[FFmpeg-devel] [PATCH]lavu/hwaccel_vaapi: Add a fixme for the missing byte_order check

[Carl Eugen Hoyos]

2016-10-05 16:39 GMT+02:00 Mark Thompson <sw at jkqxz.net>:
> On 05/10/16 13:06, Carl Eugen Hoyos wrote:
>>
>> I cannot test here but afaict, the current implementation of
>> vaapi_pix_fmt_from_fourcc() can't be correct.

>> +// FIXME: Take VAImageFormat->byte_order into account
>>  static struct {
>>      unsigned int fourcc;
>>      unsigned int rt_format;

> Have you found / had reported to you some case which
> causes a problem here?  If so, please could you offer some
> more detail about it (especially the driver being used).

No, I wouldn't even know how to use the code in question.

> In the cases I know of, the VAImageFormat structures are
> are all hard-coded such that the fourcc is really the only
> meaningful information in them:

So the byte_order field in VAImageFormat has no meaning
and is completely useless?

> <https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/state_trackers/va/image.c#n41>

This link was the reason for my mail.

> * <https://cgit.freedesktop.org/vaapi/intel-driver/tree/src/i965_drv_video.c#n246>

Not sure if this makes sense...

> This is reflected by the use in hwcontext_vaapi.c, which only
> fetches the driver's version of the structure in order to pass
> it back in vaCreateImage() calls - the other fields are never
> touched at all.

This sounds as if there is no mapping from VAImageFormat
to AVPixelFormat but I misunderstand this, no?

> So, I don't think this comment adds any value.

Do I understand correctly that one of the RGB formats
work correctly on your (little-endian) system (and looks
ugly if you replace it with anything else)?

Carl Eugen