[PATCH v3 3/9] DocBook/v4l: Add compressed video formats used on MT8173 codec driver

[tiffany lin]

Hi Nicolas,

On Tue, 2016-07-12 at 15:14 -0400, Nicolas Dufresne wrote:
> Le mardi 12 juillet 2016 à 15:08 -0400, Nicolas Dufresne a écrit :
> > Le mardi 12 juillet 2016 à 16:16 +0800, Wu-Cheng Li (李務誠) a écrit :
> > > Decoder hardware produces MT21 (compressed). Image processor can
> > > convert it to a format that can be input of display driver.
> > > Tiffany.
> > > When do you plan to upstream image processor (mtk-mdp)?
> > > > 
> > > > It can be as input format for encoder, MDP and display drivers in
> > > our
> > > > platform.
> > > I remember display driver can only accept uncompressed MT21. Right?
> > > Basically V4L2_PIX_FMT_MT21 is compressed and is like an opaque
> > > format. It's not usable until it's decompressed and converted by
> > > image
> > > processor.
> > 
> > Previously it was described as MediaTek block mode, and now as a
> > MediaTek compressed format. It makes me think you have no idea what
> > this pixel format really is. Is that right ?
> > 
> > The main reason why I keep asking, is that we often find similarities
> > between what vendor like to call their proprietary formats. Doing the
> > proper research helps not creating a mess like in Android where you
> > have a lot of formats that all point to the same format. I believe
> > there was the same concern when Samsung wanted to introduce their Z-
> > flip-Z NV12 tile format. In the end they simply provided sufficient
> > documentation so we could document it and implement software
> > converters
> > for test and validation purpose.
> 
> Here's the kind of information we want in the documentation.
> 
> https://chromium.googlesource.com/chromium/src/media/+/master/base/vide
> o_types.h#40
> 
>   // MediaTek proprietary format. MT21 is similar to NV21 except the memory
>   // layout and pixel layout (swizzles). 12bpp with Y plane followed by a 2x2
>   // interleaved VU plane. Each image contains two buffers -- Y plane and VU
>   // plane. Two planes can be non-contiguous in memory. The starting addresses
>   // of Y plane and VU plane are 4KB alignment.
>   // Suppose image dimension is (width, height). For both Y plane and VU plane:
>   // Row pitch = ((width+15)/16) * 16.
>   // Plane size = Row pitch * (((height+31)/32)*32)
> 
> Now obviously this is incomplete, as the swizzling need to be documented of course.
> 
Because it's finally a compressed format from our codec hw, we cannot
describe its swizzling.

best regards,
Tiffany

> > 
> > regards,
> > Nicolas