[Libva] keep Nalu start code in VASliceDataBufferType data

[Xiang, Haihao]

On Tue, 2016-08-30 at 08:59 +0800, Randy Li wrote:
> Hi all:
>    When I just doing the driver for us chip, we would request the
> Nalu 
> header present in the data to be process. But I found the data be 
> Rendered to with type VASliceDataBufferType is removed the Nalu start
> code. Is there any way to make the client send the data without
> remove 
> the start code ? Thank you.

Do you mean the start code prefix 0x000001?  It depends on the codec,
VA-API has this requirement for HEVC, but no for AVC.

For AVC, I don't think the existing softwares using vaapi send the
prefix to driver, you have to workaround it in your driver. but if the
application is developed by yourself, you may send the prefix with
setting the right slice_data_offset, so other drivers can work well
with your application.

> 
> P.S Thank you for the Intel guys help, I decided not to use the DRM 
> framework to implement the interface in kernel after I talked to the 
> kernel upstream. But the request API would be used.