Subject: [codec] On Processing plan of the Opus codec

From: Anisse Taleb <[email-masked]>
Date: Thu, 07 Apr 2011 07:01:42 +0000

Dear Codec Aficionados,

We have started discussing the testing including methodology, languages, item categories etc. We did not, however, discuss aspects for the processing plan for the tests. This may be premature before we agree on a test plan, however I would like to raise some issues that would be helpful to agree on in parallel. My objective is to have a processing as uniform as possible for the test labs such that the results could be repeatable. 

1) Filter masks, resampling
Since we are testing multiple bandwidths, in order to have a uniform processing, we need to agree on filters to be used for the signals under test. 

Similar and related are the resampling filters. I have seen somewhere that sox has been used for re-sampling for some tests. Not against using such tools, but I prefer to have more control over this and avoid using black-box resampling in favor of a controlled (with agreed filters) resampling.

2) Bulk processing of samples
The processing of the samples need to be performed on a large concatenated file with a preamble in order to make sure that the codec is in a steady state and avoid any bias that could result from VBR or other factors. I am not sure to what extent this has been used in the results that have been shown at the meeting.

3) Frame erasure patterns 
A modeling of potential FER patterns for the intended applications of the codec is needed. Of course we could consider random or bursty FER at x% as potential patterns, but somehow these may be too academic. 

4) Delay Jitter
Related to 3), delay patterns need also to be considered together with testing the codec with a JBM.

5) ...

This is an initial list of aspects to be considered, feel free to add more.

Kind regards,
/Anisse