[PD-dev] pbo transfert WAS: GEM passing output image later.

[Cyrille Henry]

oh, i thought the pbo message was to use a specific pbo Id.
since it's how many PBO to use, on a specific pix_texture or pix_snap, then my question was irrelevant.
ok for the ring buffer:
possible latency vs possible performance gain, and computer specific tuning.

i'll try that as soon as i can.

thx
c




Le 29/02/2012 12:18, IOhannes m zmoelnig a écrit :
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> On 2012-02-29 10:52, Cyrille Henry wrote:
>>
>>
>> Le 29/02/2012 09:34, IOhannes m zmoelnig a écrit :
>>
>>> and both [pix_texture] and [pix_snap] allow for asynchronous
>>> DMA-transfers already (though i only added PBO-tarnsfers to [pix_snap] a
>>> week ago or so).
>>> it's not really documented anywhere (yet), but you can send a [pbo $1(
>>> message to both these objects to specify the number of PBOs to use (with
>>> "0" being the default behaviour)
>>
>> Do you mean that since last week pix_snap should be lot's faster than it
>> use to be?
>
> the default behaviour is still the same (pbo==0)
> this is mainly because i found that the optimal setting varies greatly
> from machine to machine.
> e.g. on my netbook with fglrx drivers, the old non-pbo method is somehow
> faster...
> on my desktop (with some old nvidia card), using PBOs is faster.
>
>> i'd like to understand a bit more the use of single  / multiple PBO :
>> what happens if 2 pix_video / pix_texture use the same PBO : will it be
>> slower than using 2 different PBO? (since 2nd pix_texture have to wait
>> for the PBO to be free in order to use it)???
>
> each  [pix_texture] will use their own set of PBOs.
>
> when using more PBOs, you basically get a ring-buffer: while the current
> image is uploaded using PBO(n), PBO(n-1) is displayed, so the upload has
> one frametick to complete.
> it also means, you get a delay when using>1 PBOs.
>
> i haven't done any benchmarking with multiple image-sources (though the
> PBO support for [pix_texture] was implemented in order to get reasonable
> speed when displaying multiple hires videos for an installation)
>
>> same question with a pix_video / pix_texture and a pix_snap : is using 2
>> PBO lot's faster than using the same PBO (default behaviour)?
>
> just try it :-)
>
> fgmasdr
> IOhannes
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