Libav
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 };
void av_free_packet(AVPacket *pkt)
Free a packet.
Definition: avpacket.c:243
AVOption.
Definition: opt.h:234
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:129
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:2800
int size
Definition: avcodec.h:968
Format I/O context.
Definition: avformat.h:922
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:66
AVOptions.
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:2497
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:990
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
uint8_t * data
Definition: avcodec.h:967
static int flags
Definition: log.c:44
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:145
static av_cold int audio_read_header(AVFormatContext *s1)
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:81
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:105
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:123
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:150
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:168
enum AVCodecID codec_id
Definition: mov_chan.c:432
AVCodecContext * codec
Codec context associated with this stream.
Definition: avformat.h:718
enum AVCodecID audio_codec_id
Forced audio codec_id.
Definition: avformat.h:1082
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 AVCodecID *codec_id)
Open an ALSA PCM.
LIBAVUTIL_VERSION_INT
Definition: eval.c:55
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:544
AVInputFormat ff_alsa_demuxer
Stream structure.
Definition: avformat.h:699
NULL
Definition: eval.c:55
enum AVMediaType codec_type
Definition: avcodec.h:1052
enum AVCodecID codec_id
Definition: avcodec.h:1061
int sample_rate
samples per second
Definition: avcodec.h:1785
av_default_item_name
Definition: dnxhdenc.c:52
static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
static int read_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: libcdio.c:114
static const AVClass alsa_demuxer_class
Describe the class of an AVClass context structure.
Definition: log.h:33
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:265
int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
Try to recover from ALSA buffer underrun.
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:409
int channels
number of audio channels
Definition: avcodec.h:1786
void * priv_data
Format private data.
Definition: avformat.h:950
snd_pcm_t * h
Definition: alsa-audio.h:47
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:525
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.
This structure stores compressed data.
Definition: avcodec.h:944
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:960