g711_decode_c.c

在SPI 平台优化好的G.711代码,保证好用

// g711_decode.c
// G.711 decoder C demo program

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>

#define	TEST_ITEMS	256		// input items in test

// Input, output, reference filenames.
#define	INFILE		"in.bin"
#define	OUTFILE		"out.bin"
#define	REFFILE		"ref.bin" 

// Data buffers.
char		inbuf[TEST_ITEMS];	// G.711 input (bytes)
int		outbuf[TEST_ITEMS];	// PCM output (words)
int		refbuf[TEST_ITEMS];	// PCM reference

// Failure: cry and die.
void
fatal(char *msg, ...)
{
	va_list	ap;

	va_start(ap, msg);
	vfprintf(stderr, msg, ap);
	va_end(ap);
	exit(EXIT_FAILURE);
}

// Open a file, die on failure.
FILE *
xopen(char *name, char *mode)
{
	FILE	*fp;

	if ((fp = fopen(name, mode)) == NULL)
		fatal("%s: open failed\n", name);
	return fp;
}

// Read a file, die on failure.
void
xread(char *name, char *mode, void *buf, int size, int count)
{
	FILE	*fp;

	fp = xopen(name, mode);
	if (fread(buf, size, count, fp) != count)
		fatal("%s: read failed\n", name);
	fclose(fp);
}

// Decode G.711 A-law to PCM.
int
g711_decode(unsigned char data)
{
	unsigned int	i, exponent, mantissa;

	i = (data ^ 0x55) & 0x7F;		// re-toggle even bits, remove sign bit
	exponent = i >> 4;			// extract exponent
	mantissa = i & 0xF;			// extract mantissa
	if (exponent > 0)
		mantissa |= 0x10;		// restore hidden bit to mantissa
	mantissa = (mantissa << 4) | 0x08;	// left justify, add 1/2 quantization stepsize

	// Normalize mantissa if log encoding (not linear segment).
	if (exponent > 1)
		mantissa <<= exponent -1;

	// Negate if sign bit was NOT set in data.
	if ((data & 0x80) == 0)
		mantissa = -mantissa;
	return mantissa << 16;			// shift output to be MSB aligned in 32 bits
}

int
main(int argc, char *argv[])
{
	FILE		*fp;
	int		i;

	// Read input file.
	xread(INFILE, "rb", inbuf, sizeof(inbuf[0]), TEST_ITEMS);

	// Decode.
	for (i = 0; i < TEST_ITEMS; i++)
		outbuf[i] = g711_decode(inbuf[i]);

	// Dump output data.
	fp = xopen(OUTFILE, "wb");
	if (fwrite(outbuf, sizeof(outbuf[0]), TEST_ITEMS, fp) != TEST_ITEMS)

		fatal("%s: write failed\n", OUTFILE);
	fclose(fp);

	// Read reference file.
	xread(REFFILE, "rb", refbuf, sizeof(refbuf[0]), TEST_ITEMS);

	// Compare result to reference result.
	for (i = 0; i < TEST_ITEMS; i++) {
		if (outbuf[i] != refbuf[i])
			fatal("result miscompares at word %d: expected 0x%X, got 0x%X\n",
				refbuf[i], outbuf[i]);
	}

	// Done.
	printf("Success!\n");
	exit(EXIT_SUCCESS);
}

// end of g711_decode_c.c