audio.c

xmms-1.2.10.tar.gz学习使用的就下吧

		*outptr++ =					\
			(sample_type)				\
			((inptr[((x1 >> 12) << 1) + 1] *	\
			  ((1<<12) - frac) +			\
			  inptr[(((x1 >> 12) + 1) << 1) + 1] *	\
			  frac) >> 12);				\
		x += delta;					\
	}							\
	if (NOT_NATIVE_ENDIAN)					\
		swap_endian(nbuffer, nlen);			\
	w = write_all(fd, nbuffer, nlen);			\
} while (0)


#define RESAMPLE_MONO(sample_type)				\
do {								\
	const gint shift = sizeof (sample_type) - 1;		\
        gint i, x, delta, in_samples, out_samples;		\
	sample_type *inptr = (sample_type *)ob, *outptr;	\
	guint nlen = (((length >> shift) * espeed) / speed);	\
	if (nlen == 0)						\
		break;						\
	nlen <<= shift;						\
	if (NOT_NATIVE_ENDIAN)					\
		swap_endian(ob, length);			\
	if(nlen > nbuffer_size)					\
	{							\
		nbuffer = g_realloc(nbuffer, nlen);		\
		nbuffer_size = nlen;				\
	}							\
	outptr = (sample_type *)nbuffer;			\
	in_samples = length >> shift;				\
        out_samples = nlen >> shift;				\
	delta = ((length >> shift) << 12) / out_samples;	\
	for (x = 0, i = 0; i < out_samples; i++)		\
	{							\
		gint x1, frac;					\
		x1 = (x >> 12) << 12;				\
		frac = x - x1;					\
		*outptr++ =					\
			(sample_type)				\
			((inptr[x1 >> 12] * ((1<<12) - frac) +	\
			  inptr[(x1 >> 12) + 1] * frac) >> 12);	\
		x += delta;					\
	}							\
	if (NOT_NATIVE_ENDIAN)					\
		swap_endian(nbuffer, nlen);			\
	w = write_all(fd, nbuffer, nlen);			\
} while (0)


static gint oss_downsample(gpointer ob, guint length, guint speed, guint espeed)
{
	guint w = 0;
	static gpointer nbuffer = NULL;
	static gint nbuffer_size = 0;

	switch (output.format.oss)
	{
		case AFMT_S16_BE:
		case AFMT_S16_LE:
			if (output.channels == 2)
				RESAMPLE_STEREO(gint16);
			else
				RESAMPLE_MONO(gint16);
			break;
		case AFMT_U16_BE:
		case AFMT_U16_LE:
			if (output.channels == 2)
				RESAMPLE_STEREO(guint16);
			else
				RESAMPLE_MONO(guint16);
			break;
		case AFMT_S8:
			if (output.channels == 2)
				RESAMPLE_STEREO(gint8);
			else
				RESAMPLE_MONO(gint8);
			break;
		case AFMT_U8:
			if (output.channels == 2)
				RESAMPLE_STEREO(guint8);
			else
				RESAMPLE_MONO(guint8);
			break;
	}
	return w;
}

void oss_write(gpointer ptr, int length)
{
	int cnt, off = 0;

	if (!realtime)
	{
		remove_prebuffer = FALSE;

		written += length;
		while (length > 0)
		{
			cnt = MIN(length, buffer_size - wr_index);
			memcpy(buffer + wr_index, (char *)ptr + off, cnt);
			wr_index = (wr_index + cnt) % buffer_size;
			length -= cnt;
			off += cnt;
		}
	}
	else
	{
		if (paused)
			return;
		oss_write_audio(ptr, length);
		written += length;
	}
}

void oss_close(void)
{
	if (!going)
		return;
	going = 0;
	if (!realtime)
		pthread_join(buffer_thread, NULL);
	else
	{
		ioctl(fd, SNDCTL_DSP_RESET, 0);
		close(fd);
	}
	g_free(device_name);
	oss_free_convert_buffer();
	wr_index = 0;
	rd_index = 0;
}

void oss_flush(gint time)
{
	if (!realtime)
	{
		flush = time;
		while (flush != -1)
			xmms_usleep(10000);
	}
	else
	{
		ioctl(fd, SNDCTL_DSP_RESET, 0);
		close(fd);
		fd = open(device_name, O_WRONLY);
		oss_set_audio_params();
		output_time_offset = time;
		written = ((guint64)time * input.bps) / 1000;
		output_bytes = 0;
	}
}

void oss_pause(short p)
{
	if (!realtime)
	{
		if (p == TRUE)
			do_pause = TRUE;
		else
			unpause = TRUE;
	}
	else
		paused = p;

}

void *oss_loop(void *arg)
{
	gint length, cnt;
	fd_set set;
	struct timeval tv;

	while (going)
	{
		if (oss_used() > prebuffer_size)
			prebuffer = FALSE;
		if (oss_used() > 0 && !paused && !prebuffer)
		{
			tv.tv_sec = 0;
			tv.tv_usec = 10000;
			FD_ZERO(&set);
			FD_SET(fd, &set);
			if(!select_works || (select(fd + 1, NULL, &set, NULL, &tv) > 0))
			{
				length = MIN(blk_size, oss_used());
				while (length > 0)
				{
					cnt = MIN(length,buffer_size-rd_index);
					oss_write_audio(buffer + rd_index, cnt);
					rd_index=(rd_index+cnt)%buffer_size;
					length-=cnt;				
				}
				if (!oss_used())
					ioctl(fd, SNDCTL_DSP_POST, 0);
			}
		}
		else
			xmms_usleep(10000);
		oss_calc_device_buffer_used();
		if (do_pause && !paused)
		{
			do_pause = FALSE;
			paused = TRUE;
			/*
			 * We lose some data here that is sent to the
			 * soundcard, but not yet played.  I don't
			 * think this is worth fixing.
			 */
			ioctl(fd, SNDCTL_DSP_RESET, 0);
		}
		else if (unpause && paused)
		{
			unpause = FALSE;
			close(fd);
			fd = open(device_name, O_WRONLY);
			oss_set_audio_params();
			paused = FALSE;
		}

		if (flush != -1)
		{
			/*
			 * This close and open is a work around of a
			 * bug that exists in some drivers which cause
			 * the driver to get fucked up by a reset
			 */

			ioctl(fd, SNDCTL_DSP_RESET, 0);
			close(fd);
			fd = open(device_name, O_WRONLY);
			oss_set_audio_params();
			output_time_offset = flush;
			written = ((guint64)flush * input.bps) / 1000;
			rd_index = wr_index = output_bytes = 0;
			flush = -1;
			prebuffer = TRUE;
		}

	}

	ioctl(fd, SNDCTL_DSP_RESET, 0);
	close(fd);
	g_free(buffer);
	pthread_exit(NULL);
}

void oss_set_audio_params(void)
{
	int frag, stereo, ret;
	struct timeval tv;
	fd_set set;

	ioctl(fd, SNDCTL_DSP_RESET, 0);
	frag = (NFRAGS << 16) | fragsize;
	ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &frag);
	/*
	 * Set the stream format.  This ioctl() might fail, but should
	 * return a format that works if it does.
	 */
	ioctl(fd, SNDCTL_DSP_SETFMT, &output.format.oss);
	if (ioctl(fd, SNDCTL_DSP_SETFMT, &output.format.oss) == -1)
		g_warning("SNDCTL_DSP_SETFMT ioctl failed: %s",
			  strerror(errno));

	stereo = output.channels - 1;
	ioctl(fd, SNDCTL_DSP_STEREO, &stereo);
	output.channels = stereo + 1;

	oss_stereo_convert_func = oss_get_stereo_convert_func(output.channels,
							      effect.channels);
	
	if (ioctl(fd, SNDCTL_DSP_SPEED, &output.frequency) == -1)
		g_warning("SNDCTL_DSP_SPEED ioctl failed: %s", strerror(errno));

	if (ioctl(fd, SNDCTL_DSP_GETBLKSIZE, &blk_size) == -1)
		blk_size = 1L << fragsize;

	oss_convert_func =
		oss_get_convert_func(output.format.oss,
				     oss_get_format(effect.format.xmms));

	/*
	 * Stupid hack to find out if the driver support selects, some
	 * drivers won't work properly without a select and some won't
	 * work with a select :/
	 */
	
	tv.tv_sec = 0;
	tv.tv_usec = 50000;
	FD_ZERO(&set);
	FD_SET(fd, &set);
	ret = select(fd + 1, NULL, &set, NULL, &tv);
	if (ret > 0)
		select_works = TRUE;
	else
		select_works = FALSE;
}

gint oss_open(AFormat fmt, gint rate, gint nch)
{
	if (oss_cfg.use_alt_audio_device && oss_cfg.alt_audio_device)
		device_name = g_strdup(oss_cfg.alt_audio_device);
	else
	{
		if (oss_cfg.audio_device > 0)
			device_name = g_strdup_printf("%s%d", DEV_DSP, oss_cfg.audio_device);
		else
			device_name = g_strdup(DEV_DSP);
	}
	fd = open(device_name, O_WRONLY);
	if (fd == -1)
	{
		g_warning("oss_open(): Failed to open audio device (%s): %s",
			  device_name, strerror(errno));
		g_free(device_name);
		return 0;
	}

	input.format.xmms = fmt;
	input.frequency = rate;
	input.channels = nch;
	input.bps = oss_calc_bitrate(oss_get_format(fmt), rate, nch);

	oss_setup_format(fmt, rate, nch);
	
	realtime = xmms_check_realtime_priority();
	
	if(!realtime)
	{
		buffer_size = (oss_cfg.buffer_size * input.bps) / 1000;
		if (buffer_size < 8192)
			buffer_size = 8192;
		prebuffer_size = (buffer_size * oss_cfg.prebuffer) / 100;
		if (buffer_size - prebuffer_size < 4096)
			prebuffer_size = buffer_size - 4096;

		buffer_size += device_buffer_size;
		buffer = g_malloc0(buffer_size);
	}
	flush = -1;
	prebuffer = TRUE;
	wr_index = rd_index = output_time_offset = written = output_bytes = 0;
	paused = FALSE;
	do_pause = FALSE;
	unpause = FALSE;
	remove_prebuffer = FALSE;

	going = 1;
	if (!realtime)
		pthread_create(&buffer_thread, NULL, oss_loop, NULL);
	return 1;
}