ROHC compression/decompression library
Data Structures | Enumerations | Functions
interval.h File Reference

Compute the interpretation interval for LSB and W-LSB encoding. More...

#include "dllexport.h"
#include <stdlib.h>
#include <stdint.h>
Include dependency graph for interval.h:
This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Data Structures

struct  rohc_interval16
 An interval of 16-bit values. More...
struct  rohc_interval32
 An interval of 32-bit values. More...

Enumerations

enum  rohc_lsb_shift_t {
  ROHC_LSB_SHIFT_IP_ID = 0, ROHC_LSB_SHIFT_RTP_TS = 2, ROHC_LSB_SHIFT_RTP_SN = 3, ROHC_LSB_SHIFT_ESP_SN = 3,
  ROHC_LSB_SHIFT_SN = -1, ROHC_LSB_SHIFT_VAR = 1
}
 the different values of the shift parameter of the LSB algorithm More...

Functions

static int32_t rohc_interval_compute_p (const size_t k, const rohc_lsb_shift_t p)
 Compute the shift parameter p for the f function.
struct rohc_interval16 ROHC_EXPORT rohc_f_16bits (const uint16_t v_ref, const size_t k, const rohc_lsb_shift_t p)
 The f function as defined in LSB encoding for 16-bit fields.
struct rohc_interval32 ROHC_EXPORT rohc_f_32bits (const uint32_t v_ref, const size_t k, const rohc_lsb_shift_t p)
 The f function as defined in LSB encoding for 32-bit fields.

Detailed Description

Compute the interpretation interval for LSB and W-LSB encoding.

Author:
Didier Barvaux <didier.barvaux@toulouse.viveris.com>

Enumeration Type Documentation

the different values of the shift parameter of the LSB algorithm

The shift parameter is also named 'p' in some RFCs.

Some values are the real values to use directly. Some others are code that means that the real value to use shall be computed from the number of least significant bits that are transmitted.

Enumerator:
ROHC_LSB_SHIFT_IP_ID 

real value for IP-ID

ROHC_LSB_SHIFT_RTP_TS 

need to compute real value for RTP TS

ROHC_LSB_SHIFT_RTP_SN 

need to compute real value for RTP SN

ROHC_LSB_SHIFT_ESP_SN 

need to compute real value for ESP SN

ROHC_LSB_SHIFT_SN 

real value for non-RTP SN

ROHC_LSB_SHIFT_VAR 

real value is variable


Function Documentation

struct rohc_interval16 ROHC_EXPORT rohc_f_16bits ( const uint16_t  v_ref,
const size_t  k,
const rohc_lsb_shift_t  p 
) [read]

The f function as defined in LSB encoding for 16-bit fields.

Find out the interval $[v\_ref - p, v\_ref + (2^k - 1) - p]$ for a given k. See 4.5.1 in the RFC 3095 for details.

As stated RFC, the values to be encoded have a finite range and the interpretation interval can straddle the wraparound boundary. So, the min value may be greater than the max value!

Parameters:
v_refThe reference value
kThe number of least significant bits of the value that are transmitted
pThe shift parameter (may be negative)
Returns:
The computed interval
struct rohc_interval32 ROHC_EXPORT rohc_f_32bits ( const uint32_t  v_ref,
const size_t  k,
const rohc_lsb_shift_t  p 
) [read]

The f function as defined in LSB encoding for 32-bit fields.

Find out the interval $[v\_ref - p, v\_ref + (2^k - 1) - p]$ for a given k. See 4.5.1 in the RFC 3095 for details.

As stated RFC, the values to be encoded have a finite range and the interpretation interval can straddle the wraparound boundary. So, the min value may be greater than the max value!

Parameters:
v_refThe reference value
kThe number of least significant bits of the value that are transmitted
pThe shift parameter (may be negative)
Returns:
The computed interval
static int32_t rohc_interval_compute_p ( const size_t  k,
const rohc_lsb_shift_t  p 
) [inline, static]

Compute the shift parameter p for the f function.

Parameters:
kThe number of least significant bits of the value that are transmitted
pThe shift parameter (may be negative)
Returns:
The computed shift parameter p