[Athen] need help understanding current caption technology

[Prof Norm Coombs]

Because I am blind, some basic parts of actually creating captioning are 
not accessible to me.  Nevertheless, 5-10 years ago I had a fair 
understanding of how the process worked using magpie etc.  It spit out a 
SMIL file a video file a rt file with the text and they were synchronized 
through the SMIL file.
I now understand that using something like Camtasia the process can be 
simplified even allowing the end user to click on buttons to make the 
captions visible or hidden.  I am guessing this outputs just a single 
file.  I have read the Techsmith tutorial on step-by-step creation of the 
captions.
Here are my questions:
1 does this output a single file or does is still provide a group of files 
controlled by the SMIL file?

2 while a blind person does not need to find and use the player buttons to 
make captions visible or not, could a blind user with a screen reader find 
the buttons for play or pause and stop or can't a screen reader manipulate 
any of the controls

3.  can the output be set either to start when opened or set to require 
using a start button to start the actual video?

4  Are there still any reasons that someone would want to output multimedia 
using magpie and the SMIL file?  Is magpie and SMIL now irrelevant?

5.  I assume that any decent commercial product similar to Camtasia will do 
all the same things?

I need to be brought up to date on the technology so I can talk 
intelligently to people about it.

Norm Coombs