[theora] NHW Image codec

Raphael Canut nhwcodec at gmail.com
Fri Jan 23 09:31:04 PST 2015


So here is the compression scheme that I don't know if is covered by patent.

I use it on the wavelet DC parts.It outputs 1 byte (8 bits) words.There is
5 modes:

- 1(MSB) | 7 bits to store value (0->127 range)
- 01 | 6 bits to store val[n+1]-val[n] | val[n]-val[n-1] if each in the
range [-4,4]
- 001 | 5 bits to store val[n+2]-val[n+1] | val[n+1]-val[n] |
val[n]-val[n-1] if each in range
- 0001 | special case
- 0000 | 4 bits for RLE+prediction

It is a simple compression scheme, it is not as good as context modeling +
arithmetic coding, but it gives good results on my data (wavelet DC parts)
and is very fast.

My question is: Does someone know if this compression scheme is patented?
Also, as it is quite simple, maybe the patent has expired (more than 20
year old)?

Also, if someone knows a better compression scheme for DC parts (not too
complex, I don't want to use context modeling + arithmetic coding for now,
even if I know that patents on arithmetic coding have nearly all expired),
do not hesitate to let me know.


2015-01-18 10:02 GMT+01:00 Raphael Canut <nhwcodec at gmail.com>:

> Hello,
> Ok, and that's too many work to review a source code.In my codec, I have 3
> compression schemes, I think 2 are not patented, but the third... I don't
> know.For the rest, I think my codec is patent-free (I don't use
> SPIHT,EZW,zerotree methods), even the wavelet transform is new and don't
> use the lifting scheme nor the convolution product.
> Else, if you found time to review the codec, do not hesitate to let me
> know what you think of it and if you would have remarks.Would be much
> appreciated.
> Cheers,
> Raphael
> 2015-01-17 23:01 GMT+01:00 Basil Mohamed Gohar <basilgohar at librevideo.org>
> :
>> On 01/15/2015 12:39 PM, Raphael Canut wrote:
>> > Hello,
>> >
>> > Yes, that's right.I still think that it would have more weight if I
>> > could claim that Xiph has reviewed the source code and find that the NHW
>> > codec is royalty/patent-free (better than me alone claiming
>> > this...).Maybe it was in this sense that Ralph Giles answered me?
>> >
>> > Cheers,
>> > Raphael
>> That's not a guarantee that anyone can make, not even a patent attorney.
>> The current landscape is such that "being clear of patent concerns" is
>> impossible.  Someone can be destroyed by the legal process that results in
>> them being exonerated, but then left with no will nor resources to continue
>> development.
>> I don't say this to scare you away, just understand that asking Xiph to
>> "clear" the patent issues doesn't make sense.  Xiph is a non-profit
>> organization that advances the cause of free, open, and royalty-free
>> technologies, but cannot offer a technically legal service as requested.
>> --
>> Libre Video
>> http://librevideo.org
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