File: availbits.c

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/*
 *  TwoLAME: an optimized MPEG Audio Layer Two encoder
 *
 *  Copyright (C) 2001-2004 Michael Cheng
 *  Copyright (C) 2004-2006 The TwoLAME Project
 *
 *  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.
 *
 *  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.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  $Id: availbits.c 156 2007-03-20 23:57:35Z nhumfrey $
 *
 */


#include <stdio.h>

#include "twolame.h"
#include "common.h"
#include "availbits.h"


struct slotinfo {
	FLOAT average;
	FLOAT frac;
	int whole;
	FLOAT lag;
	int extra;
} slots;


/* function returns the number of available bits */
int available_bits ( twolame_options * glopts )
{
	frame_header *header = &glopts->header;
	int adb;
	
	slots.extra = 0;		/* be default, no extra slots */
	
	slots.average =
		(1152.0/ ((FLOAT)glopts->samplerate_out/1000.0) )
		* ((FLOAT)glopts->bitrate / 8.0);
	
	//fprintf(stdout,"availbits says: sampling freq is %i. version %i. bitrateindex %i slots %f\n",header->sampling_frequency, header->version, header->bitrate_index, slots.average);
	
	slots.whole = (int) slots.average;
	slots.frac = slots.average - (FLOAT) slots.whole;
	
	/* never allow padding for a VBR frame. 
	Don't ask me why, I've forgotten why I set this */
	if (slots.frac != 0 && glopts->padding && glopts->vbr == FALSE) {
		if (slots.lag > (slots.frac - 1.0)) {	/* no padding for this frame */
			slots.lag -= slots.frac;
			slots.extra = 0;
			header->padding = 0;
		} else {			/* padding */
			slots.extra = 1;
			header->padding = 1;
			slots.lag += (1 - slots.frac);
		}
	}
	
	adb = (slots.whole + slots.extra) * 8;
	
	return adb;
}


// vim:ts=4:sw=4:nowrap: