Mailing Lists: Apple Mailing Lists
 Image of Mac OS face in stamp
Re: loadmovieintoram?
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: loadmovieintoram?

Talking about QuickTime playback performance, I was considering delving deeper to gain more control over playback for the following issues :-

When playing uncompressed movies there is a pause whilst QuickTime prereads data.
I can call a preroll command with a suggested rate and then playback at that rate starts pretty instantaneously.

This is good, however in my app I cannot predict if the user is going to play forward or backwards.
So is there a way to preroll preread in both directions so that either way there is a quick response?
I tried calling Preroll twice with different rates, but the previous rate is lost.

Not only is the rate lost, but the pre-loaded media data from the first preroll is thrown away on the second.

Also can I get feedback that the preroll is complete?

If you are calling PrerollMovie yourself, it returns synchronously: the preroll is complete when it returns.

Whilst playing can I monitor the read ahead buffer to see if there is a potential under run?
I don't want to get skipped or repeated frames in the movie playback, so if under-run occurs then I want to abort playback.

There is no "potential" underrun until it actually happens. However, we are looking into providing a way to detect and report media underflow errors during playback.

-daniel


Thanks,
Adam Hall

On 19 Dec 2006, at 18:45, Daniel Steinberg wrote:

At 12:43 PM +0100 12/19/06, Guillem Palou wrote: 
is there any way to load a movie into ram asyncronously?
Or you have to create your own thread and call this function from there?

LoadMovieIntoRam, like any other movie API, must be called on the thread that the movie has been opened or migrated to.

However, why do you want to call LoadMovieIntoRam? Do you have any experimental results to show that this is improving your performance in any way? In a virtual memory environment, it is dangerous to preload movie data very far in advance, because you risk causing pageouts which are far more expensive. The QuickTIme playback engine manages media read-ahead and the virtual memory working set pretty rigorously, so in most cases it should be as good or better to preroll and play the movie than to preload it.

If you have a practical application in which preloading the media yields demonstrably better results, we'd like to hear about it. 

_______________________________________________
Do not post admin requests to the list. They will be ignored.
QuickTime-API mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden







References: 


 >loadmovieintoram? (From: "Guillem Palou" <email@hidden>)


 >Re: loadmovieintoram? (From: Daniel Steinberg <email@hidden>)


 >Re: loadmovieintoram? (From: email@hidden)























Visit the Apple Store online or at retail locations.

1-800-MY-APPLE


Contact Apple | Terms of Use | Privacy Policy


Copyright © 2011 Apple Inc. All rights reserved.