Large subtitles slow down video playback

[grazzhoppa]

Problem: When displaying large subtitles, VLC 1.0.0 will spike in CPU usage to a point where video frames are dropped resulting in choppy playback even on DVD resolution video.
Environment:

• Windows XP 32bit SP3
  4 GB DDR2 RAM
  Intel Core 2 Duo 6750 @ 3.3GHz
  NVIDIA 8800GT with driver version 186.18 (newest WHQL drivers released at time of this posting)
  
  VLC video rendering options are left to whatever the default values are.
  No other CPU intensive processes are running

I don't believe the hardware is the bottle neck here.

This amount of text will cause the video to stutter/drop frames/choppy playback. Subtitle size option is set to "Larger" in VLC preferences:


This amount, or less, of text does not cause dropped frames:


I believe the problem has to do with how many pixels the subtitles take up on screen - the more pixels covered by the subtitles, the more CPU time is taken up by VLC.
The above examples run perfectly fine with smaller sized subtitles.


And yes, having such large subtitles covering almost the entire screen is important to me, hence why I'm spending my time posting this. Choosing a smaller font for the subtitles is not really a workaround for me.