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ffmpeg-4.2.2/libavdevice/oss_enc.c 3.23 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Linux audio grab interface
   * Copyright (c) 2000, 2001 Fabrice Bellard
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "config.h"
  
  #if HAVE_UNISTD_H
  #include <unistd.h>
  #endif
  #include <fcntl.h>
  #include <sys/ioctl.h>
  #include <sys/soundcard.h>
  
  #include "libavutil/internal.h"
  
  #include "libavcodec/avcodec.h"
  
  #include "avdevice.h"
  #include "libavformat/internal.h"
  
  #include "oss.h"
  
  static int audio_write_header(AVFormatContext *s1)
  {
      OSSAudioData *s = s1->priv_data;
      AVStream *st;
      int ret;
  
      st = s1->streams[0];
      s->sample_rate = st->codecpar->sample_rate;
      s->channels = st->codecpar->channels;
      ret = ff_oss_audio_open(s1, 1, s1->url);
      if (ret < 0) {
          return AVERROR(EIO);
      } else {
          return 0;
      }
  }
  
  static int audio_write_packet(AVFormatContext *s1, AVPacket *pkt)
  {
      OSSAudioData *s = s1->priv_data;
      int len, ret;
      int size= pkt->size;
      uint8_t *buf= pkt->data;
  
      while (size > 0) {
          len = FFMIN(OSS_AUDIO_BLOCK_SIZE - s->buffer_ptr, size);
          memcpy(s->buffer + s->buffer_ptr, buf, len);
          s->buffer_ptr += len;
          if (s->buffer_ptr >= OSS_AUDIO_BLOCK_SIZE) {
              for(;;) {
                  ret = write(s->fd, s->buffer, OSS_AUDIO_BLOCK_SIZE);
                  if (ret > 0)
                      break;
                  if (ret < 0 && (errno != EAGAIN && errno != EINTR))
                      return AVERROR(EIO);
              }
              s->buffer_ptr = 0;
          }
          buf += len;
          size -= len;
      }
      return 0;
  }
  
  static int audio_write_trailer(AVFormatContext *s1)
  {
      OSSAudioData *s = s1->priv_data;
  
      ff_oss_audio_close(s);
      return 0;
  }
  
  static const AVClass oss_muxer_class = {
      .class_name     = "OSS muxer",
      .item_name      = av_default_item_name,
      .version        = LIBAVUTIL_VERSION_INT,
      .category       = AV_CLASS_CATEGORY_DEVICE_AUDIO_OUTPUT,
  };
  
  AVOutputFormat ff_oss_muxer = {
      .name           = "oss",
      .long_name      = NULL_IF_CONFIG_SMALL("OSS (Open Sound System) playback"),
      .priv_data_size = sizeof(OSSAudioData),
      /* XXX: we make the assumption that the soundcard accepts this format */
      /* XXX: find better solution with "preinit" method, needed also in
         other formats */
      .audio_codec    = AV_NE(AV_CODEC_ID_PCM_S16BE, AV_CODEC_ID_PCM_S16LE),
      .video_codec    = AV_CODEC_ID_NONE,
      .write_header   = audio_write_header,
      .write_packet   = audio_write_packet,
      .write_trailer  = audio_write_trailer,
      .flags          = AVFMT_NOFILE,
      .priv_class     = &oss_muxer_class,
  };