about Codec and PLC(packet loss concealment)

[esolve]

hi, all

I need to decode some .raw files which are encoded with a certain codec such as G711 u-law, G729 and iLBC
these .raw files are obtained from VOIP streams, so some of them are with packet loss.

I have downloaded a G729 codec, iLBC codec
I want to know

1. how to know whether these codec can decode raw files with packet loss or not?
   I know there are different PLC algorithm, so does this mean there are different decoders?
   
   \
2. Generally speaking, if I want to convert received RTP packet into .wav files, the procedures are
3. convert RTP packets into original.raw files
4. decode original.raw files into decoded.raw using decoder
5. convert decoded.raw into .wav files

I used sox to process G711 .raw files, and use the following command
sox -r 8000 -U original.raw -s -b 16 decoded.wav
does this command include all the 3 procedures listed above?
besides, if there are packet losses, are there any PLC involved in this command line?

[Gale_Andrews]

@esolve

I need to decode some .raw files which are encoded with a certain codec such as G711 u-law, G729 and iLBC
these .raw files are obtained from VOIP streams, so some of them are with packet loss.

I have downloaded a G729 codec, iLBC codec
I want to know

1. how to know whether these codec can decode raw files with packet loss or not?
   I know there are different PLC algorithm, so does this mean there are different decoders?

Please note (with reference to your previous questions too), questions about using Audacity are our main focus. Unless someone here knows answers to these sort of specialist questions, we have to spend time researching it on the internet.

From what I can gather, G711 has optional package loss concealment (PLC), it will depend if the particular decoder you use implements it or not:
http://www.adaptivedigital.com/product/vocoders/g711.htm

G729 does appear to include PLC in its mandatory standard:
http://www.adaptivedigital.com/product/vocoders/g729.htm

@esolve

2. Generally speaking, if I want to convert received RTP packet into .wav files, the procedures are
3. convert RTP packets into original.raw files
4. decode original.raw files into decoded.raw using decoder
5. convert decoded.raw into .wav files

I used sox to process G711 .raw files, and use the following command
sox -r 8000 -U original.raw -s -b 16 decoded.wav
does this command include all the 3 procedures listed above?
besides, if there are packet losses, are there any PLC involved in this command line?

The SOX manual is at http://sox.sourceforge.net/sox.html. -U and -s are deprecated but they may work. I don’t think your command is doing your step 2), and don’t know why you would want that step.

I wouldn’t like to say if PLC is done or preserved when transcoding (and it would be optional for G711 as above in any case). If you want definitive answers to the above I suggest you ask on the sox-users list.



Gale