G.726¶

Introduction¶

G.726 is an ITU-T ADPCM speech codec standard covering the transmission of voice at rates of 16, 24, 32, and 40 kbit/s.

Source Code¶

The original G.726 source code and test sequences are taken from G.191 version 2.0, 24 January 2000, and this codec passes the test cases successfully.

Multi-instance and reentrance¶

Codec hasn’t tested on multi-instance run, for more information about support of multi-instance run see codec source documentation. Codec supports reentrance in case if AGU address pointer registers (AGU_AUX_APx), AGU offset registers (AGU_AUX_OSx), AGU modifier registers (AGU_AUX_MODx), see [1] in References, will be saved and restored.

Codec-Specific Build Options¶

LTO_BUILD and REMAPITU_T options are enabled for that codec by default.

Codec-Specific Run-Time Options¶

To run G.726 codec in MetaWare Debugger (See [2] in References), use the following command:

with variable bitrate:

mdb -run -cl -nsim -tcf=<default TCF from /rules/common_hw_config.mk> vbr-g726.elf [-enc|-dec] -law [A|u|l] -rate [16|24|32|40|16-24-32-40] -frame [NoOfSamples] [-noreset] [-?|-help] <InpFile> <OutFile> [<FrameSize> [<1stBlock> [<NoOfBlocks> [<Reset>]]]]

with constant bit rate:

mdb -run -cl -nsim -tcf=<default TCF from /rules/common_hw_config.mk> g726demo.elf [-noreset] [-?|-help] <Law> <Transf> <Rate>  <InpFile> <OutFile> [<FrameSize> [<1stBlock> [<NoOfBlocks> [<Reset>]]]]

The following tables list the parameters that can be passed to G.726.

Command-Line Options Descriptions for G.726 with Variable Bitrate Support¶
Option	Description
`<input_file>`	Specifies the input file
`<output_file>`	Specifies the output file
`-enc`	Encode mode. Default: run encoder and decoder (optional)
`-dec`	Encode mode. Default: run encoder and decoder (optional)
`-law A\|u`	The letters A or a for G.711 A-law, letter u for G.711 u-law, or letter l for linear. If linear is chosen, A-law is used to compress/expand samples to/from the G.726 routines.Default is A-law (optional)
`-rate`	Bit-rate (in kbit/s): 40, 32, 24 or 16 (in kbit/s) or a combination of them using dashes (For example, 32-24 or 16-24-32). Default is 32 kbit/s (optional)
`-frame`	Number of samples per frame for switching bit rates. Default is 16 samples (optional)
`-noreset`	Do not reset the encoder/decoder (optional)
`-?\|-help`	Print help message (optional)
`FrameSize`	Frame size, in number of samples; The bitrate only changes at the boundaries of a frame. Default: 16 samples (optional)
`1stBlock`	The number of the first block of the input file to be processed. Default: first block (optional)
`NoOfBlocks`	The number of blocks to be processed, starting with block “1stBlock” (optional)
`Reset`	If specified as 1, the coder and decoder are reset at the very beginning of the processing. If 0, the processing starts with the variables in an unknown state. Default is 1 (reset ON). (optional)

Command-Line Options Descriptions for G.726 with Constant Bitrate Support¶
Option	Description
`<input_file>`	Specifies the input file
`<output_file>`	Specifies the output file
`Transf`	Desired conversion on the input file (optional):[lolo], (A/u)log -> ADPCM -> (A/u) log[load], (A/u)log -> ADPCM[adlo], ADPCM -> (A/u) log
`Law`	Desired law (either A or u) (optional)
`Rate`	The bit-rate (in kbit/s): 40, 32, 24 or 16 (in kbit/s)or a combination of them using dashes (For example, 32-24 or 16-24-32). Default is 32 kbit/s (optional)
`-frame`	Number of samples per frame for switching bit rates. Default is 16 samples (optional)
`-noreset`	Do not reset the encoder/decoder (optional)
`-?\|-help`	print help message (optional)
`FrameSize`	The frame size, in number of samples; the bitrate only changes at the boundaries of a frame. Default: 16 samples (optional)
`1stBlock`	The number of the first block of the input file to be processed. Default: first block (optional)
`NoOfBlocks`	The number of blocks to be processed, starting with block “1stBlock” (optional)
`Reset`	If specified as 1, the coder and decoder are reset at the very beginning of the processing. If 0, the processing starts with the variables in an unknown state. Default is 1 (reset ON). (optional)

Examples

The following command instructs the codec encoding and decoding audio file decoder to A-law log with variable bitrate:

mdb -run -cl -nsim -tcf=em9d_voice_audio vbr-g726.elf -q -law A -rate 16-24-32-40-32-24 ../testvectors/Ref/voice.src ../testvectors/voicvbra.tst

The following command instructs the codec to encode converting from A-law log input file to ADPCM decoded file with frame size is 16 and 1 start block:

mdb -run -cl -nsim -tcf=em9d_voice_audio g726demo.elf -q a load 16 ../testvectors/Ref/nrm.a ../testvectors/rn16fa.i 16 1 1024