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• store pcm data into file, but can not play that file

  25 mai 2016, par Peng Qu

  I am writing a simple program, which reads mp3 file and store its pcm data into another file. I could get that file now, but when I play that on windows, I failed. So is there any wrong in my code, or windows couldn’t play raw audio data ?

  #include 
  
  #include 
  
  #include <libavutil></libavutil>avutil.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  
  
  int main()
  
  {
  
  int err;
  
  FILE *fout = fopen("test.wav", "wb");
  
  av_register_all();
  
  
  
  // step 1, open file and find audio stream
  
  AVFormatContext *fmtx = NULL;
  
  err = avformat_open_input(&amp;fmtx, "melodylove.mp3", NULL, NULL);
  
  assert(!err);
  
  
  
  err = avformat_find_stream_info(fmtx, NULL);
  
  assert(!err);
  
  
  
  int audio_stream_idx = -1;
  
  AVStream *st;
  
  AVCodecContext *decx;
  
  AVCodec *dec;
  
  
  
  for (int i = 0; i &lt; fmtx->nb_streams; ++i) {
  
      audio_stream_idx = i;
  
      if (fmtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
  
          st = fmtx->streams[i];
  
          decx = st->codec;
  
          dec = avcodec_find_decoder(decx->codec_id);
  
          decx->request_channel_layout = AV_CH_LAYOUT_STEREO_DOWNMIX;
  
          decx->request_sample_fmt = AV_SAMPLE_FMT_FLT;
  
          avcodec_open2(decx, dec, NULL);
  
          break;
  
      }
  
  }
  
  assert(audio_stream_idx != -1);
  
  
  
  int channels = decx->channels;
  
  int sample_rate = decx->sample_rate;
  
  int planar = av_sample_fmt_is_planar(decx->sample_fmt);
  
  int num_planes =  planar? decx->channels : 1;
  
  const char *sample_name = av_get_sample_fmt_name(decx->sample_fmt);
  
  printf("sample name: %s, channels: %d, sample rate: %d\n",
  
          sample_name, channels, sample_rate);
  
  printf("is planar: %d, planes: %d\n", planar, num_planes);
  
  
  
  /*
  
   * above I print some infomation about mp3 file, they are:
  
   * sample name: s16p, channels: 2, sample rate: 48000
  
   * is planar: 1, planes: 2
  
   */
  
  getchar();
  
  
  
  AVPacket pkt;
  
  av_init_packet(&amp;pkt);
  
  AVFrame *frame = av_frame_alloc();
  
  
  
  while (1) {
  
      err = av_read_frame(fmtx, &amp;pkt);
  
      if (err &lt; 0) {
  
          printf("read frame fail\n");
  
          fclose(fout);
  
          exit(-1);
  
      }
  
      if (pkt.stream_index != audio_stream_idx) {
  
          printf("we don't need this stream\n");
  
          continue;
  
      }
  
      printf("data size: %d\n", pkt.size);
  
  
  
      int got_frame = 0;
  
      int bytes = avcodec_decode_audio4(decx, frame, &amp;got_frame, &amp;pkt);
  
      if (bytes &lt; 0) {
  
          printf("decode audio fail\n");
  
          continue;
  
      }
  
      printf("frame size: %d, samples: %d\n", bytes, frame->nb_samples);
  
  
  
      if (got_frame) {
  
          int input_samples = frame->nb_samples * decx->channels;
  
          int sz = input_samples / num_planes;
  
          short buffer1[input_samples];
  
  
  
          for (int j = 0; j &lt; frame->nb_samples; ++j) {
  
              for (int i = 0; i &lt; num_planes; ++i) {
  
                  short *d = (short *)frame->data[i];
  
                  buffer1[j*2+i] = d[j];
  
              }
  
          }
  
  
  
          fwrite(buffer1, input_samples, 2, fout);
  
      } else {
  
          printf("why not get frame???");
  
      }
  
  }
  
  }

• Streaming audio file conversion process

  11 janvier 2017, par YAL

  I am integrating IBM Speech to Text API to my Django project. The problem that I have right now is that we allow users to upload audio files and majority of them are in the format of MP3 or MP4. However, the API only takes FLAC or WAV format.

  I am currently using FFMPEG for file conversion. However, this audio conversion library loads the entire audio file in memory as opposed to doing it in chunks.

  I wonder what would be a good solution to this problem or other packages that I should use ?

• No such file or directory Error with custom FFMPEG + CarrierWave method

  10 juillet 2013, par dodgerogers747

  I am using AWS CORS to upload videos to my site, all of which works as planned.

  I have the following model method which runs as an after_create callback (for speed) to take a screenshot from the video file on AWS. I plan to move this out into a delayed job but I don't think this will solve this particular issue. Please advise if mistaken.

  I use FFMPEG to take a screenshot from the AWS self.file location, I then send the file to CarrierWave by saving the file to self.screenshot where it is uploaded to AWS.

  Approx. 50% of the time it errors out with Errno::ENOENT - No such file or directory for the location of the screenshot image.

  How can I rectify my code to remove this error and how come it only occurs around 50% of the time ? If anyone needs more code just shout.

  video.rb

  after_create :take_screenshot
  
  
  
  mount_uploader :screenshot, ImageUploader
  
  
  
    def take_screenshot
  
      location = "#{Rails.root}/public/uploads/tmp/screenshots/#{unique}_#{File.basename(file)}.jpg"
  
      system `ffmpeg #{log_level} -i #{self.file} -ss 00:00:0#{time_frame} -vframes 1 #{location}`
  
      logger.debug "Trying to take screenshot from #{self.file}"
  
      #pass the actual file to CarrierWave to handle the image upload
  
      self.screenshot = File.open(location)
  
      self.save
  
      logger.debug "Deleting tmp file: #{location}: #{File.delete(location)}" if self.screenshot.present?
  
    end
  
  
  
  def unique
  
      (0..6).map{(65+rand(26)).chr}.join
  
    end
  
  
  
  def log_level
  
      "-loglevel panic"
  
    end
  
  
  
    def time_frame
  
      rand(0..3)
  
    end

  Stack trace :

  Started POST "/videos" for 127.0.0.1 at 2013-07-10 03:58:49 +0800
  
  Processing by VideosController#create as JS
  
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"6M1Ia+Ag2E3HVKH2PO/p7jewxSpMPdWeVHGA933Bzjw=", "video"=>{"file"=>"http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v"}}
  
    User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 9 LIMIT 1
  
     (0.1ms)  BEGIN
  
    SQL (0.2ms)  INSERT INTO `videos` (`created_at`, `file`, `question_id`, `screenshot`, `updated_at`, `user_id`) VALUES ('2013-07-09 19:58:49', 'http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v', NULL, NULL, '2013-07-09 19:58:49', 9)
  
  Trying to take screenshot from http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v
  
     (0.8ms)  ROLLBACK
  
  Completed 500 Internal Server Error in 3550ms
  
  
  
  Errno::ENOENT - No such file or directory - /Users/me/rails/project/public/uploads/tmp/screenshots/WCACLIC_Good_7iron.m4v.jpg:
  
    app/models/video.rb:24:in `initialize'
  
    app/models/video.rb:24:in `open'
  
    app/models/video.rb:24:in `take_screenshot'