CODEWITHSUNDEEP
c#
vondip
vondip

Reputation:

Writing File using System.IO.BinaryWriter

I am trying to write an audio file using C#'s System.IO.BinaryWriter class.

It works fine when I perform this action:

File.WriteAllBytes(@"C:\TestFile\File1", br.ReadBytes((int)br.BaseStream.Length));

However it does not work when I do the following:

Encoding e = Encoding.ASCII;
char[] reslts = e.GetChars(br.ReadBytes((int)br.BaseStream.Length));
br.BaseStream.Position = 0;
File.WriteAllBytes((@"C:\TestFile\File2",e.GetBytes(reslts));

I checked out the byte arrays, in both cases the array contained the same values ( I copied their value into a separate excel file and checked to see if there are any differences, there are none).

In both cases the base stream position is set to 0.

The code itself works, the file is created successfully. The problem occurs when I open the file, the first file works fine, the second file is not recognized by Windows Media Player.

Does anyone have any ideas of what I could be doing wrong?

Upvotes: 0

Views: 3718

Answers (4)

Guffa
Guffa

Reputation: 700152

Encoding is used to encode a string into bytes, then back into a string.

You are using it backwards, decoding something that wasn't a string to begin with.

Upvotes: 0

to StackOverflow
to StackOverflow

Reputation: 124686

With most encodings, including Encoding.ASCII, converting bytes to chars and back again will not give you back the same data. For example, IIRC Encoding.ASCII maps all bytes in the range 128-255 to the '?' character. Then when you convert back to bytes, they will all convert back to the same value.

An exception is the Latin1 aka ISO-8859-1 aka Code Page 28591 encoding, which will map all bytes with hex values are in the range 0-255 to the Unicode character with the same hex value. The following should give the result you want:

Encoding e = Encoding.GetEncoding(28591);
// or either of the following is equivalent
// Encoding.GetEncoding("Latin1");
// Encoding.GetEncoding("ISO-8859-1");

char[] reslts = e.GetChars(br.ReadBytes((int)br.BaseStream.Length));
br.BaseStream.Position = 0;
File.WriteAllBytes((@"C:\TestFile\File2",e.GetBytes(reslts));

Nevertheless, unless you have a good reason to do so, I wouldn't convert bytes to chars in this way.

Upvotes: 1

Jon Skeet
Jon Skeet

Reputation: 1499760

Never, ever read arbitrary binary data as if it's text. It always goes wrong, because they're just not the same thing.

Also, don't rely on a stream's length - it could change, or it might not support fetching it anyway.

You want something like this:

public static byte[] CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[16*1024];
    int read;
    while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
    {
        output.Write(buffer, 0, read);
    }
}

Then just open a FileStream to wherever you want to write the data, and call

CopyStream(inputStream, outputFile);

You haven't shown where you're getting the input from, but basically you don't really need the BinaryReader. It's not like you're using BinaryReader for its normal purpose, which is to read individual primitive values, length-prefixed strings etc. You just want to copy data verbatim - and a Stream is fine for that.

Upvotes: 1

Adrian Godong
Adrian Godong

Reputation: 8911

Encoding e = Encoding.ASCII;

That looks suspicious. I know not of any audio format that is encoded using ASCII.

Upvotes: 1

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