opus - Jul 2011 - Scanning the compressed celt for an artifact

I need to test the latency of a system that I ported CELT to.  I'd like 
to set a flag when the stream "changes".

In order to see the stream "change", I'd like to be able to scan
the
compressed CELT directly to set the flag.  ie.  I'd like to be able to 
find a byte or two that change reliably between two values when the 
stream "changes".  I don't want to have to decompress the CELT and
then
analyze the PCM (that would take too long given the CPU power available).


I can construct the streams to change in a way that would make the 
compressed CELT change in an easily detectable way.


My first thought was simply to build a stream that consists of two tones 
separated sufficiently in frequency.  Since CELT encodes power into 
bins, there should basically be a few numbers somewhere that should 
exhibit a very large magnitude change if I do this.

The only difficulty is that I would have to dig very deep into the 
source code to figure out whether this was A) possible and B) what bytes 
in the compressed bitstream change


Can anybody with more CELT knowledge than me give me some pointers?

Thanks,
-a

On Sat, Jul 16, 2011 at 8:51 PM, Andrew Lentvorski <bsder at allcaps.org>
wrote:
> I need to test the latency of a system that I ported CELT to. ?I'd like
> to set a flag when the stream "changes".
[snip]
> Can anybody with more CELT knowledge than me give me some pointers?

Send in digital silence. That is the most trivially detected.