[CELT-dev] C55x Fixed Point PLC Stack Usage and Audio Quality

Bob Bang bob.bang2 at gmail.com
Mon Sep 19 14:09:26 PDT 2011

Hello everyone, I just wanted to see if anyone else is using PLC on the C55x
and having success? I am seeing some issues and was curious if I was doing
anything wrong/stupid or maybe I have found a bug?

I am using:

   - the CELT library from OPUS 0.9.5 ( I checked the git repo and no check
   ins have comments about PLC, I assume it hasn't been updated)
   - FRAME_SIZE: 240
   - PACKET_SIZE: 40
   - SAMPLE_RATE: 48000
   - TI 5509, 5505, 5504

To utilize the PLC functionality I pass a NULL pointer in place of the
buffer of encoded bytes.  At first my program would crash, but realized PLC
was eating up my entire stack. PLC required I provide the stack an
additional 0x900 bytes (2300 bytes) to not crash. That sounds fishy.

Also, is there a correct method to calling PLC? Is there a limit to the
number of times you should call it consecutively? Can I only call it once
per so many packets? It is supposed to fade out? When I believe PLC is
working correctly, I get what sounds like a repeated buffer of constant
level noise similar in character to the audio at the time of passing the
NULL pointer.

Any one have any insights? Does PLC on the TI platform work like this for

Thanks as always,

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