User`s manual
AMBE-3000™-HDK Development Board
User’s Manual Version 1.1
Page 52
DVSI Confidential Proprietary
Section 6 – Appendix
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File Formats
The HDKCOM.EXE program uses three types of files for storing input and/or output data transferred
to/from the HDK-3000™. The 3 file formats are as follows:
1. PCM File. A PCM file is a binary file that contains 16-bit PCM speech samples sampled at 8 kHz.
The file does not contain any header information. It contains only speech data. The data may be
input to the encoder or or output from the decoder. Each speech sample occupies two
successive bytes in the file. The first byte contains the least significant 8-bits of the PCM sample
and the second byte contains the most significant 8-bits of the PCM sample. To illustrate this
assume that the following 16-bit PCM samples are stored in a PCM file:
0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000, 0x8000
The order in which the bytes are read from the file is as follows:
0x01, 0x00, 0x02, 0x00, 0x04, 0x00, 0x08, 0x00,
0x10, 0x00, 0x20, 0x00, 0x40, 0x00, 0x80, 0x00,
0x00, 0x01, 0x00, 0x02, 0x00, 0x04, 0x00, 0x08,
0x00, 0x10, 0x00, 0x20, 0x00, 0x40, 0x00, 0x80.
2. Hard-Decision Bit File. A hard-decision bit file contains compressed speech data output by the
encoder. The bit file can be used as input to the decoder. The data is packed using 8 bits per
byte. For hard-decision, each bit must be 0 or 1. If the 16 bits
a, b, c, d, e f, g, h, i, j, k, l, m, n, o, p
are the first 16 bits stored in a hard-decision bit file. Then the first two bytes of the file will be
binary abcdefgh and ijklmnop where a and i are the msb of each byte.
3. Soft-Decision Bit File. A soft-decision bit file contains compressed speech data output by the
encoder that has then been converted to 4-bit soft-decision format. Soft-decsion format is not
output directly by the encoder, but it can be input directly to the decoder when soft-decision
decoding is specified. The data is packed using two soft-decision bits per byte. Each soft
decision bit must be a 4-bit value in the range from 0x0 to 0xF. A binary “0” is represented as
0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, or 0x7, with 0x0 being the most confident “0” and 0x7 being the
least confident “0”. A binary “1” is represented as 0xF, 0xE, 0xD, 0xC, 0xB, 0xA, 0x9, or 0x8,
with 0xF being the most confident “1” and 0x8 being the least confident “1”. If a soft-decision bit
file is derived directly from a hard-decsion bit file, then each bit will have maximum confidence
and will be equal to either 0x0 for “0” or 0xF for “1”. If the 16 bits
a, b, c, d, e f, g, h, i, j, k, l, m, n, o, p
are the first 16 bits stored in a hard-decision bit file. Then the first eight bytes of the converted
soft-decision format file will be binary
aaaabbbb ccccdddd eeeeffff gggghhhh iiiijjjj kkkkllll mmmmnnnn oooopppp.