Fwd: [Tremor] 64 bit math

[Niklas Barsk]

Pete sent me a response that he somehow was unable to send to the list
too. So here is his response:

---------- Forwarded message ----------
From: Pete <pete261 at yahoo.com>
Date: Tue, 30 Nov 2004 06:48:51 -0800 (PST)
Subject: Re: [Tremor] 64 bit math
To: Niklas Barsk <nibarius at gmail.com>


Niklas,

So I guess this board is not dead after all!

I think there are some earlier posts on this mailing list about this.  See for
example http://lists.xiph.org/pipermail/tremor/2004-October/thread.html,
http://lists.xiph.org/pipermail/tremor/2004-July/thread.html, etc.

I get the impression from
http://lists.xiph.org/pipermail/tremor/2004-July/000995.html that you do need
to implement 64-bit math.

I am working on a port for another processor that can't do 64-bit math.  I took
the trouble to go through all the code and change the relevant lines to use the
64-bit functions that someone posted here a while back: set64_int, cmp64_64,
mul64_int, etc.  I have not tested the code yet, but I would be happy to give
you a copy of my files if you like.

You also may have a problem with "int"s, which are assumed in the original code
to be 32 bits...

If you want, you could add an entry with notes about porting for your platform
to http://wiki.xiph.org/index.php/Tremor ;)

Pete



--- Niklas Barsk <nibarius at gmail.com> wrote:

> Hi
>
> I am currently trying to port Tremor (nobyte lowmem branch) to a
> platform that does not have any 64 bit integer datatype (in fact it
> only has 24 and 48 bit datatypes). So I am running it in low accuracy
> mode to avoid the most of the 64 bit
> math, but there still are some 64 bit datatypes in use (granulepos and such).
>
> Now to my question, is the 64 bit precision really needed or can the
> 48 bit long be used instead for the ogg_int64_t datatype?
>
> I have only tried decoding very short files, about a second in length,
> but it worked fine with only 48 bit precision.
>
> Best regards
> /Niklas
> _______________________________________________
> Tremor mailing list
> Tremor at xiph.org
> http://lists.xiph.org/mailman/listinfo/tremor
>


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