audio.c

MP3解码源代码,能够对于MP3进行解码,效率不错

#include "amp.h"

#include <sys/types.h>
#include <sys/stat.h>

#ifndef __BEOS__
#include <sys/uio.h>
#endif

#include <sys/socket.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define AUDIO
#include "audio.h"
#include "formats.h"
#include "getbits.h"
#include "huffman.h"
#include "layer2.h"
#include "layer3.h"
#include "position.h"
#include "rtbuf.h"
#include "transform.h"
#include "controldata.h"
#include "guicontrol.h"

#ifndef __BEOS__
typedef int bool;
#endif

void statusDisplay(struct AUDIO_HEADER *header, int frameNo)
{
	int minutes,seconds;

	if ((A_SHOW_CNT || A_SHOW_TIME) && !(frameNo%10))
		msg("\r");
	if (A_SHOW_CNT && !(frameNo%10) ) {
		msg("{ %d } ",frameNo);
	}
	if (A_SHOW_TIME && !(frameNo%10)) {
		seconds=frameNo*1152/t_sampling_frequency[header->ID][header->sampling_frequency];
		minutes=seconds/60;
		seconds=seconds % 60;
		msg("[%d:%02d]",minutes,seconds);
	}
	if (A_SHOW_CNT || A_SHOW_TIME)
		fflush(stderr);
}

int decodeMPEG(void)
{
struct AUDIO_HEADER header;
int cnt,g,snd_eof;
uid_t my_uid = getuid();

#ifdef LINUX_REALTIME
	set_realtime_priority();

	setreuid(my_uid, my_uid);

	prefetch_initial_fill();
#endif /* LINUX_REALTIME */  

	initialise_globals();

#ifndef LINUX_REALTIME
	if (A_FORMAT_WAVE) wav_begin();
#endif /* LINUX_REALTIME */
	
	if ((g=gethdr(&header))!=0) {
		report_header_error(g);
		return -1;
	}

	if (header.protection_bit==0) getcrc();

#ifdef LINUX_REALTIME
	if (setup_fancy_audio(&header)!=0) {
		warn("Cannot set up direct-to-DMA audio. Exiting\n");
		return -1;
	}
#else
	if (setup_audio(&header)!=0) {
		warn("Cannot set up audio. Exiting\n");
		return -1;
	}
#endif /* LINUX_REALTIME */

	
	show_header(&header);

	if (header.layer==1) {
		if (layer3_frame(&header,cnt)) {
			warn(" error. blip.\n");
			return -1;
		}
	} else if (header.layer==2)
		if (layer2_frame(&header,cnt)) {
			warn(" error. blip.\n");
			return -1;
		}

#ifdef LINUX_REALTIME
	if (start_fancy_audio(&header)!=0) {
		warn("Cannot start direct-to-DMA audio. Exiting\n");
		return -1;
	}
#endif /* LINUX_REALTIME */


	/*
	 * decoder loop **********************************
	 */
	snd_eof=0;
	cnt=0;
	while (!snd_eof) {
		while (!snd_eof && ready_audio()) {
			if ((g=gethdr(&header))!=0) {
				report_header_error(g);
#ifdef LINUX_REALTIME
				cleanup_fancy_audio();
#else
				if (g==GETHDR_EOF && A_FORMAT_WAVE) wav_end(&header);
#endif /* LINUX_REALTIME */
				snd_eof=1;
				break;
                	}

			if (header.protection_bit==0) getcrc();

			statusDisplay(&header,cnt);	

			if (header.layer==1) {
				if (layer3_frame(&header,cnt)) {
					warn(" error. blip.\n");
					return -1;
				}
			} else if (header.layer==2)
				if (layer2_frame(&header,cnt)) {
					warn(" error. blip.\n");
					return -1;
				}
			cnt++;
		}
#ifdef LINUX_REALTIME
		if (block_fancy_audio(snd_eof)!=0) {
			warn("Problems with direct-to-DMA audio\n");
			return -1;
		}
#endif
	}
#ifdef LINUX_REALTIME
	if (stop_fancy_audio()!=0) {
		warn("Cannot stop direct-to-DMA audio. Exiting\n");
		return -1;
	}
#endif
	return 0;
}

int main(int argc,char **argv)
{
int argPos;

	argPos=args(argc,argv); /* process command line arguments */

	initialise_decoder();	/* initialise decoder */

	if (argc == 1) { 	/* Start amp as a GUI backend. */
		A_QUIET = TRUE;	/* TODO: change this to A_GUI_CONTROLLED */
#ifndef OS_SunOS
      		gui_control();
#endif
    	} else {
		if (A_AUDIO_PLAY) {	/* play each specified file */
			if (argPos<argc)
				for(;argPos<argc;argPos++) {
#ifdef LINUX_REALTIME
                                if (geteuid() != 0) 
                                        die("effective UID not root, cannot use realtime buffering\n");
				rt_play(argv[argPos]);
#else /* LINUX_REALTIME */
				play(argv[argPos],0);
#endif /* LINUX_REALTIME */
				}
			else
				displayUsage();
	 	} else {		/* convert the file to some format */
			if ((argPos+2)==argc)
				play(argv[argPos],argv[argPos+1]);
			else {
				warn("Invalid number of parameters\n");
				displayUsage();
				die("");
			}
	}

	msg("\nThank you for using amp!\n");
	exit(0);
    }
  exit(0);
}

/* call this once at the beginning
 */
void initialise_decoder(void)
{
	premultiply();
	imdct_init();
	calculate_t43();
}

/* call this before each file is played
 */
void initialise_globals(void)
{
	append=data=nch=0; 
        f_bdirty=TRUE;
        bclean_bytes=0;

	memset(s,0,sizeof s);
	memset(res,0,sizeof res);
}

void report_header_error(int err)
{
	switch (err) {
		case GETHDR_ERR: die("error reading mpeg bitstream. exiting.\n");
					break;
		case GETHDR_NS : warn("this is a file in MPEG 2.5 format, which is not defined\n");
				 warn("by ISO/MPEG. It is \"a special Fraunhofer format\".\n");
				 warn("amp does not support this format. sorry.\n");
					break;
		case GETHDR_FL1: warn("ISO/MPEG layer 1 is not supported by amp (yet).\n");
					break;
		case GETHDR_FF : warn("free format bitstreams are not supported. sorry.\n");
					break;	
		case GETHDR_SYN: warn("oops, we're out of sync.\n");
					break;
		case GETHDR_EOF: 
		default: 		; /* some stupid compilers need the semicolon */
	}	
}

/* TODO: there must be a check here to see if the audio device has been opened
 * successfuly. This is a bitch because it requires all 6 or 7 OS-specific functions
 * to be changed. Is anyone willing to do this at all???
 */
int setup_audio(struct AUDIO_HEADER *header)
{
	if (A_AUDIO_PLAY)  
		if (AUDIO_BUFFER_SIZE==0)
			audioOpen(t_sampling_frequency[header->ID][header->sampling_frequency],
					(header->mode!=3 && !A_DOWNMIX),A_SET_VOLUME);
		else
			audioBufferOpen(t_sampling_frequency[header->ID][header->sampling_frequency],
					(header->mode!=3 && !A_DOWNMIX),A_SET_VOLUME);
	return 0;
}

void close_audio(void)
{
	if (A_AUDIO_PLAY)
		if (AUDIO_BUFFER_SIZE!=0)
			audioBufferClose();
		else
			audioClose();
}

int ready_audio(void)
{
#ifdef LINUX_REALTIME
	return ready_fancy_audio();
#else
	return 1;
#endif
}

/* TODO: add some kind of error reporting here
 */
void play(char *inFileStr, char *outFileStr)
{
	if (strcmp(inFileStr,"-")==0)
		in_file=stdin;
	else {
		if ((in_file=fopen(inFileStr,"r"))==NULL) {
			warn("Could not open file: %s\n",inFileStr);
			return;
		}
	}
	if (outFileStr) {
		if (strcmp(outFileStr,"-")==0)
			out_file=stdout;
	else
		if ((out_file=fopen(outFileStr,"w"))==NULL) {
			warn("Could not write to file: %s\n",outFileStr);
			return;
		}
		msg("Converting: %s\n",inFileStr);
	}

	if (A_AUDIO_PLAY)
		msg("Playing: %s\n",inFileStr);

	/*
	 * 
	 */

	decodeMPEG();
	
	close_audio();
	fclose(in_file);
	if (!A_AUDIO_PLAY) fclose(out_file);
	msg("\n");
}