[FFmpeg-devel] [PATCH] hwcontext_opencl: choose the first device if multiple devices are available

[Xiang, Haihao]

On Di, 2024-01-23 at 02:52 +0000, Xiang, Haihao wrote:
> On Ma, 2024-01-22 at 20:32 +0000, Mark Thompson wrote:
> > On 17/01/2024 07:36, Xiang, Haihao wrote:
> > > From: Haihao Xiang <haihao.xiang at intel.com>
> > > 
> > > This makes '-init_hw_device opencl' work in a multiple-device system.
> > 
> > Under what circumstances is this more useful than the existing behaviour
> > which
> > prompts the user to select the device they intend?
> 
> @item -init_hw_device
> @var{type}[=@var{name}][:@var{device}[, at var{key=value}...]]
> 
> My understanding is that only @var{type} is mandatory, @var{device} (and
> others)
> is optional, indeed '-init_hw_device opencl' works well in a single-device
> system, however the same command doesn't work in a multiple-device system. It
> is
> not a good experience for me. 
> 
> > 
> > There is no particular ordering to devices, the first one is just random. 
> > Having your process fail with an opaque message (because the device picked
> > lacks some operation) or run many times slower than expected (because the
> > smallest device happened to be first in the list) or do something different
> > on
> > a machine which looks the same (because it has an extra driver for something
> > else) rather than just saying up front that there are multiple devices and
> > the
> > user needs to pick seems worse to me, since it is much harder to see where
> > the
> > problem is.
> 
> I understand your concern, how about making the default works while prompting
> a
> warning about the device selection ? 

Hi Mark, 

Do you have more comments ? 

Thanks
Haihao