Save hex datas of .mjpeg file as a .mjpeg formatted file in C#

Question

I have a text file filled with hex datas(like "FFD8FE00..") of a .mjpeg formatted file. I have to play it with a converter. So, i am trying to write the data in a .mjpeg file with these lines:

string myData  = File.ReadAllText("hexData.txt");
string newData;
int remainder  = myData.Length%500;
byte[] data_toWrite=newByte[250];

for(int i=0;i<myData.Length-remainder; i+=500)
{
    newData     = myData.Substring(i,500);
    data_toWrite = StringToByteArray(newData);
    File.WriteAllBytes("video.mjpeg",data_toWrite);
}

newData     = myData.Substring(myData.Length-remainder,remainder);
data_toWrite = StringToByteArray(newData);
File.WriteAllBytes("video.mjpeg",data_toWrite);

public static byte[] StringToByteArray(String hex)
{
  int NumberChars = hex.Length;
  byte[] bytes = new byte[NumberChars / 2];
  for (int i = 0; i < NumberChars; i += 2)
  bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
  return bytes;
}

But i couldn't make it play. I don't know where I am wrong at. I tried to convert newData to ascii then byte array but it failed,too.

Any ideas,many thanks!

Kane

Answer 1

This

File.WriteAllBytes("video.mjpeg",data_toWrite);

overwrites the file every time, not appends.

I'm sure better code can be written, but this should be enough:

string input = "test.hex";
string output = "output.bin";

using (var sr = new StreamReader(input))
using (var fs = File.Create(output))
{
    // We accumulate the 2 hex digits needed for a byte here
    string h = string.Empty;

    while (true)
    {
        int ch1 = sr.Read();

        if (ch1 == -1)
        {
            // The file finished but we have a pending partial hex code
            if (h.Length == 1)
            {
                throw new Exception("Malformed file");
            }

            break;
        }

        char ch2 = (char)ch1;

        // Skip white space and end-of-line
        if (char.IsWhiteSpace(ch2))
        {
            continue;
        }

        h += ch2;

        // We have collected 2 hex digits, so we have 1 byte
        if (h.Length == 2)
        {
            byte b = Convert.ToByte(h, 16);
            fs.WriteByte(b);
            h = string.Empty;
        }
    }
}

Note that both StreamReader and File.Create (that returns a FileStream) do some buffering, so no explicit buffering is needed. My hands are quivering because they want to remove the string h buffer and do the parsing hex digit by hex digit directly in the byte b. But I'll try to not overcomplicate the code :-)