[GEM-dev] Video Codecs Seek performance... *sigh*

Etienne Desautels titi at sat.qc.ca
Sun Nov 6 20:34:53 CET 2005

Hi Patrick,

On 05-11-06, at 08:17, patrick wrote:

> chris clepper wrote:
>> On 11/5/05, patrick <puredata at 11h11.com> wrote:
>>> hi,
>>> i was wondering about mac os X ? what is the best codec for mixing 
>>> (blending, seeking) videos? quicktime for sure, but what codec and 
>>> size: 720x480 DV or 640x480 with a codec like mpeg4, photojpeg? it's 
>>> a g4 laptop, with 512 ram.... 50 videos, 2 seconds each.
>> I get at least 3 NTSC DV clips playing 30 fps at once on a 1 Ghz G4
>> laptop using the internal drive.  A fourth might be possible using a
>> Firewire drive.  I hope you aren't trying to play all 50 at once
>> though.
>> Photo-JPEG is less efficient but has the advantage of working at any
>> resolution (it also has a lower data rate at the same size as DV). 
>> Motion-JPEG is the same as Photo-JPEG, but uses two interlaced fields
>> per frame.
>> I highly recommend avoiding anything with MPEG in the name if
>> performance and image resolution are required.
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> hi chris,
> no no. i'm not trying to play 50 clips at the same time. but, i would 
> like to be able to load a clip without visual glitch or freeze. is 
> this possible?
> also, i'm wondering about the correct size of a clip if i know the 
> projection will be @ 800x600. should i crop my dv (720x480) to 640x480 
> to keep the ratio size. if yes, i will be forced to use a codec like 
> photo jpeg right?

No you should not crop your DV. DV are 720x480 because they have 
non-square pixels. Their size ratio is still 4:3. DV is the best choice 
but you can only get full resolution (720x480). If you need other 
resolutions, use mjpeg or photo-jpeg. And it's quicker to load one big 
file that contain all your 50 files and just seek in it, if your setup 
permit this. Unfortunately it's not easy in PD-Gem to seek in quictime 
file and have a smooth playback because to have a smooth playback you 
need to use "auto" and when you use "auto" the seeking function doesn't 
work very well, at least in the version I was using (Gem 0.9 I think).

Good luck


> pat
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