source: svn/newcon3bcm2_21bu/BSEAV/lib/utils/bvlc.h @ 46

/***************************************************************************

 *     Copyright (c) 2005-2010, Broadcom Corporation

 *     All Rights Reserved

 *     Confidential Property of Broadcom Corporation

 *

 *  THIS SOFTWARE MAY ONLY BE USED SUBJECT TO AN EXECUTED SOFTWARE LICENSE

 *  AGREEMENT  BETWEEN THE USER AND BROADCOM.  YOU HAVE NO RIGHT TO USE OR

 *  EXPLOIT THIS MATERIAL EXCEPT SUBJECT TO THE TERMS OF SUCH AN AGREEMENT.

 *

 * $brcm_Workfile: bvlc.h $

 * $brcm_Revision: Hydra_Software_Devel/2 $

 * $brcm_Date: 9/23/10 3:09p $

 *

 * Module Description: Converts startcode index to bcmplayer index

 *

 * Revision History:

 *

 * $brcm_Log: /magnum/commonutils/vlc/bvlc.h $

 * 

 * Hydra_Software_Devel/2   9/23/10 3:09p jtna

 * SW7405-4865: cleaned up header and added an example

 * 

 * Hydra_Software_Devel/1   9/20/10 3:03p jtna

 * SW7405-4865: added vlc

 * 

 * $old_brcm_Workfile: bvlc.h $

 * $old_brcm_Revision: 4 $

 * $old_brcm_Date: 9/1/05 3:36p $

 *

 * $old_brcm_Log: /BSEAV/lib/utils/bvlc.h $

 *

 * 4   9/1/05 3:36p erickson

 * PR16964: added const to parameter

 * 

 * 3   7/8/05 10:05a erickson

 * PR16155: modified b_vlc_decode to require current_index instead of

 * always starting from data[0]. This makes keeping track of where you

 * are in the buffer much easier for the application. Also changed and

 * expanded the examples.

 * 

 * 2   4/6/05 5:17p erickson

 * PR14708: use bstd.h if at all possible for maximum portability

 * 

 * 1   3/21/05 3:43p erickson

 * PR14451: added generic vlc decode algorithm

 * 

 ************************************************************/

#ifndef BVLC_H__

#define BVLC_H__



#include "bstd.h"



#ifdef __cplusplus

extern "C" {

#endif



/* for backward compatibility */

#define b_vlc_decode BVLC_Decode

#define b_vlc_skip BVLC_Skip



/***************************************************************************

BVLC is a set of Broadcom VLC (Variable Length Coding) decode algorithms.



Examples:

    unsigned char data[size];

    int next_index, next_bit;



    // Decode 3 contiguous vlc values

    val1 = BVLC_Decode(data, size, 0, 7, &next_index, &next_bit);

    val2 = BVLC_Decode(data, size, next_index, next_bit, &next_index, &next_bit);

    val3 = BVLC_Decode(data, size, next_index, next_bit, NULL, NULL);



    // Decode the 4th vlc value

    BVLC_Skip(data, size, 0, 7, &next_index, &next_bit);

    BVLC_Skip(data, size, next_index, next_bit, &next_index, &next_bit);

    BVLC_Skip(data, size, next_index, next_bit, &next_index, &next_bit);

    val = BVLC_Decode(data, size, next_index, next_bit, NULL, NULL);



    // Decode a vlc value which is an index of the subsequent vlc value to decode.

    val = BVLC_Decode(data, size, 0, 7, &next_index, &next_bit);

    while (val--)

        BVLC_Skip(data, size, next_index, next_bit, &next_index, &next_bit);

    val = BVLC_Decode(data, size, next_index, next_bit, NULL, NULL);





Examples:

    // Decode a vlc value and calculate the number of bits the processed

    // by the last BVLC_Decode or BVLC_Skip call.



    int current_index, current_bit, num_bits;



    // save next_index and next_bit before BVLC_Decode

    current_index = next_index;

    current_bit = next_bit;



    BVLC_Decode(data, size, next_index, next_bit, &next_index, &next_bit);



    num_bits = (next_index-current_index)*8 + (current_bit-next_bit);



    

***************************************************************************/



/***************************************************************************

Summary:

    Decodes a VLC value in a byte stream.



Description:



Input:

    data            - [size_is(size)] Array of bytes which contain a vlc

                      encoded value

    size            - Size of data.

    current_index   - The starting index the data array.

    current_bit     - The bit in data[current_index] where the vlc decode

                      should start.

    next_index      - [out] the index in data which should be used for an

                      adjacent vlc decode. Can be NULL.

    next_bit        - [out] the bit in data[index] which should be used for

                      an adjacent vlc decode. Can be NULL.



Returns:

    Returns a VLC decoded value if >= 0. 

    If -1 there was a VLC decode failure.



See Also:



***************************************************************************/



int BVLC_Decode( 

    const uint8_t *data,

    unsigned size,

    unsigned current_index,

    unsigned current_bit, 

    unsigned *next_index, 

    unsigned *next_bit

    );





/***************************************************************************

Summary:

    This works by short circuiting the VLC decode algorithm in order to skip

    over a VLC encoded value.



Description:



Input:

    data            - [size_is(size)] see BVLC_Decode

    size            - see BVLC_Decode

    current_index   - see BVLC_Decode

    current_bit     - see BVLC_Decode

    next_index      - [out] the index in data which should be used for an 

                      adjacent vlc decode. Required.

    next_bit        - [out] the bit in data[index] which should be used for 

                      an adjacent vlc decode. Required.



Returns:

    0 if successfully skipped. next_index and next_bit are updated.

    If -1 there was a VLC decode failure.



See Also:

    BVLC_Decode

***************************************************************************/

int BVLC_Skip( 

    const uint8_t *data,

    unsigned size,

    unsigned current_index,

    unsigned current_bit, 

    unsigned *next_index,

    unsigned *next_bit

    );



#ifdef __cplusplus

}

#endif



#endif /* #ifndef BVLC_H__ */

/* End of File */