ref: 164821c259bd23ef7b93a6541048bc977bf5783f
dir: /src/h264bsd_vlc.c/
/*
* Copyright (C) 2009 The Android Open Source Project
* Modified for use by h264bsd standalone library
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*------------------------------------------------------------------------------
Table of contents
1. Include headers
2. External compiler flags
3. Module defines
4. Local function prototypes
5. Functions
h264bsdDecodeExpGolombUnsigned
h264bsdDecodeExpGolombSigned
h264bsdDecodeExpGolombMapped
h264bsdDecodeExpGolombTruncated
------------------------------------------------------------------------------*/
/*------------------------------------------------------------------------------
1. Include headers
------------------------------------------------------------------------------*/
#include "h264bsd_vlc.h"
#include "basetype.h"
#include "h264bsd_stream.h"
#include "h264bsd_util.h"
/*------------------------------------------------------------------------------
2. External compiler flags
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
3. Module defines
------------------------------------------------------------------------------*/
/* definition of special code num, this along with the return value is used
* to handle code num in the range [0, 2^32] in the DecodeExpGolombUnsigned
* function */
#define BIG_CODE_NUM 0xFFFFFFFFU
/* Mapping tables for coded_block_pattern, used for decoding of mapped
* Exp-Golomb codes */
static const u8 codedBlockPatternIntra4x4[48] = {
47,31,15,0,23,27,29,30,7,11,13,14,39,43,45,46,16,3,5,10,12,19,21,26,28,35,
37,42,44,1,2,4,8,17,18,20,24,6,9,22,25,32,33,34,36,40,38,41};
static const u8 codedBlockPatternInter[48] = {
0,16,1,2,4,8,32,3,5,10,12,15,47,7,11,13,14,6,9,31,35,37,42,44,33,34,36,40,
39,43,45,46,17,18,20,24,19,21,26,28,23,27,29,30,22,25,38,41};
/*------------------------------------------------------------------------------
4. Local function prototypes
------------------------------------------------------------------------------*/
/*------------------------------------------------------------------------------
5.1 Function: h264bsdDecodeExpGolombUnsigned
Functional description:
Decode unsigned Exp-Golomb code. This is the same as codeNum used
in other Exp-Golomb code mappings. Code num (i.e. the decoded
symbol) is determined as
codeNum = 2^leadingZeros - 1 + GetBits(leadingZeros)
Normal decoded symbols are in the range [0, 2^32 - 2]. Symbol
2^32-1 is indicated by BIG_CODE_NUM with return value HANTRO_OK
while symbol 2^32 is indicated by BIG_CODE_NUM with return value
HANTRO_NOK. These two symbols are special cases with code length
of 65, i.e. 32 '0' bits, a '1' bit, and either 0 or 1 represented
by 32 bits.
Symbol 2^32 is out of unsigned 32-bit range but is needed for
DecodeExpGolombSigned to express value -2^31.
Inputs:
pStrmData pointer to stream data structure
Outputs:
codeNum decoded code word is stored here
Returns:
HANTRO_OK success
HANTRO_NOK failure, no valid code word found, note exception
with BIG_CODE_NUM
------------------------------------------------------------------------------*/
u32 h264bsdDecodeExpGolombUnsigned(strmData_t *pStrmData, u32 *codeNum)
{
/* Variables */
u32 bits, numZeros;
/* Code */
ASSERT(pStrmData);
ASSERT(codeNum);
bits = h264bsdShowBits32(pStrmData);
/* first bit is 1 -> code length 1 */
if (bits >= 0x80000000)
{
h264bsdFlushBits(pStrmData, 1);
*codeNum = 0;
return(HANTRO_OK);
}
/* second bit is 1 -> code length 3 */
else if (bits >= 0x40000000)
{
if (h264bsdFlushBits(pStrmData, 3) == END_OF_STREAM)
return(HANTRO_NOK);
*codeNum = 1 + ((bits >> 29) & 0x1);
return(HANTRO_OK);
}
/* third bit is 1 -> code length 5 */
else if (bits >= 0x20000000)
{
if (h264bsdFlushBits(pStrmData, 5) == END_OF_STREAM)
return(HANTRO_NOK);
*codeNum = 3 + ((bits >> 27) & 0x3);
return(HANTRO_OK);
}
/* fourth bit is 1 -> code length 7 */
else if (bits >= 0x10000000)
{
if (h264bsdFlushBits(pStrmData, 7) == END_OF_STREAM)
return(HANTRO_NOK);
*codeNum = 7 + ((bits >> 25) & 0x7);
return(HANTRO_OK);
}
/* other code lengths */
else
{
#ifndef H264DEC_NEON
numZeros = 4 + h264bsdCountLeadingZeros(bits, 28);
#else
numZeros = h264bsdCountLeadingZeros(bits);
#endif
/* all 32 bits are zero */
if (numZeros == 32)
{
*codeNum = 0;
h264bsdFlushBits(pStrmData,32);
bits = h264bsdGetBits(pStrmData, 1);
/* check 33rd bit, must be 1 */
if (bits == 1)
{
/* cannot use h264bsdGetBits, limited to 31 bits */
bits = h264bsdShowBits32(pStrmData);
if (h264bsdFlushBits(pStrmData, 32) == END_OF_STREAM)
return(HANTRO_NOK);
/* code num 2^32 - 1, needed for unsigned mapping */
if (bits == 0)
{
*codeNum = BIG_CODE_NUM;
return(HANTRO_OK);
}
/* code num 2^32, needed for unsigned mapping
* (results in -2^31) */
else if (bits == 1)
{
*codeNum = BIG_CODE_NUM;
return(HANTRO_NOK);
}
}
/* if more zeros than 32, it is an error */
return(HANTRO_NOK);
}
else
h264bsdFlushBits(pStrmData,numZeros+1);
bits = h264bsdGetBits(pStrmData, numZeros);
if (bits == END_OF_STREAM)
return(HANTRO_NOK);
*codeNum = (1 << numZeros) - 1 + bits;
}
return(HANTRO_OK);
}
/*------------------------------------------------------------------------------
5.2 Function: h264bsdDecodeExpGolombSigned
Functional description:
Decode signed Exp-Golomb code. Code num is determined by
h264bsdDecodeExpGolombUnsigned and then mapped to signed
representation as
symbol = (-1)^(codeNum+1) * (codeNum+1)/2
Signed symbols shall be in the range [-2^31, 2^31 - 1]. Symbol
-2^31 is obtained when codeNum is 2^32, which cannot be expressed
by unsigned 32-bit value. This is signaled as a special case from
the h264bsdDecodeExpGolombUnsigned by setting codeNum to
BIG_CODE_NUM and returning HANTRO_NOK status.
Inputs:
pStrmData pointer to stream data structure
Outputs:
value decoded code word is stored here
Returns:
HANTRO_OK success
HANTRO_NOK failure, no valid code word found
------------------------------------------------------------------------------*/
u32 h264bsdDecodeExpGolombSigned(strmData_t *pStrmData, i32 *value)
{
/* Variables */
u32 status, codeNum = 0;
/* Code */
ASSERT(pStrmData);
ASSERT(value);
status = h264bsdDecodeExpGolombUnsigned(pStrmData, &codeNum);
if (codeNum == BIG_CODE_NUM)
{
/* BIG_CODE_NUM and HANTRO_OK status means codeNum 2^32-1 which would
* result in signed integer valued 2^31 (i.e. out of 32-bit signed
* integer range) */
if (status == HANTRO_OK)
return(HANTRO_NOK);
/* BIG_CODE_NUM and HANTRO_NOK status means codeNum 2^32 which results
* in signed integer valued -2^31 */
else
{
*value = (i32)(2147483648U);
return (HANTRO_OK);
}
}
else if (status == HANTRO_OK)
{
/* (-1)^(codeNum+1) results in positive sign if codeNum is odd,
* negative when it is even. (codeNum+1)/2 is obtained as
* (codeNum+1)>>1 when value is positive and as (-codeNum)>>1 for
* negative value */
/*lint -e702 */
*value = (codeNum & 0x1) ? (i32)((codeNum + 1) >> 1) :
-(i32)((codeNum + 1) >> 1);
/*lint +e702 */
return(HANTRO_OK);
}
return(HANTRO_NOK);
}
/*------------------------------------------------------------------------------
5.3 Function: h264bsdDecodeExpGolombMapped
Functional description:
Decode mapped Exp-Golomb code. Code num is determined by
h264bsdDecodeExpGolombUnsigned and then mapped to codedBlockPattern
either for intra or inter macroblock. The mapping is implemented by
look-up tables defined in the beginning of the file.
Inputs:
pStrmData pointer to stream data structure
isIntra flag to indicate if intra or inter mapping is to
be used
Outputs:
value decoded code word is stored here
Returns:
HANTRO_OK success
HANTRO_NOK failure, no valid code word found
------------------------------------------------------------------------------*/
u32 h264bsdDecodeExpGolombMapped(strmData_t *pStrmData, u32 *value,
u32 isIntra)
{
/* Variables */
u32 status, codeNum;
/* Code */
ASSERT(pStrmData);
ASSERT(value);
status = h264bsdDecodeExpGolombUnsigned(pStrmData, &codeNum);
if (status != HANTRO_OK)
return (HANTRO_NOK);
else
{
/* range of valid codeNums [0,47] */
if (codeNum > 47)
return (HANTRO_NOK);
if (isIntra)
*value = codedBlockPatternIntra4x4[codeNum];
else
*value = codedBlockPatternInter[codeNum];
return(HANTRO_OK);
}
}
/*------------------------------------------------------------------------------
5.4 Function: h264bsdDecodeExpGolombTruncated
Functional description:
Decode truncated Exp-Golomb code. greaterThanOne flag indicates
the range of the symbol to be decoded as follows:
FALSE -> [0,1]
TRUE -> [0,2^32-1]
If flag is false the decoding is performed by reading one bit
from the stream with h264bsdGetBits and mapping this to decoded
symbol as
symbol = bit ? 0 : 1
Otherwise, i.e. when flag is TRUE, code num is determined by
h264bsdDecodeExpGolombUnsigned and this is used as the decoded
symbol.
Inputs:
pStrmData pointer to stream data structure
greaterThanOne flag to indicate if range is wider than [0,1]
Outputs:
value decoded code word is stored here
Returns:
HANTRO_OK success
HANTRO_NOK failure, no valid code word found
------------------------------------------------------------------------------*/
u32 h264bsdDecodeExpGolombTruncated(
strmData_t *pStrmData,
u32 *value,
u32 greaterThanOne)
{
/* Variables */
/* Code */
ASSERT(pStrmData);
ASSERT(value);
if (greaterThanOne)
{
return(h264bsdDecodeExpGolombUnsigned(pStrmData, value));
}
else
{
*value = h264bsdGetBits(pStrmData,1);
if (*value == END_OF_STREAM)
return (HANTRO_NOK);
*value ^= 0x1;
}
return (HANTRO_OK);
}