On 6 October 2011 16:41, Tom Gall tom.gall@linaro.org wrote:
On Thu, Oct 6, 2011 at 9:30 AM, Christian Robottom Reis kiko@linaro.org wrote:
On Thu, Oct 06, 2011 at 08:44:01AM +0300, Fathi Boudra wrote:
On 6 October 2011 00:43, Mans Rullgard mans.rullgard@linaro.org wrote:
On 5 October 2011 18:35, Christian Robottom Reis kiko@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 and provide a higher image quality.
I really question this statement based on what Mans and Darrell have both said (a number of times now). Where is the hard data that shows this is true?
Sounds like there needs to be a discussion with Bill. I would be interested how he is measuring image "quality.
IIRC v7 or v8 made some changes to the quantisation, which could in theory improve quality at a set target size. I haven't done any tests myself so I can't say if it works as intended. Also, what improves one image might degrade another. On top of that, image quality is very subjective and hard to measure. A change improving a metric like PSNR can very well decrease subjective visual quality.