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• FFmpeg av_interleaved_write_frame to buffer

  2 juin 2022, par phantasm

  Hi I am using FFmpeg Autogen C#. Everything works when I use mkv output as a file and h264 rtsp stream as input. Codec is libx264

  


    ffmpeg.avio_open(&container->pb, filename, 2),
  fmpeg.avformat_write_header(container, null)
  ffmpeg.av_read_frame(inputContainer, &pkt)
  ffmpeg.av_interleaved_write_frame(container, &pkt).


  


  Mkv file output is working perfect.
But when I am trying to open AVIOContext to the buffer

  


  ffmpeg.avio_alloc_context(avio_ctx_buffer, 32768, 1, &bd, null, write, seek)


  


  Seek Function

  


  unsafe long seek(void* opaque, long offset, int whence)
    {
        buffer_data* bd = (buffer_data*)opaque;
        switch (whence)
        {
            case 0:
                bd->ptr = bd->buf + offset;
                return (long)bd->ptr;
            case 1:
                bd->ptr += offset;
                break;
            case 2:
                bd->ptr = (bd->buf + bd->size) + offset;
                return (long)bd->ptr;
            case 65536:
                return bd->size;
            default:
                return -1;
        }
        return 1;
    }


  


  Write Function

  


   unsafe int write(void* opaque, byte* buf, int buf_size)
        {

            buffer_data* bd = (buffer_data*)opaque;
            while ((ulong)buf_size > bd->room)
            {
                long offset = bd->ptr - bd->buf;
                bd->buf = (byte*)ffmpeg.av_realloc_f(bd->buf, 2, (ulong)bd->size);
                if (bd->buf == null)
                    return ffmpeg.AVERROR(ffmpeg.ENOMEM);
                bd->size *= 2;
                bd->ptr = bd->buf + offset;
                bd->room = (ulong)(bd->size - offset);
            } 
            memcpy((IntPtr)bd->ptr, (IntPtr)buf, (UIntPtr)buf_size); 
            bd->ptr += buf_size;
            bd->room -= (ulong)buf_size;
            byte[] b = new byte[buf_size];
            Marshal.Copy((IntPtr)buf, b, 0, buf_size);
            using (var fs = new FileStream(@"D:\file1.mkv", FileMode.Append, FileAccess.Write, FileShare.ReadWrite))
            {
                using (BinaryWriter writer = new BinaryWriter(fs))
                {
                    writer.Write(b);
                }

            }
            return buf_size;
        }


  


  Buffer Data

  


  public unsafe struct buffer_data
        {
            public byte* buf;
            public long size;
            public byte* ptr;
            public ulong room; ///< size left in the buffer
        };


  


  Result I am getting is 1 second mkv video(its size increases but vlc player is unable to play it).Also notice that writing to file is just for testing I am trying to keep mkv data in buffer.Thank you !!!. If smth missing please comment I will add

  


• Combine mp4 init file and m4s segments to a single mp4 file

  5 août 2020, par David Oz

  In my Nodejs server, I'm trying to combine init-file in mp4 format, with some m4s segments.
I've used Buffer.concat() and it partially worked, it seems like the segments hold an offset because they are taken from the middle of a video that is played with mpeg-dash, which causes an incorrect start time. when I use the fluent-ffmpeg npm library, the file is fixed, but it takes way too long (about as long as the video itself).
I was wondering if is it possible to fix the problem by changing some bytes in the buffer or anything faster like that.

  


• How to add audio to video file at a specific time using ffmpeg

  7 avril 2017, par LEM

  I have an avi and a wav file. Let’s suppose the video file is one hour long, and the audio file 30 minutes long and it’s associated with the last 30 minutes of the video file.

  Is there a way to create a new video file with the video and audio combined but audio starting after the first 30 minutes of the video ?