alsa-audio-dec.c
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1 /*
2  * ALSA input and output
3  * Copyright (c) 2007 Luca Abeni ( lucabe72 email it )
4  * Copyright (c) 2007 Benoit Fouet ( benoit fouet free fr )
5  *
6  * This file is part of Libav.
7  *
8  * Libav is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * Libav is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
48 #include <alsa/asoundlib.h>
49 #include "libavformat/avformat.h"
50 #include "libavformat/internal.h"
51 #include "libavutil/opt.h"
52 
53 #include "alsa-audio.h"
54 
57 {
58  AlsaData *s = s1->priv_data;
59  AVStream *st;
60  int ret;
61  enum CodecID codec_id;
62  snd_pcm_sw_params_t *sw_params;
63 
64  st = avformat_new_stream(s1, NULL);
65  if (!st) {
66  av_log(s1, AV_LOG_ERROR, "Cannot add stream\n");
67 
68  return AVERROR(ENOMEM);
69  }
70  codec_id = s1->audio_codec_id;
71 
72  ret = ff_alsa_open(s1, SND_PCM_STREAM_CAPTURE, &s->sample_rate, s->channels,
73  &codec_id);
74  if (ret < 0) {
75  return AVERROR(EIO);
76  }
77 
78  if (snd_pcm_type(s->h) != SND_PCM_TYPE_HW)
80  "capture with some ALSA plugins, especially dsnoop, "
81  "may hang.\n");
82 
83  ret = snd_pcm_sw_params_malloc(&sw_params);
84  if (ret < 0) {
85  av_log(s1, AV_LOG_ERROR, "cannot allocate software parameters structure (%s)\n",
86  snd_strerror(ret));
87  goto fail;
88  }
89 
90  snd_pcm_sw_params_current(s->h, sw_params);
91  snd_pcm_sw_params_set_tstamp_mode(s->h, sw_params, SND_PCM_TSTAMP_ENABLE);
92 
93  ret = snd_pcm_sw_params(s->h, sw_params);
94  snd_pcm_sw_params_free(sw_params);
95  if (ret < 0) {
96  av_log(s1, AV_LOG_ERROR, "cannot install ALSA software parameters (%s)\n",
97  snd_strerror(ret));
98  goto fail;
99  }
100 
101  /* take real parameters */
103  st->codec->codec_id = codec_id;
104  st->codec->sample_rate = s->sample_rate;
105  st->codec->channels = s->channels;
106  avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */
107 
108  return 0;
109 
110 fail:
111  snd_pcm_close(s->h);
112  return AVERROR(EIO);
113 }
114 
116 {
117  AlsaData *s = s1->priv_data;
118  AVStream *st = s1->streams[0];
119  int res;
120  snd_htimestamp_t timestamp;
121  snd_pcm_uframes_t ts_delay;
122 
123  if (av_new_packet(pkt, s->period_size) < 0) {
124  return AVERROR(EIO);
125  }
126 
127  while ((res = snd_pcm_readi(s->h, pkt->data, pkt->size / s->frame_size)) < 0) {
128  if (res == -EAGAIN) {
129  av_free_packet(pkt);
130 
131  return AVERROR(EAGAIN);
132  }
133  if (ff_alsa_xrun_recover(s1, res) < 0) {
134  av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n",
135  snd_strerror(res));
136  av_free_packet(pkt);
137 
138  return AVERROR(EIO);
139  }
140  }
141 
142  snd_pcm_htimestamp(s->h, &ts_delay, &timestamp);
143  ts_delay += res;
144  pkt->pts = timestamp.tv_sec * 1000000LL
145  + (timestamp.tv_nsec * st->codec->sample_rate
146  - ts_delay * 1000000000LL + st->codec->sample_rate * 500LL)
147  / (st->codec->sample_rate * 1000LL);
148 
149  pkt->size = res * s->frame_size;
150 
151  return 0;
152 }
153 
154 static const AVOption options[] = {
155  { "sample_rate", "", offsetof(AlsaData, sample_rate), AV_OPT_TYPE_INT, {.dbl = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
156  { "channels", "", offsetof(AlsaData, channels), AV_OPT_TYPE_INT, {.dbl = 2}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
157  { NULL },
158 };
159 
160 static const AVClass alsa_demuxer_class = {
161  .class_name = "ALSA demuxer",
162  .item_name = av_default_item_name,
163  .option = options,
164  .version = LIBAVUTIL_VERSION_INT,
165 };
166 
168  .name = "alsa",
169  .long_name = NULL_IF_CONFIG_SMALL("ALSA audio input"),
170  .priv_data_size = sizeof(AlsaData),
174  .flags = AVFMT_NOFILE,
175  .priv_class = &alsa_demuxer_class,
176 };