Block noise? when trying to send dv stream to video camera

[Alexander Nedotsukov]

Hidetoshi Shimokawa wrote:

>How log does the noise-less image last? a few seconds or shorter?
>
>  
>
>>square blocks and some parts of those blocks stay gray while
>>another contains correct image. Blocks are moving. The size of blocks
>>may vary. Time before video get corrupted as well from 0 to 50 sec. Do 
>>you have any idea what it can be and what is much better how to fix the 
>>situation?
>>I running one week old -CURRENT world+kernel.
>>
>>Thanks,
>>Alexander.
>>    
>>
>
>Every DV frame has a timestamp on the packet. The DV specification
>said that the timestamp must be synced with the bus cycle timer.
>Some DV equipments are very sensitive to it and if it's out of sync,
>we often observe block noises.
>
>Current iso transmit code start transmit at specific bus cycle to
>ensure that the timestamp must be synced at the start.
>The following packets have timestamps which are calculated under
>the assumption that a packet is sent for each bus cycle.
>If the assumption is broken for some reason(bus is busy to transmit
>a packer, the host is too slow to feed the packet and etc.),
>the timestamp will be out of sync.
>
>Do you use PAL or NTSC?
>  
>
Well now things become a little bit clear :-) Thanks for explanation.
I use NTSC and regilar 4:3 video format. The time I can see noise-less 
image vary. Some time it 40-50 sec before noise come and some time I see 
it right after start fwcontrol -S. After you explained me this timing 
issues I tried to start fwcontrol from system console (not from 
gnome-terminal window as I did before) and yahoo block noise gone. But 
there is still a problem. Now Video plays nicely about 5-10 mins and 
stops then. I can see (EAGAIN) errors reported by fwcontrol utility and 
this on the system console:
...
fwohci0: IT DMA underrun (0x3ab08011)
fwohci0: IT DMA underrun (0x3ab08011)
fwohci0: IT DMA underrun (0x3ab08011)
fwohci0: IT DMA underrun (0x3ab08011)
...
Few notes about system performance. I have PIII 1GHz machine here with 
UDMA66 disk. cpu is 100% idle all the time video transmitted to the camera.

All the best,
Alexander.