Preloading tracks in QuickTime

Mikuro

Mikuro

Crotchety UI Nitpicker
In QuickTime Player, there's an otption to "preload" tracks into memory to increase performance. You can see this feature by opening any movie, going to the Movie Properties window, selecting a track, and going to the Other Settings tab.

I have one question about this: Errr...What does it do?!?

I've played around with the "Preload This Track" and "Cache (hint)" check boxes a lot, and yet I've seen no evidence of any preloading or caching actually being done. Activity Monitor shows that no extra memory is being used. And I'm pretty sure I'm still seeing skips from my fragmented disk.

I've tried this with movs and avis. I've tried saving and re-opening. Always the same result. The files I tested were all smaller than my "free" memory (as reported by Activity Monitor), so in theory it should be able to dump it all into RAM with no trouble.

I'm currently using QT 7 on Tiger. But I've tried to use this feature in QT6 with the same (lack of) results. Back then I assumed it was just because I didn't have much RAM in my system, but that shouldn't be a problem now.

Is this a dead feature, or do I just not understand what it's supposed to do?
 
Don't those have something to do with setting up the movie for streaming? I know that "hinting" does, but not sure about preloading.

I don't think hinting or preloading is going to do anything with a local QuickTime movie -- any chance you could try it streaming?
 
the cache is for when you download movies or watch streams on the web, where it stores the video files for access during play. However, you can access the same file later w/o internet in the cache and it doesn't have to load again
 
Hmm. The QuickTime 7 user's guide makes it seem like it's for local files. To quote:
Loading Movies Into RAM for Better Playback
QuickTime has two memory (RAM) options you can use to improve playback
performance. Preload puts the entire movie into memory before it is played; Cache
keeps movie data in memory after it has played. This option is useful for small files you
want to loop.
Click to expand...
I've run across several similar functions in the QuickTime API that mention loading an entire movie into RAM, which I assume is exactly what they're talking about here. None of them refer to streaming at all.

The "for small files" bit seems relevent, though. I did some more testing, with both settings enabled on every track in every movie:
• I played and replayed a 25MB MPEG, and it read it from the disk every time.
• I took a 10 second clip from an AVI, saved it as a self-contained movie, and looped it. The first time through, it read from the disk. Every time after that it was from memory.
• I played the full AVI that 10 second clip came from, which was 50+MB, and it always read from the disk.

So it seems like the "cache" option does indeed work for local files, but only if they're small. I still can't get the "preload" option to work under any circumstances, though.
 
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