On 18/11/2019 11:51, Oleg Dobkin wrote:
I've changed enum into a flag and moved it into
AVCUDADeviceContextInternal.

Can't one just call cuCtxGetDevice on the context to get the device?

Not sure the cuCtxGetDevice can be used for the primary context; also,
according to documentation it returns device id not handle. Anyway, is
it that bad to store an additional handle?

It's public API, and once something is there, it has to stay there for quite a while. So I'm not too much a fan of adding something there, which can already easily be gotten from existing fields.

The CUdevice, which you intended to store there, and which cuCtxGetDevice returns, _is_ the device ID. It's a typedef to int.
I'm not aware of there being anything beyond that.

Storing it in the internal struct is fine though, for the sake of not having to call cuCtxGetDevice each time.

Also needs configure updated for the higher ffnvcodec version

I'm looking at the configure and can't figure out how ffnvcodec version
is enforced. The script seems to accept several ranges of ffnvcodec
versions. I could just increment the top-level check, but I'm not sure
this is the correct way.

FFmpeg supports multiple tracks of the Video Codec SDK, to support older drivers and legacy GPUs that way. Since the version number only tracks the Video SDK Version, and not the CUDA loader version, what needs to be done is to set the new minimum version for each supported track. So far, there was no need to add explicit checks for SDK 9.1, but that will be required for this.
Also, since SDK 8.0 is effectively dead, it can be dropped.

I immediately bump the version on ffnvcodec git after every release, so the correct versions to check for in configure right now are:
9.1.23.1, 9.0.18.3, 8.2.15.10 and 8.1.24.11

On Sun, 2019-11-17 at 23:31 +0100, Timo Rothenpieler wrote:
On 17.11.2019 15:58, Oleg Dobkin wrote:

Add AVCUDADeviceContextFlags to control the creation of CUDA device
context for the hardware CUDA decoder.

The current values are 0 (default behavior) - new context will be
created for each decoder, and 1 - primary CUDA context will be used.

There are several reasons for using primary device context instead of
creating a new one:

   - This is the recommended way to handle device contexts (see

https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__CTX.html#group__CUDA__CTX_1g65dc0012348bc84810e2103a40d8e2cf
)

   - Memory allocations, kernels and other state are associated with
the
current device context. Currently, the context is not accessible from
FFmpeg API, so, technically, the memory created by the hardware
decoder
(the video frame) can't be safely read.

Signed-off-by: Oleg Dobkin <ol...@anyvision.co>
---
   libavutil/hwcontext_cuda.c | 20 +++++++++++++++-----
   libavutil/hwcontext_cuda.h |  7 +++++++
   2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
index cca39e9fc7..608ea57569 100644
--- a/libavutil/hwcontext_cuda.c
+++ b/libavutil/hwcontext_cuda.c
@@ -281,8 +281,12 @@ static void cuda_device_uninit(AVHWDeviceContext
*device_ctx)
       if (hwctx->internal) {
           CudaFunctions *cu = hwctx->internal->cuda_dl;
           if (hwctx->internal->is_allocated && hwctx->cuda_ctx) {
-            CHECK_CU(cu->cuCtxDestroy(hwctx->cuda_ctx));
+            if (hwctx->flags == DCF_CREATE_CONTEXT)

Should actually be checking for the flag, not equality.


+                CHECK_CU(cu->cuCtxDestroy(hwctx->cuda_ctx));
+            else
+                CHECK_CU(cu->cuDevicePrimaryCtxRelease(hwctx-
cuda_device));
               hwctx->cuda_ctx = NULL;
+            hwctx->cuda_device = NULL;
           }
           cuda_free_functions(&hwctx->internal->cuda_dl);
       }
@@ -322,7 +326,6 @@ static int cuda_device_create(AVHWDeviceContext
*device_ctx,
   {
       AVCUDADeviceContext *hwctx = device_ctx->hwctx;
       CudaFunctions *cu;
-    CUdevice cu_device;
       CUcontext dummy;
       int ret, device_idx = 0;
@@ -338,18 +341,25 @@ static int cuda_device_create(AVHWDeviceContext
*device_ctx,
       if (ret < 0)
           goto error;
- ret = CHECK_CU(cu->cuDeviceGet(&cu_device, device_idx));
+    ret = CHECK_CU(cu->cuDeviceGet(&hwctx->cuda_device,
device_idx));
       if (ret < 0)
           goto error;
- ret = CHECK_CU(cu->cuCtxCreate(&hwctx->cuda_ctx,
CU_CTX_SCHED_BLOCKING_SYNC, cu_device));
+    hwctx->flags = flags;
+
+    if (flags == DCF_CREATE_CONTEXT)
+        ret = CHECK_CU(cu->cuCtxCreate(&hwctx->cuda_ctx,
CU_CTX_SCHED_BLOCKING_SYNC, hwctx->cuda_device));
+    else
+        ret = CHECK_CU(cu->cuDevicePrimaryCtxRetain(&hwctx-
cuda_ctx, hwctx->cuda_device));
+
       if (ret < 0)
           goto error;
// Setting stream to NULL will make functions automatically use
the default CUstream
       hwctx->stream = NULL;
- CHECK_CU(cu->cuCtxPopCurrent(&dummy));
+    if (flags == DCF_CREATE_CONTEXT)
+        CHECK_CU(cu->cuCtxPopCurrent(&dummy));
hwctx->internal->is_allocated = 1; diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
index 81a0552cab..bab5eefe54 100644
--- a/libavutil/hwcontext_cuda.h
+++ b/libavutil/hwcontext_cuda.h
@@ -34,6 +34,11 @@
    * AVBufferRefs whose data pointer is a CUdeviceptr.
    */
+enum AVCUDADeviceContextFlags {
+    DCF_CREATE_CONTEXT = 0,
+    DCF_USE_PRIMARY_CONTEXT = 1
+};

I'd only define a flag for the new behavior. If it's not set, keep
old
behavior.


   typedef struct AVCUDADeviceContextInternal
AVCUDADeviceContextInternal;
/**
@@ -43,6 +48,8 @@ typedef struct AVCUDADeviceContext {
       CUcontext cuda_ctx;
       CUstream stream;
       AVCUDADeviceContextInternal *internal;
+    CUdevice cuda_device;

Can't one just call cuCtxGetDevice on the context to get the device?


+    enum AVCUDADeviceContextFlags flags;

The device_create/av_hwdevice_ctx_create function already has a (at
the
moment unused) flags parameter. So there should be no need to add
this here.
If need be, the information should be stored in
AVCUDADeviceContextInternal instead.


   } AVCUDADeviceContext;
Also needs configure updated for the higher ffnvcodec version that's
required after this patch, and probably deserved a lavu micro bump.


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