Content for TS 26.443 Word version: 18.0.0

4.1 Contents of the C source code 4.2 Program execution 5.1 Input/output file format 5.2 Rate switching profile (encoder input) 5.3 Parameter bitstream file (encoder output / decoder input) 5.4 VoIP parameter bitstream file (decoder input) 5.5 Bandwidth switching profile (encoder input) 5.6 Channel-aware configuration file (encoder input and decoder output) 5.7 JBM trace file (decoder output)

4 C code structure p. 6

This clause gives an overview of the structure of the floating-point C code and provides an overview of the contents and organization of the C code attached to the present document.

The ANSI-C code has been verified on the following platforms:

IBM PC compatible computers with Windows 7 operating systems and Microsoft Visual C++ 2010 compiler, 32-bit.

ANSI-C was selected as the programming language because portability was desirable.

4.1 Contents of the C source code p. 7

The C code is organized as follows:

Table 1: Source code directory structure

Directory	Description
README.txt	information on how to compile
Makefile	UNIX style encoder Makefile
Workspace_msvc/	Directory for the MSVC 2008 (or newer) project files
lib_com/	Source code files used both in encoder and decoder
lib_dec/	Source code files used solely in the decoder
lib_enc/	Source code files used solely in the encoder

The distributed files with suffix "c" contain the source code and the files with suffix "h" are the header files. The ROM data is contained in files named "rom_xxx" with suffix "c".

Makefiles are provided for the platforms in which the C code has been verified (listed above). Once the software is installed, this directory will have a compiled version of the encoder (named EVS_cod) and the decoder (named EVS_dec).

4.2 Program execution p. 7

The codec for Enhanced Voice Services is implemented in two programs:

EVS_cod: encoder;
EVS_dec: decoder.

The programs should be called like:

EVS_cod [encoder options] <input file> <bitstream file>;
EVS_dec [decoder options]<bitstream file> < output file>.

The input and output files contain 16-bit linear encoded PCM samples and the bitstream file contains encoded data.

The encoder and decoder options will be explained by running the programs without any input arguments. See the file readme.txt for more information on how to run the encoder and decoder programs.

5 File formats p. 7

This clause describes the file formats used by the encoder and decoder programs. The test sequences defined in TR 21.905 also use the file formats described here.

5.1 Input/output file format p. 7

Input files read by the encoder and output files written by the decoder consist of 16-bit integer words per each data sample. The byte order in each word depends on the host architecture (e.g. LSB first on PCs, etc.). Both the encoder and the decoder program process complete frames corresponding to multiples of 20 ms. The remaining samples are discarded.

The encoder will pad the last frame to integer multiples of 20ms frames, i.e. n speech frames will be produced from an input file with a length between [(n-1)*20ms+1 sample; n*20ms]. The files produced by the decoder will always have a length of n*20ms.

5.2 Rate switching profile (encoder input) p. 8

The encoder program can optionally read in a rate switching profile file which specifies the encoding bitrate for each frame of the input data. The rate switching profile is a binary file, generated by 'gen-rate-profile' tool, which is part of STL 2009, as contained in ITU-T G.191 [10]. The rate switching profile contains 32-bit integer words where each word represents the encoding bitrate for each particular frame. The rate switching profile is recycled if it contains less entries than the total number of frames in the input file. The rate switching profile can contain EVS primary mode bitrates and AMR-WB IO mode bitrates arbitrarily. I.e. switching between the two modes can be specified by the rate switching profile.

5.3 Parameter bitstream file (encoder output / decoder input) p. 8

The files produced by the speech/audio encoder/expected by the speech decoder contain an arbitrary number of frames in the following available formats.

5.3.1 ITU-T G.192 compliant format p. 8

SYNC_WORD	DATA_LENGTH	B1	B2	…	Bnn

Each box corresponds to one Word16 value in the bitstream file, for a total of 2+nn words or 4+2nn bytes per frame, where nn is the number of encoded bits in the frame. Each encoded bit is represented as follows: Bit 0 = 0x007f, Bit 1 = 0x0081. The fields have the following meaning:

SYNC_WORD: Word to ensure correct frame synchronization between the encoder and the decoder. It is also used to indicate the occurrences of bad frames.
In the encoder output: (0x6b21)
In the decoder input:

Good frames: (0x6b21)
Bad frames: (0x6b20)
DATA_LENGTH: Length of the speech data. Codec mode and frame type is extracted in the decoder using this parameter

5.3.2 Compact storage format file p. 8

The encoder and decoder programs can optionally write and read a file in the octet-based compact storage format. The compact storage format is specified in Annex A.2.6 of TS 26.445.

5.4 VoIP parameter bitstream file (decoder input) p. 8

Packet size	Arrival time	RTP header	G.192 format (see clause 5.3.1)

The fields have the following size and meaning:

Packet size: 32 bit unsigned integer (= 12 + 2 + DATA_LENGTH).
Arrival time: 32 bit unsigned integer in ms.
RTP header: 96 bits (see RFC 3550), including RTP timestamp and SSRC.

5.5 Bandwidth switching profile (encoder input) p. 9

The encoder program can optionally read in a bandwidth switching profile, which specifies the encoding bandwidth for each frame of speech processed. The file is a text file where each line contains "nb_frames B". B specifies the signal bandwidth that is one of the supported four bandwidths, i.e. NB, WB, SWB or FB. And "nb_frames" is an integer number of frames and specifies the duration of activation of the accompanied signal bandwidth B.

5.6 Channel-aware configuration file (encoder input and decoder output) p. 9

The encoder program can optionally read in a configuration file which specifies the values of FEC indicator p and FEC offset o, where FEC indicator, p: LO or HI, and FEC offset, o: 2, 3, 5, or 7 in number of frames. Each line of the configuration file contains the values of p and o separated by a space.

The channel-aware configuration file is meant to simulate channel feedback from a receiver to a sender, i.e. the decoder would generate FEC indication and FEC offset values for receiver feedback that correspond to the current transmission channel characteristics, thereby allowing optimization of the transmission by the encoder which applies the FEC offset and FEC indication when in the channel-aware mode.

5.7 JBM trace file (decoder output) p. 9

The decoder can generate a JBM trace file with the –Tracefile switch as a by-product of the decoder operation in case of JBM operation (which is triggered with the –VOIP switch on the decoder side).

The trace file is a CSV file with semi-colon as separator. The trace file starts with one header line that contains the column names in the following order:

rtpSeqNo;rtpTs;rcvTime;playtime;active

For each played out speech frame one entry is written to the trace file. The interval of the playtime values is usually 20ms, but may differ, depending on the JBM operation. Each entry is a line in the trace file that contains values as specified in Table 2.

Table 2: JBM trace file entry format

Name	Unit	Description
rtpSeqNo	1	RTP sequence number of played out speech frame. -1 if no corresponding RTP packet for the speech frame exists.
rtpTs	ms	RTP time stamp of played out speech frame. -1 if no corresponding RTP packet for the speech frame exists
rcvTime	ms	Absolute reception time of the RTP packet that corresponds to the speech frame. -1 if no corresponding RTP packet for the speech frame exists.
playtime	ms	Absolute play time (i.e. the time at which the PCM data is made available by the decoder). Can be floating-point value.
active	0 or 1	Binary entry, which is set to 1 for active speech frames (i.e. frames that are neither SID nor NO_DATA)