Hi all,
Sorry for the slightly off-topic question, as it does not fully relate
to V4L.
Lately I have been experiencing undesired effects when capturing from 3
bt878-based capture boards at the same time. Several horizontal lines
across the image appear randomly. I am afraid it might be due to
conflicts accessing the PCI bus (3 cards are capturing 640x240 YUV4:2:0,
and images from one of them is being transmitted MPEG compressed),
leading to bt878 fifo overruns. These are relevant facts:
- I set-up the driver to capture FBUS (bit 12 INT_MASK) interrups
supposed to be raised when FIFO overruns due to high PCI bus latencies,
and noticed the following:
+ The number of FBUS ints. when the three capture cards are streaming
and images are transmitted (PCI ethernet card, see HW list below) is
about 1500-2000 per sec.
+ In cases when just one card was plugged into the bus, still some of
these ints came up (about 5-10 per sec.).
I guess this all may be due to PCI configuration latencies or maybe to
lack of mother board optimisation settings (or just the board is just
not good enough for this PCI load), but I have no experience on the
subject and I thought someone on the list could drop any help (which I
would really appreciate!).
This is a list of the HW I am using. I am also sending as an attachment
several other relevant information.
- Microstar MS6368 mother board (see attached "cat /proc/pci").
- On-board RealTek RTL-8139 PCI Ethernet card.
- Three custom bt878-based video capture board (using bttv2 V4L2
driver).
I am really wondering how it is possible to have the FBUS int. raised
even when just one card is plugged to the PCI bus. Maybe this is a
normal fact I am not aware of. Does anyone have an explanation?
Also, and more important, I wonder whether there exist a means to get
rid of those nasty stripes across the images. BTW, they also appear on
recorded MPEG video streams, not just when transimtted, which is the
first cause we thought of.
That's all. As I said, I will appreciate any feedback on the subject. I
surely am happy to share my experiences with any of you who is may be
interested. Sorry for the length of the mail!
Thanks in avance for the time and help,
Best regards,
Miguel
PCI devices found:
Bus 0, device 0, function 0:
Host bridge: VIA Technologies, Inc. VT8601 [Apollo ProMedia] (rev 5).
Master Capable. Latency=32.
Prefetchable 32 bit memory at 0xd0000000 [0xd3ffffff].
Bus 0, device 1, function 0:
PCI bridge: VIA Technologies, Inc. VT8601 [Apollo ProMedia AGP] (rev 0).
Master Capable. No bursts. Min Gnt=12.
Bus 0, device 7, function 0:
ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South] (rev 64).
Bus 0, device 7, function 1:
IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 6).
Master Capable. Latency=32.
I/O at 0xe000 [0xe00f].
Bus 0, device 7, function 4:
Class 0080: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 64).
Bus 0, device 8, function 0:
Multimedia video controller: Brooktree Corporation Bt878 (rev 17).
IRQ 10.
Master Capable. Latency=32. Min Gnt=16.Max Lat=40.
Prefetchable 32 bit memory at 0xd8006000 [0xd8006fff].
Bus 0, device 9, function 0:
Multimedia video controller: Brooktree Corporation Bt878 (#2) (rev 17).
IRQ 5.
Master Capable. Latency=32. Min Gnt=16.Max Lat=40.
Prefetchable 32 bit memory at 0xd8001000 [0xd8001fff].
Bus 0, device 10, function 0:
Multimedia video controller: Brooktree Corporation Bt878 (#3) (rev 17).
IRQ 7.
Master Capable. Latency=32. Min Gnt=16.Max Lat=40.
Prefetchable 32 bit memory at 0xd8003000 [0xd8003fff].
Bus 0, device 8, function 1:
Multimedia controller: Brooktree Corporation Bt878 (rev 17).
IRQ 10.
Master Capable. Latency=32. Min Gnt=4.Max Lat=255.
Prefetchable 32 bit memory at 0xd8000000 [0xd8000fff].
Bus 0, device 9, function 1:
Multimedia controller: Brooktree Corporation Bt878 (#2) (rev 17).
IRQ 5.
Master Capable. Latency=32. Min Gnt=4.Max Lat=255.
Prefetchable 32 bit memory at 0xd8002000 [0xd8002fff].
Bus 0, device 10, function 1:
Multimedia controller: Brooktree Corporation Bt878 (#3) (rev 17).
IRQ 7.
Master Capable. Latency=32. Min Gnt=4.Max Lat=255.
Prefetchable 32 bit memory at 0xd8004000 [0xd8004fff].
Bus 0, device 14, function 0:
Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139 (rev 16).
IRQ 11.
Master Capable. Latency=2. Min Gnt=32.Max Lat=64.
I/O at 0xec00 [0xecff].
Non-prefetchable 32 bit memory at 0xd8005000 [0xd80050ff].
Bus 1, device 0, function 0:
VGA compatible controller: Trident Microsystems CyberBlade/i1 (rev 106).
IRQ 10.
Master Capable. Latency=32.
Non-prefetchable 32 bit memory at 0xd5800000 [0xd5ffffff].
Non-prefetchable 32 bit memory at 0xd6000000 [0xd601ffff].
Non-prefetchable 32 bit memory at 0xd5000000 [0xd57fffff].
CPU0
0: 7402334 XT-PIC timer
1: 3956 XT-PIC keyboard
2: 0 XT-PIC cascade
5: 128880 XT-PIC alvista
7: 66433 XT-PIC alvista
8: 1 XT-PIC rtc
10: 132394 XT-PIC alvista
11: 213790 XT-PIC eth0
12: 474 XT-PIC PS/2 Mouse
14: 63087 XT-PIC ide0
NMI: 0
ERR: 0
