FFmpeg
alsa_enc.c
Go to the documentation of this file.
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: output
26  * @author Luca Abeni ( lucabe72 email it )
27  * @author Benoit Fouet ( benoit fouet free fr )
28  *
29  * This avdevice encoder can play audio to an ALSA (Advanced Linux
30  * Sound Architecture) device.
31  *
32  * The filename parameter is the name of an ALSA PCM device capable of
33  * capture, for example "default" or "plughw:1"; see the ALSA documentation
34  * for naming conventions. The empty string is equivalent to "default".
35  *
36  * The playback period is set to the lower value available for the device,
37  * which gives a low latency suitable for real-time playback.
38  */
39 
40 #include <alsa/asoundlib.h>
41 
42 #include "libavutil/internal.h"
43 #include "libavutil/time.h"
44 
45 
46 #include "libavformat/internal.h"
47 #include "avdevice.h"
48 #include "alsa.h"
49 
51 {
52  AlsaData *s = s1->priv_data;
53  AVStream *st = NULL;
54  unsigned int sample_rate;
55  enum AVCodecID codec_id;
56  int res;
57 
58  if (s1->nb_streams != 1 || s1->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_AUDIO) {
59  av_log(s1, AV_LOG_ERROR, "Only a single audio stream is supported.\n");
60  return AVERROR(EINVAL);
61  }
62  st = s1->streams[0];
63 
65  codec_id = st->codecpar->codec_id;
66  res = ff_alsa_open(s1, SND_PCM_STREAM_PLAYBACK, &sample_rate,
67  st->codecpar->channels, &codec_id);
68  if (sample_rate != st->codecpar->sample_rate) {
70  "sample rate %d not available, nearest is %d\n",
72  goto fail;
73  }
74  avpriv_set_pts_info(st, 64, 1, sample_rate);
75 
76  return res;
77 
78 fail:
79  snd_pcm_close(s->h);
80  return AVERROR(EIO);
81 }
82 
84 {
85  AlsaData *s = s1->priv_data;
86  int res;
87  int size = pkt->size;
88  uint8_t *buf = pkt->data;
89 
90  size /= s->frame_size;
91  if (pkt->dts != AV_NOPTS_VALUE)
92  s->timestamp = pkt->dts;
93  s->timestamp += pkt->duration ? pkt->duration : size;
94 
95  if (s->reorder_func) {
96  if (size > s->reorder_buf_size)
98  return AVERROR(ENOMEM);
99  s->reorder_func(buf, s->reorder_buf, size);
100  buf = s->reorder_buf;
101  }
102  while ((res = snd_pcm_writei(s->h, buf, size)) < 0) {
103  if (res == -EAGAIN) {
104 
105  return AVERROR(EAGAIN);
106  }
107 
108  if (ff_alsa_xrun_recover(s1, res) < 0) {
109  av_log(s1, AV_LOG_ERROR, "ALSA write error: %s\n",
110  snd_strerror(res));
111 
112  return AVERROR(EIO);
113  }
114  }
115 
116  return 0;
117 }
118 
119 static int audio_write_frame(AVFormatContext *s1, int stream_index,
120  AVFrame **frame, unsigned flags)
121 {
122  AlsaData *s = s1->priv_data;
123  AVPacket pkt;
124 
125  /* ff_alsa_open() should have accepted only supported formats */
127  return av_sample_fmt_is_planar(s1->streams[stream_index]->codecpar->format) ?
128  AVERROR(EINVAL) : 0;
129  /* set only used fields */
130  pkt.data = (*frame)->data[0];
131  pkt.size = (*frame)->nb_samples * s->frame_size;
132  pkt.dts = (*frame)->pkt_dts;
133  pkt.duration = (*frame)->pkt_duration;
134  return audio_write_packet(s1, &pkt);
135 }
136 
137 static void
139  int64_t *dts, int64_t *wall)
140 {
141  AlsaData *s = s1->priv_data;
142  snd_pcm_sframes_t delay = 0;
143  *wall = av_gettime();
144  snd_pcm_delay(s->h, &delay);
145  *dts = s->timestamp - delay;
146 }
147 
149 {
150  return ff_alsa_get_device_list(device_list, SND_PCM_STREAM_PLAYBACK);
151 }
152 
153 static const AVClass alsa_muxer_class = {
154  .class_name = "ALSA outdev",
155  .item_name = av_default_item_name,
156  .version = LIBAVUTIL_VERSION_INT,
158 };
159 
161  .name = "alsa",
162  .long_name = NULL_IF_CONFIG_SMALL("ALSA audio output"),
163  .priv_data_size = sizeof(AlsaData),
164  .audio_codec = DEFAULT_CODEC_ID,
165  .video_codec = AV_CODEC_ID_NONE,
169  .write_uncoded_frame = audio_write_frame,
170  .get_device_list = audio_get_device_list,
171  .get_output_timestamp = audio_get_output_timestamp,
172  .flags = AVFMT_NOFILE,
173  .priv_class = &alsa_muxer_class,
174 };
AVOutputFormat::name
const char * name
Definition: avformat.h:497
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
audio_write_frame
static int audio_write_frame(AVFormatContext *s1, int stream_index, AVFrame **frame, unsigned flags)
Definition: alsa_enc.c:119
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:310
AVPacket::data
uint8_t * data
Definition: packet.h:373
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:391
sample_rate
sample_rate
Definition: ffmpeg_filter.c:156
audio_get_output_timestamp
static void audio_get_output_timestamp(AVFormatContext *s1, int stream, int64_t *dts, int64_t *wall)
Definition: alsa_enc.c:138
DEFAULT_CODEC_ID
#define DEFAULT_CODEC_ID
Definition: alsa.h:42
AVCodecParameters::channels
int channels
Audio only.
Definition: codec_par.h:166
fail
#define fail()
Definition: checkasm.h:127
audio_write_packet
static int audio_write_packet(AVFormatContext *s1, AVPacket *pkt)
Definition: alsa_enc.c:83
alsa_muxer_class
static const AVClass alsa_muxer_class
Definition: alsa_enc.c:153
pkt
AVPacket * pkt
Definition: movenc.c:59
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
av_cold
#define av_cold
Definition: attributes.h:90
s
#define s(width, name)
Definition: cbs_vp9.c:257
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
s1
#define s1
Definition: regdef.h:38
av_sample_fmt_is_planar
int av_sample_fmt_is_planar(enum AVSampleFormat sample_fmt)
Check if the sample format is planar.
Definition: samplefmt.c:112
ff_alsa_open
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:167
ff_alsa_extend_reorder_buf
int ff_alsa_extend_reorder_buf(AlsaData *s, int min_size)
Definition: alsa.c:340
codec_id
enum AVCodecID codec_id
Definition: vaapi_decode.c:369
AVFormatContext
Format I/O context.
Definition: avformat.h:1193
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1088
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
NULL
#define NULL
Definition: coverity.c:32
write_trailer
static int write_trailer(AVFormatContext *s1)
Definition: v4l2enc.c:98
AlsaData
Definition: alsa.h:48
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:235
time.h
ff_alsa_close
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
Definition: alsa.c:303
AVCodecParameters::sample_rate
int sample_rate
Audio only.
Definition: codec_par.h:170
AVCodecID
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: codec_id.h:47
AVPacket::size
int size
Definition: packet.h:374
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
size
int size
Definition: twinvq_data.h:10344
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
AVFMT_NOFILE
#define AVFMT_NOFILE
Demuxer will use avio_open, no opened file should be provided by the caller.
Definition: avformat.h:464
avdevice.h
AVPacket::dts
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed.
Definition: packet.h:372
write_packet
static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int unqueue)
Definition: ffmpeg.c:727
AV_CODEC_ID_NONE
@ AV_CODEC_ID_NONE
Definition: codec_id.h:48
AVOutputFormat
Definition: avformat.h:496
internal.h
AV_CLASS_CATEGORY_DEVICE_AUDIO_OUTPUT
@ AV_CLASS_CATEGORY_DEVICE_AUDIO_OUTPUT
Definition: log.h:42
alsa.h
AVStream
Stream structure.
Definition: avformat.h:928
AVClass::class_name
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:71
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
AVDeviceInfoList
List of devices.
Definition: avdevice.h:465
avpriv_set_pts_info
void avpriv_set_pts_info(AVStream *st, 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:1186
ff_alsa_xrun_recover
int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
Try to recover from ALSA buffer underrun.
Definition: alsa.c:319
av_gettime
int64_t av_gettime(void)
Get the current time in microseconds.
Definition: time.c:39
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:60
AVPacket
This structure stores compressed data.
Definition: packet.h:350
AV_WRITE_UNCODED_FRAME_QUERY
@ AV_WRITE_UNCODED_FRAME_QUERY
Query whether the feature is possible on this stream.
Definition: internal.h:880
ff_alsa_get_device_list
int ff_alsa_get_device_list(AVDeviceInfoList *device_list, snd_pcm_stream_t stream_type)
Definition: alsa.c:357
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
h
h
Definition: vp9dsp_template.c:2038
write_header
static void write_header(FFV1Context *f)
Definition: ffv1enc.c:347
audio_write_header
static av_cold int audio_write_header(AVFormatContext *s1)
Definition: alsa_enc.c:50
ff_alsa_muxer
const AVOutputFormat ff_alsa_muxer
Definition: alsa_enc.c:160
audio_get_device_list
static int audio_get_device_list(AVFormatContext *h, AVDeviceInfoList *device_list)
Definition: alsa_enc.c:148