Editing G.711 (section)

=== μ-law ===
{{Main|μ-law algorithm}}
The μ-law (sometimes referred to as ulaw, G.711Mu, or G.711μ) encoding takes a 14-bit signed linear audio sample in [[two's complement]] representation as input, inverts all bits after the sign bit if the value is negative, adds 33 (binary 100001) and converts it to an 8 bit value as follows:

{| class="wikitable" style="text-align:left"
|-
! Linear input value<br><ref group=note>This value is produced by taking the [[two's complement]] representation of the input value, inverting all bits after the sign bit if the value is negative, and adding 33.</ref>
! Compressed code<br>XOR 11111111
! Linear output value<br><ref group=note>[[Signed magnitude]] representation. Final result is produced by decreasing the magnitude of this value by 33.</ref>
|-
| <code>s00000001abcdx</code> || <code>s000abcd</code> || <code>s00000001abcd1</code>
|-
| <code>s0000001abcdxx</code> || <code>s001abcd</code> || <code>s0000001abcd10</code>
|-
| <code>s000001abcdxxx</code> || <code>s010abcd</code> || <code>s000001abcd100</code>
|-
| <code>s00001abcdxxxx</code> || <code>s011abcd</code> || <code>s00001abcd1000</code>
|-
| <code>s0001abcdxxxxx</code> || <code>s100abcd</code> || <code>s0001abcd10000</code>
|-
| <code>s001abcdxxxxxx</code> || <code>s101abcd</code> || <code>s001abcd100000</code>
|-
| <code>s01abcdxxxxxxx</code> || <code>s110abcd</code> || <code>s01abcd1000000</code>
|-
| <code>s1abcdxxxxxxxx</code> || <code>s111abcd</code> || <code>s1abcd10000000</code>
|}
<references group=note/>

Where {{code|s}} is the sign bit, and bits marked {{code|x}} are discarded.

In addition, the standard specifies that the encoded bits are inverted before the octet is transmitted. Thus, a silent μ-law encoded PCM channel has the 8 bit samples transmitted 0xFF instead of 0x00 in the octets.

Adding 33 is necessary so that all values fall into a compression group and it is subtracted back when decoding. 

Breaking the encoded value formatted as <code>seeemmmm</code> into 4 bits of mantissa {{var|m}}, 3 bits of exponent {{var|e}} and 1 sign bit {{var|s}}, the decoded linear value {{var|y}} is given by formula
:<math>y = (-1)^s \cdot [(33 + 2m) \cdot 2^e - 33],</math>
which is a 14-bit signed integer in the range ±0 to ±8031.

Note that 0 is transmitted as 0xFF, and −1 is transmitted as 0x7F, but when received the result is 0 in both cases.