[Elphel-support] datarate issue - HDD recording, while streaming.

[Oleg K Dzhimiev]

Nathan,

I was able to reduce the PHP's cpu usage and could run recording
1920x1088 at 25fps, quality 93, with streamer working, single frame size
~300K-~400K,
streamer ~60% cpu, camogm ~30% cpu (same w/o streamer).

The problem is that the php calls (status requests) are "too frequent" so
that they eat ~30%. I used my own interface (originally for our panorama
camera) for recording where the status calls interval can be programmed.
So that interval was 5 sec - can be more frequent, 2 sec worked also.

It could be a solution if Sebastian implements it in his GUI.

Regards,
Oleg

On 11 October 2011 22:24, Nathan Clark <nathan at nathanclark.com.au> wrote:

> Forwarding a short discussion regarding datarate limitations recording to
> HDD while running streamer simultaneously. Continuing discussion here so
> that others may benefit.
>
> *Problem: *
> Cannot record to HDD with high datarates when streamer is running.
>
> *Cause:*
> Streamer running with high datarate results in high CPU usage causing
> bottleneck.
>
> *Fix:*
> • Reduce CPU requirements of webserver
> • Reduce CPU requirements of streamer
>
> *Is it possible to have the streamer skip every n frames?*
> This would potentially halve the datarate (if skipping every 2nd frame) and
> as such significantly lower the cpu requirement.
> The reduced temporal resolution of the stream would still be okay for
> viewing in many circumstances.
>
> Oleg,
>
> • I get a similar cpu% usage for php instances.
> • I do need the use of the streamer, while recording to SSD over sata.
>
> Cheers,
>
> Nathan
>
> ---------- Forwarded message ----------
> From: Oleg K Dzhimiev
>
> Also, can we move the discussion to our mailing list.
> Thanks
>
> On 11 October 2011 12:41, Oleg K Dzhimiev wrote:
>
>> Nathan,
>>
>> What's the CPU usage for php while recording? I got ~(24+27)% from two php
>> instances. That might be causing the problem - too many php calls from the
>> GUI.
>>
>> In your application do you use the streamer while recording?
>>
>> Best regards,
>> Oleg
>>
>>
>> On 11 October 2011 05:55, Nathan Clark wrote:
>>
>>> As Sebastian advised, I tested the CPU with streamer enabled...
>>> We have a problem!
>>>
>>> CPU usage for streamer is up at 67%
>>> (at 1920x1088, rgb, 25fps, quality 90 - data rate 6.9MB/s)
>>>
>>> The CPU usage directly correlates with data rate, reducing quality to 20
>>> (0.86MB/s) results in streamer CPU usage between 3-9%
>>>
>>> It looks like the streamer is causing this recording issue by
>>> bottlenecking the CPU and thus causing the buffer to overrun...
>>>
>>> But how to circumvent this issue?
>>>
>>>
>>> On 11/10/2011, at 21:23, Sebastian Pichelhofer wrote:
>>>
>>> > Hi Oleg, I suggested we continue this discussion via email.
>>> >
>>> > Below is Nathans original PM to me:
>>> >
>>> >
>>> >
>>> > Hey Sebastian,
>>> >
>>> > As time escapes me, its getting closer and closer to Winnie shooting
>>> > her experimental film for her stereoscopic PHD research...
>>> > I am not ready :|
>>> >
>>> > With problems with my lenses and this sata datarate pain, it's
>>> > becoming quite scary :shock:
>>> >
>>> > But there is always times of stress with all projects! And ultimately,
>>> > I just remind myself how amazing what we have created really is! :D
>>> >
>>> > ----------------
>>> >
>>> > Did you have time to verify the external HDD recording datarate limits
>>> > we talked about some time ago?
>>> >
>>> > Regards Sebastian
>>>
>>>
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