but I'm going to export to multiple formats later.

  


  var arguments = "-vsync passthrough  
-f rawvideo 
-pix_fmt bgra 
-video_size {width}x{height} 
-i -  
-loop 0 
-lavfi palettegen=stats_mode=diff[pal],[0:v][pal]paletteuse=new=1:dither=sierra2_4a:diff_mode=rectangle 
-f gif 
-y \"C:\Users\User\Desktop\test.gif\"";

var process = new Process
{
    StartInfo = new ProcessStartInfo
    {
        FileName = "./ffmpeg.exe",
        Arguments = arguments.Replace("{width}", width.ToString()).Replace("{height}", height.ToString()),
        RedirectStandardInput = true,
        RedirectStandardOutput = true,
        UseShellExecute = false,
        CreateNoWindow = true
    }
};

_process.Start();



  


  Then on my render loop, I'm trying to send the frames and their timestamps one by one.

  


  public void EncodeFrame(IntPtr bufferAddress, int bufferStride, int width, int height, int index, long timestamp, int delay)
{
    var frameSize = height * bufferStride;
    var frameBytes = new byte[frameSize];
    System.Runtime.InteropServices.Marshal.Copy(bufferAddress, frameBytes, 0, frameSize);

    _process.StandardInput.BaseStream.Write(frameBytes, 0, frameSize);
    _process.StandardInput.BaseStream.Write(_delimiter, 0, _delimiter.Length);
    _process.StandardInput.BaseStream.Write(BitConverter.GetBytes(timestamp), 0, sizeof(long));
}


  


  The issue is that I'm getting an IOException (The pipe has been ended), so probably I'm not sending the frames correctly (not sending the delimiter and timestamp doesn't help).

  


  Is this even possible ?

  


• MoviePy : Concatenating video clips causes weird glitches in final video

  16 mai 2022, par JohnSmithy1266

  Is there a way to successfully always patch up any clips together in such a way that prevents weird glitches ? I put together a .mp4 from smaller .mp4 files and I got a final video with weird glitches. I am running Python 3.6.1 on Windows 10 through Sublime Text 3. I used MoviePy to do the concatenation.

  



  The code :

  



  from moviepy.editor import VideoFileClip, concatenate_videoclips
import os.path

path = "C:/Users/blah/videos/out/"

cliparray = []

for filename in os.listdir(path):
    cliparray.append(VideoFileClip(path + filename))

final_clip = concatenate_videoclips(cliparray)

final_clip.write_videofile(path + "concatenatedvideo.mp4", codec = "libx264")


  



  The weird glitches :

  



  

  1. One of the clips turns into a 3x3 grid of smaller clips.

  


  2. Another has the audio not lined up with the video

  


  3. Another is sped up faster than what was normal.

  


  


• Compression rate (final size) ffmpeg with h263 as codec, can be improved ?

  29 août 2013, par voskyc

  With the following data :

  Sample 1 :
  vcodec : H263
  Duration : 4seconds
  Resolution:1288/720
  FR : 30fps/s
  datarate : 195.135 kB/s
  MP3 : 44HZ, 16bits

  ---

  Size file : 5.84MB.

  Sample 2 :
  vcodec : H263
  Duration : 4seconds
  Resolution:640/480
  FR : 30fps/s
  datarate : 195.135 kB/s
  MP3 : 44HZ, 16bits

  ---

  Size file = 3.34MB.

  Both in flv container.

  Aren't those sizes a little bit high for 4 second video ?

  I believe we are doing some kind of error or missing an optimization.
  Should we decrease the datarate ?
  Maybe we are missing some option for h263 encoding with FFMPEG ?.

  Thanks a lot in advance for your suggestions.

  Note : no, we "can not" use h264. :-)