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.
16 #include <sys/types.h>
18 #include <alsa/asoundlib.h>
27 #include "alsa_write.cmdline.h"
30 /** always use 16 bit little endian */
31 #define FORMAT SND_PCM_FORMAT_S16_LE
33 /** Data specific to the alsa writer. */
34 struct private_alsa_write_data {
35 /** The alsa handle */
37 /** Determined and set by alsa_open(). */
39 /** The approximate maximum buffer duration in us. */
41 /* Number of frames that fit into the buffer. */
42 unsigned buffer_frames;
44 * The samplerate given by command line option or the decoder
45 * of the writer node group.
49 * The number of channels, given by command line option or the
50 * decoder of the writer node group.
55 /* Install PCM software and hardware configuration. */
56 static int alsa_init(struct private_alsa_write_data *pad,
57 struct alsa_write_args_info *conf)
59 snd_pcm_hw_params_t *hwparams;
60 snd_pcm_sw_params_t *swparams;
61 snd_pcm_uframes_t buffer_size, start_threshold, stop_threshold;
62 snd_pcm_uframes_t period_size;
65 err = snd_pcm_open(&pad->handle, conf->device_arg,
66 SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
70 snd_pcm_hw_params_alloca(&hwparams);
71 snd_pcm_sw_params_alloca(&swparams);
72 if (snd_pcm_hw_params_any(pad->handle, hwparams) < 0)
73 return -E_BROKEN_CONF;
74 if (snd_pcm_hw_params_set_access(pad->handle, hwparams,
75 SND_PCM_ACCESS_RW_INTERLEAVED) < 0)
76 return -E_ACCESS_TYPE;
77 if (snd_pcm_hw_params_set_format(pad->handle, hwparams, FORMAT) < 0)
78 return -E_SAMPLE_FORMAT;
79 if (snd_pcm_hw_params_set_channels(pad->handle, hwparams,
81 return -E_CHANNEL_COUNT;
82 if (snd_pcm_hw_params_set_rate_near(pad->handle, hwparams,
83 &pad->samplerate, NULL) < 0)
85 err = snd_pcm_hw_params_get_buffer_time_max(hwparams,
86 &pad->buffer_time, NULL);
87 if (err < 0 || !pad->buffer_time)
88 return -E_GET_BUFFER_TIME;
89 PARA_INFO_LOG("buffer time: %d\n", pad->buffer_time);
90 if (snd_pcm_hw_params_set_buffer_time_near(pad->handle, hwparams,
91 &pad->buffer_time, NULL) < 0)
92 return -E_SET_BUFFER_TIME;
93 if (snd_pcm_hw_params(pad->handle, hwparams) < 0)
95 snd_pcm_hw_params_get_period_size(hwparams, &period_size, NULL);
96 snd_pcm_hw_params_get_buffer_size(hwparams, &buffer_size);
97 PARA_INFO_LOG("buffer size: %lu, period_size: %lu\n", buffer_size,
99 if (period_size == buffer_size)
100 return -E_BAD_PERIOD;
101 snd_pcm_sw_params_current(pad->handle, swparams);
102 snd_pcm_sw_params_set_avail_min(pad->handle, swparams, period_size);
106 start_threshold = PARA_MIN(buffer_size,
107 (snd_pcm_uframes_t)pad->samplerate);
108 if (snd_pcm_sw_params_set_start_threshold(pad->handle, swparams,
109 start_threshold) < 0)
110 return -E_START_THRESHOLD;
111 stop_threshold = buffer_size;
112 if (snd_pcm_sw_params_set_stop_threshold(pad->handle, swparams,
114 return -E_STOP_THRESHOLD;
115 if (snd_pcm_sw_params(pad->handle, swparams) < 0)
116 PARA_WARNING_LOG("unable to install sw params\n");
117 pad->bytes_per_frame = snd_pcm_format_physical_width(FORMAT)
119 if (pad->bytes_per_frame <= 0)
120 return -E_PHYSICAL_WIDTH;
121 PARA_INFO_LOG("bytes per frame: %d\n", pad->bytes_per_frame);
122 if (snd_pcm_nonblock(pad->handle, 1))
123 PARA_ERROR_LOG("failed to set nonblock mode\n");
124 pad->buffer_frames = 1000 * pad->buffer_time / pad->samplerate;
125 PARA_INFO_LOG("max buffered frames: %d\n", pad->buffer_frames);
129 /* Open an instance of the alsa writer. */
130 static int alsa_open(struct writer_node *wn)
132 struct alsa_write_args_info *conf = wn->conf;
133 struct writer_node_group *wng = wn->wng;
134 struct private_alsa_write_data *pad = para_calloc(sizeof(*pad));
136 wn->private_data = pad;
137 if (!conf->samplerate_given && wng->samplerate)
138 pad->samplerate = *wng->samplerate;
140 pad->samplerate = conf->samplerate_arg;
141 if (!conf->channels_given && wng->channels)
142 pad->channels = *wng->channels;
144 pad->channels = conf->channels_arg;
145 PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate);
149 static int alsa_write_pre_select(struct sched *s, struct writer_node *wn)
151 struct private_alsa_write_data *pad = wn->private_data;
152 struct writer_node_group *wng = wn->wng;
154 snd_pcm_sframes_t avail, underrun;
158 if (*wng->loaded - wn->written < pad->bytes_per_frame)
161 * Data is available to be written to the alsa handle. Compute number
162 * of milliseconds until next buffer underrun would occur.
164 * snd_pcm_avail_update() updates the current available count of
165 * samples for writing. It is a light method to obtain current stream
166 * position, because it does not require the user <-> kernel context
167 * switch, but the value is less accurate, because ring buffer pointers
168 * are updated in kernel drivers only when an interrupt occurs.
170 avail = snd_pcm_avail_update(pad->handle);
173 underrun = (pad->buffer_frames - avail) * pad->buffer_time
174 / pad->buffer_frames / 1000;
178 ms2tv(underrun, &tv);
179 if (tv_diff(&s->timeout, &tv, NULL) > 0)
184 static int alsa_write_post_select(__a_unused struct sched *s,
185 struct writer_node *wn)
187 struct private_alsa_write_data *pad = wn->private_data;
188 struct writer_node_group *wng = wn->wng;
189 size_t bytes = *wng->loaded - wn->written;
190 unsigned char *data = (unsigned char*)*wng->bufp + wn->written;
191 snd_pcm_sframes_t ret, frames, avail;
193 if (*wng->input_error < 0 && (!pad->handle || bytes < pad->bytes_per_frame)) {
194 wn->written = *wng->loaded;
195 return *wng->input_error;
197 if (!bytes) /* no data available */
200 int err = alsa_init(pad, wn->conf);
204 frames = bytes / pad->bytes_per_frame;
205 if (!frames) /* less than a single frame available */
207 avail = snd_pcm_avail_update(pad->handle);
210 frames = PARA_MIN(frames, avail);
211 ret = snd_pcm_writei(pad->handle, data, frames);
213 wn->written += ret * pad->bytes_per_frame;
216 PARA_WARNING_LOG("%s\n", snd_strerror(-ret));
218 snd_pcm_prepare(pad->handle);
223 return -E_ALSA_WRITE;
226 static void alsa_close(struct writer_node *wn)
228 struct private_alsa_write_data *pad = wn->private_data;
229 PARA_INFO_LOG("closing writer node %p\n", wn);
232 snd_pcm_drain(pad->handle);
233 snd_pcm_close(pad->handle);
234 snd_config_update_free_global();
239 __malloc static void *alsa_parse_config(const char *options)
242 struct alsa_write_args_info *conf
243 = para_calloc(sizeof(struct alsa_write_args_info));
245 PARA_INFO_LOG("options: %s, %zd\n", options, strcspn(options, " \t"));
246 ret = alsa_cmdline_parser_string(options, conf, "alsa_write");
249 PARA_INFO_LOG("help given: %d\n", conf->help_given);
257 * the init function of the alsa writer
259 * \param w pointer to the writer to initialize
263 void alsa_write_init(struct writer *w)
265 struct alsa_write_args_info dummy;
267 alsa_cmdline_parser_init(&dummy);
269 w->close = alsa_close;
270 w->pre_select = alsa_write_pre_select;
271 w->post_select = alsa_write_post_select;
272 w->parse_config = alsa_parse_config;
273 w->shutdown = NULL; /* nothing to do */
274 w->help = (struct ggo_help) {
275 .short_help = alsa_write_args_info_help,
276 .detailed_help = alsa_write_args_info_detailed_help
278 alsa_cmdline_parser_free(&dummy);