On 28/12/2021 19:04, Soft Works wrote:>> -----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Mark
Thompson
Sent: Tuesday, December 28, 2021 1:54 PM
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 3/3] libavutil/hwcontext_opencl: fix a bug
for mapping qsv frame to opencl
On 28/12/2021 01:17, Soft Works wrote:
-----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Mark
Thompson
Sent: Tuesday, December 28, 2021 12:46 AM
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 3/3] libavutil/hwcontext_opencl: fix a
bug
for mapping qsv frame to opencl
On 27/12/2021 20:31, Soft Works wrote:>> -----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Mark
Thompson
Sent: Monday, December 27, 2021 7:51 PM
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 3/3] libavutil/hwcontext_opencl: fix
a
bug
for mapping qsv frame to opencl
On 16/11/2021 08:16, Wenbin Chen wrote:
From: nyanmisaka <nst799610...@gmail.com>
mfxHDLPair was added to qsv, so modify qsv->opencl map function as
well.
Now the following commandline works:
ffmpeg -v verbose -init_hw_device vaapi=va:/dev/dri/renderD128 \
-init_hw_device qsv=qs@va -init_hw_device opencl=ocl@va -
filter_hw_device
ocl \
-hwaccel qsv -hwaccel_output_format qsv -hwaccel_device qs -c:v
h264_qsv
\
-i input.264 -vf
"hwmap=derive_device=opencl,format=opencl,avgblur_opencl,
\
hwmap=derive_device=qsv:reverse=1:extra_hw_frames=32,format=qsv" \
-c:v h264_qsv output.264
Signed-off-by: nyanmisaka <nst799610...@gmail.com>
Signed-off-by: Wenbin Chen <wenbin.c...@intel.com>
---
libavutil/hwcontext_opencl.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libavutil/hwcontext_opencl.c
b/libavutil/hwcontext_opencl.c
index 26a3a24593..4b6e74ff6f 100644
--- a/libavutil/hwcontext_opencl.c
+++ b/libavutil/hwcontext_opencl.c
@@ -2249,7 +2249,8 @@ static int opencl_map_from_qsv(AVHWFramesContext
*dst_fc, AVFrame *dst,
#if CONFIG_LIBMFX
if (src->format == AV_PIX_FMT_QSV) {
mfxFrameSurface1 *mfx_surface = (mfxFrameSurface1*)src-
data[3];
- va_surface = *(VASurfaceID*)mfx_surface->Data.MemId;
+ mfxHDLPair *pair = (mfxHDLPair*)mfx_surface->Data.MemId;
+ va_surface = *(VASurfaceID*)pair->first;
} else
#endif
if (src->format == AV_PIX_FMT_VAAPI) {
Since these frames can be user-supplied, this implies that the user-
facing
API/ABI for AV_PIX_FMT_QSV has changed.
It looks like this was broken by using HDLPairs when D3D11 was
introduced,
which silently changed the existing API for DXVA2 and VAAPI as well.
Could someone related to that please document it properly (clearly not
all
possible valid mfxFrameSurface1s are allowed), and note in APIchanges
when
the API change happened?
Hi Mark,
QSV contexts always need to be backed by a child context, which can be
DXVA2,
D3D11VA or VAAPI. You can create a QSV context either by deriving from
one
of
those contexts or when create a new QSV context, it automatically creates
an
appropriate child context - either implicitly (auto mode) or explicitly,
like
the ffmpeg implementation does in most cases.
... or by using the one the user supplies when they create it.
When working with "user-supplied" frames on Linux, you need to create a
VAAPI
context with those frames and derive a QSV context from that context.
There is no way to create or supply QSV frames directly.
??? The ability for the user to set up their own version of these things
is
literally the whole point of the split alloc/init API.
// Some user stuff involving libmfx - has a D3D or VAAPI backing, but this
code doesn't need to care about it.
// It has a session and creates some surfaces to use with MemId filled
compatible with ffmpeg.
user_session = ...;
user_surfaces = ...;
// No ffmpeg involved before this, now we want to pass these surfaces
we've
got into ffmpeg.
// Create a device context using the existing session.
mfx_ctx = av_hwdevice_ctx_alloc(MFX);
dc = mfx_ctx->data;
mfx_dc = dc->hwctx;
mfx_dc->session = user_session;
av_hwdevice_ctx_init(mfx_ctx);
// Create a frames context out of the surfaces we've got.
mfx_frames = av_hwframes_ctx_alloc(mfx_ctx);
fc = mfx_frames->data;
fc.pool = user_surfaces.allocator;
fc.width = user_surfaces.width;
// etc.
mfx_fc = fc->hwctx;
mfx_fc.surfaces = user_surfaces.array;
mfx_fc.nb_surfaces = user_surfaces.count;
mfx_fc.frame_type = user_surfaces.memtype;
av_hwframe_ctx_init(frames);
// Do stuff with frames.
I wouldn't consider an mfxSession as an entity that could or should be
shared between implementations. IMO, this is not a valid use case.
A consumer of the mfx API needs to make certain choices regarding
the usage of the API, one of which is the way how frames are allocated
and managed.
This is not something that is meant to be shared between implementations.
Even inside ffmpeg, we don't use a single mfx session. We use separate
sessions for decoding, encoding and filtering that are joined together
via MFXJoinSession.
When an (ffmpeg-)API consumer is creating its own MFX session and its
own frame allocator implementation, it shouldn't be and allowed
scenario to create an ffmpeg hw context using this session.
The user is also aware of the thread safety rules. I was giving the example
above entirely serially to avoid that, but if they were using libmfx
elsewhere in parallel with the above then indeed they would need a bit more
care (create another session, some sort of locking to ensure serialisation)
when passing it to ffmpeg.
This shouldn't be considered a public API of ffmpeg because it doesn't
make sense to share an mfx session like this.
So, to clarify, your opinion is that none of hwcontext_qsv.h should be public
API? If it were actually removed (not visible in installed headers) then I
agree that would fix the problem.
I think that exposing the mfx session handle is OK in order to allow an
API user to interop in a way that you create (and manage) your own session
and your own surface allocation, and use the exposes mfx session handle to
join the ffmpeg-created (and managed) session.
I'm not sure what you gain by making this one direction only. Setting it is
currently supported, and hasn't had an API-breaking internal change like the
MemIds.
Besides that, is there any ffmpeg documentation indicating that
the memId field of mfxFrameSurface1 could be casted to VASurfaceId?
It is user-visible API, and it matched the behaviour of the libmfx examples
for D3D9 (identical pointer to IDirect3DSurface9) and VAAPI (a compatible
pointer to a structure with the VASurfaceID as the first member) so doing the
obvious thing worked.
Also I think it's OK to expose the array of mfxSurface1 pointers allowing
to use them in a opaque way (without making use of and any assumptions
about the mfxMemId field).
This would allow an API user to interoperate with a joined session, e.g.
taking frames from a joined ffmpeg session as input to a user-created
session doing custom VPP operations where the output frames are from (and
managed by) the user-created session.
On the other side, when and API user wants to access and interop with frames
directly, then the proper way would be to use derive-from or derive-to
(VAAPI, D3D9, D3D11) to get an appropriate frames context to work with.
That's how I would see it. What do you think?
I don't much like the idea of a special-case for read-only structures here,
unlike all other hwcontexts.
Any users will already have been broken by the API change. Is there any reason
to believe that it will change again? If not, we could document the new
behaviour and say that's the new API.
If we do expect it to change further, then I guess that what you say is
probably the least-bad option. (It would want some extra code to disallow
external pools so that users can't get into the bad case again, too.)
- Mark
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