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

Thu Apr 26 00:12:51 PDT 2012

>
> Hello, Andrey, thanks for the quick response!
>
You are welcome , Flavio

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

Not that late he - less than 1AM :-)

>
> 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?
>

Yes, the cards are in PIO mode so seem to be disabled. And as I wrote - it
is not only that they are ~16/2.8 ~= 5.5 times slower than those in DMA
mode, they use CPU much more during recording, so no resources fro other
CPU tasks.

 Can you try them with hdparm -I and send the reply? The CPU-limited
recording rate in DMA mode should be ~16MB/s

>
> 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.
>

Yes that is so - 90% is really good quality. It may also make sense to
fine-tune coring value () in addition to JPEG quality to find the best
overall quality/image size ratio.
 With Eyesis we use 97-98%, but that is only because we use aberration
correction by de-convolution that amplifies the noise and artifacts. BTW -
here are our last panoramas made with the new camera (viewing requires good
videocard and WebGL-capable browser)
http://community.elphel.com/files/eyesis/pano-db-3/webgl_panorama_editor.html?kml=mainstreet_ro.kml&proto=mainstreet_ro.kml&ntxt=2&as_camera=95&start=result_1334548264_780764_1.jpeg&range=95&labels=false&keepzoom=false&closest2d=false&seethrough=0.4&transition=5&mask=&azimuth=23.2&elevation=-70.5&zoom=0.386&follow=false&mv3d=false

>
> 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...
>

I'll ask here tomorrow, but I think recently we only used that card
(different capacities)

Andrey

>
> 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
> >
>
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