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 
56 {
57  AlsaData *s = s1->priv_data;
58  AVStream *st;
59  int ret;
60  enum AVCodecID codec_id;
61  snd_pcm_sw_params_t *sw_params;
62 
63  st = avformat_new_stream(s1, NULL);
64  if (!st) {
65  av_log(s1, AV_LOG_ERROR, "Cannot add stream\n");
66 
67  return AVERROR(ENOMEM);
68  }
69  codec_id = s1->audio_codec_id;
70 
71  ret = ff_alsa_open(s1, SND_PCM_STREAM_CAPTURE, &s->sample_rate, s->channels,
72  &codec_id);
73  if (ret < 0) {
74  return AVERROR(EIO);
75  }
76 
77  if (snd_pcm_type(s->h) != SND_PCM_TYPE_HW)
79  "capture with some ALSA plugins, especially dsnoop, "
80  "may hang.\n");
81 
82  ret = snd_pcm_sw_params_malloc(&sw_params);
83  if (ret < 0) {
84  av_log(s1, AV_LOG_ERROR, "cannot allocate software parameters structure (%s)\n",
85  snd_strerror(ret));
86  goto fail;
87  }
88 
89  snd_pcm_sw_params_current(s->h, sw_params);
90  snd_pcm_sw_params_set_tstamp_mode(s->h, sw_params, SND_PCM_TSTAMP_ENABLE);
91 
92  ret = snd_pcm_sw_params(s->h, sw_params);
93  snd_pcm_sw_params_free(sw_params);
94  if (ret < 0) {
95  av_log(s1, AV_LOG_ERROR, "cannot install ALSA software parameters (%s)\n",
96  snd_strerror(ret));
97  goto fail;
98  }
99 
100  /* take real parameters */
102  st->codec->codec_id = codec_id;
103  st->codec->sample_rate = s->sample_rate;
104  st->codec->channels = s->channels;
105  avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */
106 
107  return 0;
108 
109 fail:
110  snd_pcm_close(s->h);
111  return AVERROR(EIO);
112 }
113 
115 {
116  AlsaData *s = s1->priv_data;
117  AVStream *st = s1->streams[0];
118  int res;
119  snd_htimestamp_t timestamp;
120  snd_pcm_uframes_t ts_delay;
121 
122  if (av_new_packet(pkt, s->period_size) < 0) {
123  return AVERROR(EIO);
124  }
125 
126  while ((res = snd_pcm_readi(s->h, pkt->data, pkt->size / s->frame_size)) < 0) {
127  if (res == -EAGAIN) {
128  av_free_packet(pkt);
129 
130  return AVERROR(EAGAIN);
131  }
132  if (ff_alsa_xrun_recover(s1, res) < 0) {
133  av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n",
134  snd_strerror(res));
135  av_free_packet(pkt);
136 
137  return AVERROR(EIO);
138  }
139  }
140 
141  snd_pcm_htimestamp(s->h, &ts_delay, &timestamp);
142  ts_delay += res;
143  pkt->pts = timestamp.tv_sec * 1000000LL
144  + (timestamp.tv_nsec * st->codec->sample_rate
145  - (int64_t)ts_delay * 1000000000LL + st->codec->sample_rate * 500LL)
146  / (st->codec->sample_rate * 1000LL);
147 
148  pkt->size = res * s->frame_size;
149 
150  return 0;
151 }
152 
153 static const AVOption options[] = {
154  { "sample_rate", "", offsetof(AlsaData, sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
155  { "channels", "", offsetof(AlsaData, channels), AV_OPT_TYPE_INT, {.i64 = 2}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
156  { NULL },
157 };
158 
159 static const AVClass alsa_demuxer_class = {
160  .class_name = "ALSA demuxer",
161  .item_name = av_default_item_name,
162  .option = options,
163  .version = LIBAVUTIL_VERSION_INT,
164 };
165 
167  .name = "alsa",
168  .long_name = NULL_IF_CONFIG_SMALL("ALSA audio input"),
169  .priv_data_size = sizeof(AlsaData),
173  .flags = AVFMT_NOFILE,
174  .priv_class = &alsa_demuxer_class,
175 };