getbit.c

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/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */

/*
 * Disclaimer of Warranty
 *
 * These software programs are available to the user without any license fee or
 * royalty on an "as is" basis.  The MPEG Software Simulation Group disclaims
 * any and all warranties, whether express, implied, or statuary, including any
 * implied warranties or merchantability or of fitness for a particular
 * purpose.  In no event shall the copyright-holder be liable for any
 * incidental, punitive, or consequential damages of any kind whatsoever
 * arising from the use of these programs.
 *
 * This disclaimer of warranty extends to the user of these programs and user's
 * customers, employees, agents, transferees, successors, and assigns.
 *
 * The MPEG Software Simulation Group does not represent or warrant that the
 * programs furnished hereunder are free of infringement of any third-party
 * patents.
 *
 * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
 * are subject to royalty fees to patent holders.  Many of these patents are
 * general enough such that they are unavoidable regardless of implementation
 * design.
 *
 */

/*
 * All modifications (mpeg2decode -> DVD2AVI) are Copyright (C) Chia-chen Kuo - Jan 2001
 */

#include "global.h"
#include "getbit.h"

__forceinline static unsigned int Get_Short(void);


void Initialize_Buffer()
{
	Rdptr = Rdbfr + BUFFER_SIZE;
	Rdmax = Rdptr;
	if (SystemStream_Flag)
	{
		if (Rdptr >= Rdmax)
			Next_Packet();
		CurrentBfr = *Rdptr++ << 24;

		if (Rdptr >= Rdmax)
			Next_Packet();
		CurrentBfr += *Rdptr++ << 16;

		if (Rdptr >= Rdmax)
			Next_Packet();
		CurrentBfr += *Rdptr++ << 8;

		if (Rdptr >= Rdmax)
			Next_Packet();
		CurrentBfr += *Rdptr++;

		Fill_Next();
	}
	else
	{
		Fill_Buffer();
		CurrentBfr = (*Rdptr << 24) + (*(Rdptr+1) << 16) + (*(Rdptr+2) << 8) + *(Rdptr+3);
		Rdptr += 4;
		Fill_Next();
	}
	
	BitsLeft = 32;
}

void Next_Packet(void)
{
	static short volume;
	static int i, j, Packet_Length, Packet_Header_Length, size;
	static unsigned int code, AUDIO_ID, VOBCELL_Count, AC3_Track, MPA_Track;

	for (; Fault_Flag == 0;)
	{
		code = Get_Short();
		code = (code<<16) + Get_Short();

		// remove system layer byte stuffing
		while (!Fault_Flag && (code & 0xffffff00) != 0x00000100)
			code = (code<<8) + Get_Byte();
		if (Fault_Flag)
		{
			return;
		}

		switch (code)
		{
			case PACK_START_CODE:
				Rdptr += 8;
				VOBCELL_Count = 0;
				break;

			case PRIVATE_STREAM_2:
				Packet_Length = Get_Short();

				if (++VOBCELL_Count==2)
				{
					Rdptr += 25;
					VOB_ID = Get_Short();
					CELL_ID = Get_Short();
					Rdptr += Packet_Length - 29;
				}
				else
					Rdptr += Packet_Length;
				break;

			case VIDEO_ELEMENTARY_STREAM:
				Packet_Length = Get_Short();
				Rdmax = Rdptr + Packet_Length;

				code = Get_Byte();

				if ((code & 0xc0)==0x80)
				{
					code = Get_Byte();
					Packet_Header_Length = Get_Byte();

					if (code>=0x80 && !Rip_Flag)
					{
						code = Get_Byte();
						VideoPTS = (code & 0x0e) << 29;
						VideoPTS |= (Get_Short() & 0xfffe) << 14;
						VideoPTS |= (Get_Short()>>1) & 0x7fff;
						VideoPTS /= 90;

						Rdptr += Packet_Header_Length-5;
					}
					else
						Rdptr += Packet_Header_Length;

					Bitrate_Meter += Rdmax-Rdptr;
					return;
				}
				else
					Rdptr += Packet_Length-1;
				break;

			default:
				if (code>=SYSTEM_START_CODE)
				{
					Packet_Length = Get_Short();
					Rdptr += Packet_Length;
				}
				break;
		}
	}
}

unsigned int Get_Bits_All(unsigned int N)
{
	N -= BitsLeft;
	Val = (CurrentBfr << (32 - BitsLeft)) >> (32 - BitsLeft);

	if (N)
		Val = (Val << N) + (NextBfr >> (32 - N));

	CurrentBfr = NextBfr;
	BitsLeft = 32 - N;
	Fill_Next();

	return Val;
}

void Flush_Buffer_All(unsigned int N)
{
	CurrentBfr = NextBfr;
	BitsLeft = BitsLeft + 32 - N;
	Fill_Next();
}

void Fill_Buffer()
{
	int readsize = BUFFER_SIZE;
	if (gIsEOS)
	{
		int available = GetAvailableInSmartCache();
		if (available == 0)
		{
			// Force to exit from decoding cycle
			Fault_Flag = ERROR_FLUSH;
		}
		if (available < BUFFER_SIZE)
		{
			readsize = available;
		}		
	}
	Read = FetchDataFromSmartCache(Rdbfr, readsize);

	Rdptr = Rdbfr;
	Rdmax = Rdbfr + Read;
	Bitrate_Meter += Read;
}

static unsigned int Get_Short()
{
	unsigned int i = Get_Byte();
	return (i<<8) | Get_Byte();
}