about G729 framing details

Started by renzhengshu3 July 20, 2011
HI, all

I have a question on G729 framing details

I used a G729 codec to encode a .wav file

before encoding, it is about 300 KB
after encoding using G729 without VAD , the encoded G729 file is still about 300 KB, why isn't there any compression on bytes?

after encoding using G729 with VAD, the encoded file is about 250KB, only 50 KB smaller?

Besides, according to a post, the first word(two bytes) in the G729 file is 0x6b21, what does this mean?

and the second word is
1) 0x10 this means SID, and it means there are 16 words in each 10 ms frame
2) 0x50 this means VAD on,and it means there are 80 words in each 10 ms frame
3) 0 this means VAD off

so I'm very confused, my questions are
1) whether I encoded with VAD no without VAD, I noticed the second words are always 0x50, what is the reason?

2) I know that in a 10 milli-second G711 frame, there are 80 bytes. However, here in G729, the number of bytes are either 32(16 words) or 160(80 words) in a 10 ms frame, it seems to me the G729 compression is worse than G711???

3) when the second word is 0, what does it mean?

4) what does 0x6b21 mean

5) why the size of the G729 file is nearly the same as the .wav files
?

thanks!
On Mon, July 18, 2011 11:30 am, renzhengshu3 wrote:
> HI, all
>
> I have a question on G729 framing details
>
> I used a G729 codec to encode a .wav file
>
> before encoding, it is about 300 KB
> after encoding using G729 without VAD , the encoded G729 file is still
> about 300 KB, why isn't there any compression on bytes?

Hello,

Please answer these questions first so we can be sure we understand each
other:

1. What encoding is used in the original .wav file? (16 bit PCM, U-law,
GSM, etc.)
2. What container format is your output file?
3. Are you using reference code?
4. Are you sure you are getting a compacted bit stream?
--
Phil Frisbie, Jr.
Hawk Software
hawksoft.com
Thank you very much!

1. What encoding is used in the original .wav file? (16 bit PCM, U-law,
GSM, etc.)
--------------------
16bit PCM

2. What container format is your output file?
-------------------------
I think it is binary file and there is no container

3. Are you using reference code?
-----------
yes, I downloaded it from ITU

4. Are you sure you are getting a compacted bit stream?
------------------------
I don't understand what is a compacted bit stream
________________________________
From: "Phil Frisbie, Jr." <p...@hawksoft.com>
To: renzhengshu3 <r...@yahoo.com>
Cc: s...
Sent: Thursday, July 21, 2011 1:17 AM
Subject: Re: [speechcoding] about G729 framing details
On Mon, July 18, 2011 11:30 am, renzhengshu3 wrote:
> HI, all
>
> I have a question on G729 framing details
>
> I used a G729 codec to encode a .wav file
>
> before encoding, it is about 300 KB
> after encoding using G729 without VAD , the encoded G729 file is still
> about 300 KB, why isn't there any compression on bytes?

Hello,

Please answer these questions first so we can be sure we understand each
other:

1. What encoding is used in the original .wav file? (16 bit PCM, U-law,
GSM, etc.)
2. What container format is your output file?
3. Are you using reference code?
4. Are you sure you are getting a compacted bit stream?
--
Phil Frisbie, Jr.
Hawk Software
hawksoft.com
On Thu, July 21, 2011 11:57 am, Wen Liu wrote:
> Thank you very much!
>
> 1. What encoding is used in the original .wav file? (16 bit PCM, U-law,
> GSM, etc.)
> --------------------
> 16bit PCM
>
> 2. What container format is your output file?
> -------------------------
> I think it is binary file and there is no container
>
> 3. Are you using reference code?
> -----------
> yes, I downloaded it from ITU
>
> 4. Are you sure you are getting a compacted bit stream?
> ------------------------
> I don't understand what is a compacted bit stream

Just as I suspected. The ITU reference code output stream is made for
ease of verification; it is not compacted to be used in an actual software
product. Look at the output code and you will see what you need to do.

--
Phil Frisbie, Jr.
Hawk Software
hawksoft.com
Wen-

> I have a question on G729 framing details
>
> I used a G729 codec to encode a .wav file
>
> before encoding, it is about 300 KB
> after encoding using G729 without VAD , the encoded G729 file is still
> about 300 KB, why isn't there any compression on bytes?

Answer is here:

http://www.dsprelated.com/groups/speechcoding/show/1012.php

Note the part about a value of "2" being represented by 16-bit word 0x0002.

The ITU G729 download has been available for many years, so its reference file output format is well-documented.

-Jeff

> ________________________________
> From: "Phil Frisbie, Jr."
> To: renzhengshu3
> Cc: s...
> Sent: Thursday, July 21, 2011 1:17 AM
> Subject: Re: [speechcoding] about G729 framing details
> On Mon, July 18, 2011 11:30 am, renzhengshu3 wrote:
> > HI, all
> >
> > I have a question on G729 framing details
> >
> > I used a G729 codec to encode a .wav file
> >
> > before encoding, it is about 300 KB
> > after encoding using G729 without VAD , the encoded G729 file is still
> > about 300 KB, why isn't there any compression on bytes?
>
> Hello,
>
> Please answer these questions first so we can be sure we understand each
> other:
>
> 1. What encoding is used in the original .wav file? (16 bit PCM, U-law,
> GSM, etc.)
> 2. What container format is your output file?
> 3. Are you using reference code?
> 4. Are you sure you are getting a compacted bit stream?
> --
> Phil Frisbie, Jr.
> Hawk Software
> hawksoft.com