[opus] Opus for ASR - update and questions
rossb-lists at audiomulch.com
Thu Dec 6 21:04:59 PST 2012
Did you try googling for "packet loss model"
I don't have a model for you but a few ideas. I worked on some packet
delay models last year.. not exactly the same thing but similar.
In my experience, late packets are more prevalent than completely lost
packets. Really late packets are as good as dropped.
So you could look at using some kind of queuing delay model and then
threshold the delay time to determine which packets were effectively
Another approach might be to use a uniform distribution of "drop events"
-- a drop event might consist of a random number of sequentially dropped
Or you could just run a bunch of real-world streams, capture the
results, and use either the actual drop events, or the statistics of the
tests as the basis of your tests or models.
I've observed a number of pathologies that are specific to particular
routers, drivers and system setups (my home router puts huge 1 sec delay
spikes in the traffic from time to time). WiFi packet scheduling can
have some funky behavior too.. with respect to delays caused by channel
scanning etc. So you would want to think about what parts of the system
you're modelling (just copper/fibre network loss on a carrier-grade
network? or also real-world domestic conditions).
I don't know how deeply you want to go into it but there's a field
called Queuing Theory that will give you the mathematical tools to do
the formal analysis. Kleinrock is the classic text I believe.
On 7/12/2012 3:32 PM, Young, Milan wrote:
> Unfortunately, a uniform model is going to make the simulation behave
> better than it would in real-world busty conditions. If anyone has
> alternate model suggestions, please let me know. I need a good
> simulation and I'd be happy to donate code.
>> -----Original Message----- From: opus-bounces at xiph.org
>> [mailto:opus-bounces at xiph.org] On Behalf Of Timothy B. Terriberry
>> Sent: Thursday, December 06, 2012 6:46 PM To: opus at xiph.org
>> Subject: Re: [opus] Opus for ASR - update and questions
>> Young, Milan wrote:
>>> One more follow-up question regarding the decoder's
>> parameter. What distribution model is being used to simulate
>> packet loss? Is this a uniform model, or something that resembles
>> the bursty nature of real world conditions?
>> The best answer here is to read the code (from opus_demo.c): lost =
>> len[toggle]==0 || (packet_loss_perc>0 && rand()%100 <
>> So, uniform. _______________________________________________ opus
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