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• lame mp3 change bitrate cpp

  23 mai 2019, par user2018761

  I need to change mp3 bitrate, I’m using lame for cpp project under Windows and Linux. I think I need to convert mp3 to wav and then wav to mp3 with desired bitrate.

  For wav to mp3 I already have the code (using lame) it works.
  For mp3 to wav there is problem with app crashing on hip_decode.
  Probably due to ID3 tags at the beginning of the file.
  How to skip the ID3 tags or is this a different problem ?

  This is code I’m using

  bool Helper::convert2Wav(QString fromFile, QString toFile) {
  
      int read, write;
  
      int ctn = 0;
  
  
  
      FILE *mp3_in =fopen(fromFile.toLocal8Bit().data(),"rb");
  
      //this should be WAV
  
      FILE *pcm_out =fopen(toFile.toLocal8Bit().data(),"wb");
  
  
  
      const int PCM_SIZE = 4096;
  
      const int MP3_SIZE = 4096;
  
  
  
      short int pcm_buffer[PCM_SIZE*2];
  
      short int pcm_buffer1[PCM_SIZE];
  
      short int pcm_buffer2[PCM_SIZE];
  
      unsigned char mp3_buffer[MP3_SIZE];
  
  
  
  
  
      memset(pcm_buffer, 0, sizeof(pcm_buffer));
  
      memset(pcm_buffer1, 0, sizeof(pcm_buffer1));
  
      memset(pcm_buffer2, 0, sizeof(pcm_buffer2));
  
      memset(mp3_buffer, 0, sizeof(mp3_buffer));
  
  
  
      lame_t lame = lame_init();
  
      hip_t l = hip_decode_init();
  
      lame_set_in_samplerate(lame, 44100);
  
      //lame_set_VBR(lame, vbr_default);
  
      //lame_set_mode(lame, MONO);
  
      lame_init_params(lame);
  
  
  
      qDebug()<<"start decoding";
  
  
  
      do {
  
          ctn += 4096;
  
          qDebug()<<"a message:"</read = hip_decode(l, mp3_buffer, MP3_SIZE, pcm_buffer1,pcm_buffer2);
  
  
  
          //memcpy(pcm_buffer, pcm_buffer1, sizeof(pcm_buffer1));
  
          //memcpy(&pcm_buffer[PCM_SIZE], pcm_buffer2, sizeof(pcm_buffer2));
  
          //write = lame_encode_buffer_interleaved(lame, pcm_buffer, read,mp3_buffer, MP3_SIZE);
  
          //fwrite(pcm_buffer, 1, sizeof(pcm_buffer), pcm_out);
  
  
  
      } while (read != 0);
  
  
  
      hip_decode_exit(l);
  
      lame_close(lame);
  
      fclose(pcm_out);
  
      fclose(mp3_in);
  
  
  
      return true;
  
  }

  It is crashing with an output :

  start decoding
  
  a message: 4096
  
  a message: 8192
  
  a message: 12288
  
  1   ??                                 0x7ffff7b8f0b5     
  
  2   hip_decode1_headers                0x7ffff7b8f34b     
  
  3   hip_decode1_headers                0x7ffff7b8f385     
  
  4   hip_decode_headers                 0x7ffff7b8f42d     
  
  5   hip_decode                         0x7ffff7b8f47c     
  
  6   Helper::convert2Wav helper.cpp 498 0x5555555b0fe7     
  
  7   ??                                 0x4490551063006a0  
  
  
  
          MP3_SIZE    258346945   int
  
          PCM_SIZE    234884892   int
  
          ctn 189860957   int
  
          l   1050198802094820962 hip_t
  
          lame    1165886731226582744 lame_t
  
          mp3_buffer  "\005\0029lM^J\035�xo�R����(����Rj\172175r�V�����ԡCb٥���0a�ע�r�4�A��7Xj�Q0u�\033Os��L5�S$D2\002\016� UxCp\014s��08\004+7��@"�r"... (4096)   unsigned char[4096]
  
          mp3_in  0xe0b0e1e0e060d4a   FILE*
  
          pcm_buffer  @0x7fffffff89a0 short[8192]
  
          pcm_buffer1 @0x7fffffff69a0 short[4096]
  
          pcm_buffer2 @0x7fffffff49a0 short[4096]
  
          pcm_out 0xc460bb00bb40c82   FILE*
  
          read    229772669   int
  
          write   <optimized out="out"> 
  
  </optimized>

  it seems this is not ID3 issue, I have used this code https://searchcode.com/file/31230698/ID3.cpp to read ID3 and it shows there is no ID3 tags
  But still crashing at the same point :

  Has ID3v2 Tag: No
  
    Tag size: 0
  
  start decoding skip tag_size: 0
  
  a message: 4096
  
  a message: 8192
  
  a message: 12288

• How to compute the number of extra samples added by LAME or FFMPEG

  24 janvier 2018, par actuallyaswin

  I am attempting to build a MP3 decoder / parser in Python which supports files encoded by LAME or FFMPEG.

  My encoding shell script is shown here :

  #!/bin/bash
  
  for i in wav/*.wav; do
  
      i=${i##*/};
  
      lame --nores --strictly-enforce-ISO -t --cbr -b 64 -h "wav/${i}" "mpeg/lame/${i%.wav}.mp3";
  
      ffmpeg -i "wav/${i}" -codec:a libmp3lame -qscale:a 2 "mpeg/ffmpeg/${i%.wav}.mp3";
  
  done

  This scripts reads WAVE files located in ./wav/ and produces a controlled-bitrate MP3 of 64kbps in my ./mp3/lame/ directory, and a variable-bitrate MP3 of quality 2 in my ./mp3/ffmpeg/.

  I have written a Python script that iterates through both resultant MP3s, counting the number of frames and samples. Both the LAME and FFMPEG results are equivalent (in terms of frames and samples), but their binary files are different.

  The LAME/FFMPEG sample count was done by iterating through the binary MP3 files, locating and parsing the frame header, then using the MP3 spec to determine the number of samples per frame.

  • Number of MP3 data-frames : 112 (ignoring the Xing/Info first frame)
  • Number of output frames : 112*576 = 64512

  Here is a comparison of the sample count for a single 4-second input file :

  • Input WAV # of samples = 62996
  • Output LAME/FFMPEG # of samples = 64512
  • Difference = 1516

  I understand that according to the LAME FAQ file, resultant MP3 files are zero padded in the front and back to make sure the inverse MDCT is performed properly, but also because the windows overlap.

  What I can’t ascertain from the above FAQ, or from any previous StackOverflow post, is how to compute the number of artificially added samples. If I can be sure that all 1516 of these samples are zeros, and I can be sure of their position in the bytestream, I’d like to be able to confidently toss them out. Since there are 1516 "extra" samples and there are 576 samples per frame for a V2LIII encoding, then there must be more than two (but less than three) erroneous MPEG frames here.

  Is anyone here savvy enough with MPEG encoding/decoding to know how many samples are added, and in which frames those samples will be in ? In other words, will the first frame and last frame always contain blank data, or are there more frames ?

• lame mp3 to wav crashing (need to skip ID3 tag ?)

  18 janvier 2018, par user2018761

  I need to change mp3 bitrate, I’m using lame for cpp project under Windows and Linux. I think I need to convert mp3 to wav and then wav to mp3 with desired bitrate.
  For wav to mp3 I already have the code (using lame) it works.
  For mp3 to wav there is problem with app crashing on hip_decode.
  Probably due to ID3 tags at the beginning of the file.
  How to skip the ID3 tags or is this a different problem ?

  This is code I’m using

  bool Helper::convert2Wav(QString fromFile, QString toFile) {
  
      int read, write;
  
      int ctn = 0;
  
  
  
      FILE *mp3_in =fopen(fromFile.toLocal8Bit().data(),"rb");
  
      //this should be WAV
  
      FILE *pcm_out =fopen(toFile.toLocal8Bit().data(),"wb");
  
  
  
      const int PCM_SIZE = 4096;
  
      const int MP3_SIZE = 4096;
  
  
  
      short int pcm_buffer[PCM_SIZE*2];
  
      short int pcm_buffer1[PCM_SIZE];
  
      short int pcm_buffer2[PCM_SIZE];
  
      unsigned char mp3_buffer[MP3_SIZE];
  
  
  
  
  
      memset(pcm_buffer, 0, sizeof(pcm_buffer));
  
      memset(pcm_buffer1, 0, sizeof(pcm_buffer1));
  
      memset(pcm_buffer2, 0, sizeof(pcm_buffer2));
  
      memset(mp3_buffer, 0, sizeof(mp3_buffer));
  
  
  
      lame_t lame = lame_init();
  
      hip_t l = hip_decode_init();
  
      lame_set_in_samplerate(lame, 44100);
  
      //lame_set_VBR(lame, vbr_default);
  
      //lame_set_mode(lame, MONO);
  
      lame_init_params(lame);
  
  
  
      qDebug()<<"start decoding";
  
  
  
      do {
  
          ctn += 4096;
  
          qDebug()<<"a message:"</read = hip_decode(l, mp3_buffer, MP3_SIZE, pcm_buffer1,pcm_buffer2);
  
  
  
          //memcpy(pcm_buffer, pcm_buffer1, sizeof(pcm_buffer1));
  
          //memcpy(&pcm_buffer[PCM_SIZE], pcm_buffer2, sizeof(pcm_buffer2));
  
          //write = lame_encode_buffer_interleaved(lame, pcm_buffer, read,mp3_buffer, MP3_SIZE);
  
          //fwrite(pcm_buffer, 1, sizeof(pcm_buffer), pcm_out);
  
  
  
      } while (read != 0);
  
  
  
      hip_decode_exit(l);
  
      lame_close(lame);
  
      fclose(pcm_out);
  
      fclose(mp3_in);
  
  
  
      return true;
  
  }

  It is crashing with an output :

  start decoding
  
  a message: 4096
  
  a message: 8192
  
  a message: 12288
  
  1   ??                                 0x7ffff7b8f0b5     
  
  2   hip_decode1_headers                0x7ffff7b8f34b     
  
  3   hip_decode1_headers                0x7ffff7b8f385     
  
  4   hip_decode_headers                 0x7ffff7b8f42d     
  
  5   hip_decode                         0x7ffff7b8f47c     
  
  6   Helper::convert2Wav helper.cpp 498 0x5555555b0fe7     
  
  7   ??                                 0x4490551063006a0  
  
  
  
          MP3_SIZE    258346945   int
  
          PCM_SIZE    234884892   int
  
          ctn 189860957   int
  
          l   1050198802094820962 hip_t
  
          lame    1165886731226582744 lame_t
  
          mp3_buffer  "\005\0029lM^J\035�xo�R����(����Rj\172175r�V�����ԡCb٥���0a�ע�r�4�A��7Xj�Q0u�\033Os��L5�S$D2\002\016� UxCp\014s��08\004+7��@"�r"... (4096)   unsigned char[4096]
  
          mp3_in  0xe0b0e1e0e060d4a   FILE*
  
          pcm_buffer  @0x7fffffff89a0 short[8192]
  
          pcm_buffer1 @0x7fffffff69a0 short[4096]
  
          pcm_buffer2 @0x7fffffff49a0 short[4096]
  
          pcm_out 0xc460bb00bb40c82   FILE*
  
          read    229772669   int
  
          write   <optimized out="out"> 
  
  </optimized>

  it seems this is not ID3 issue, I have used this code https://searchcode.com/file/31230698/ID3.cpp to read ID3 and it shows there is no ID3 tags
  But still crashing at the same point :

  Has ID3v2 Tag: No
  
    Tag size: 0
  
  start decoding skip tag_size: 0
  
  a message: 4096
  
  a message: 8192
  
  a message: 12288

  Best Regards

  Marek