[ACTIVITY] Multimedia WG - Weekly Status for wk39.2011 (20110926-20110930)
ricardo.salveti at linaro.org
Thu Oct 6 18:04:04 UTC 2011
On Thu, Oct 6, 2011 at 7:28 AM, Mans Rullgard <mans.rullgard at linaro.org> wrote:
> On 6 October 2011 06:44, Fathi Boudra <fathi.boudra at linaro.org> wrote:
>> On 6 October 2011 00:43, Mans Rullgard <mans.rullgard at linaro.org> wrote:
>>> On 5 October 2011 18:35, Christian Robottom Reis <kiko at linaro.org> wrote:
>>>> On Wed, Oct 05, 2011 at 08:09:03PM +0300, Fathi Boudra wrote:
>>>>> Debian/Ubuntu P are going to move to libjpeg8 by default making
>>>>> current package obsolete in the future.
>>>> Note that when we asked Darrell about this he questioned the performance
>>>> benefits of version 8. Mans probably knows more.
>>> There is no benefit to v8. v7 added support for the rarely/never used
>>> arithmetic coding option, left out of earlier versions due to patent
>>> issues. Since nobody uses this mode, supporting it is irrelevant.
>>> v8 only adds some experimental, non-standard coding options even less
>>> relevant to any real-world uses. What is relevant is, however, that
>>> v8 is significantly slower than v6 in the default configuration. I
>>> don't remember if this slowdown was present already in v7.
>> According to Bill Allombert, v8 support more image format
> Yes, v8 (and v7) supports the arithmetic coding mode defined in the
> JPEG spec. Since nobody ever uses this, it is not important. If you
> mean more non-JPEG formats are supported by the cjpeg/djpeg tools,
> that is of little importance since nobody uses those in "production"
>> and provide a higher image quality.
> Maybe. I have not seen any tests to substantiate this claim.
> When *decoding* v8 actually produces poorer results in some cases
> due to using dct-based upscaling of chroma planes (this is also
> the cause of the slowdown).
>> There's probably benefit to v8 if a distribution switch
>> from v6 to v8.
> Distributions sometimes do things without good reasons.
And it seems it's not yet clear for distro maintainers which libjpeg
is the best one to use. A few projects already use it by default, like
Firefox, Chromium, Fedora, but it seems we still need to prove the
benefits by showing the numbers across platforms.
Would like to have at least one session for this topic at UDS,
comparing the results and discussing Debian's plans, so we can agree
and try the transition as soon P cycle starts.
Ricardo Salveti de Araujo
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