bitstream.c

一个简单的RTSP客户端实现源码

/**********
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)

This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
more details.
**********/


#include "bitstream.h"
#include <stdio.h>
#include <memory.h>
#include <stdlib.h>         /* For _MAX_PATH definition */
#include <malloc.h>

/////////////////////////////////////
uint32_t *bitstream;
///////////////////////
/* reads n bits from bitstream without changing the stream pos */

uint32_t BitstreamShowBits(Bitstream * bs,uint32_t bits)
{
	int nbit = (bits + bs->pos) - 32;
	uint32_t ret_value;
	
	if (nbit > 0) 
	{
		ret_value =  ((bs->bufa & (0xffffffff >> bs->pos)) << nbit) |
				(bs->bufb >> (32 - nbit));
	}
	else 
	{
		ret_value = (bs->bufa & (0xffffffff >> bs->pos)) >> (32 - bs->pos - bits);
	}
//	fprintf(stderr,"show 2 bufa :%x; bufb :%x ;pos :%u;\n",bs->bufa,bs->bufb,bs->pos);
//	fprintf(stderr,"showbits %d %x\n", bits, ret_value);
	
	return ret_value;
}

/* skip n bits forward in bitstream */

void BitstreamSkip(Bitstream * bs,uint32_t bits)
{
	uint32_t tmp;
	bs->pos += bits;
	if (bs->pos >= 32) 
	{
		bs->bufa = bs->bufb;
		tmp = *((uint32_t *)bs->tail + 2);
		bs->bufb = tmp;
		bs->tail++;
		bs->pos -= 32;
	}
//	fprintf(stderr,"skip 2 bufa :%x; bufb :%x ;pos :%u;\n",bs->bufa,bs->bufb,bs->pos);
	//fprintf(stderr,"used %d\n", bits);
}


/* bitstream length (unit bits) */

uint32_t BitstreamPos(Bitstream * bs)
{
    return 8 * ((uint32_t)bs->tail - (uint32_t)bs->start) + bs->pos;
}


/*	flush the bitstream & return length (unit bytes)
	NOTE: assumes no futher bitstream functions will be called.
 */

uint32_t BitstreamLength(Bitstream * bs)
{
	uint32_t len = (uint32_t) bs->tail - (uint32_t) bs->start;
	uint32_t b;
    if (bs->pos)
    {
		b = bs->buf;
		*bs->tail = b;

		len += (bs->pos + 7) / 8;
    }

	return len;
}


/* read n bits from bitstream */

uint32_t BitstreamGetBits(Bitstream * bs,uint32_t n)
{
	uint32_t ret = BitstreamShowBits(bs, n);
	BitstreamSkip(bs, n);
	return ret;
}


/* read single bit from bitstream */

uint32_t BitstreamGetBit(Bitstream * const bs)
{
	return BitstreamGetBits(bs, 1);
}


////////////////////////////////////


int log2bin(int value)
{
	int n = 0;
	while (value)
	{
		value >>= 1;
		n++;
	}
	return n;
}


static const uint32_t intra_dc_threshold_table[] =
{
	32,	/* never use */
	13,
	15,
	17,
	19,
	21,
	23,
	1,
};

////////////////////////////
void BitstreamByteAlign(Bitstream *bs)
{
	uint32_t remainder = bs->pos % 8;
	if (remainder)
	{
		BitstreamSkip(bs, 8 - remainder);
	}
}

/*
decode headers
returns coding_type, or -1 if error
*/

int BitstreamReadHeaders(Bitstream * bs, XVID_DEC_PARAM * param,int findvol)
{
	uint32_t rounding; 
	uint32_t quant;
	uint32_t fcode;
	uint32_t intra_dc_threshold;
	static uint32_t vol_ver_id = 0;
	static uint32_t time_inc_resolution = 0;
	static uint32_t time_inc_bits = 0;
	static uint32_t coding_type = 0;
	static uint32_t fixed_vop_time_increment = 0;
	uint32_t start_code;
	static uint32_t width = 0, height = 0;
	static uint32_t shape = 0;
	static uint32_t interlacing = 0;
	static uint32_t top_field_first = 0;
	static uint32_t alternate_vertical_scan = 0;
	static uint32_t quant_bits = 0;
	static uint32_t quant_type = 0;
	static uint32_t quarterpel = 0;
	static uint32_t have_short_header = 0;
	int hours, minutes, seconds;
	uint32_t temp_width=0, temp_height=0;
	uint32_t horiz_mc_ref, vert_mc_ref;
	uint32_t source_format;
	

	do
	{
		BitstreamByteAlign(bs);
		start_code = BitstreamShowBits(bs, 32);
//		fprintf(stderr,"1 start_code is %x\n",start_code);
		//BitstreamSkip(bs,32);
		
		if (start_code == VISOBJSEQ_START_CODE)
		{
			BitstreamSkip(bs, 32);				// visual_object_sequence_start_code
			BitstreamSkip(bs, 8);					// profile_and_level_indication
		}
		else if (start_code == VISOBJSEQ_STOP_CODE)
		{
			BitstreamSkip(bs, 32);				// visual_object_sequence_stop_code
		}
		else if (start_code == VISOBJ_START_CODE)
		{
			BitstreamSkip(bs,32);					// visual_object_start_code
			if (BitstreamGetBit(bs))				// is_visual_object_identified
			{
				vol_ver_id = BitstreamGetBits(bs,4);	// visual_object_ver_id
				BitstreamSkip(bs, 3);				// visual_object_priority
			}
			else
			{
				vol_ver_id = 1;
			}

			if (BitstreamShowBits(bs, 4) != VISOBJ_TYPE_VIDEO)	// visual_object_type
			{
//				DEBUG("visual_object_type != video");
				return -1;
			}
			BitstreamSkip(bs, 4);

			// video_signal_type

			if (BitstreamGetBit(bs))				// video_signal_type
			{
	//			DEBUG("+ video_signal_type");
				BitstreamSkip(bs, 3);				// video_format
				BitstreamSkip(bs, 1);				// video_range
				if (BitstreamGetBit(bs))			// color_description
				{
		//			DEBUG("+ color_description");
					BitstreamSkip(bs, 8);			// color_primaries
					BitstreamSkip(bs, 8);			// transfer_characteristics
					BitstreamSkip(bs, 8);			// matrix_coefficients
				}
			}
		}
		else if ((start_code & ~0x1f) == VIDOBJ_START_CODE)
		{
			fprintf(stderr,"video_object_start_code \n");
			BitstreamSkip(bs, 32);		// video_object_start_code
			
		} 
		else if ((start_code & ~0xf) == VIDOBJLAY_START_CODE)
		{
			// DEBUG("video_object_layer");
			BitstreamSkip(bs, 32);					// video_object_layer_start_code

			BitstreamSkip(bs, 1);									// random_accessible_vol

			// video_object_type_indication
			if (BitstreamShowBits(bs, 8) != VIDOBJLAY_TYPE_SIMPLE &&
				BitstreamShowBits(bs, 8) != VIDOBJLAY_TYPE_CORE &&
				BitstreamShowBits(bs, 8) != VIDOBJLAY_TYPE_MAIN &&
				BitstreamShowBits(bs, 8) != 0)		// BUGGY DIVX
			{
			//	DEBUG1("video_object_type_indication not supported", BitstreamShowBits(bs, 8));
				fprintf(stderr,"video_object_type_indication not supported %d\n", BitstreamShowBits(bs, 8));
				return -1;
			}
			BitstreamSkip(bs, 8);


			if (BitstreamGetBit(bs))					// is_object_layer_identifier
			{
				//DEBUG("+ is_object_layer_identifier");
				vol_ver_id = BitstreamGetBits(bs,4);		// video_object_layer_verid
				BitstreamSkip(bs, 3);					// video_object_layer_priority
			}
			else
			{
				vol_ver_id = 1;
			}
			//DEBUGI("vol_ver_id", vol_ver_id);

			if (BitstreamGetBits(bs, 4) == VIDOBJLAY_AR_EXTPAR)	// aspect_ratio_info
			{
				//DEBUG("+ aspect_ratio_info");
				BitstreamSkip(bs, 8);						// par_width
				BitstreamSkip(bs, 8);						// par_height
			}

			if (BitstreamGetBit(bs))		// vol_control_parameters
			{
				//DEBUG("+ vol_control_parameters");
				BitstreamSkip(bs, 2);						// chroma_format
				BitstreamSkip(bs, 1);						// low_delay
				if (BitstreamGetBit(bs))					// vbv_parameters
				{
					//DEBUG("+ vbv_parameters");
					BitstreamSkip(bs, 15);				// first_half_bitrate
					READ_MARKER();
					BitstreamSkip(bs, 15);				// latter_half_bitrate
					READ_MARKER();
					BitstreamSkip(bs, 15);				// first_half_vbv_buffer_size
					READ_MARKER();
					BitstreamSkip(bs, 3);					// latter_half_vbv_buffer_size
					BitstreamSkip(bs, 11);				// first_half_vbv_occupancy
					READ_MARKER();
					BitstreamSkip(bs, 15);				// latter_half_vbv_occupancy
					READ_MARKER();
				
				}
			}

			shape = BitstreamGetBits(bs, 2);	// video_object_layer_shape
			// DEBUG1("shape", dec->shape);
			
			if (shape == VIDOBJLAY_SHAPE_GRAYSCALE && vol_ver_id != 1)
			{
				BitstreamSkip(bs, 4);		// video_object_layer_shape_extension
			}

			READ_MARKER();

			time_inc_resolution = BitstreamGetBits(bs, 16);	// vop_time_increment_resolution
			//time_inc_resolution--;
			fprintf(stderr,"time_inc_resolution is %u\n",time_inc_resolution);
			if (time_inc_resolution > 0)
			{
				time_inc_bits = log2bin(time_inc_resolution);
			}
			else
			{
				// dec->time_inc_bits = 0;

				// for "old" xvid compatibility, set time_inc_bits = 1
				time_inc_bits = 1;
			}
			READ_MARKER();

			if (BitstreamGetBit(bs))						// fixed_vop_rate
			{
				//BitstreamSkip(bs, time_inc_bits);	// fixed_vop_time_increment
				fixed_vop_time_increment = BitstreamGetBits(bs, time_inc_bits);	// fixed_vop_time_increment
				param->framerate = time_inc_resolution*1000/fixed_vop_time_increment;
				fixed_vop_rate = 1;
			}
			else
			{
				param->framerate = time_inc_resolution*1000/1001;
			}

			if (shape != VIDOBJLAY_SHAPE_BINARY_ONLY)
			{

				if (shape == VIDOBJLAY_SHAPE_RECTANGULAR)
				{
					READ_MARKER();
					temp_width = BitstreamGetBits(bs, 13);			// video_object_layer_width
					//DEBUGI("width", width);
					//fprintf(stderr,"width is %u\n",width);
					READ_MARKER();
					temp_height = BitstreamGetBits(bs, 13);		// video_object_layer_height
					//DEBUGI("height", height);	
					//fprintf(stderr,"height is %u\n",height);
					READ_MARKER();

					if (findvol == 0) 
					{
					  if (temp_width != width || temp_height != height)
					    {
					      fprintf(stderr,"FATAL: video dimension discrepancy ***");
					      fprintf(stderr,"bitstream width %u /height %u\n", temp_width, temp_height);
					      fprintf(stderr,"param width %u /height %u\n", width, height);
					      return -1;
					    }
					} 
					else 
					{
					  width = temp_width;
					  height = temp_height;
					}
										

				}

				if ((interlacing = BitstreamGetBit(bs)))
				{
					fprintf(stderr,"vol: interlacing\n");
				}

				if (!BitstreamGetBit(bs))				// obmc_disable
				{
					fprintf(stderr,"IGNORED/TODO: !obmc_disable\n");
					// TODO
					// fucking divx4.02 has this enabled
				}

				if (BitstreamGetBits(bs, (vol_ver_id == 1 ? 1 : 2)))  // sprite_enable
				{
					fprintf(stderr,"sprite_enable; not supported\n");
					return -1;
				}
			
				if (vol_ver_id != 1 && shape != VIDOBJLAY_SHAPE_RECTANGULAR)
				{