TSWriter checks the free disk space once before time shifting is started.
TVLibrary checks the free disk space every time before a "new" time shifting is started (Channel Change!). Thats results in a no free disk space dialog and the time shifting is stopped even though TSWriter would still do time shifting.

h4. Steps to Reproduce
Limit a drive (USB/Ramdisk) to 500MB
Set the file size to 200MB
Start time shifting (Watch TV)
After 2 Files were created change the channel and a "no free disk space" dialog should appear.

Result:
First file is created with 200MB (300MB left on the drive)
After amount of time second file is created(400 MB left 100)
And now you can wait on the same channel forever time shifting works great here!!!
But after channel change TVLibrary do the free disk space check again and that's results in the "no free disk space" dialog. Cause 100MB space left but 400 space needed.