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 };
AVOption.
Definition: opt.h:244
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the pts for a given stream.
Definition: utils.c:3828
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:60
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:117
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:275
int size
Definition: avcodec.h:909
AVOptions.
Format I/O context.
Definition: avformat.h:863
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:38
#define av_cold
Definition: attributes.h:71
AVStream ** streams
Definition: avformat.h:908
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
static int read_header(FFV1Context *f)
Definition: ffv1.c:1513
uint8_t * data
Definition: avcodec.h:908
static int flags
Definition: log.c:34
void av_free_packet(AVPacket *pkt)
Free a packet.
Definition: avpacket.c:151
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:140
enum CodecID codec_id
Definition: mov_chan.c:417
static const AVOption options[]
#define AVERROR(e)
Definition: error.h:43
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:191
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:140
AVStream * avformat_new_stream(AVFormatContext *s, AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:2776
AVCodecContext * codec
codec context
Definition: avformat.h:623
int channels
number of channels set by user
Definition: alsa-audio.h:51
av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode, unsigned int *sample_rate, int channels, enum CodecID *codec_id)
Open an ALSA PCM.
LIBAVUTIL_VERSION_INT
Definition: eval.c:50
AVInputFormat ff_alsa_demuxer
Stream structure.
Definition: avformat.h:620
enum CodecID audio_codec_id
Forced audio codec_id.
Definition: avformat.h:1037
NULL
Definition: eval.c:50
enum AVMediaType codec_type
Definition: avcodec.h:1574
int sample_rate
samples per second
Definition: avcodec.h:1456
av_default_item_name
Definition: dnxhdenc.c:43
static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:111
static int read_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: libcdio.c:109
static const AVClass alsa_demuxer_class
Describe the class of an AVClass context structure.
Definition: log.h:33
int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
Try to recover from ALSA buffer underrun.
#define s1
Definition: regdef.h:38
int period_size
bytes per sample * channels
Definition: alsa-audio.h:49
Main libavformat public API header.
#define AVFMT_NOFILE
Demuxer will use avio_open, no opened file should be provided by the caller.
Definition: avformat.h:368
CodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:83
int channels
number of audio channels
Definition: avcodec.h:1457
void * priv_data
Format private data.
Definition: avformat.h:883
snd_pcm_t * h
Definition: alsa-audio.h:47
static av_cold int audio_read_header(AVFormatContext *s1, AVFormatParameters *ap)
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:460
int frame_size
preferred size for reads and writes
Definition: alsa-audio.h:48
int sample_rate
sample rate set by user
Definition: alsa-audio.h:50
ALSA input and output: definitions and structures.
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:901
enum CodecID codec_id
Definition: avcodec.h:1575