Have you tried it all in AS3? The FLVPlaybackCaptioning tutorial works just fine for me:
I mean, create the FLVPlayback component in AS3. You're assigning a variable to an instance reference:
var flvControl:FLVPlayback = display;
Creating it in AS3 would like so, with no instance added to the stage:
var flvControl:FLVPlayback = new FLVPlayback();
Then instead of using the Flash component inspector to select the skin, manually grab the correct skin and apply it yourself, e.g.:
flvControl.skin = "SkinOverAll.swf";
Of course you need that SWF loaded on your server. I build in FlashBuilder 4.7 so I still just use Flash CS5.5 for making quick graphics and I find my FLVPlayback controls in this folder:
C:\Program Files (x86)\Adobe\Adobe Flash CS5.5\Common\Configuration\FLVPlayback Skins\ActionScript 3.0
Adjust for your version of Flash. See if your Closed Caption button appears.
Bottom line is there's no reason you should need to create a custom skin unless you want to and by what you said it doesn't appear that you want to. CC buttons exist in the premade skins.
So, I did try your solution. Changed the code to that :
var flvDisplay : FLVPlayback;
var flvSource : String = "videos/P01_Intro.flv";
var flvCaption : FLVPlaybackCaptioning;
var flvCaptionSource : String = "intro.xml"
flvDisplay = new FLVPlayback();
flvDisplay.skin = "SkinUnderPlaySeekCaption.swf";
flvDisplay.source = flvSource;
flvDisplay.width = 757;
flvDisplay.height = 530;
flvCaption = new FLVPlaybackCaptioning();
flvCaption.source = flvCaptionSource;
flvCaption.showCaptions = true;
I temporarily put the code related to the progress bar in comment, so I didn't add it to the post.
You know what's bizarre? The caption button still doesn't appear! The captions do work though. I just can't turn them off since the button isn't there. :/
So basically, I return to my first problem : is there any way to "access" the seekbar scroller trough code? Then my first solution would "work".
Here's a quick CS4 project I made to demonstrate it for you. All it does is play some random portion of a Phone Arena YouTube video for 30 seconds and has a caption from 0-9 seconds, 10-19 seconds, 20-29 seconds.. Caption button shows up, works, text shows up just fine, very easy code.
Ugly but gets the point across. Don't forget to set the FLVPlaybackCaptioning.flvPlayback to the instance name of the FLVPlayback (you'll see it in my simple source). I have zero error checking in here nor am I assuring the XML is loading, etc, but you'll get the idea.
Looks like my file was corrupted! When I copy-paste your code instead of mine in my file : the caption button still disappeared. But, if I use your code on your file and just change the value for the .xml and .flv, it worked just fine.
All this time for a corrupted file. So, so sad.
Thank you for your help. It is highly appreciated!