topic USC Speech Codec in Intel® Integrated Performance Primitives

USC Speech Codec

pchapman — Sun, 23 Apr 2006 21:06:27 GMT

Hi,

I'm currently trying to decode some G.711 u-law 8-bit audio using the USC G729 codec. The ultimate goal is to package the encoded bit stream into a payload format that can be transmitted over RTP.

To test the functionality of the USC I'm using the example code from the USC API. The result of the encode gives 80-bits (10bytes) bitstream.

I then pass the output buffer to the decode function. When I try to play out the encoded/decoded data over RTP, the payload is not correct.

So I have a few questions....

1. What format is the decompressed data in? 16-bits representing a byte?

2. What would have to be done to the bitstream, in order for it to be a valid G.729 RTP packet payload?

Any help would be greatly appreciated.

Kind Regards,

Paul Chapman

Junior Software Engineer

Re: USC Speech Codec

Igor_B_Intel1 — Mon, 24 Apr 2006 18:10:44 GMT

Hi, Paul.

USC G729 codec doesn't support 8 bit u-law input. For such kind of bitstream please use USC G711 codec.

As for USC G729 codec:

>1. What format is the decompressed data in? 16-bits representing a byte?

16 bits signed word (two bytes).

>2. What would have to be done to the bitstream, in order for it to be a valid G.729 RTP packet payload?

Nothing special. USC G729 codec operates with 10ms frame. G729 RTP profile needs 20 ms data. So in case of VAD turned off you need to concatenate two frames.

Igor S. Belyakov

Re: USC Speech Codec

pchapman — Tue, 25 Apr 2006 14:24:53 GMT

Thank you for your reply. This will explain the problems I have been having. What input is valid for the G.729 codec? Could I call ippsMuLawToLin_8u16s()to change the input from u-law to liniar input?

Regards,

Paul Chapman

Message Edited by pchapman@telesoft-technologies.com on 04-25-200612:31 AM

Re: USC Speech Codec

Igor_B_Intel1 — Wed, 10 May 2006 12:46:12 GMT

Yes, of course you can use ippsMuLawToLin_8u16s()function toconvert from u-law to liniar PCM.

On the other hand USC G711 codec can do this convertion and additionally it has got VAD and PLC modes.

Igor S. Belyakov