i.MX8M nano ISI output buffer line pitch

[OTan]

Hi NXP,

Our customer  use ISI convert YUV422 to YUV420P，as the limit of the output buffer line pitch in theCHNL_OUT_BUF_PITCH[LINE_PITCH] register as below:

The line pitch is same for all image componentsirrespective of they being stored in 1-planar, 2-planar,or 3-planar. In 2 and 3-planar output, the U and Vcomponent will have the same line pitch as the Ycomponent.

As the limit, it seems like it need to add more 0x0 on 2 and 3-planar output( U and Vcomponent) to keep the color normal, but it will waste more buffer space, and if continue to encode YUV420P  to JPG, it will spend more time. 

Why have this limit?  are there any way to solve this problem? thanks a lot

[igorpadykov]

Hi Olivia

line buffer limit is described in sect.13.4.1.4 Design Overview

i.MX 8M Nano Applications Processor Reference Manual

Each processing channel has one line buffer associated with it. Each line buffer can store up to
2048 pixels with 8-bits per color component. For processing higher resolution images
(like 4K), line buffer from other channels can be combined to provide more storage.
However, in this case, the channels from which line buffers are borrowed will remain

disabled and cannot function. There is a restriction on software that buffers from adjacent
channels can only be concatenated. This means channel 1 line buffer can be connected to
channel 2 line buffer and no other channel.

Best regards
igor