[flac-dev] [PATCH] Improve LPC order guess

Olivier Tristan o.tristan at uvi.net
Wed Dec 3 09:17:37 PST 2014

Le 03/12/2014 18:14, Brian Willoughby a écrit :
> On Dec 3, 2014, at 8:30 AM, Martijn van Beurden <mvanb1 at gmail.com> wrote:
>> Op 03-12-14 om 16:48 schreef Olivier Tristan:
>>> This patch changes the settings associated with compression
>>> levels 6, 7 and 8. With this patch, -e is no longer used, but
>>> instead apodization functions are added. This should improve
>>> compression with at least 95% of all material. Independent tests
>>> show that this is probably the case.
>> As it turns out, the material for which the compression didn't
>> improve is mostly 'quiet' material.
> I would like to point out that 'quiet' material is common when making original recordings.
> I do a great deal of live recording, and the levels are always quiet in order to guard against clipping. These live recordings are then archived via FLAC to make sure nothing is lost.
> There are also field recording units that record directly to FLAC, and they will also see relatively 'quiet' recordings compared to fully mastered commercial CD music. Even though those recorders might not be updated to the latest FLAC sources, I would hope that things are not getting worse for a whole category of FLAC users.
> Basically, I'm worried that the FLAC sources are being fine-tuned to handle only the subset of audio represented by commercial CDs, without regard for 24-bit or raw tracks that have not been fully mastered. It's interesting to note that the original FLAC algorithms performed quite well across the board, but recent 'improvements' are sacrificing performance in one area to enhance performance in another area. Are these the sorts of things that can be handled by expanding the compression options, rather than thwarting existing performance?

It's the case actually
-l 12 -b 4096 -m -e -r 6
will bring the previous --best behavior if understand correctly

Olivier Tristan
Research & Development

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