OMAP4430 (Pandaboard) video scaling and DSS writeback

Karol Sobczak

Hi,

I am trying to write an application that would perform some custom image processing on OMAP4430 (Pandaboard). Basically, I need video to be decoded, downscaled (e.g to 32x32), converted to RGB888 color space and then feed to my application. Using public TI Linux repositories I managed to decode video using gstreamer ducati acceleration. However, ducati seems not to support scaling. Therefore, I decided that I will look at DSS writeback in order to get downscaled, RGB888 video frames. Is it the best approach? Should I try NEON instruction for scaling and color space conversion (would they be fast enough)?

I tried to find useful source with DSS writeback examples, but there doesn't seem to be any (apart from outdated http://omappedia.org/wiki/Write_Back_pipeline_usage_guide). Could you point me to some DSS writeback examples with the 3.4.0 linux kernel?

Thanks,

Karol

over 12 years ago

0 Mayank Mangla over 12 years ago

TI__Mastermind 24525 points

You can refer to Android release (http://omappedia.org/wiki/4AJ.2.5_OMAP4_Jelly_Bean_Release_Notes ). WiFi Display in Android uses writeback pipeline.

0 Karol Sobczak over 12 years ago in reply to Mayank Mangla

Prodigy 30 points

Hi,

I have downloaded this Android release as you have pointed out. However, I am not sure which code is responsible for DSS writeback management (is it mydroid/frameworks/av/media/libstagefright/wifi-display?). Which component actually implements writeback? Does WIFI Display use v4l2 for writeback or is it some other mechanism? Does Android use the same DSS drivers as Ubuntu?

Karol

0 Mayank Mangla over 12 years ago in reply to Karol Sobczak

TI__Mastermind 24525 points

media/libstagefright/wifi-display is the user space code. Driver is in kernel space - drivers/video/omap2/dss/wb.c

0 Karol Sobczak over 12 years ago in reply to Mayank Mangla

Prodigy 30 points

Thanks. From what I see, the Android kernel uses some newer (customized?) omap2 video drivers, which are absent in TI kernel branch. Are there any plans to port those drivers from Android kernel to normal kernel?

Kind regards,

Karol

0 Mayank Mangla over 12 years ago in reply to Karol Sobczak

TI__Mastermind 24525 points

As far as I know, those changes were made to align with Android WiFi Display architecture and there is no plan to port them to generic Linux kernel.

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OMAP4430 (Pandaboard) video scaling and DSS writeback