[GEM-dev] media loading problem

[Mathieu Bouchard]

(resending my reply...)

On Fri, 1 Apr 2005, IOhannes m zmoelnig wrote:
> Tim Blechmann wrote:
>> hi gem-devs ...
>> i experienced something very strange with gem on a few machines ...
>> i'm using gem to display images and play back videos ... but on one
>> point (after a few hours), it refuses to load images / videos ...
>> the strange thing ... i was able to load exactly these files before ...
>> the version of gem is 0.90...
>> any ideas?
> the last time i had this behaviour, it was the first sign of an upcoming hard 
> crash of my harddrive. probably you better run...

Hi. I have a different warning for you, in a similar situation. Let me explain.

On the last installation I worked on (a museum in Quebec City) I've had a 
problem with one of the subtitles, which was encoded in QuickTime-PNG (because 
I needed alpha), and then the PNG decoder would yell "CRC Error!" and then 
crash because I didn't have an error handler for *that*. Well it's a good thing 
it crashed, else I wouldn't have noticed and it would've been very bad. But 
then it wasn't crashing an hour earlier, so what was going on? I rebooted and 
then everything was fine again.

Turns out that on a 512M RAM bar there was *1* bit which was occasionally 
failing, and the disk cache chose that spot to hold a compressed frame of the 
subtitle. It also explains a corrupted directory (that fsck wouldn't handle!) 
that appeared upon installing Linux, and some files being mysteriously 
different on backups than on the originals.

I strongly recommend testing the RAM with http://memtest86.com/ or similar. 
However I also fried a CPU last summer, although it only got up to 80 celcius 
(AMD specs say 95 celcius max). The difference is that CPU failure will look 
like random noise in memtest86 (change every time, no pattern in addresses), 
whereas RAM failure will show definite patterns (the errors stay the same and 
might even show periodicity, for example exactly 256k apart).

On a related note, I just had a major hard disk crash (accompanied with 
feelings of guilt about backups being too old). However, the disk had suddenly 
died, so it was only the controller. Surface damage is more insidious but also 
you have more time to do backups. I would like to thank Christian Klippel (the 
multio/vdsp/karma guy) for suggesting swapping controllers with the one of an 
identical harddisk I happened to have.

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