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2ba45a60 DM |
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 FFmpeg. | |
7 | * | |
8 | * FFmpeg 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 | * FFmpeg 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 FFmpeg; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
21 | */ | |
22 | ||
23 | /** | |
24 | * @file | |
25 | * ALSA input and output: input | |
26 | * @author Luca Abeni ( lucabe72 email it ) | |
27 | * @author Benoit Fouet ( benoit fouet free fr ) | |
28 | * @author Nicolas George ( nicolas george normalesup org ) | |
29 | * | |
30 | * This avdevice decoder allows to capture audio from an ALSA (Advanced | |
31 | * Linux Sound Architecture) device. | |
32 | * | |
33 | * The filename parameter is the name of an ALSA PCM device capable of | |
34 | * capture, for example "default" or "plughw:1"; see the ALSA documentation | |
35 | * for naming conventions. The empty string is equivalent to "default". | |
36 | * | |
37 | * The capture period is set to the lower value available for the device, | |
38 | * which gives a low latency suitable for real-time capture. | |
39 | * | |
40 | * The PTS are an Unix time in microsecond. | |
41 | * | |
42 | * Due to a bug in the ALSA library | |
43 | * (https://bugtrack.alsa-project.org/alsa-bug/view.php?id=4308), this | |
44 | * decoder does not work with certain ALSA plugins, especially the dsnoop | |
45 | * plugin. | |
46 | */ | |
47 | ||
48 | #include <alsa/asoundlib.h> | |
49 | #include "libavformat/internal.h" | |
50 | #include "libavutil/opt.h" | |
51 | #include "libavutil/mathematics.h" | |
52 | #include "libavutil/time.h" | |
53 | ||
54 | #include "avdevice.h" | |
55 | #include "alsa-audio.h" | |
56 | ||
57 | static av_cold int audio_read_header(AVFormatContext *s1) | |
58 | { | |
59 | AlsaData *s = s1->priv_data; | |
60 | AVStream *st; | |
61 | int ret; | |
62 | enum AVCodecID codec_id; | |
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 | /* take real parameters */ | |
79 | st->codec->codec_type = AVMEDIA_TYPE_AUDIO; | |
80 | st->codec->codec_id = codec_id; | |
81 | st->codec->sample_rate = s->sample_rate; | |
82 | st->codec->channels = s->channels; | |
83 | avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */ | |
84 | /* microseconds instead of seconds, MHz instead of Hz */ | |
85 | s->timefilter = ff_timefilter_new(1000000.0 / s->sample_rate, | |
86 | s->period_size, 1.5E-6); | |
87 | if (!s->timefilter) | |
88 | goto fail; | |
89 | ||
90 | return 0; | |
91 | ||
92 | fail: | |
93 | snd_pcm_close(s->h); | |
94 | return AVERROR(EIO); | |
95 | } | |
96 | ||
97 | static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt) | |
98 | { | |
99 | AlsaData *s = s1->priv_data; | |
100 | int res; | |
101 | int64_t dts; | |
102 | snd_pcm_sframes_t delay = 0; | |
103 | ||
104 | if (av_new_packet(pkt, s->period_size * s->frame_size) < 0) { | |
105 | return AVERROR(EIO); | |
106 | } | |
107 | ||
108 | while ((res = snd_pcm_readi(s->h, pkt->data, s->period_size)) < 0) { | |
109 | if (res == -EAGAIN) { | |
110 | av_free_packet(pkt); | |
111 | ||
112 | return AVERROR(EAGAIN); | |
113 | } | |
114 | if (ff_alsa_xrun_recover(s1, res) < 0) { | |
115 | av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n", | |
116 | snd_strerror(res)); | |
117 | av_free_packet(pkt); | |
118 | ||
119 | return AVERROR(EIO); | |
120 | } | |
121 | ff_timefilter_reset(s->timefilter); | |
122 | } | |
123 | ||
124 | dts = av_gettime(); | |
125 | snd_pcm_delay(s->h, &delay); | |
126 | dts -= av_rescale(delay + res, 1000000, s->sample_rate); | |
127 | pkt->pts = ff_timefilter_update(s->timefilter, dts, s->last_period); | |
128 | s->last_period = res; | |
129 | ||
130 | pkt->size = res * s->frame_size; | |
131 | ||
132 | return 0; | |
133 | } | |
134 | ||
f6fa7814 DM |
135 | static int audio_get_device_list(AVFormatContext *h, AVDeviceInfoList *device_list) |
136 | { | |
137 | return ff_alsa_get_device_list(device_list, SND_PCM_STREAM_CAPTURE); | |
138 | } | |
139 | ||
2ba45a60 DM |
140 | static const AVOption options[] = { |
141 | { "sample_rate", "", offsetof(AlsaData, sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM }, | |
142 | { "channels", "", offsetof(AlsaData, channels), AV_OPT_TYPE_INT, {.i64 = 2}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM }, | |
143 | { NULL }, | |
144 | }; | |
145 | ||
146 | static const AVClass alsa_demuxer_class = { | |
147 | .class_name = "ALSA demuxer", | |
148 | .item_name = av_default_item_name, | |
149 | .option = options, | |
150 | .version = LIBAVUTIL_VERSION_INT, | |
151 | .category = AV_CLASS_CATEGORY_DEVICE_AUDIO_INPUT, | |
152 | }; | |
153 | ||
154 | AVInputFormat ff_alsa_demuxer = { | |
155 | .name = "alsa", | |
156 | .long_name = NULL_IF_CONFIG_SMALL("ALSA audio input"), | |
157 | .priv_data_size = sizeof(AlsaData), | |
158 | .read_header = audio_read_header, | |
159 | .read_packet = audio_read_packet, | |
160 | .read_close = ff_alsa_close, | |
f6fa7814 | 161 | .get_device_list = audio_get_device_list, |
2ba45a60 DM |
162 | .flags = AVFMT_NOFILE, |
163 | .priv_class = &alsa_demuxer_class, | |
164 | }; |