| 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 | |
| 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 | |
| 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, |
| 161 | .get_device_list = audio_get_device_list, |
| 162 | .flags = AVFMT_NOFILE, |
| 163 | .priv_class = &alsa_demuxer_class, |
| 164 | }; |