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Intensity Shuttle Diminishing Framerate

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Chad Pearson
Intensity Shuttle Diminishing Framerate
on Jul 30, 2010 at 8:57:59 pm

I am using an Intensity Shuttle on driver version 7.7.3 and am able to get it working with my 1080i 59.94 as well as 480i 29.97 sources in Media Express, Adobe FMLE, Microsoft Expression Encoder and even VirtualDub.

However, when not using Media Express (ie. FMLE, VirtualDub, aka the DirectShow driver) the frame rate starts out ok, but over time (~2-3 minutes) the video begins to lag behind, get choppy, and degrade the framerate from 29.97 to 25 to 20 all the way down to 5 fps.

This happens with both source types even when not encoding, just idling the application with the preview screen up.

If I click the Device settings button in any of the applications (to bring up the Blackmagic Video Format and Timcode dialog box), and click ok, the preview screen resets and the video and framerate goes back to normal for another 2-3 minutes and then degrades again.

Is this a problem with the Blackmagic DirectShow driver, or something else?


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Joshua Helling
Re: Intensity Shuttle Diminishing Framerate
on Aug 4, 2010 at 10:18:24 pm

Hi,

So what are you trying to capture to (codec wise) while using the DirectShow interface? Obviously Media Express is only going to support the formats that we control and know will capture properly in real time. But if you are using a different compression type the additional CPU overhead may be causing the capture to drift off.

Is it possible for you to capture with our codecs using these other utilities (they should be exposed) and let us know if those captures work fine or if they drift off too.

Sincerely,

Joshua
Director of Support
Blackmagic Design Inc.


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Chad Pearson
Re: Intensity Shuttle Diminishing Framerate
on Aug 31, 2010 at 12:53:35 am

I potentially have more information which may be of help.

Background: The Adobe Flash Media Live Encoder software (like many video capture applications) has 2 video preview windows so you can see the effect of whatever settings you apply alongside the original input stream.

While capturing (in my case to H.264) if you disable the "Input Video" preview window (the original stream) and just leave the "Output Video" (ie. compressed/resized stream) there is no sync or framerate issue even after 30 minutes. If you enable the "Input Video" window (whether by itself, or alongside the "Output" window) the video gets out of sync and the framerate starts to drop after only a minute or so.

However, while NOT capturing, the "Input Video" and "Output Video" are essentially one and the same (probably pulled from the same DirectShow buffer). So while NOT capturing having either the Input, Output (or BOTH) showing causes the sync/framerate issue.


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