codecs_v2/video/avc_h264/dec/src/avc_bitstream.cpp - platform/external/opencore - Git at Google

 /* ------------------------------------------------------------------
  * Copyright (C) 2008 PacketVideo
  *
  * 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.
  * -------------------------------------------------------------------
  */
 #include "avcdec_bitstream.h"

 /* Swapping may not be needed anymore since we read one byte at a time and perform
 EBSP to RBSP conversion in bitstream. */
 #ifdef LITTLE_ENDIAN
 #if (WORD_SIZE==32)  /* this can be replaced with assembly instructions */
 #define SWAP_BYTES(x) ((((x)&0xFF)<<24) | (((x)&0xFF00)<<8) | (((x)&0xFF0000)>>8) | (((x)&0xFF000000)>>24))
 #else  /* for 16-bit */
 #define SWAP_BYTES(x) ((((x)&0xFF)<<8) | (((x)&0xFF00)>>8))
 #endif
 #else
 #define SWAP_BYTES(x) (x)
 #endif


 /* array for trailing bit pattern as function of number of bits */
 /* the first one is unused. */
 const static uint8 trailing_bits[9] = {0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80};

 /* ======================================================================== */
 /*	Function : BitstreamInit()												*/
 /*	Date     : 11/4/2003													*/
 /*	Purpose  : Populate bitstream structure with bitstream buffer and size 	*/
 /*			   it also initializes internal data							*/
 /*	In/out   :																*/
 /*	Return   : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if failed.				*/
 /*	Modified :																*/
 /* ======================================================================== */
 /* |--------|--------|----~~~~~-----|---------|---------|---------|
    ^                                          ^read_pos			  ^data_end_pos
    bitstreamBuffer					<--------->
 									current_word

    |xxxxxxxxxxxxx----|  = current_word 32 or 16 bits
     <------------>
 	 bit_left
  ======================================================================== */


 /* ======================================================================== */
 /*	Function : BitstreamNextWord()											*/
 /*	Date     : 12/4/2003													*/
 /*	Purpose  : Read up to machine word.										*/
 /*	In/out   :																*/
 /*	Return   : Next word with emulation prevention code removed. Everything
 	in the bitstream structure got modified except current_word				*/
 /*	Modified :																*/
 /* ======================================================================== */

 AVCDec_Status BitstreamInit(AVCDecBitstream *stream, uint8 *buffer, int size)
 {
     EBSPtoRBSP(buffer, &size);

     stream->incnt = 0;
     stream->incnt_next = 0;
     stream->bitcnt = 0;
     stream->curr_word = stream->next_word = 0;
     stream->read_pos = 0;

     stream->bitstreamBuffer = buffer;

     stream->data_end_pos = size;

     stream->nal_size = size;

     return AVCDEC_SUCCESS;
 }
 /* ======================================================================== */
 /*	Function : AVC_BitstreamFillCache()											*/
 /*	Date     : 1/1/2005														*/
 /*	Purpose  : Read up to machine word.										*/
 /*	In/out   :																*/
 /*	Return   : Read in 4 bytes of input data								*/
 /*	Modified :																*/
 /* ======================================================================== */

 AVCDec_Status AVC_BitstreamFillCache(AVCDecBitstream *stream)
 {
     uint8 *bitstreamBuffer = stream->bitstreamBuffer;
     uint8 *v;
     int num_bits, i;

     stream->curr_word |= (stream->next_word >> stream->incnt);   // stream->incnt cannot be 32
     stream->next_word <<= (31 - stream->incnt);
     stream->next_word <<= 1;
     num_bits = stream->incnt_next + stream->incnt;
     if (num_bits >= 32)
     {
         stream->incnt_next -= (32 - stream->incnt);
         stream->incnt = 32;
         return AVCDEC_SUCCESS;
     }
     /* this check can be removed if there is additional extra 4 bytes at the end of the bitstream */
     v = bitstreamBuffer + stream->read_pos;

     if (stream->read_pos > stream->data_end_pos - 4)
     {
         if (stream->data_end_pos <= stream->read_pos)
         {
             stream->incnt = num_bits;
             stream->incnt_next = 0;
             return AVCDEC_SUCCESS;
         }

         stream->next_word = 0;

         for (i = 0; i < stream->data_end_pos - stream->read_pos;i++)
         {
             stream->next_word |= (v[i] << ((3 - i) << 3));
         }

         stream->read_pos = stream->data_end_pos;
         stream->curr_word |= (stream->next_word >> num_bits); // this is safe

         stream->next_word <<= (31 - num_bits);
         stream->next_word <<= 1;
         num_bits = i << 3;
         stream->incnt += stream->incnt_next;
         stream->incnt_next = num_bits - (32 - stream->incnt);
         if (stream->incnt_next < 0)
         {
             stream->incnt +=  num_bits;
             stream->incnt_next = 0;
         }
         else
         {
             stream->incnt = 32;
         }
         return AVCDEC_SUCCESS;
     }

     stream->next_word = ((uint32)v[0] << 24) | (v[1] << 16) | (v[2] << 8) | v[3];
     stream->read_pos += 4;

     stream->curr_word |= (stream->next_word >> num_bits); // this is safe
     stream->next_word <<= (31 - num_bits);
     stream->next_word <<= 1;
     stream->incnt_next += stream->incnt;
     stream->incnt = 32;
     return AVCDEC_SUCCESS;

 }
 /* ======================================================================== */
 /*	Function : BitstreamReadBits()											*/
 /*	Date     : 11/4/2003													*/
 /*	Purpose  : Read up to machine word.										*/
 /*	In/out   :																*/
 /*	Return   : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits	*/
 /*				is greater than the word-size, AVCDEC_PACKET_LOSS or		*/
 /*				AVCDEC_NO_DATA if callback to get data fails.				*/
 /*	Modified :																*/
 /* ======================================================================== */
 AVCDec_Status BitstreamReadBits(AVCDecBitstream *stream, int nBits, uint *code)
 {
     if (stream->incnt < nBits)
     {
         /* frame-based decoding */
         AVC_BitstreamFillCache(stream);
     }
     *code = stream->curr_word >> (32 - nBits);
     BitstreamFlushBits(stream, nBits);
     return AVCDEC_SUCCESS;
 }


 /* ======================================================================== */
 /*	Function : BitstreamShowBits()											*/
 /*	Date     : 11/4/2003													*/
 /*	Purpose  : Show up to machine word without advancing the pointer.		*/
 /*	In/out   :																*/
 /*	Return   : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits	*/
 /*				is greater than the word-size, AVCDEC_NO_DATA if it needs	*/
 /*				to callback to get data.									*/
 /*	Modified :																*/
 /* ======================================================================== */
 AVCDec_Status BitstreamShowBits(AVCDecBitstream *stream, int nBits, uint *code)
 {
     if (stream->incnt < nBits)
     {
         /* frame-based decoding */
         AVC_BitstreamFillCache(stream);
     }

     *code = stream->curr_word >> (32 - nBits);

     return AVCDEC_SUCCESS;
 }

 /* ======================================================================== */
 /*	Function : BitstreamRead1Bit()											*/
 /*	Date     : 11/4/2003													*/
 /*	Purpose  : Read 1 bit from the bitstream.								*/
 /*	In/out   :																*/
 /*	Return   : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits	*/
 /*				is greater than the word-size, AVCDEC_PACKET_LOSS or		*/
 /*				AVCDEC_NO_DATA if callback to get data fails.				*/
 /*	Modified :																*/
 /* ======================================================================== */

 AVCDec_Status BitstreamRead1Bit(AVCDecBitstream *stream, uint *code)
 {
     if (stream->incnt < 1)
     {
         /* frame-based decoding */
         AVC_BitstreamFillCache(stream);
     }
     *code = stream->curr_word >> 31;
     BitstreamFlushBits(stream, 1);
     return AVCDEC_SUCCESS;
 }


 AVCDec_Status BitstreamByteAlign(AVCDecBitstream  *stream)
 {
     uint n_stuffed;

     n_stuffed = (8 - (stream->bitcnt & 0x7)) & 0x7; /*  07/05/01 */

     stream->bitcnt += n_stuffed;
     stream->incnt -= n_stuffed;

     if (stream->incnt < 0)
     {
         stream->bitcnt += stream->incnt;
         stream->incnt = 0;
     }
     stream->curr_word <<= n_stuffed;
     return AVCDEC_SUCCESS;
 }

 /* check whether there are more RBSP data. */
 /* ignore the emulation prevention code, assume it has been taken out. */
 bool more_rbsp_data(AVCDecBitstream *stream)
 {
     int total_bit_left;
     uint code;

     if (stream->read_pos >= stream->nal_size)
     {
         total_bit_left = stream->incnt_next + stream->incnt;
         if (total_bit_left <= 0)
         {
             return FALSE;
         }
         else if (total_bit_left <= 8)
         {
             BitstreamShowBits(stream, total_bit_left, &code);
             if (code == trailing_bits[total_bit_left])
             {
                 return FALSE;
             }
         }
     }

     return TRUE;
 }
	/* ------------------------------------------------------------------
	* Copyright (C) 2008 PacketVideo
	*
	* 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.
	* -------------------------------------------------------------------
	*/
	#include "avcdec_bitstream.h"

	/* Swapping may not be needed anymore since we read one byte at a time and perform
	EBSP to RBSP conversion in bitstream. */
	#ifdef LITTLE_ENDIAN
	#if (WORD_SIZE==32) /* this can be replaced with assembly instructions */
	#define SWAP_BYTES(x) ((((x)&0xFF)<<24) \| (((x)&0xFF00)<<8) \| (((x)&0xFF0000)>>8) \| (((x)&0xFF000000)>>24))
	#else /* for 16-bit */
	#define SWAP_BYTES(x) ((((x)&0xFF)<<8) \| (((x)&0xFF00)>>8))
	#endif
	#else
	#define SWAP_BYTES(x) (x)
	#endif


	/* array for trailing bit pattern as function of number of bits */
	/* the first one is unused. */
	const static uint8 trailing_bits[9] = {0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80};

	/* ======================================================================== */
	/* Function : BitstreamInit() */
	/* Date : 11/4/2003 */
	/* Purpose : Populate bitstream structure with bitstream buffer and size */
	/* it also initializes internal data */
	/* In/out : */
	/* Return : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if failed. */
	/* Modified : */
	/* ======================================================================== */
	/* \|--------\|--------\|----~~~~~-----\|---------\|---------\|---------\|
	^ ^read_pos ^data_end_pos
	bitstreamBuffer <--------->
	current_word

	\|xxxxxxxxxxxxx----\| = current_word 32 or 16 bits
	<------------>
	bit_left
	======================================================================== */


	/* ======================================================================== */
	/* Function : BitstreamNextWord() */
	/* Date : 12/4/2003 */
	/* Purpose : Read up to machine word. */
	/* In/out : */
	/* Return : Next word with emulation prevention code removed. Everything
	in the bitstream structure got modified except current_word */
	/* Modified : */
	/* ======================================================================== */

	AVCDec_Status BitstreamInit(AVCDecBitstream stream, uint8 buffer, int size)
	{
	EBSPtoRBSP(buffer, &size);

	stream->incnt = 0;
	stream->incnt_next = 0;
	stream->bitcnt = 0;
	stream->curr_word = stream->next_word = 0;
	stream->read_pos = 0;

	stream->bitstreamBuffer = buffer;

	stream->data_end_pos = size;

	stream->nal_size = size;

	return AVCDEC_SUCCESS;
	}
	/* ======================================================================== */
	/* Function : AVC_BitstreamFillCache() */
	/* Date : 1/1/2005 */
	/* Purpose : Read up to machine word. */
	/* In/out : */
	/* Return : Read in 4 bytes of input data */
	/* Modified : */
	/* ======================================================================== */

	AVCDec_Status AVC_BitstreamFillCache(AVCDecBitstream *stream)
	{
	uint8 *bitstreamBuffer = stream->bitstreamBuffer;
	uint8 *v;
	int num_bits, i;

	stream->curr_word \|= (stream->next_word >> stream->incnt); // stream->incnt cannot be 32
	stream->next_word <<= (31 - stream->incnt);
	stream->next_word <<= 1;
	num_bits = stream->incnt_next + stream->incnt;
	if (num_bits >= 32)
	{
	stream->incnt_next -= (32 - stream->incnt);
	stream->incnt = 32;
	return AVCDEC_SUCCESS;
	}
	/* this check can be removed if there is additional extra 4 bytes at the end of the bitstream */
	v = bitstreamBuffer + stream->read_pos;

	if (stream->read_pos > stream->data_end_pos - 4)
	{
	if (stream->data_end_pos <= stream->read_pos)
	{
	stream->incnt = num_bits;
	stream->incnt_next = 0;
	return AVCDEC_SUCCESS;
	}

	stream->next_word = 0;

	for (i = 0; i < stream->data_end_pos - stream->read_pos;i++)
	{
	stream->next_word \|= (v[i] << ((3 - i) << 3));
	}

	stream->read_pos = stream->data_end_pos;
	stream->curr_word \|= (stream->next_word >> num_bits); // this is safe

	stream->next_word <<= (31 - num_bits);
	stream->next_word <<= 1;
	num_bits = i << 3;
	stream->incnt += stream->incnt_next;
	stream->incnt_next = num_bits - (32 - stream->incnt);
	if (stream->incnt_next < 0)
	{
	stream->incnt += num_bits;
	stream->incnt_next = 0;
	}
	else
	{
	stream->incnt = 32;
	}
	return AVCDEC_SUCCESS;
	}

	stream->next_word = ((uint32)v[0] << 24) \| (v[1] << 16) \| (v[2] << 8) \| v[3];
	stream->read_pos += 4;

	stream->curr_word \|= (stream->next_word >> num_bits); // this is safe
	stream->next_word <<= (31 - num_bits);
	stream->next_word <<= 1;
	stream->incnt_next += stream->incnt;
	stream->incnt = 32;
	return AVCDEC_SUCCESS;

	}
	/* ======================================================================== */
	/* Function : BitstreamReadBits() */
	/* Date : 11/4/2003 */
	/* Purpose : Read up to machine word. */
	/* In/out : */
	/* Return : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits */
	/* is greater than the word-size, AVCDEC_PACKET_LOSS or */
	/* AVCDEC_NO_DATA if callback to get data fails. */
	/* Modified : */
	/* ======================================================================== */
	AVCDec_Status BitstreamReadBits(AVCDecBitstream stream, int nBits, uint code)
	{
	if (stream->incnt < nBits)
	{
	/* frame-based decoding */
	AVC_BitstreamFillCache(stream);
	}
	*code = stream->curr_word >> (32 - nBits);
	BitstreamFlushBits(stream, nBits);
	return AVCDEC_SUCCESS;
	}



	/* ======================================================================== */
	/* Function : BitstreamShowBits() */
	/* Date : 11/4/2003 */
	/* Purpose : Show up to machine word without advancing the pointer. */
	/* In/out : */
	/* Return : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits */
	/* is greater than the word-size, AVCDEC_NO_DATA if it needs */
	/* to callback to get data. */
	/* Modified : */
	/* ======================================================================== */
	AVCDec_Status BitstreamShowBits(AVCDecBitstream stream, int nBits, uint code)
	{
	if (stream->incnt < nBits)
	{
	/* frame-based decoding */
	AVC_BitstreamFillCache(stream);
	}

	*code = stream->curr_word >> (32 - nBits);

	return AVCDEC_SUCCESS;
	}

	/* ======================================================================== */
	/* Function : BitstreamRead1Bit() */
	/* Date : 11/4/2003 */
	/* Purpose : Read 1 bit from the bitstream. */
	/* In/out : */
	/* Return : AVCDEC_SUCCESS if successed, AVCDEC_FAIL if number of bits */
	/* is greater than the word-size, AVCDEC_PACKET_LOSS or */
	/* AVCDEC_NO_DATA if callback to get data fails. */
	/* Modified : */
	/* ======================================================================== */

	AVCDec_Status BitstreamRead1Bit(AVCDecBitstream stream, uint code)
	{
	if (stream->incnt < 1)
	{
	/* frame-based decoding */
	AVC_BitstreamFillCache(stream);
	}
	*code = stream->curr_word >> 31;
	BitstreamFlushBits(stream, 1);
	return AVCDEC_SUCCESS;
	}



	AVCDec_Status BitstreamByteAlign(AVCDecBitstream *stream)
	{
	uint n_stuffed;

	n_stuffed = (8 - (stream->bitcnt & 0x7)) & 0x7; /* 07/05/01 */

	stream->bitcnt += n_stuffed;
	stream->incnt -= n_stuffed;

	if (stream->incnt < 0)
	{
	stream->bitcnt += stream->incnt;
	stream->incnt = 0;
	}
	stream->curr_word <<= n_stuffed;
	return AVCDEC_SUCCESS;
	}

	/* check whether there are more RBSP data. */
	/* ignore the emulation prevention code, assume it has been taken out. */
	bool more_rbsp_data(AVCDecBitstream *stream)
	{
	int total_bit_left;
	uint code;

	if (stream->read_pos >= stream->nal_size)
	{
	total_bit_left = stream->incnt_next + stream->incnt;
	if (total_bit_left <= 0)
	{
	return FALSE;
	}
	else if (total_bit_left <= 8)
	{
	BitstreamShowBits(stream, total_bit_left, &code);
	if (code == trailing_bits[total_bit_left])
	{
	return FALSE;
	}
	}
	}

	return TRUE;
	}