[TYPO3-english] splitted Imagecaption with tt_content.uploads

[David ARNOULT - Edition & Internet Operations]

Hi !
 
I am trying to modify behaviour of tt_content.uploads content in 4.5, showing an imagecaption as alt/title tag with this TYPOSCRIPT: 
 
tt_content.uploads.20.linkProc.iconCObject.file.width = 100
tt_content.uploads.20.itemRendering.20 >
tt_content.uploads.20.itemRendering.wrap >
tt_content.uploads.20.linkProc.iconCObject.altText.data = field:imagecaption
tt_content.uploads.20.linkProc.iconCObject.titleText.data = field:imagecaption

In FE, it works but captions are not splitted and are all the same for all images.
I have tried to add tt_content.uploads.20.linkProc.iconCObject.imageTextSplit = 1 with no result.
 
How to split and match caption1 for image1, caption2 for image 2 etc?
 
Many thanks indeed!
 
David