[theora-dev] DC prediction

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Fri Mar 25 05:52:02 PDT 2011

On 03/25/2011 07:38 AM, Jonathan Fabrizio wrote:
> * Truncate DC to a 16-bit representation by dropping any higher-order bits.
> But why dropping higher-order bits ?

1. In practice, this overflow does not occur.  A non-buggy encoder is very
unlikely to produce streams that overflow because this would result in bad

2. Checking for overflow (which occurs not at all or very rarely) would
waste CPU time, because most processors do not have fast saturating

3. Theora is designed to be backwards-compatible with On2 VP3, so the core
decoding algorithms could not be changed.


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