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I'm currently trying to decipher WAV files. From headers to the PCM data.
I've found a PDF (http://www.tdt.com/T2Support/technical_notes/tn0132.pdf) detailing the anatomy of a WAV file, and I've been able to extract and make sense of the appropriate header data using Ghex2. But my questions are:
Why are the integers bytes stored backwards? I.e. dec. 20 is stored as 0x14000000 instead of 0x00000014.
Are the integers of the PCM data also stored backwards?
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Endianness and Character DataIf you store any ASCII character string in memory, it always looks the same, no matter what the Endianness of the hardware, since each character is one byte long and the start character of the string is always stored at the lowest memory location.
The advantages of Little Endian are: It's easy to read the value in a variety of type sizes. For example, the variable A = 0x13 in 64-bit value in memory at the address B will be 1300 0000 0000 0000 . A will always be read as 19 regardless of using 8, 16, 32, 64-bit reads.
Broadly speaking, the endianness in use is determined by the CPU. Because there are a number of options, it is unsurprising that different semiconductor vendors have chosen different endianness for their CPUs.
The case for little-endian This addition moves everything to the right. In a number stored in little-endian fashion, the least significant bytes can stay where they are. New digits are added to the right at a higher address. This means some computer operations may be simpler and faster to perform.
WAV files are little-endian (least significant bytes first) because the format originated for operating systems running on intel processor based machines which use the little endian format to store numbers.
If you think about it kind of makes sense because if you want to cast a long integer to a short one or even a character the starting address remains the same you just look at less bytes.
Consequently, for 16 bit encoding upwards, little-endian format will be used for the PCM as well. This is quite handy since you will be able to pull them in as integers. don't forget they will be stored as two's complement signed integers if they are 16 bit, but not if they are 8 bit. (see http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html for more detail)
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"Backwards" is subjective. Some machines are big-endian, others are little-endian. In byte-oriented contexts like file formats and network protocols, the order is arbitrary. Some formats like to specify big- or little-endian, others like to be flexible and accept either form, with a flag indicating which is in use.
Looks like WAV files just like little-endian.
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