Type 1 : Voice Data

 ┌────┬──┬──┬──┬────┬──────┬─----------─┐
 │ 01 │ BLKLEN │ SR │ PACK │ VOICE DATA │
 └────┴──┴──┴──┴────┴──────┴─----------─┛

 This BLKTYPE indicates that this sub-block is a new set of voice data. It
 may use different sampling rate or packing method.

 The SR field(1 byte) is the Sampling Rate. It is defined as

    SR = 256 - 1000000/sampling rate

 For instance, if the sampling rate is 10,000 Hz, SR is set to 156.

 The PACK field (1 byte) is the Packing method used for this sub-block of
 voice data. It is defined as:

  ╔══════╤════════════════════════╗
  ║ PACK │ Description            ║
  ╠══════╪════════════════════════╣
  ║   0  │ 8-bit raw or unpacked  ║
  ║   1  │ 4-bit packed           ║
  ║   2  │ 2.6-bit packed         ║
  ║   3  │ 2-bit packed           ║
  ╚══════╧════════════════════════╝

 The voice data length is calculated as follows:

   voice data length = BLKLEN - 2