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