Fifostream.cs

 public class FifoStream : Stream
    {
        private readonly Queue<byte[]> _localBuffer = new Queue<byte[]>();
        private int _currentStreamOffset = 0;
        private long _length;

        public override void Flush()
        {
            throw new NotImplementedException();
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            throw new NotImplementedException();
        }

        public override void SetLength(long value)
        {
            throw new NotImplementedException();
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            var currentReadBytes = 0;
            while (currentReadBytes < count && _localBuffer.Any())
            {
                var enqueuedByteArray = _localBuffer.Peek();
                var amo = enqueuedByteArray.Length - _currentStreamOffset;
                if (amo > count)
                {
                    amo = count;
                }

                Array.Copy(enqueuedByteArray, _currentStreamOffset, buffer, currentReadBytes, amo);
                currentReadBytes += amo;
                _currentStreamOffset += amo;

                if (_currentStreamOffset >= enqueuedByteArray.Length)
                {
                    _localBuffer.Dequeue();
                    _length -= count;
                    _currentStreamOffset = 0;
                }
            }

            return currentReadBytes;
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            var currentWriteBytes = new byte[count];
            Array.Copy(buffer, offset, currentWriteBytes, 0, count);

            _localBuffer.Enqueue(currentWriteBytes);
            _length += count;
        }

        public override bool CanRead { get; }
        public override bool CanSeek { get; }
        public override bool CanWrite { get; }

        public override long Length => _length;
        // _locBuf.Sum(m=>m.Length);

        public override long Position { get; set; }
    }
    


///usage
private static void Main(string[] args)
        {
            using (var ms = new FifoStream())
            using (var fs = File.OpenRead(@"G:\FileArchive\Filme\BigMovie.mkv"))
            using (var fd = File.Create(@"F:\bd\BigMovie-cop.mkv"))
            {
                int fsr = 0;
                int msr = 0;
                var buf = new byte[10 * 1024 * 1024];
                var buf2 = new byte[10 * 1024 * 1024];
                while ((fsr = fs.Read(buf, 0, buf.Length)) != 0)
                {
                    ms.Write(buf, 0, fsr);
                    while ((msr = ms.Read(buf2, 0, buf2.Length)) != 0)
                    {
                        fd.Write(buf2, 0, msr);
                    }
                }
                Console.Read();
            }

            Console.Read();
        }