[FFmpeg-devel] [PATCH 5/5] amfenc: Remove spurious initialisations

[Alexander Kravchenko]

> -----Original Message-----
> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf Of Rostislav Pehlivanov
> Sent: Tuesday, April 24, 2018 4:04 PM
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 5/5] amfenc: Remove spurious initialisations
> 
> On 24 April 2018 at 12:29, Alexander Kravchenko <akravchenko188 at gmail.com>
> wrote:
> 
> >
> >
> > > -----Original Message-----
> > > From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> > > Behalf
> > Of Mark Thompson
> > > Sent: Sunday, April 22, 2018 6:37 PM
> > > To: ffmpeg-devel at ffmpeg.org
> > > Subject: Re: [FFmpeg-devel] [PATCH 5/5] amfenc: Remove spurious
> > initialisations
> > >
> > > On 15/04/18 20:45, Alexander Kravchenko wrote:
> > > >> -----Original Message-----
> > > >> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> > > >> Behalf Of Mark Thompson
> > > >> Sent: Sunday, April 15, 2018 7:31 PM
> > > >> To: ffmpeg-devel at ffmpeg.org
> > > >> Subject: Re: [FFmpeg-devel] [PATCH 5/5] amfenc: Remove spurious
> > > >> initialisations
> > > >>
> > > >>
> > > >>> I am waiting patches to be applied to propose new patch with
> > hwcontext_amf in libavutil.
> > > >>
> > > >> Can you explain what you're intending to use that for?  It's not
> > > >> clear to me how an extra wrapper around the D3D(9|11) surfaces is
> > > >> going to help, given that the support for them with AMF is
> > > >> already pretty good.  (Compare the Intel libmfx stuff (the
> > > >> misleadingly- named "qsv") where the extra wrapping does help for
> > > >> some cases because the underlying library has weird constraints,
> > > >> but overall adds a lot of complexity (and failure modes) for
> > > >> rather unclear benefit.  It's also inconvenient in that it
> > > >> promotes the existence of antifeatures like the "_qsv" decoders
> > > >> which are inferior to the builtin hwaccels in pretty much every
> > > >> respect.)
> > > >>
> > > >
> > > > Hi Mark,
> > > > I am intending to create amf common helpers(tools) in libavutil.
> > > > They will be used in amfenc and vf_scaleamf. (vf_scaleamf is
> > > > hw-accelerated color-space converter and scaler)
> > > >
> > > > amf helpers should provide:
> > > > * amf_library: functions to load/unload amf dll based on reference
> > > > count mechanism
> > > > * amf_context: functions to create AMFContext derived from DXVA2,
> > > > D3D11, opencl and Vulcan in future
> > > > * av_frame <-> AMFSurface map functions (move from amfenc.c)
> > > >
> > > > amfav_context can be implemented like hwdevice_ctx
> > > > (AVAMFDeviceContext) and can be managed by
> > > > av_hwdevice_ctx_create_derived (in case of incoming hw frames) and
> > > > av_hwdevice_ctx_create or it can be implemented not using of
> > > > av_hwdevice_ctx* mechanism
> > > >
> > > > I think don’t need AVAMFFrameContext, and amf components will
> > > > send/receive hwframes based on existing framecontexts
> > > > (dxva/opencl...)
> > > >
> > > > Could you recommend the best way how to do this fit in current
> > architecture?
> > >
> > > I agree that using a hwdevice context here makes sense, since it
> > > wraps
> > all of the right properties (in particular, derivation from other
> > > devices).
> > >
> > > It's less clear to me what to do with the frames.  A hwframes
> > > context
> > could work just for derivation because you don't actually need to
> > > implement the allocation stuff (the existing DRM hwcontext does
> > > this,
> > since it's only for interop).  What other approach would you
> > > think of taking?  Adding special external API to use internally
> > > between
> > libraries is not nice and we try to avoid it quite strongly.
> > >
> >
> > Hi Mark,
> > I agree it is good to stay within current API (hwdevice and hwframes),
> > but I am not sure it is always possible.
> >
> > is it ok create hwcontext_amf_internal.h which can be placeholder for
> > the API like the following, or probably some helper functions can be
> > published as pointers in AVAMFDeviceContext structure:
> > amf_set_property_buffer
> > amf_get_property_buffer
> > amf_create_buffer_with_frame_ref
> > amf_release_buffer_with_frame_ref
> >
> 
> No, I think there should be no avpriv functions for hwcontexts, nor any public API changes. Better duplicate that code in lavfi.

Ok, if avutil is not proper place to put shared code between libavcodec and libavfilter, may be there should be another place?
Duplicating code will increase cost of maintenance, which is not good. 
Probably there should be some other place to put shared code?
May be shared code can be just set of static functions and macroses are put in headers?

Thanks,
Alexander