[FFmpeg-devel] [PATCH v3 1/1] avutils/hwcontext: When deriving a hwdevice, search for existing device in both directions
Lynne
dev at lynne.ee
Thu Nov 25 06:09:07 EET 2021
25 Nov 2021, 03:58 by softworkz at hotmail.com:
>
>
>> -----Original Message-----
>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
>> Lynne
>> Sent: Wednesday, November 24, 2021 12:27 PM
>> To: FFmpeg development discussions and patches <ffmpeg-
>> devel at ffmpeg.org>
>> Subject: Re: [FFmpeg-devel] [PATCH v3 1/1] avutils/hwcontext: When
>> deriving a hwdevice, search for existing device in both directions
>>
>> 19 Nov 2021, 17:24 by softworkz at hotmail.com:
>>
>> >
>> >
>> >> -----Original Message-----
>> >> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
>> >> Xiang, Haihao
>> >> Sent: Monday, October 18, 2021 6:48 AM
>> >> To: ffmpeg-devel at ffmpeg.org
>> >> Subject: Re: [FFmpeg-devel] [PATCH v3 1/1] avutils/hwcontext: When
>> >> deriving a hwdevice, search for existing device in both directions
>> >>
>> >> On Mon, 2021-10-11 at 04:19 +0000, Soft Works wrote:
>> >> > The test /libavutil/tests/hwdevice checks that when deriving a
>> >> device
>> >> > from a source device and then deriving back to the type of the
>> >> source
>> >> > device, the result is matching the original source device, i.e.
>> the
>> >> > derivation mechanism doesn't create a new device in this case.
>> >> >
>> >> > Previously, this test was usually passed, but only due to two
>> >> different
>> >> > kind of flaws:
>> >> >
>> >> > 1. The test covers only a single level of derivation (and back)
>> >> >
>> >> > It derives device Y from device X and then Y back to the type of
>> X
>> >> and
>> >> > checks whether the result matches X.
>> >> >
>> >> > What it doesn't check for, are longer chains of derivation like:
>> >> >
>> >> > CUDA1 > OpenCL2 > CUDA3 and then back to OpenCL4
>> >> >
>> >> > In that case, the second derivation returns the first device
>> (CUDA3
>> >> ==
>> >> > CUDA1), but when deriving OpenCL4, hwcontext.c was creating a
>> new
>> >> > OpenCL4 context instead of returning OpenCL2, because there was
>> no
>> >> link
>> >> > from CUDA1 to OpenCL2 (only backwards from OpenCL2 to CUDA1)
>> >> >
>> >> > If the test would check for two levels of derivation, it would
>> have
>> >> > failed.
>> >> >
>> >> > This patch fixes those (yet untested) cases by introducing
>> forward
>> >> > references (derived_device) in addition to the existing back
>> >> references
>> >> > (source_device).
>> >> >
>> >> > 2. hwcontext_qsv didn't properly set the source_device
>> >> >
>> >> > In case of QSV, hwcontext_qsv creates a source context
>> internally
>> >> > (vaapi, dxva2 or d3d11va) without calling
>> >> av_hwdevice_ctx_create_derived
>> >> > and without setting source_device.
>> >> >
>> >> > This way, the hwcontext test ran successful, but what
>> practically
>> >> > happened, was that - for example - deriving vaapi from qsv
>> didn't
>> >> return
>> >> > the original underlying vaapi device and a new one was created
>> >> instead:
>> >> > Exactly what the test is intended to detect and prevent. It just
>> >> > couldn't do so, because the original device was hidden (= not
>> set
>> >> as the
>> >> > source_device of the QSV device).
>> >> >
>> >> > This patch properly makes these setting and fixes all derivation
>> >> > scenarios.
>> >> >
>> >> > (at a later stage, /libavutil/tests/hwdevice should be extended
>> to
>> >> check
>> >> > longer derivation chains as well)
>> >> >
>> >> > Signed-off-by: softworkz <softworkz at hotmail.com>
>> >> > ---
>> >> > v3: avoid double-release as suggested by Haihao
>> >> >
>> >> > libavutil/hwcontext.c | 38
>> >> ++++++++++++++++++++++++++++++++++
>> >> > libavutil/hwcontext.h | 1 +
>> >> > libavutil/hwcontext_internal.h | 6 ++++++
>> >> > libavutil/hwcontext_qsv.c | 16 ++++++++++----
>> >> > 4 files changed, 57 insertions(+), 4 deletions(-)
>> >> >
>> >> > diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
>> >> > index 31c7840dba..1a50635018 100644
>> >> > --- a/libavutil/hwcontext.c
>> >> > +++ b/libavutil/hwcontext.c
>> >> > @@ -122,6 +122,7 @@ static const AVClass hwdevice_ctx_class = {
>> >> > static void hwdevice_ctx_free(void *opaque, uint8_t *data)
>> >> > {
>> >> > AVHWDeviceContext *ctx = (AVHWDeviceContext*)data;
>> >> > + int i;
>> >> >
>> >> > /* uninit might still want access the hw context and the
>> user
>> >> > * free() callback might destroy it, so uninit has to be
>> >> called first */
>> >> > @@ -132,6 +133,8 @@ static void hwdevice_ctx_free(void *opaque,
>> >> uint8_t *data)
>> >> > ctx->free(ctx);
>> >> >
>> >> > av_buffer_unref(&ctx->internal->source_device);
>> >> > + for (i = 0; i < AV_HWDEVICE_TYPE_NB; i++)
>> >> > + av_buffer_unref(&ctx->internal->derived_devices[i]);
>> >> >
>> >> > av_freep(&ctx->hwctx);
>> >> > av_freep(&ctx->internal->priv);
>> >> > @@ -643,6 +646,26 @@ fail:
>> >> > return ret;
>> >> > }
>> >> >
>> >> > +static AVBufferRef* find_derived_hwdevice_ctx(AVBufferRef
>> >> *src_ref, enum
>> >> > AVHWDeviceType type)
>> >> > +{
>> >> > + AVBufferRef *tmp_ref;
>> >> > + AVHWDeviceContext *src_ctx;
>> >> > + int i;
>> >> > +
>> >> > + src_ctx = (AVHWDeviceContext*)src_ref->data;
>> >> > + if (src_ctx->type == type)
>> >> > + return src_ref;
>> >> > +
>> >> > + for (i = 0; i < AV_HWDEVICE_TYPE_NB; i++)
>> >> > + if (src_ctx->internal->derived_devices[i]) {
>> >> > + tmp_ref = find_derived_hwdevice_ctx(src_ctx-
>> >internal-
>> >> > >derived_devices[i], type);
>> >> > + if (tmp_ref)
>> >> > + return tmp_ref;
>> >> > + }
>> >> > +
>> >> > + return NULL;
>> >> > +}
>> >> > +
>> >> > int av_hwdevice_ctx_create_derived_opts(AVBufferRef
>> **dst_ref_ptr,
>> >> > enum AVHWDeviceType
>> type,
>> >> > AVBufferRef *src_ref,
>> >> > @@ -666,6 +689,16 @@ int
>> >> av_hwdevice_ctx_create_derived_opts(AVBufferRef
>> >> > **dst_ref_ptr,
>> >> > tmp_ref = tmp_ctx->internal->source_device;
>> >> > }
>> >> >
>> >> > + tmp_ref = find_derived_hwdevice_ctx(src_ref, type);
>> >> > + if (tmp_ref) {
>> >> > + dst_ref = av_buffer_ref(tmp_ref);
>> >> > + if (!dst_ref) {
>> >> > + ret = AVERROR(ENOMEM);
>> >> > + goto fail;
>> >> > + }
>> >> > + goto done;
>> >> > + }
>> >> > +
>> >> > dst_ref = av_hwdevice_ctx_alloc(type);
>> >> > if (!dst_ref) {
>> >> > ret = AVERROR(ENOMEM);
>> >> > @@ -687,6 +720,11 @@ int
>> >> av_hwdevice_ctx_create_derived_opts(AVBufferRef
>> >> > **dst_ref_ptr,
>> >> > ret = AVERROR(ENOMEM);
>> >> > goto fail;
>> >> > }
>> >> > + tmp_ctx->internal->derived_devices[type] =
>> >> > av_buffer_ref(dst_ref);
>> >> > + if (!tmp_ctx->internal->derived_devices[type])
>> {
>> >> > + ret = AVERROR(ENOMEM);
>> >> > + goto fail;
>> >> > + }
>> >> > ret = av_hwdevice_ctx_init(dst_ref);
>> >> > if (ret < 0)
>> >> > goto fail;
>> >> > diff --git a/libavutil/hwcontext.h b/libavutil/hwcontext.h
>> >> > index 04d19d89c2..56077963e6 100644
>> >> > --- a/libavutil/hwcontext.h
>> >> > +++ b/libavutil/hwcontext.h
>> >> > @@ -37,6 +37,7 @@ enum AVHWDeviceType {
>> >> > AV_HWDEVICE_TYPE_OPENCL,
>> >> > AV_HWDEVICE_TYPE_MEDIACODEC,
>> >> > AV_HWDEVICE_TYPE_VULKAN,
>> >> > + AV_HWDEVICE_TYPE_NB, ///< number of hw device
>> types
>> >> > };
>> >> >
>> >> > typedef struct AVHWDeviceInternal AVHWDeviceInternal;
>> >> > diff --git a/libavutil/hwcontext_internal.h
>> >> b/libavutil/hwcontext_internal.h
>> >> > index e6266494ac..f6fb67c491 100644
>> >> > --- a/libavutil/hwcontext_internal.h
>> >> > +++ b/libavutil/hwcontext_internal.h
>> >> > @@ -109,6 +109,12 @@ struct AVHWDeviceInternal {
>> >> > * context it was derived from.
>> >> > */
>> >> > AVBufferRef *source_device;
>> >> > +
>> >> > + /**
>> >> > + * An array of reference to device contexts which
>> >> > + * were derived from this device.
>> >> > + */
>> >> > + AVBufferRef *derived_devices[AV_HWDEVICE_TYPE_NB];
>> >> > };
>> >> >
>> >> > struct AVHWFramesInternal {
>> >> > diff --git a/libavutil/hwcontext_qsv.c
>> b/libavutil/hwcontext_qsv.c
>> >> > index c18747f7eb..7b559e2b47 100644
>> >> > --- a/libavutil/hwcontext_qsv.c
>> >> > +++ b/libavutil/hwcontext_qsv.c
>> >> > @@ -223,7 +223,7 @@ static void
>> qsv_frames_uninit(AVHWFramesContext
>> >> *ctx)
>> >> > av_buffer_unref(&s->child_frames_ref);
>> >> > }
>> >> >
>> >> > -static void qsv_pool_release_dummy(void *opaque, uint8_t *data)
>> >> > +static void qsv_release_dummy(void *opaque, uint8_t *data)
>> >> > {
>> >> > }
>> >> >
>> >> > @@ -236,9 +236,9 @@ static AVBufferRef *qsv_pool_alloc(void
>> >> *opaque, size_t
>> >> > size)
>> >> > if (s->nb_surfaces_used < hwctx->nb_surfaces) {
>> >> > s->nb_surfaces_used++;
>> >> > av_buffer_create((uint8_t*)(s->handle_pairs_internal +
>> s-
>> >> > >nb_surfaces_used - 1),
>> >> > - sizeof(*s-
>> >handle_pairs_internal),
>> >> > qsv_pool_release_dummy, NULL, 0);
>> >> > + sizeof(*s-
>> >handle_pairs_internal),
>> >> > qsv_release_dummy, NULL, 0);
>> >> > return av_buffer_create((uint8_t*)(s->surfaces_internal
>> +
>> >> s-
>> >> > >nb_surfaces_used - 1),
>> >> > - sizeof(*hwctx->surfaces),
>> >> > qsv_pool_release_dummy, NULL, 0);
>> >> > + sizeof(*hwctx->surfaces),
>> >> qsv_release_dummy,
>> >> > NULL, 0);
>> >> > }
>> >> >
>> >> > return NULL;
>> >> > @@ -1528,8 +1528,16 @@ static int
>> >> qsv_device_create(AVHWDeviceContext *ctx,
>> >> > const char *device,
>> >> > child_device = (AVHWDeviceContext*)priv->child_device_ctx-
>> >> >data;
>> >> >
>> >> > impl = choose_implementation(device, child_device_type);
>> >> > + ret = qsv_device_derive_from_child(ctx, impl, child_device,
>> >> 0);
>> >> > + if (ret >= 0) {
>> >> > + ctx->internal->source_device = av_buffer_ref(priv-
>> >> >child_device_ctx);
>> >> > + child_device->internal->derived_devices[ctx->type] =
>> >> > av_buffer_create((uint8_t*)ctx, sizeof(*ctx), qsv_release_dummy,
>> >> ctx, 0);
>> >> > + if (!child_device->internal->derived_devices[ctx-
>> >type]) {
>> >> > + return AVERROR(ENOMEM);
>> >> > + }
>> >> > + }
>> >> >
>> >> > - return qsv_device_derive_from_child(ctx, impl,
>> child_device,
>> >> 0);
>> >> > + return ret;
>> >> > }
>> >> >
>> >> > const HWContextType ff_hwcontext_type_qsv = {
>> >>
>> >> LGTM,
>> >>
>> >> -Haihao
>> >>
>> >
>> > @Hendrik: You had some concerns regarding the initial version,
>> which I have
>> > addressed. Could you please check whether it looks good to you now?
>> >
>> > @Wenbin, @Xu: Could you confirm whether this patch eliminates the
>> need for
>> > the other workarounds you currently have in place on cartwheel?
>> >
>> > For making things work like "qsv->vaapi->vulkan->vaapi->qsv
>> pipeline"
>> > (https://github.com/intel-media-ci/cartwheel-
>> ffmpeg/commit/564169857f552d585f827dbc1387b6abf6526139)
>> >
>> > @Lynne, @haasm, @Wu: This patch might also be relevant for working
>> Vulkan
>> > context derivation as it prevents the creation of new hardware
>> contexts
>> > in non-trivial derivation chains.
>> >
>> > I think this patch is essential for properly working with derived
>> hw contexts
>> > and I'd be glad to hear some more thoughts about it.
>>
>
> Hi,
>
>> This is indeed relevant to working Vulkan derivation, especially with
>> VAAPI.
>> I've hit this limitation before.
>> I've reviewed the patch, it looks good,
>>
>
> thanks a lot for taking the time.
>
>
>> except a small coding style
>> nit,
>> do not put brackets on one-line statements, look at `if
>> (!child_device->internal->derived_devices[ctx->type]) {`,
>>
>
> Fixed, new patch submitted.
>
>> and you should also add a comment to AV_HWDEVICE_TYPE_NB where
>> it says "Not part of the API, do not use.".
>>
>
> Can't find that place. Anyway I'm not sure whether it matters
> in this case what it "public" api or not. My code is using it
> just internally and both live in libavutil.
>
It's in AVHWDeviceType.
Internal or not, it's in a public API header. If someone does decide to use
it, it'll be really bad as we wouldn't be able to add a new hwcontext
without also adding a new AV_HWDEVICE_TYPE_NB2.
I'll add the note when I apply it.
>> Apart from that, I think if no one responds in a day or two, you
>> should
>> push it.
>>
>
> I have no permission, so I need to wait and hope for somebody
> feeling responsible or sympathizing with the submitted code. 😉
>
I'll push it later alongside the Vulkan changes when they're ready.
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