yading@10: /*
yading@10:  * ALSA input and output
yading@10:  * Copyright (c) 2007 Luca Abeni ( lucabe72 email it )
yading@10:  * Copyright (c) 2007 Benoit Fouet ( benoit fouet free fr )
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * ALSA input and output: output
yading@10:  * @author Luca Abeni ( lucabe72 email it )
yading@10:  * @author Benoit Fouet ( benoit fouet free fr )
yading@10:  *
yading@10:  * This avdevice encoder allows to play audio to an ALSA (Advanced Linux
yading@10:  * Sound Architecture) device.
yading@10:  *
yading@10:  * The filename parameter is the name of an ALSA PCM device capable of
yading@10:  * capture, for example "default" or "plughw:1"; see the ALSA documentation
yading@10:  * for naming conventions. The empty string is equivalent to "default".
yading@10:  *
yading@10:  * The playback period is set to the lower value available for the device,
yading@10:  * which gives a low latency suitable for real-time playback.
yading@10:  */
yading@10: 
yading@10: #include <alsa/asoundlib.h>
yading@10: 
yading@10: #include "libavutil/time.h"
yading@10: #include "libavformat/internal.h"
yading@10: #include "avdevice.h"
yading@10: #include "alsa-audio.h"
yading@10: 
yading@10: static av_cold int audio_write_header(AVFormatContext *s1)
yading@10: {
yading@10:     AlsaData *s = s1->priv_data;
yading@10:     AVStream *st;
yading@10:     unsigned int sample_rate;
yading@10:     enum AVCodecID codec_id;
yading@10:     int res;
yading@10: 
yading@10:     st = s1->streams[0];
yading@10:     sample_rate = st->codec->sample_rate;
yading@10:     codec_id    = st->codec->codec_id;
yading@10:     res = ff_alsa_open(s1, SND_PCM_STREAM_PLAYBACK, &sample_rate,
yading@10:         st->codec->channels, &codec_id);
yading@10:     if (sample_rate != st->codec->sample_rate) {
yading@10:         av_log(s1, AV_LOG_ERROR,
yading@10:                "sample rate %d not available, nearest is %d\n",
yading@10:                st->codec->sample_rate, sample_rate);
yading@10:         goto fail;
yading@10:     }
yading@10:     avpriv_set_pts_info(st, 64, 1, sample_rate);
yading@10: 
yading@10:     return res;
yading@10: 
yading@10: fail:
yading@10:     snd_pcm_close(s->h);
yading@10:     return AVERROR(EIO);
yading@10: }
yading@10: 
yading@10: static int audio_write_packet(AVFormatContext *s1, AVPacket *pkt)
yading@10: {
yading@10:     AlsaData *s = s1->priv_data;
yading@10:     int res;
yading@10:     int size     = pkt->size;
yading@10:     uint8_t *buf = pkt->data;
yading@10: 
yading@10:     size /= s->frame_size;
yading@10:     if (s->reorder_func) {
yading@10:         if (size > s->reorder_buf_size)
yading@10:             if (ff_alsa_extend_reorder_buf(s, size))
yading@10:                 return AVERROR(ENOMEM);
yading@10:         s->reorder_func(buf, s->reorder_buf, size);
yading@10:         buf = s->reorder_buf;
yading@10:     }
yading@10:     while ((res = snd_pcm_writei(s->h, buf, size)) < 0) {
yading@10:         if (res == -EAGAIN) {
yading@10: 
yading@10:             return AVERROR(EAGAIN);
yading@10:         }
yading@10: 
yading@10:         if (ff_alsa_xrun_recover(s1, res) < 0) {
yading@10:             av_log(s1, AV_LOG_ERROR, "ALSA write error: %s\n",
yading@10:                    snd_strerror(res));
yading@10: 
yading@10:             return AVERROR(EIO);
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static void
yading@10: audio_get_output_timestamp(AVFormatContext *s1, int stream,
yading@10:     int64_t *dts, int64_t *wall)
yading@10: {
yading@10:     AlsaData *s  = s1->priv_data;
yading@10:     snd_pcm_sframes_t delay = 0;
yading@10:     *wall = av_gettime();
yading@10:     snd_pcm_delay(s->h, &delay);
yading@10:     *dts = s1->streams[0]->cur_dts - delay;
yading@10: }
yading@10: 
yading@10: AVOutputFormat ff_alsa_muxer = {
yading@10:     .name           = "alsa",
yading@10:     .long_name      = NULL_IF_CONFIG_SMALL("ALSA audio output"),
yading@10:     .priv_data_size = sizeof(AlsaData),
yading@10:     .audio_codec    = DEFAULT_CODEC_ID,
yading@10:     .video_codec    = AV_CODEC_ID_NONE,
yading@10:     .write_header   = audio_write_header,
yading@10:     .write_packet   = audio_write_packet,
yading@10:     .write_trailer  = ff_alsa_close,
yading@10:     .get_output_timestamp = audio_get_output_timestamp,
yading@10:     .flags          = AVFMT_NOFILE,
yading@10: };