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Subject: Re: CRC checks in codecs

Re: CRC checks in codecs

From: Dave Hooper <dave_at_beermex.com>
Date: Tue, 29 Jun 2010 17:37:59 +0100

'How often do files just go bad' - well I guess part of the reason for the
crc is that nobody really knows the answer to that. Ever downloaded a
corrupted file from the internet, or a torrent with missing (unavailable)
chunks? Without crc checking the frame, you could easily crash rockbox with
malformed/garbage data, since I doubt all data is validated/sanity checked
in all code paths. That's just vorbis though (which iirc actually does do a
reasonable job of sanity checking most things along the way), other codecs
might have less sanity checking -- do we do crc checking on mp3? If not
then, I suppose, we could remove it from vorbis also (and see who complains
after the next release..)

Or alternatively see if the crc loop could be optimised more perhaps?

On 29 Jun 2010 17:17, "Nils Wallménius" <nils.wallmenius_at_gmail.com> wrote:

Several of our codecs do crc checking on data before playing it back.
In my opinion it is completely wasted battery time and cpu cycles, how
often do files just go bad? I found a profile run from an ipod video
and crc checking takes about 1% of the time spent decoding vorbis on
that.
So is it ok to disable it or should i make a setting for it?

Nils
Received on 2010-06-29


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