Reading format, channels and bits-per-sample Therefore the value of unsigned and signed interpretation are identical.The first 2 bytes of this 4 byte value are: 0x00 00 = 0.So, reading just the first 2 bytes (=16 bit) is sufficient for representing the decimal value of 48000.Maximum value of 16 bit unsigned is: 65535.This only works if the value is less-or-equal than 65535. In case you wonder, why the value 48000 shows up in "signed 32 bit" as well as "unsigned 16 bit", the reasons are as follows: Therefore, the value "48000" (=48 kHz) is displayed in the "unsigned 32 bit" data display field at the bottom. ![]() Since we've selected "Show little endian encoding", the bytes are read from right-to-left, resulting in: In this case, that's not a valid samplerate. If you read it from left-to-right (in the order the data bytes are displayed), its interpretation would be: Let's convert this hex value to decimal - but: remember endianess? As the name suggests: It's data located at the beginning - the "head" - of a file, usually containing structural information about the payload data to come.įor example in a WAV file, as you can see in its specification, the header contains information like this:Īnnotated WAV header in hex Reading the audio samplerateĪnd as you can see, I've put the editing cursor (red mark) at the offset of the samplerate. So here we go: First, you have to know about the so called " File Header". Intentionally - and knowing what you're doing. Okay, now editing text was fun already, but imagine that you're actually going to manipulate binary data! O.O If you want to replace it with a shorter text, just add "space" characters to fill it up until its "null-terminated" end. So please: If you edit text strings, stay inside their boundaries. ![]() When doing this to a media file, pixels might be ill-colored, or the whole image falls apart, or all colors are wrong - or the viewing application crashes. If it's an executable, it might crash when trying to read that string, or access the data that you deleted by replacing it with your text. If you change a text string in a binary file and you overwrite its end (=the 0x00 byte), you overwrite actual code. Otherwise, bad things may - and probably will - happen to your file and to your system." It was endless fun translating English to Austrian slang, and share this personalized version with friends :Dīut when my father showed us this "hacker tool", he advised us: Maybe I chose this, because that was the first thing I did with a hex editor when I was a kid: I changed text phrases in my favorite computer games. But let's start with editing text in binary files. The hex editor can be used to edit binary files. That's how you know where one term ends and another one begins. The metadata fields inside a PNG for example, are separated by a 0x00 character. Therefore they're called " null-terminated strings". Text strings inside a binary file often end with the hex character "0x00". If you see the text displayed with dots, use multi-byte encoding, otherwise single-byte. Now, when searching for text inside a binary file, some editors allow to specify if you search for 1 or 2 byte encoded strings. Therefore the letters between the dots :) Thanks to downwards compatiblity with single-byte ASCII mapping, the basic alphanumeric characters are still readable in their 1-byte representation. The dots between the letters in Unicode are not to indicate an abbreviation, or some ASCII-Art: The dots represent non-printable characters. Single- and multi-byte character encoding of "hello" next to each other (separated by a space character "0x20") Here's a bogus example how these 2 encodings would look in a hex editor: If it's a number, you already know what to do, but if it's text you may find 2 different ways in which its displayed in the text column: In order to read embedded metadata, you need to know at which byte offsets to find which data field and how to interpret it. If you look at a lossy compressed audio file like MP3 or MP4, it's quite likely to contain descriptive metadata embedded. Handling text in binary files Searching TextĪs already mentioned, you'll encounter text phrases inside binary files. There is also a PDF version of this document available for download, as well as its Markdown source code. This article is mainly aimed at archivists with digital preservation needs, and maybe a bit for data forensic beginners. ![]() This part is about handling the data in the file itself, such as searching or editing text or reading and editing binary data with the use of a file format specification paper. In the previous part, we've covered the basics of "what is hex?" and how to use a hex editor for binary files. ![]()
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