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Opened 9 years ago

Last modified 9 years ago

#247 new defect

IPECamera adds 16 bytes before the header

Reported by: Suren A. Chilingaryan Owned by:
Priority: minor Milestone:
Component: UFO Camera Version:
Keywords: Cc: Matthias Balzer, Michele Caselle, Matthias Vogelgesang

Description

When starting the grabbing process, sometimes before first frame magic there are extra 16 bytes of padding. Just an example:

00000000 00 00 00 00 │ 00 00 00 00 │ 00 00 00 00 │ EF BE AD DE
00000010 11 11 11 51 │ 22 22 22 52 │ 33 33 33 53 │ 44 44 44 54
00000020 55 55 55 55 │ 40 04 00 50 │ D8 7E 00 55 │ 09 0B 90 50

This results that every so often the 32-byte header is split between 2 DMA packets. With ipecamera r267 I have implemented a workaround and it is of no consequences so far.

However, if we have to use GPUDirect/DirectGMA technologies, this will become an issue. GPU architecture is only optimal for processing of large volumes with static layout. All preprocessing steps to find where the packet actually begins, etc. will kill the performance.

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Change History (2)

comment:1 Changed 9 years ago by Suren A. Chilingaryan

Summary: IPECamera adds pads 16 bytes before the header → IPECamera adds 16 bytes before the header

comment:2 Changed 9 years ago by Suren A. Chilingaryan

It seems to be triggered by switching between manual and auto triggering modes. Using the following strategy it seems pretty persistent: 

reset.sh --all
grab.sh --stream
wait for a while
grab.sh --single

Switching stream and single produces the problem as well.

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