Re: Re: [libdc1394-devel] Bytes per Packet Questions

[Korkut G. <kor...@gm...>]

Hi,

Thanks for your explanation, i tried what you told immediately. Well,
it didnt helped at 640*480 with bytes per packet at 4096, i am still
getting 50 ~ fps with minimal shutter rate.

However, whenever i reduce packet size to 3892 it jumps back to nice
old 101 fps. When i query the camera, it returns me with suggested
rate of 4092 bytes per packet. If i use that number, fps drops back
again.

More than finding a problem in libdc, i am trying to find out, what I
AM doing wrong ?

May video1394 any other 1394 drivers causing this ? 

Today's Topics:

  1. Re: Bytes per Packet Questions (Wayne Dawe)

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Message: 1
Subject: Re: [libdc1394-devel] Bytes per Packet Questions
From: Wayne Dawe <wa...@in...>
To: lib...@li...
Organization: Interactive Sports Technologies
Date: Tue, 05 Apr 2005 09:27:36 -0400

To achieve maximum framerate your image size needs to be divisible by
your packet size with no remainder otherwise the last packet will be
padded with null data when transmitting an image. This means that for
maximum throughput you need to change the packet size when you change
the image size. 4096 is optimum for 640 by 480 but is not optimum for
656 by 491. My guess would be that the windows driver is calculating the
optimum packet size for you and ignoring what you try to set.