frame_samples.h

/****************************************************************************
 * modules/include/audio/utilities/frame_samples.h
 *
 *   Copyright 2019 Sony Semiconductor Solutions Corporation
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#ifndef MODULES_INCLUDE_AUDIO_UTILITIES_FRAME_SAMPLES_H
#define MODULES_INCLUDE_AUDIO_UTILITIES_FRAME_SAMPLES_H
 
#include "audio/audio_common_defs.h"
 
/* When MP3 encode and fs is 16kHz, 22.05kHz, 24kHz, sample num of
 * 1au(access unit) is 1152/2 = 576 (It depend on MPEG2 compliant).
 * Therefore, at first, value is (#1)"CapSampleNumPerFrame[m_codec_type] / 2".
 * And sample num of captured and SRC filterd data is to be 576,
 * return ((#1) * 48000 / m_sampling_rate(Hz)).
 *
 * The process below is only for fs is 48kHz, 16kHz.
 * To correspontd to 32000Hz, 44100Hz..., need conversion process to 
 * sample num per 1au to be 1152.
 */
 
 
inline uint32_t getCapSampleNumPerFrame(uint8_t codec_type, uint32_t fs)
{
  const uint32_t CapSampleNumPerFrame[] =
  {
    1152,  /* MP3 */
    768,   /* WAV */ /* Any integer in capable */
    1024,  /* AAC */
    160,   /* OPUS */
    1024,  /* AAC */
    768,   /* LPCM */
  };
 
  if (codec_type > AS_CODECTYPE_LPCM)
    {
      return 0;
    }
 
  if (codec_type == AS_CODECTYPE_MP3 && fs < 32000)
    {
      return (CapSampleNumPerFrame[codec_type] / 2 * 48000 /
        fs);
    }
  else if (codec_type == AS_CODECTYPE_OPUS)
    {
      /* 20ms. */
 
      return ((fs / 50) * (48000 / fs));
    }
  else
    {
    }
 
  return CapSampleNumPerFrame[codec_type];
}
 
#endif /* MODULES_INCLUDE_AUDIO_UTILITIES_FRAME_SAMPLES_H */