2 * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file alsa_write.c paraslash's alsa output plugin */
10 * Based in parts on aplay.c from the alsa-utils-1.0.8 package,
11 * Copyright (c) by Jaroslav Kysela <perex@suse.cz>, which is
12 * based on the vplay program by Michael Beck.
15 #include <sys/types.h>
17 #include <alsa/asoundlib.h>
26 #include "alsa_write.cmdline.h"
29 /** always use 16 bit little endian */
30 #define FORMAT SND_PCM_FORMAT_S16_LE
32 /** Data specific to the alsa writer. */
33 struct private_alsa_write_data {
34 /** The alsa handle */
36 /** Determined and set by alsa_open(). */
38 /** The approximate maximum buffer duration in us. */
40 /* Number of frames that fit into the buffer. */
41 unsigned buffer_frames;
43 * The samplerate given by command line option or the decoder
44 * of the writer node group.
48 * The number of channels, given by command line option or the
49 * decoder of the writer node group.
54 /* Install PCM software and hardware configuration. */
55 static int alsa_init(struct private_alsa_write_data *pad,
56 struct alsa_write_args_info *conf)
58 snd_pcm_hw_params_t *hwparams;
59 snd_pcm_sw_params_t *swparams;
60 snd_pcm_uframes_t buffer_size, start_threshold, stop_threshold;
61 snd_pcm_uframes_t period_size;
64 err = snd_pcm_open(&pad->handle, conf->device_arg,
65 SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
69 snd_pcm_hw_params_alloca(&hwparams);
70 snd_pcm_sw_params_alloca(&swparams);
71 if (snd_pcm_hw_params_any(pad->handle, hwparams) < 0)
72 return -E_BROKEN_CONF;
73 if (snd_pcm_hw_params_set_access(pad->handle, hwparams,
74 SND_PCM_ACCESS_RW_INTERLEAVED) < 0)
75 return -E_ACCESS_TYPE;
76 if (snd_pcm_hw_params_set_format(pad->handle, hwparams, FORMAT) < 0)
77 return -E_SAMPLE_FORMAT;
78 if (snd_pcm_hw_params_set_channels(pad->handle, hwparams,
80 return -E_CHANNEL_COUNT;
81 if (snd_pcm_hw_params_set_rate_near(pad->handle, hwparams,
82 &pad->samplerate, 0) < 0)
84 err = snd_pcm_hw_params_get_buffer_time_max(hwparams, &pad->buffer_time, 0);
85 if (err < 0 || !pad->buffer_time)
86 return -E_GET_BUFFER_TIME;
87 PARA_INFO_LOG("buffer time: %d\n", pad->buffer_time);
88 if (snd_pcm_hw_params_set_buffer_time_near(pad->handle, hwparams,
89 &pad->buffer_time, 0) < 0)
90 return -E_SET_BUFFER_TIME;
91 if (snd_pcm_hw_params(pad->handle, hwparams) < 0)
93 snd_pcm_hw_params_get_period_size(hwparams, &period_size, 0);
94 snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);
95 PARA_INFO_LOG("buffer size: %lu, period_size: %lu\n", buffer_size,
97 if (period_size == buffer_size)
99 snd_pcm_sw_params_current(pad->handle, swparams);
100 snd_pcm_sw_params_set_avail_min(pad->handle, swparams, period_size);
104 start_threshold = PARA_MIN(buffer_size,
105 (snd_pcm_uframes_t)pad->samplerate);
106 if (snd_pcm_sw_params_set_start_threshold(pad->handle, swparams,
107 start_threshold) < 0)
108 return -E_START_THRESHOLD;
109 stop_threshold = buffer_size;
110 if (snd_pcm_sw_params_set_stop_threshold(pad->handle, swparams,
112 return -E_STOP_THRESHOLD;
113 if (snd_pcm_sw_params(pad->handle, swparams) < 0)
114 PARA_WARNING_LOG("unable to install sw params\n");
115 pad->bytes_per_frame = snd_pcm_format_physical_width(FORMAT)
117 if (pad->bytes_per_frame <= 0)
118 return -E_PHYSICAL_WIDTH;
119 PARA_INFO_LOG("bytes per frame: %d\n", pad->bytes_per_frame);
120 if (snd_pcm_nonblock(pad->handle, 1))
121 PARA_ERROR_LOG("failed to set nonblock mode\n");
122 pad->buffer_frames = 1000 * pad->buffer_time / pad->samplerate;
123 PARA_INFO_LOG("max buffered frames: %d\n", pad->buffer_frames);
127 /* Open an instance of the alsa writer. */
128 static int alsa_open(struct writer_node *wn)
130 struct alsa_write_args_info *conf = wn->conf;
131 struct writer_node_group *wng = wn->wng;
132 struct private_alsa_write_data *pad = para_calloc(sizeof(*pad));
134 wn->private_data = pad;
135 if (!conf->samplerate_given && wng->samplerate)
136 pad->samplerate = *wng->samplerate;
138 pad->samplerate = conf->samplerate_arg;
139 if (!conf->channels_given && wng->channels)
140 pad->channels = *wng->channels;
142 pad->channels = conf->channels_arg;
143 PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate);
147 static int alsa_write_pre_select(struct sched *s, struct writer_node *wn)
149 struct private_alsa_write_data *pad = wn->private_data;
150 struct writer_node_group *wng = wn->wng;
152 snd_pcm_sframes_t avail, underrun;
156 if (*wng->loaded - wn->written < pad->bytes_per_frame)
159 * Data is available to be written to the alsa handle. Compute number
160 * of milliseconds until next buffer underrun would occur.
162 * snd_pcm_avail_update() updates the current available count of
163 * samples for writing. It is a light method to obtain current stream
164 * position, because it does not require the user <-> kernel context
165 * switch, but the value is less accurate, because ring buffer pointers
166 * are updated in kernel drivers only when an interrupt occurs.
168 avail = snd_pcm_avail_update(pad->handle);
171 underrun = (pad->buffer_frames - avail) * pad->buffer_time
172 / pad->buffer_frames / 1000;
176 ms2tv(underrun, &tv);
177 if (tv_diff(&s->timeout, &tv, NULL) > 0)
182 static int alsa_write_post_select(__a_unused struct sched *s,
183 struct writer_node *wn)
185 struct private_alsa_write_data *pad = wn->private_data;
186 struct writer_node_group *wng = wn->wng;
187 size_t bytes = *wng->loaded - wn->written;
188 unsigned char *data = (unsigned char*)*wng->bufp + wn->written;
189 snd_pcm_sframes_t ret, frames, avail;
191 if (*wng->input_error < 0 && (!pad->handle || bytes < pad->bytes_per_frame)) {
192 wn->written = *wng->loaded;
193 return *wng->input_error;
195 if (!bytes) /* no data available */
198 int err = alsa_init(pad, wn->conf);
202 frames = bytes / pad->bytes_per_frame;
203 if (!frames) /* less than a single frame available */
205 avail = snd_pcm_avail_update(pad->handle);
208 frames = PARA_MIN(frames, avail);
209 ret = snd_pcm_writei(pad->handle, data, frames);
211 wn->written += ret * pad->bytes_per_frame;
214 PARA_WARNING_LOG("%s\n", snd_strerror(-ret));
216 snd_pcm_prepare(pad->handle);
221 return -E_ALSA_WRITE;
224 static void alsa_close(struct writer_node *wn)
226 struct private_alsa_write_data *pad = wn->private_data;
227 PARA_INFO_LOG("closing writer node %p\n", wn);
230 snd_pcm_drain(pad->handle);
231 snd_pcm_close(pad->handle);
232 snd_config_update_free_global();
237 __malloc static void *alsa_parse_config(const char *options)
240 struct alsa_write_args_info *conf
241 = para_calloc(sizeof(struct alsa_write_args_info));
243 PARA_INFO_LOG("options: %s, %zd\n", options, strcspn(options, " \t"));
244 ret = alsa_cmdline_parser_string(options, conf, "alsa_write");
247 PARA_INFO_LOG("help given: %d\n", conf->help_given);
255 * the init function of the alsa writer
257 * \param w pointer to the writer to initialize
261 void alsa_write_init(struct writer *w)
263 struct alsa_write_args_info dummy;
265 alsa_cmdline_parser_init(&dummy);
267 w->close = alsa_close;
268 w->pre_select = alsa_write_pre_select;
269 w->post_select = alsa_write_post_select;
270 w->parse_config = alsa_parse_config;
271 w->shutdown = NULL; /* nothing to do */
272 w->help = (struct ggo_help) {
273 .short_help = alsa_write_args_info_help,
274 .detailed_help = alsa_write_args_info_detailed_help
276 alsa_cmdline_parser_free(&dummy);