JPG use in IM - to cache or not to cache?

[Jingo]

Hi Mario - quick question for you.  So, I only have JPG's in my database and this seems to suit my workflow just fine at the moment.  I have the Cache JPG option set to ON (which should not be caching JPG's and instead loading them from disk).  When the file system is quiet (nothing else going on), my images seem to load in abut 445ms - this seems to be true whether caching is enabled or not.  In viewing the log, I also see IM "caches" the next 6 images.. however, moving from image to image within this cache ALSO seems to still take 450-600ms.  Obviously, quite fast and not an issue, but it got me wondering if I SHOULD be using cache for JPG's anyway.... and/or should the next 6 images that get cached (assuming just in Memory) load even faster?

Thx! - Andy.

[Mario]

No caching needed, unless you plan to take your files off-line and still want to be able to view then at 100%.

0.3 to 0.4 seconds per file sounds about right. Depending a bit on the MP and color profile. IMatch loads files for the Viewer / Quick View Panel directly via WIC into the GPU.

[Jingo]

Thanks Mario - as I expected.  I was investigating this because I was encountering 4-5 second load times per image but I was also performing a large move outside of IM on my file system (different drives and low resource usage - but enough I guess to slow down the image loading).  Once this stopped - I noticed the 450ms loads which is great.  Was curious about the 6 image cache ahead as well.. lots going in by IM for sure!

[Mario]

IMatch uses a dynamic background look-ahead cache (preloading images in the background) in both the Quick View Panel and the Viewer. The QVP aims at low resource utilization while the Viewer can preload until 85% of the available RAM are used or the GPU causes errors. This again depends on various factors, e.g. the scroll direction, how the user interacts with the Viewer, available system resources etc.

Usually, unless you scroll faster than IMatch can load files in the background or you "jump" around wildly and thus invalidate the preload cache often,switching between images in the Viewer should be instantaneous.

Note that, for some unknown reason, WIC sometimes has issues with certain JPEG files, resulting in really slow (several seconds) load times. I have seen that mostly with images that have a non-neutral  EXIF orientation (and that is even more strange because WIC does not apply the orientation during loading the file, this has to be done in an extra step). Only Microsoft could possibly explain that. But that is really rare.
In general, the WIC JPEG coder is highly optimized and loads even my 80MP (8000 x 10000  pixel, digital back) in about 0.5 seconds from the cache.