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• How to convert mp3 data to wav data ?

  12 mai 2023, par Yali

  I have a wav audio file and i extracted data from that wav using python pydub module and i got this data

  


  [-139 18 -215 34 -196 6 -295 -31 -301 -35 -211 13 -93 47
-60 39 -58 7 -17 2]

  


  (this is first 10 data i got more than 1 million data)

  


  from pydub import AudioSegment
import numpy as np

song = AudioSegment.from_file("test.wav")
extract_data = np.array(song.get_array_of_samples())
print(extract_data[:10])


  


  then i converted wav to mp3 using that module and again extracted data from mp3 file and i got this data

  


  [-108 7 -193 24 -223 11 -239 -31 -248 -43 -203 -10 -101 23
-14 24 10 15 24 16]

  


  (this is first 10 data i got more than 1 million data)

  


  song = AudioSegment.from_file("test.wav")
song.export("test.mp3")
mp3_song = AudioSegment.from_file("test.mp3")
extract_data = np.array(mp3_song.get_array_of_samples())
print(extract_data[:10])


  


  and again i converted mp3 to wav now i got mp3 data instead of wav data.

  


  mp3_song = AudioSegment.from_file("test.mp3")
mp3_song.export("test1.wav", format="wav")

song = AudioSegment.from_file("test1.wav")
extract_data = np.array(song.get_array_of_samples())
print(extract_data[:10])


  


  My point is how to convert mp3 data to original wav data ?

  


  please help me,

  


  Thanks.

  


• convert pcm stream data to encoded aac data

  24 décembre 2019, par Kumar

  I tried to convert pulse-audio pcm stream data to aac encoded data using ffmpeg.
  But after encoding I get noise-full data, not the correct one. Here I post my code, anyone help me with some ideas.

  Initial configuration :

      av_register_all();
  
  
  
      int error;
  
      if ((error = avio_open(&output_io_context,"out.aac",AVIO_FLAG_WRITE))<0) {
  
              printf("could not open output file\n");
  
      }
  
  
  
      if (!(output_format_context = avformat_alloc_context())) {
  
              printf("output_format_context error\n");
  
      }
  
  
  
      output_format_context->pb = output_io_context;
  
  
  
      if(!(output_format_context->oformat = av_guess_format(NULL, "out.aac", NULL))) {
  
              printf("guess format error\n");
  
      }
  
  
  
      codec = avcodec_find_encoder(AV_CODEC_ID_AAC);
  
      if (codec == NULL) {
  
              printf("avcodec_find_encoder: ERROR\n");
  
      }
  
  
  
      if (!(stream = avformat_new_stream(output_format_context, NULL))) {
  
              printf("stream create error\n");
  
      }
  
      output_codec_context = avcodec_alloc_context3(codec);
  
      if(!output_codec_context) {
  
              printf("output_codec_context is null\n");
  
      }
  
  
  
      output_codec_context->channels       = CHANNELS;
  
      output_codec_context->channel_layout = av_get_default_channel_layout(CHANNELS);
  
      output_codec_context->sample_rate    = SAMPLE_RATE; //input_codec_context->sample_rate;
  
      output_codec_context->sample_fmt     = codec->sample_fmts[0];
  
      output_codec_context->bit_rate       = 48000; //OUTPUT_BIT_RATE;
  
  
  
      stream->time_base.den = SAMPLE_RATE;//input_codec_context->sample_rate;
  
      stream->time_base.num = 1;
  
  
  
      if(output_format_context->oformat->flags & AVFMT_GLOBALHEADER)
  
              output_codec_context->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      if ((error = avcodec_open2(output_codec_context, codec, NULL)) < 0) {
  
          printf("error");
  
      }
  
  
  
      error = avcodec_parameters_from_context(stream->codecpar, output_codec_context);
  
  
  
      if (write_output_file_header(output_format_context)) {
  
              printf("write header failure...\n");
  
      }

  Data encoding :

  AVFrame *output_frame;
  
  int frame_pos = 0, ctx_frame_size = output_codec_context->frame_size;
  
  int size = av_samples_get_buffer_size(NULL, CHANNELS,
  
                output_codec_context->frame_size,output_codec_context->sample_fmt, 1);
  
  if((x =  avcodec_fill_audio_frame(output_frame, CHANNELS,
  
                 output_codec_context->sample_fmt, data, length, 1)) < 0) {
  
        printf("avcodec_fill_audio_frame error : %s\n", av_err2str(x));
  
  }
  
  
  
   int data_written;
  
   if (encode_audio_frame(output_frame, output_format_context,
  
              output_codec_context, &data_written)) {
  
          printf("encode_audio_frame error\n");
  
    }
  
  
  
    av_frame_free(&output_frame);

  helper_function :

   int encode_audio_frame(AVFrame *frame,AVFormatContext *output_format_context,
  
                AVCodecContext *output_codec_context, int *data_present)
  
   {
  
     AVPacket output_packet;
  
     int error;
  
     init_packet(&output_packet);
  
  
  
     if (frame) {
  
        frame->pts = pts;
  
        pts += frame->nb_samples;
  
     }
  
  
  
     error = avcodec_send_frame(output_codec_context, frame);
  
     if (error == AVERROR_EOF) {
  
       error = 0;
  
       goto cleanup;
  
     } else if (error < 0) {
  
        fprintf(stderr, "Could not send packet for encoding (error '%s')\n",
  
              av_err2str(error));
  
        return error;
  
     }
  
  
  
     error = avcodec_receive_packet(output_codec_context, &output_packet);
  
     if (error == AVERROR(EAGAIN)) {
  
       error = 0;
  
       goto cleanup;
  
     } else if (error == AVERROR_EOF) {
  
        error = 0;
  
        goto cleanup;
  
     } else if (error < 0) {
  
        fprintf(stderr, "Could not encode frame (error '%s')\n",
  
              av_err2str(error));
  
        goto cleanup;
  
     } else {
  
        *data_present = 1;
  
    }
  
  
  
    if (*data_present &&
  
        (error = av_write_frame(output_format_context, &output_packet)) < 0) {
  
        fprintf(stderr, "Could not write frame (error '%s')\n",
  
               av_err2str(error));
  
        goto cleanup;
  
    }
  
  
  
    cleanup:
  
        av_packet_unref(&output_packet);
  
        return error;
  
   }

  • Do we need to fill AVFrame with sizeof(av_samples_get_buffer_size) or context->frame_size ?
    

  TYIA :) !!

• Revision 8ef6dadbbe : test-data.mk : fix perf test data dependency both the encode and decode perf tes

  27 février 2015, par James Zern

  Changed Paths :
   Modify /test/test-data.mk

  
  
  test-data.mk : fix perf test data dependency

  both the encode and decode perf tests require niklas_1280_720_30.yuv
  broken since :
  28eebf3 Merge "tests : add a shorter 720p test clip"
  7839d03 tests : add a shorter 720p test clip

  Change-Id : I51ebbf7261832e25d8f2c1da5c7df5c2e47f748e