FreeRDP/channels/rdpsnd/client/alsa/rdpsnd_alsa.c

/**
 * FreeRDP: A Remote Desktop Protocol Implementation
 * Audio Output Virtual Channel
 *
 * Copyright 2009-2011 Jay Sorg
 * Copyright 2010-2011 Vic Lee
 * Copyright 2015 Thincast Technologies GmbH
 * Copyright 2015 DI (FH) Martin Haimberger <martin.haimberger@thincast.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

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

#include <winpr/crt.h>
#include <winpr/cmdline.h>
#include <winpr/sysinfo.h>
#include <winpr/collections.h>

#include <alsa/asoundlib.h>

#include <freerdp/types.h>
#include <freerdp/codec/dsp.h>
#include <freerdp/channels/log.h>

#include "rdpsnd_main.h"

typedef struct rdpsnd_alsa_plugin rdpsndAlsaPlugin;

struct rdpsnd_alsa_plugin
{
	rdpsndDevicePlugin device;

	int latency;
	int wformat;
	int block_size;
	char* device_name;
	snd_pcm_t* pcm_handle;
	snd_mixer_t* mixer_handle;
	UINT32 source_rate;
	UINT32 actual_rate;
	UINT32 wLocalTimeClose;
	snd_pcm_format_t format;
	UINT32 source_channels;
	UINT32 actual_channels;
	int bytes_per_channel;
	snd_pcm_uframes_t buffer_size;
	snd_pcm_uframes_t period_size;
	FREERDP_DSP_CONTEXT* dsp_context;
};

#define SND_PCM_CHECK(_func, _status) \
	if (_status < 0) \
	{ \
		WLog_ERR(TAG,  "%s: %d\n", _func, _status); \
		return -1; \
	}

static int rdpsnd_alsa_set_hw_params(rdpsndAlsaPlugin* alsa)
{
	int status;
	snd_pcm_hw_params_t* hw_params;
	snd_pcm_uframes_t buffer_size_max;

	status = snd_pcm_hw_params_malloc(&hw_params);
	SND_PCM_CHECK("snd_pcm_hw_params_malloc", status);

	status = snd_pcm_hw_params_any(alsa->pcm_handle, hw_params);
	SND_PCM_CHECK("snd_pcm_hw_params_any", status);

	/* Set interleaved read/write access */
	status = snd_pcm_hw_params_set_access(alsa->pcm_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	SND_PCM_CHECK("snd_pcm_hw_params_set_access", status);

	/* Set sample format */
	status = snd_pcm_hw_params_set_format(alsa->pcm_handle, hw_params, alsa->format);
	SND_PCM_CHECK("snd_pcm_hw_params_set_format", status);

	/* Set sample rate */
	status = snd_pcm_hw_params_set_rate_near(alsa->pcm_handle, hw_params, &alsa->actual_rate, NULL);
	SND_PCM_CHECK("snd_pcm_hw_params_set_rate_near", status);

	/* Set number of channels */
	status = snd_pcm_hw_params_set_channels(alsa->pcm_handle, hw_params, alsa->actual_channels);
	SND_PCM_CHECK("snd_pcm_hw_params_set_channels", status);

	/* Get maximum buffer size */
	status = snd_pcm_hw_params_get_buffer_size_max(hw_params, &buffer_size_max);
	SND_PCM_CHECK("snd_pcm_hw_params_get_buffer_size_max", status);

	/**
	 * ALSA Parameters
	 *
	 * http://www.alsa-project.org/main/index.php/FramesPeriods
	 *
	 * buffer_size = period_size * periods
	 * period_bytes = period_size * bytes_per_frame
	 * bytes_per_frame = channels * bytes_per_sample
	 *
	 * A frame is equivalent of one sample being played,
	 * irrespective of the number of channels or the number of bits
	 *
	 * A period is the number of frames in between each hardware interrupt.
	 *
	 * The buffer size always has to be greater than one period size.
	 * Commonly this is (2 * period_size), but some hardware can do 8 periods per buffer.
	 * It is also possible for the buffer size to not be an integer multiple of the period size.
	 */

	int interrupts_per_sec_near = 50;
	int bytes_per_sec = (alsa->actual_rate * alsa->bytes_per_channel * alsa->actual_channels);

	alsa->buffer_size = buffer_size_max;
	alsa->period_size = (bytes_per_sec / interrupts_per_sec_near);

	if (alsa->period_size > buffer_size_max)
	{
		WLog_ERR(TAG, "Warning: requested sound buffer size %lu, got %lu instead\n",
				 alsa->buffer_size, buffer_size_max);
		alsa->period_size = (buffer_size_max / 8);
	}

	/* Set buffer size */
	status = snd_pcm_hw_params_set_buffer_size_near(alsa->pcm_handle, hw_params, &alsa->buffer_size);
	SND_PCM_CHECK("snd_pcm_hw_params_set_buffer_size_near", status);

	/* Set period size */
	status = snd_pcm_hw_params_set_period_size_near(alsa->pcm_handle, hw_params, &alsa->period_size, NULL);
	SND_PCM_CHECK("snd_pcm_hw_params_set_period_size_near", status);

	status = snd_pcm_hw_params(alsa->pcm_handle, hw_params);
	SND_PCM_CHECK("snd_pcm_hw_params", status);

	snd_pcm_hw_params_free(hw_params);

	return 0;
}

static int rdpsnd_alsa_set_sw_params(rdpsndAlsaPlugin* alsa)
{
	int status;
	snd_pcm_sw_params_t* sw_params;

	status = snd_pcm_sw_params_malloc(&sw_params);
	SND_PCM_CHECK("snd_pcm_sw_params_malloc", status);

	status = snd_pcm_sw_params_current(alsa->pcm_handle, sw_params);
	SND_PCM_CHECK("snd_pcm_sw_params_current", status);

	status = snd_pcm_sw_params_set_avail_min(alsa->pcm_handle, sw_params, (alsa->bytes_per_channel * alsa->actual_channels));
	SND_PCM_CHECK("snd_pcm_sw_params_set_avail_min", status);

	status = snd_pcm_sw_params_set_start_threshold(alsa->pcm_handle, sw_params, alsa->block_size);
	SND_PCM_CHECK("snd_pcm_sw_params_set_start_threshold", status);

	status = snd_pcm_sw_params(alsa->pcm_handle, sw_params);
	SND_PCM_CHECK("snd_pcm_sw_params", status);

	snd_pcm_sw_params_free(sw_params);

	status = snd_pcm_prepare(alsa->pcm_handle);
	SND_PCM_CHECK("snd_pcm_prepare", status);

	return 0;
}

static int rdpsnd_alsa_validate_params(rdpsndAlsaPlugin* alsa)
{
	int status;
	snd_pcm_uframes_t buffer_size;
	snd_pcm_uframes_t period_size;

	status = snd_pcm_get_params(alsa->pcm_handle, &buffer_size, &period_size);
	SND_PCM_CHECK("snd_pcm_get_params", status);

	return 0;
}

static int rdpsnd_alsa_set_params(rdpsndAlsaPlugin* alsa)
{
	snd_pcm_drop(alsa->pcm_handle);

	if (rdpsnd_alsa_set_hw_params(alsa) < 0)
		return -1;

	if (rdpsnd_alsa_set_sw_params(alsa) < 0)
		return -1;

	return rdpsnd_alsa_validate_params(alsa);
}

static BOOL rdpsnd_alsa_set_format(rdpsndDevicePlugin* device, AUDIO_FORMAT* format, int latency)
{
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (format)
	{
		alsa->source_rate = format->nSamplesPerSec;
		alsa->actual_rate = format->nSamplesPerSec;
		alsa->source_channels = format->nChannels;
		alsa->actual_channels = format->nChannels;

		switch (format->wFormatTag)
		{
			case WAVE_FORMAT_PCM:
				switch (format->wBitsPerSample)
				{
					case 8:
						alsa->format = SND_PCM_FORMAT_S8;
						alsa->bytes_per_channel = 1;
						break;

					case 16:
						alsa->format = SND_PCM_FORMAT_S16_LE;
						alsa->bytes_per_channel = 2;
						break;
				}
				break;

			case WAVE_FORMAT_ADPCM:
			case WAVE_FORMAT_DVI_ADPCM:
				alsa->format = SND_PCM_FORMAT_S16_LE;
				alsa->bytes_per_channel = 2;
				break;
		}

		alsa->wformat = format->wFormatTag;
		alsa->block_size = format->nBlockAlign;
	}

	alsa->latency = latency;

	return (rdpsnd_alsa_set_params(alsa) == 0);
}

static BOOL rdpsnd_alsa_open_mixer(rdpsndAlsaPlugin* alsa)
{
	int status;

	if (alsa->mixer_handle)
		return TRUE;

	status = snd_mixer_open(&alsa->mixer_handle, 0);
	if (status < 0)
	{
		WLog_ERR(TAG, "snd_mixer_open failed");
		return FALSE;
	}

	status = snd_mixer_attach(alsa->mixer_handle, alsa->device_name);
	if (status < 0)
	{
		WLog_ERR(TAG, "snd_mixer_attach failed");
		snd_mixer_close(alsa->mixer_handle);
		return FALSE;
	}

	status = snd_mixer_selem_register(alsa->mixer_handle, NULL, NULL);
	if (status < 0)
	{
		WLog_ERR(TAG, "snd_mixer_selem_register failed");
		snd_mixer_close(alsa->mixer_handle);
		return FALSE;
	}

	status = snd_mixer_load(alsa->mixer_handle);
	if (status < 0)
	{
		WLog_ERR(TAG, "snd_mixer_load failed");
		snd_mixer_close(alsa->mixer_handle);
		return FALSE;
	}

	return TRUE;
}

static BOOL rdpsnd_alsa_open(rdpsndDevicePlugin* device, AUDIO_FORMAT* format, int latency)
{
	int mode;
	int status;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (alsa->pcm_handle)
		return TRUE;

	mode = 0;
	/*mode |= SND_PCM_NONBLOCK;*/

	status = snd_pcm_open(&alsa->pcm_handle, alsa->device_name, SND_PCM_STREAM_PLAYBACK, mode);
	if (status < 0)
	{
		WLog_ERR(TAG, "snd_pcm_open failed");
		return FALSE;
	}

	freerdp_dsp_context_reset_adpcm(alsa->dsp_context);

	return rdpsnd_alsa_set_format(device, format, latency) &&
			rdpsnd_alsa_open_mixer(alsa);
}

static void rdpsnd_alsa_close(rdpsndDevicePlugin* device)
{
	int status;
	snd_htimestamp_t tstamp;
	snd_pcm_uframes_t frames;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (!alsa->pcm_handle)
		return;

	status = snd_pcm_htimestamp(alsa->pcm_handle, &frames, &tstamp);

	if (status != 0)
		frames = 0;

	alsa->wLocalTimeClose = GetTickCount();
	alsa->wLocalTimeClose += (((frames * 1000) / alsa->actual_rate) / alsa->actual_channels);
}

static void rdpsnd_alsa_free(rdpsndDevicePlugin* device)
{
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (alsa->pcm_handle)
	{
		snd_pcm_drain(alsa->pcm_handle);
		snd_pcm_close(alsa->pcm_handle);
		alsa->pcm_handle = 0;
	}

	if (alsa->mixer_handle)
	{
		snd_mixer_close(alsa->mixer_handle);
		alsa->mixer_handle = NULL;
	}

	free(alsa->device_name);

	freerdp_dsp_context_free(alsa->dsp_context);

	free(alsa);
}

static BOOL rdpsnd_alsa_format_supported(rdpsndDevicePlugin* device, AUDIO_FORMAT* format)
{
	switch (format->wFormatTag)
	{
		case WAVE_FORMAT_PCM:
			if (format->cbSize == 0 &&
				format->nSamplesPerSec <= 48000 &&
				(format->wBitsPerSample == 8 || format->wBitsPerSample == 16) &&
				(format->nChannels == 1 || format->nChannels == 2))
			{
				return TRUE;
			}
			break;

		case WAVE_FORMAT_ADPCM:
		case WAVE_FORMAT_DVI_ADPCM:
			if (format->nSamplesPerSec <= 48000 &&
				format->wBitsPerSample == 4 &&
				(format->nChannels == 1 || format->nChannels == 2))
			{
				return TRUE;
			}
			break;

		case WAVE_FORMAT_ALAW:
		case WAVE_FORMAT_MULAW:
		case WAVE_FORMAT_GSM610:
		default:
			break;
	}

	return FALSE;
}

static UINT32 rdpsnd_alsa_get_volume(rdpsndDevicePlugin* device)
{
	long volume_min;
	long volume_max;
	long volume_left;
	long volume_right;
	UINT32 dwVolume;
	UINT16 dwVolumeLeft;
	UINT16 dwVolumeRight;
	snd_mixer_elem_t* elem;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	dwVolumeLeft = ((50 * 0xFFFF) / 100); /* 50% */
	dwVolumeRight = ((50 * 0xFFFF) / 100); /* 50% */

	if (!alsa->mixer_handle)
		rdpsnd_alsa_open_mixer(alsa);

	for (elem = snd_mixer_first_elem(alsa->mixer_handle); elem; elem = snd_mixer_elem_next(elem))
	{
		if (snd_mixer_selem_has_playback_volume(elem))
		{
			snd_mixer_selem_get_playback_volume_range(elem, &volume_min, &volume_max);
			snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_FRONT_LEFT, &volume_left);
			snd_mixer_selem_get_playback_volume(elem, SND_MIXER_SCHN_FRONT_RIGHT, &volume_right);

			dwVolumeLeft = (UINT16) (((volume_left * 0xFFFF) - volume_min) / (volume_max - volume_min));
			dwVolumeRight = (UINT16) (((volume_right * 0xFFFF) - volume_min) / (volume_max - volume_min));

			break;
		}
	}

	dwVolume = (dwVolumeLeft << 16) | dwVolumeRight;

	return dwVolume;
}

static BOOL rdpsnd_alsa_set_volume(rdpsndDevicePlugin* device, UINT32 value)
{
	long left;
	long right;
	long volume_min;
	long volume_max;
	long volume_left;
	long volume_right;
	snd_mixer_elem_t* elem;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (!alsa->mixer_handle && !rdpsnd_alsa_open_mixer(alsa))
			return FALSE;

	left = (value & 0xFFFF);
	right = ((value >> 16) & 0xFFFF);
	
	for (elem = snd_mixer_first_elem(alsa->mixer_handle); elem; elem = snd_mixer_elem_next(elem))
	{
		if (snd_mixer_selem_has_playback_volume(elem))
		{
			snd_mixer_selem_get_playback_volume_range(elem, &volume_min, &volume_max);
			volume_left = volume_min + (left * (volume_max - volume_min)) / 0xFFFF;
			volume_right = volume_min + (right * (volume_max - volume_min)) / 0xFFFF;
			if ((snd_mixer_selem_set_playback_volume(elem, SND_MIXER_SCHN_FRONT_LEFT, volume_left) < 0) ||
				(snd_mixer_selem_set_playback_volume(elem, SND_MIXER_SCHN_FRONT_RIGHT, volume_right) < 0))
			{
				WLog_ERR(TAG, "error setting the volume\n");
				return FALSE;
			}
		}
	}

	return TRUE;
}

static BYTE* rdpsnd_alsa_process_audio_sample(rdpsndDevicePlugin* device, BYTE* data, int* size)
{
	int frames;
	BYTE* srcData;
	int srcFrameSize;
	int dstFrameSize;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	if (alsa->wformat == WAVE_FORMAT_ADPCM)
	{
		alsa->dsp_context->decode_ms_adpcm(alsa->dsp_context,
			data, *size, alsa->source_channels, alsa->block_size);

		*size = alsa->dsp_context->adpcm_size;
		srcData = alsa->dsp_context->adpcm_buffer;
	}
	else if (alsa->wformat == WAVE_FORMAT_DVI_ADPCM)
	{
		alsa->dsp_context->decode_ima_adpcm(alsa->dsp_context,
			data, *size, alsa->source_channels, alsa->block_size);

		*size = alsa->dsp_context->adpcm_size;
		srcData = alsa->dsp_context->adpcm_buffer;
	}
	else
	{
		srcData = data;
	}

	srcFrameSize = alsa->source_channels * alsa->bytes_per_channel;
	dstFrameSize = alsa->actual_channels * alsa->bytes_per_channel;

	if ((*size % srcFrameSize) != 0)
		return NULL;

	if (!((alsa->source_rate == alsa->actual_rate) && (alsa->source_channels == alsa->actual_channels)))
	{
		alsa->dsp_context->resample(alsa->dsp_context, srcData, alsa->bytes_per_channel,
			alsa->source_channels, alsa->source_rate, *size / srcFrameSize,
			alsa->actual_channels, alsa->actual_rate);

		frames = alsa->dsp_context->resampled_frames;

		*size = frames * dstFrameSize;
		srcData = alsa->dsp_context->resampled_buffer;
	}

	data = srcData;

	return data;
}

static BOOL rdpsnd_alsa_wave_decode(rdpsndDevicePlugin* device, RDPSND_WAVE* wave)
{
	int size;
	BYTE* data;

	size = wave->length;
	data = rdpsnd_alsa_process_audio_sample(device, wave->data, &size);

	wave->data = (BYTE*) malloc(size);
	if (!wave->data)
		return FALSE;
	CopyMemory(wave->data, data, size);
	wave->length = size;

	return TRUE;
}

static void rdpsnd_alsa_wave_play(rdpsndDevicePlugin* device, RDPSND_WAVE* wave)
{
	BYTE* data;
	int offset;
	int length;
	int status;
	int frame_size;
	UINT32 wCurrentTime;
	snd_htimestamp_t tstamp;
	snd_pcm_uframes_t frames;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	offset = 0;
	data = wave->data;
	length = wave->length;
	frame_size = alsa->actual_channels * alsa->bytes_per_channel;

	if (alsa->wLocalTimeClose)
	{
		wCurrentTime = GetTickCount();

		if (snd_pcm_htimestamp(alsa->pcm_handle, &frames, &tstamp) == -EPIPE)
		{
			if (wCurrentTime > alsa->wLocalTimeClose)
				snd_pcm_recover(alsa->pcm_handle, -EPIPE, 1);
		}

		alsa->wLocalTimeClose = 0;
	}

	while (offset < length)
	{
		status = snd_pcm_writei(alsa->pcm_handle, &data[offset], (length - offset) / frame_size);

		if (status == -EPIPE)
		{
			snd_pcm_recover(alsa->pcm_handle, status, 0);
			status = 0;
		}
		else if (status == -EAGAIN)
		{
			status = 0;
		}
		else if (status < 0)
		{
			WLog_ERR(TAG,  "status: %d\n", status);
			snd_pcm_close(alsa->pcm_handle);
			alsa->pcm_handle = NULL;
			rdpsnd_alsa_open((rdpsndDevicePlugin*) alsa, NULL, alsa->latency);
			break;
		}

		offset += status * frame_size;
	}

	free(data);

	/* From rdpsnd_main.c */
	wave->wTimeStampB = wave->wTimeStampA + wave->wAudioLength + 65;
	wave->wLocalTimeB = wave->wLocalTimeA + wave->wAudioLength + 65;
}

static COMMAND_LINE_ARGUMENT_A rdpsnd_alsa_args[] =
{
	{ "dev", COMMAND_LINE_VALUE_REQUIRED, "<device>", NULL, NULL, -1, NULL, "device" },
	{ NULL, 0, NULL, NULL, NULL, -1, NULL, NULL }
};

/**
 * Function description
 *
 * @return 0 on success, otherwise a Win32 error code
 */
static UINT rdpsnd_alsa_parse_addin_args(rdpsndDevicePlugin* device, ADDIN_ARGV* args)
{
	int status;
	DWORD flags;
	COMMAND_LINE_ARGUMENT_A* arg;
	rdpsndAlsaPlugin* alsa = (rdpsndAlsaPlugin*) device;

	flags = COMMAND_LINE_SIGIL_NONE | COMMAND_LINE_SEPARATOR_COLON | COMMAND_LINE_IGN_UNKNOWN_KEYWORD;

	status = CommandLineParseArgumentsA(args->argc, (const char**) args->argv, rdpsnd_alsa_args, flags, alsa, NULL, NULL);
	if (status < 0)
	{
		WLog_ERR(TAG, "CommandLineParseArgumentsA failed!");
		return CHANNEL_RC_INITIALIZATION_ERROR;
	}

	arg = rdpsnd_alsa_args;

	do
	{
		if (!(arg->Flags & COMMAND_LINE_VALUE_PRESENT))
			continue;

		CommandLineSwitchStart(arg)

		CommandLineSwitchCase(arg, "dev")
		{
			alsa->device_name = _strdup(arg->Value);
			if (!alsa->device_name)
				return CHANNEL_RC_NO_MEMORY;
		}

		CommandLineSwitchEnd(arg)
	}
	while ((arg = CommandLineFindNextArgumentA(arg)) != NULL);

	return CHANNEL_RC_OK;
}

#ifdef BUILTIN_CHANNELS
#define freerdp_rdpsnd_client_subsystem_entry	alsa_freerdp_rdpsnd_client_subsystem_entry
#else
#define freerdp_rdpsnd_client_subsystem_entry	FREERDP_API freerdp_rdpsnd_client_subsystem_entry
#endif

/**
 * Function description
 *
 * @return 0 on success, otherwise a Win32 error code
 */
UINT freerdp_rdpsnd_client_subsystem_entry(PFREERDP_RDPSND_DEVICE_ENTRY_POINTS pEntryPoints)
{
	ADDIN_ARGV* args;
	rdpsndAlsaPlugin* alsa;
	UINT error;

	alsa = (rdpsndAlsaPlugin*) calloc(1, sizeof(rdpsndAlsaPlugin));
	if (!alsa)
	{
		WLog_ERR(TAG, "calloc failed!");
		return CHANNEL_RC_NO_MEMORY;
	}

	alsa->device.Open = rdpsnd_alsa_open;
	alsa->device.FormatSupported = rdpsnd_alsa_format_supported;
	alsa->device.SetFormat = rdpsnd_alsa_set_format;
	alsa->device.GetVolume = rdpsnd_alsa_get_volume;
	alsa->device.SetVolume = rdpsnd_alsa_set_volume;
	alsa->device.WaveDecode = rdpsnd_alsa_wave_decode;
	alsa->device.WavePlay = rdpsnd_alsa_wave_play;
	alsa->device.Close = rdpsnd_alsa_close;
	alsa->device.Free = rdpsnd_alsa_free;

	args = pEntryPoints->args;
	if (args->argc > 1)
	{
		if ((error = rdpsnd_alsa_parse_addin_args((rdpsndDevicePlugin *) alsa, args)))
		{
			WLog_ERR(TAG, "rdpsnd_alsa_parse_addin_args failed with error %"PRIu32"", error);
			goto error_parse_args;
		}
	}


	if (!alsa->device_name)
	{
		alsa->device_name = _strdup("default");
		if (!alsa->device_name)
		{
			WLog_ERR(TAG, "_strdup failed!");
			error = CHANNEL_RC_NO_MEMORY;
			goto error_strdup;
		}
	}

	alsa->pcm_handle = 0;
	alsa->source_rate = 22050;
	alsa->actual_rate = 22050;
	alsa->format = SND_PCM_FORMAT_S16_LE;
	alsa->source_channels = 2;
	alsa->actual_channels = 2;
	alsa->bytes_per_channel = 2;

	alsa->dsp_context = freerdp_dsp_context_new();
	if (!alsa->dsp_context)
	{
		WLog_ERR(TAG, "freerdp_dsp_context_new failed!");
		error = CHANNEL_RC_NO_MEMORY;
		goto error_dsp_context;
	}

	pEntryPoints->pRegisterRdpsndDevice(pEntryPoints->rdpsnd, (rdpsndDevicePlugin*) alsa);

	return CHANNEL_RC_OK;

error_dsp_context:
	freerdp_dsp_context_free(alsa->dsp_context);
error_strdup:
	free(alsa->device_name);
error_parse_args:
	free(alsa);
	return error;
}