Libav
alsa_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 
50 #include "libavutil/internal.h"
51 #include "libavutil/opt.h"
52 
53 #include "libavformat/avformat.h"
54 #include "libavformat/internal.h"
55 
56 #include "alsa.h"
57 
59 {
60  AlsaData *s = s1->priv_data;
61  AVStream *st;
62  int ret;
63  enum AVCodecID codec_id;
64  snd_pcm_sw_params_t *sw_params;
65 
66  st = avformat_new_stream(s1, NULL);
67  if (!st) {
68  av_log(s1, AV_LOG_ERROR, "Cannot add stream\n");
69 
70  return AVERROR(ENOMEM);
71  }
72  codec_id = s1->audio_codec_id;
73 
74  ret = ff_alsa_open(s1, SND_PCM_STREAM_CAPTURE, &s->sample_rate, s->channels,
75  &codec_id);
76  if (ret < 0) {
77  return AVERROR(EIO);
78  }
79 
80  if (snd_pcm_type(s->h) != SND_PCM_TYPE_HW)
82  "capture with some ALSA plugins, especially dsnoop, "
83  "may hang.\n");
84 
85  ret = snd_pcm_sw_params_malloc(&sw_params);
86  if (ret < 0) {
87  av_log(s1, AV_LOG_ERROR, "cannot allocate software parameters structure (%s)\n",
88  snd_strerror(ret));
89  goto fail;
90  }
91 
92  snd_pcm_sw_params_current(s->h, sw_params);
93  snd_pcm_sw_params_set_tstamp_mode(s->h, sw_params, SND_PCM_TSTAMP_ENABLE);
94 
95  ret = snd_pcm_sw_params(s->h, sw_params);
96  snd_pcm_sw_params_free(sw_params);
97  if (ret < 0) {
98  av_log(s1, AV_LOG_ERROR, "cannot install ALSA software parameters (%s)\n",
99  snd_strerror(ret));
100  goto fail;
101  }
102 
103  /* take real parameters */
105  st->codecpar->codec_id = codec_id;
106  st->codecpar->sample_rate = s->sample_rate;
107  st->codecpar->channels = s->channels;
108  avpriv_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in us */
109 
110  return 0;
111 
112 fail:
113  snd_pcm_close(s->h);
114  return AVERROR(EIO);
115 }
116 
118 {
119  AlsaData *s = s1->priv_data;
120  AVStream *st = s1->streams[0];
121  int res;
122  snd_htimestamp_t timestamp;
123  snd_pcm_uframes_t ts_delay;
124 
125  if (av_new_packet(pkt, s->period_size) < 0) {
126  return AVERROR(EIO);
127  }
128 
129  while ((res = snd_pcm_readi(s->h, pkt->data, pkt->size / s->frame_size)) < 0) {
130  if (res == -EAGAIN) {
131  av_packet_unref(pkt);
132 
133  return AVERROR(EAGAIN);
134  }
135  if (ff_alsa_xrun_recover(s1, res) < 0) {
136  av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n",
137  snd_strerror(res));
138  av_packet_unref(pkt);
139 
140  return AVERROR(EIO);
141  }
142  }
143 
144  snd_pcm_htimestamp(s->h, &ts_delay, &timestamp);
145  ts_delay += res;
146  pkt->pts = timestamp.tv_sec * 1000000LL
147  + (timestamp.tv_nsec * st->codecpar->sample_rate
148  - (int64_t)ts_delay * 1000000000LL + st->codecpar->sample_rate * 500LL)
149  / (st->codecpar->sample_rate * 1000LL);
150 
151  pkt->size = res * s->frame_size;
152 
153  return 0;
154 }
155 
156 static const AVOption options[] = {
157  { "sample_rate", "", offsetof(AlsaData, sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
158  { "channels", "", offsetof(AlsaData, channels), AV_OPT_TYPE_INT, {.i64 = 2}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
159  { NULL },
160 };
161 
162 static const AVClass alsa_demuxer_class = {
163  .class_name = "ALSA demuxer",
164  .item_name = av_default_item_name,
165  .option = options,
166  .version = LIBAVUTIL_VERSION_INT,
167 };
168 
170  .name = "alsa",
171  .long_name = NULL_IF_CONFIG_SMALL("ALSA audio input"),
172  .priv_data_size = sizeof(AlsaData),
176  .flags = AVFMT_NOFILE,
177  .priv_class = &alsa_demuxer_class,
178 };
AVOption.
Definition: opt.h:234
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:130
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:2986
static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
Definition: alsa_dec.c:117
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3483
int size
Definition: avcodec.h:1347
av_log(ac->avr, AV_LOG_TRACE, "%d samples - audio_convert: %s to %s (%s)\, len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt), use_generic ? ac->func_descr_generic :ac->func_descr)
ALSA input and output: definitions and structures.
Format I/O context.
Definition: avformat.h:940
static const AVOption options[]
Definition: alsa_dec.c:156
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:39
#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:2648
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1008
uint8_t * data
Definition: avcodec.h:1346
static int flags
Definition: log.c:50
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:145
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:84
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:193
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:124
#define AVERROR(e)
Definition: error.h:43
Definition: alsa.h:45
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:148
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3479
#define fail()
Definition: checkasm.h:80
common internal API header
enum AVCodecID audio_codec_id
Forced audio codec_id.
Definition: avformat.h:1100
enum AVCodecID codec_id
Definition: avconv_vaapi.c:149
int channels
number of channels set by user
Definition: alsa.h:51
LIBAVUTIL_VERSION_INT
Definition: eval.c:55
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:546
Stream structure.
Definition: avformat.h:705
NULL
Definition: eval.c:55
av_default_item_name
Definition: dnxhdenc.c:55
int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
Try to recover from ALSA buffer underrun.
Definition: alsa.c:327
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:347
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
Definition: alsa.c:318
static int read_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: libcdio.c:114
Describe the class of an AVClass context structure.
Definition: log.h:34
#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 period_size
bytes per sample * channels
Definition: alsa.h:49
int sample_rate
Audio only.
Definition: avcodec.h:3564
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:412
void * priv_data
Format private data.
Definition: avformat.h:968
static av_cold int audio_read_header(AVFormatContext *s1)
Definition: alsa_dec.c:58
snd_pcm_t * h
Definition: alsa.h:47
int channels
Audio only.
Definition: avcodec.h:3560
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:529
int frame_size
preferred size for reads and writes
Definition: alsa.h:48
int sample_rate
sample rate set by user
Definition: alsa.h:50
AVCodecParameters * codecpar
Definition: avformat.h:831
static const AVClass alsa_demuxer_class
Definition: alsa_dec.c:162
AVInputFormat ff_alsa_demuxer
Definition: alsa_dec.c:169
This structure stores compressed data.
Definition: avcodec.h:1323
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1339
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.
Definition: alsa.c:186