topic VPU and sub-frame synchronisation in i.MX Processors

VPU and sub-frame synchronisation

stéphanemancini — Fri, 18 Nov 2016 09:48:42 GMT

Hi,

I'd like to know if the sub-frame synchronisation is enabled in the IMX6QPlus family.

In particular, the IMX6QPlus reference manual says yes BUT the IMX Linux API says no !!

Do you if sub-frame sync is enabled ?

Also, is there some info about the en-to-end latency for video transmission

between two IMX, with wifi dongles (over USB ?)

Best regards

Re: VPU and sub-frame synchronisation

igorpadykov — Mon, 21 Nov 2016 05:46:42 GMT

Hi Stéphane

linux may implement less functionality than hardware has, please use

attached Linux Manual describing drivers implemented in NXP BSPs.

Typical latency is about 3 frame and depends on video, also one can check

https://community.freescale.com/thread/323418

Best regards
igor
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Re: VPU and sub-frame synchronisation

stéphanemancini — Mon, 21 Nov 2016 10:52:26 GMT

Dear Igor,

I read this file and also

IMX6DQPRM.pdf

i.MX_VPU_Application_Programming_Interface_Linux_Reference_Manual.pdf

Please, do you know if SUB-FRAME sync is enabled in the Linux driver ?

Is there a way to use this hardware feature ?

It should theoretically reduce the end-to-end latency by 2 frames (one at compression one at de-compression).

How is it possible to use it ?

Also, i.MX6 Video Latency reports a end-to-end latency of 59ms thanks to the appropriate driver.

Unfortunately the frame rate and resolution informations are missing.

The thread you provide is about imx53 and the reported delay is 200 to 300 ms (nothing relates).

Also, some guys https://community.nxp.com/message/498952 reports 'zero delay' thanks to intra refresh frames but they do not provide numbers.

Does NXP has a benchmark reference ?

Best regards

Stéphane

Re: VPU and sub-frame synchronisation

igorpadykov — Tue, 22 Nov 2016 01:05:53 GMT

Hi Stéphane

seems there is some misunderstanding regarding "sub-frame sync" - it is done

on system level, that is linux or software does not affect it, as it is always enabled.

From RM:

also please check attached Linux Manual Chapter 18
Video Processing Unit (VPU) Driver describing linux vpu driver.

I am not aware of any vpu latency "benchmark reference".

Best regards
igor