Issue in tb(v) decoding description

[forayr]

In 9.4 Parsing process for truncated binary codes, the derivation of variable th is incomplete. For all maxVal below 256, the calculation in the specification return th = 7, which is not the case in the vtm.

In the spec:

thVal = 1 << 8
th = 8
while( thVal <= maxVal ) {
	th++
	thVal <<= 1
}
th−−

In vtm:

  int uiThresh;
  if( uiMaxSymbol > 256 )
  {
    int uiThreshVal = 1 << 8;
    uiThresh = 8;
    while( uiThreshVal <= uiMaxSymbol )
    {
      uiThresh++;
      uiThreshVal <<= 1;
    }
    uiThresh--;
  }
  else
  {
    uiThresh = g_tbMax[uiMaxSymbol];
  }

By the way, in the line 'b = n - val', 'n' is not defined in the spec and should be replaced by maxVal.

[nanhu]

For the variable 'th',
A fix could be:

thVal = 1
th = -1
while (thVal <= maxVal) {

th++
thVal <<= 1

}

In the line 'b = n - val', I agree that 'n' should be replaced by maxVal.

[bbross]

Fixed in D5 v7