[Elphel-support] Recording fullHD JP4 being limited to 7 seconds

[flavio soares]

Hello, Andrey, thanks for the quick response!

I'm also online (here it is 3:40am) =)

My Kingston cards are not listed in the blacklist. Let's get them to
work and see how far they go. Here are the results of the tests, I'm
ssh-ed into the cam:

[root at Elphel353 /mnt/0]944# time dd if=/dev/circbuf of=/dev/null
38656+0 records in
38656+0 records out
real	0m 0.42s
user	0m 0.03s
sys	0m 0.39s
[root at Elphel353 /mnt/0]944# time dd if=/dev/circbuf of=/dev/hdb1
38656+0 records in
38656+0 records out
real	0m 6.75s
user	0m 0.19s
sys	0m 2.46s
[root at Elphel353 /mnt/0]944#

If I understood correctly, my card takes 6.75 seconds to write the
19MB and 19 MB / 6.75 = 2.8MB/s should be the maximum data rate my
cards can handle, is that it?

Meanwhile, I've tested normal HD JP4, at 720p and observed that
compression 100% is a killer, but at about 90%, the recording
proceeded without cutting the video, even tough the gui refresh rate
suffered.

ps.: I considered buying the Sundisk Extreme III, but I saw they were
not being sold at B&H at the moment. =/  If there is any other you
would recommend...

Thanks!

flavio

2012/4/26, Andrey Filippov <support-list at support.elphel.com>:
> Hello Flavio,
>
> Most likely the problem is related to the CF - as I wrote in that old
> article, most CF cards in IDE mode lie about support of the DMA mode. They
> do support UDMA so most people never notice that small lie. But Axis CPU
> used in the camera has a bug of it's own - and this bug is related to the
> UDMA. If the card would hostly report that it does not support DMA camera
> driver would just go to PIO mode (ABSOLUTELY NOT SUITABLE for the video
> recording - both slow and using to much of the camera CPU resources), but
> it does not, so camera may hang up and never come out of the boot scripts.
> So what we did was to add some known "bad" cards to the driver black list:
>
>
> http://elphel.cvs.sourceforge.net/viewvc/elphel/elphel353-8.0/os/linux-2.6-tag--devboard-R2_10-4/drivers/ide/ide-dma.c?view=markup(lines
> 130..136).
>
> At some point we black-listed all no-name cards (we did not find any among
> them that did support  DMA) You may use hdparm -I  (from
> http://192.168.0.9/phpshell.php, telnet or serial console that you should
> have cable for) and the only way to re-enable (if you card matches the
> black-listed one) the card is to modify that file and recompile the camera
> firmware. The only type of CF cards we use ourselves is "Sandisk Extreme
> III".
>
> When the card is blacklisted, camera bots correctly and is able to mount
> (and use) the card - it can be used to save images or very slow video
> (still useful for timelapse), but not the normal video.
>
> You may test the speed of the CF card (that test will destroy data on it!)
> with the following command (again - phpshell, telnet, serial console):
>
> time dd if=/dev/circbuf of=/dev/hda #(or hdb - depending how is the card
> inserted/configured)
>
> /dev/circbuf is the circular buffer ~19MB in size that is very fast to read
> for the camera, so the speed will be related to the CF itself
>
> You may try it on /dev/null first:
>
> [root at Goniometer /dev]16713# time dd if=/dev/circbuf of=/dev/null
> 38656+0 records in
> 38656+0 records out
> real    0m 0.43s
> user    0m 0.11s
> sys     0m 0.32s
>
> With phpshell you may just open the following link (provided you have the
> default IP) - just replace all spaces in the command line with "+" signs
> http://192.168.0.9/phpshell.php?command=time+dd+if=/dev/circbuf+of=/dev/null
>
> Then divide 19MB by the time measured.
>
> Andrey
>