Re: Core Video CIFilters/ playback / compression suggestions?
Re: Core Video CIFilters/ playback / compression suggestions?
- Subject: Re: Core Video CIFilters/ playback / compression suggestions?
- From: douglas welton <email@hidden>
- Date: Fri, 15 Jan 2010 14:55:00 -0500
Travis,
I suspect that your issue might be related to compression. To achieve a smaller size takes time. Decompressing a video frame can take longer than you have to display it. Try compressing your video with the Animation codec as opposed to the H.264 codec. File size will balloon, but decompression time will go down and perhaps facilitate your playback.
If you want to know more about which video compression to use, I would suggest that you take this discussion to either the QT-dev or QT-users list. Those folks are the subject experts.
later,
douglas
On Jan 15, 2010, at 12:29 PM, Travis Kirton wrote:
> Hey Jean-Daniel,
>
> Thanks for the advice. We've already noticed that the main object that's taking up the most CPU seems to be whichever decoder we're using (jpegdecompress... etc). I haven't looked into it thoroughly enough yet, but hope that using GCD to distribute blocks of code across the 8 cores we're running.
>
> I'm not really versed enough to know whether one codec is better than another for what we're doing, even though it seems that using movies compressed with Apple Video is lighter on the CPU than even H.264...
>
> T
>
> On 2010-01-15, at 12:47 AM, Jean-Daniel Dupas wrote:
>
>>
>> Le 14 janv. 2010 à 20:11, Travis Kirton a écrit :
>>
>>> Hi,
>>>
>>> We're working with Core Video to play back videos @ 1024 x 768 resolution.
>>> The videos are stacked on top of one another and revealed as a user draws over top of them. To achieve this "drawing into" the stack of videos, we're filtering using CIImage to create alpha masks over top of an individual video.
>>>
>>> Playback is very choppy, and we haven't been able to determine if it's the compression we're using (i.e. the video assets themselves) or anything to do with the combination of Core Video, Core Image & the 1024x768 format.
>>>
>>> Some problems we're facing is that even if we're only using 2 videos and not doing any filtering, the videos lag.
>>>
>>> We initially we compressed our original files out, so that the overall file size is much smaller. Even still, with 2 movies @ approx. 50MB each we're having problems.
>>>
>>> Using TOP, from terminal, to overall system usage we're getting results that the system is chewing up to 180% cpu.
>>>
>>> We'd be really greatful for any help on whether this is an asset, a code, or a compression issue (or all three).
>>>
>>> Cheers,
>>
>> Ask Instruments, it is the only one able to tell you what's going on.
>> The simplest way to do this is to use the Xcode Menu Run > Run with Performance Tool > Time Profiler.
>>
>>
>> -- Jean-Daniel
>>
>>
>>
>>
>
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