Re: [PATCH v2 1/2] media: uapi: Add VP8 stateless decoder API

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 04 Jul 2019 10:00:33 -0300
Ezequiel Garcia <ezequiel@collabora.com> wrote:


> 
> Oops, this is just an internal note, it seems I forgot to remove this one.
> 
> > I am right to think that this is basically the size in bits of the
> > frame header ? Maybe it could be another way to formulate it ? I'm just
> > trying to think of formulation that will better guide the developers
> > implementing the parser feeding this. You basically need to parse the
> > header to get this size (as everything is dynamically sized).
> >   
> 
> Depending what you call "frame header", then yes, it's the size in bits.
> 
>                              first_part_size          parttion_sizes[0]
>                                 ^                     ^
>                                 |                     |
>                        +--------+------+        +-----+-----+
>                        | control part  |        |           |
>    +--------+----------------+------------------+-----------+-----+-----------+
>    | tag 3B | extra 7B | hdr | mb_data | dct sz | dct part0 | ... | dct partn |
>    +--------+-----------------------------------+-----------+-----+-----------+
> 
> The above shows a VP8 frame, "macroblock_bit_offset" is the size in bits of
> the "hdr" portion: i.e. the header of the first partition (aka control partition).
> 
> Thinking about it, the current description is quite confusing.
> 
> How about:
> 
> "Size in bits of the frame header. In other words, this the size in bits of the header
> portion of the first partition".

How about having a similar diagram somewhere in the spec? It's usually
much clearer than a sentence, at least that's my opinion.