[theora] NHW codec - progress 2

Raphael Canut nhwcodec at gmail.com
Thu Mar 24 09:15:52 PDT 2016


Just a quick message to correct what I have said in my previous post.It
finally seems not that easy to code small wavelet coefficients to have a
good precision, and SPIHT is certainly a very good algorithm for that, -and
I know there are SPIHT experts that can make very good SPIHT-based
codecs-.I have chosen a new and different approach, the multistage residual
coding, so I will try to keep it and get the best of it.

I estimate that I need an additional 10Ko in average to code low contrast
information (and avoid artifacts).So I will need to remove 10Ko of
information in high contrast and give it to low contrast.I think in a first
time, I will only use residual coding for the low contrast area errors.I
will try to do this next month if I can find time, and will let you know
what it gives.

I am also aware that with all this, it will be very very difficult to beat
HEVC, VP9/10, Daala.The entropy coding is certainly the most interesting
part of my codec.

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