Hi, Sir.
I am one of TI audio chip users. Currently I am using tlv320aic1110, a PCM codec chip to design a handheld system. In order to understand this PCM codec, I did certain measurements and tests for this chip’s performance and characteristics. During certain tests and analysis, I went through certain TI’s more classic voice codec/filter combos. To test voice code channel (transmit path)’s performance, I saw a key parameter, named, “Virtual Decision Value”. This parameter is defined by the standard of ITU G.711. According to G.711’s definition, decision value xn: 4096 as normalized value units correspond to Tmax=3.14dBm0, while, the quantized value (value at decoder output) yn, has no physical number to match 4096, the decision value xn. In contrast, the maximum quantized value yn-max is 4032, which being lower than decision value xn-max=4096.
As described above, my question is if I want to measure Tmax, according to the definition, the virtual decision value should be 4096, corresponding to 3.14dBm0. However, physically at decoder output, I can only get maximum value number 4032. Is there any approach for us to get 4096’s corresponding value 3.14dBm0? Or actual way is maximum quantized value number 4032’s corresponding value (analog level ) as Tmax?
The table copied below is partial table of A-law, positive input values of Table 1a/G.711.
Attached is ITU-T G.711 General Aspects of Digital Transmission System Standard.
Your quick response is highly appreciated.
Looking forward to your reply.
Thanks a lot.
Sincerely yours,
User
File attached: ITU-T G.711
