code:

writer = new BinaryWriter(myProcess.StandardInput.BaseStream);

                for (int z = 1; z <= image.FrameCount; z++)
                {
                    MemoryStream mem = (MemoryStream)frameBits[z];
                    mem.Position = 0;
                    writer.Write(mem.ToArray());

                    // test to see if png's are good, dump them to disk
                    File.WriteAllBytes(@"C:\temp\test\images\image" + z + ".png", mem.ToArray());
                }

                writer.Flush();
                writer.Close(); // if i dont do this here.... it just hangs at frame 55 see below


results:

rame=   48 fps=5.0 q=0.0 size=    2074kB time=00:00:01.92 bitrate=8849.0kbits/s
frame=   52 fps=5.0 q=0.0 size=    2230kB time=00:00:02.08 bitrate=8783.2kbits/s
frame=   55 fps=5.0 q=0.0 size=    2367kB time=00:00:02.20 bitrate=8815.3kbits/s
pipe:0: Input/output error
frame=   56 fps=2.8 q=0.0 size=    2429kB time=00:00:02.24 bitrate=8881.7kbits/s
frame=   58 fps=2.8 q=0.0 Lsize=    2559kB time=00:00:02.32 bitrate=9037.0kbits/s
video:2558kB audio:0kB subtitle:0 global headers:0kB muxing overhead 0.055894%