[FFmpeg-devel] [PATCH] avutil/hwcontext_cuda: add AVCUDAFramesContext and AVCUDAFramesContext.flags

[Timo Rothenpieler]

Frames can be mapped from nvdec/cuvid, not needing any actual memory
allocation, but all other features of the hw_frames_ctx.
Hence the dummy-mode, which does not allocate any (notable amounts of)
memory but otherwise behaves the exact same.
---
 doc/APIchanges             |  3 +++
 libavutil/hwcontext_cuda.c | 12 +++++++++++-
 libavutil/hwcontext_cuda.h | 22 +++++++++++++++++++++-
 libavutil/version.h        |  2 +-
 4 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index ede5b186ae..82ec888fd8 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,6 +15,9 @@ libavutil:     2017-10-21
 
 API changes, most recent first:
 
+2018-05-xx - xxxxxxxxxx - lavu 56.19.100 - hwcontext.h
+  Add AVCUDAFramesContext and AVCUDAFramesContext.flags.
+
 2018-04-xx - xxxxxxxxxx - lavu 56.18.100 - pixdesc.h
   Add AV_PIX_FMT_FLAG_ALPHA to AV_PIX_FMT_PAL8.
 
diff --git a/libavutil/hwcontext_cuda.c b/libavutil/hwcontext_cuda.c
index 37827a770c..b0b4bf24ae 100644
--- a/libavutil/hwcontext_cuda.c
+++ b/libavutil/hwcontext_cuda.c
@@ -161,6 +161,7 @@ static int cuda_frames_init(AVHWFramesContext *ctx)
 
 static int cuda_get_buffer(AVHWFramesContext *ctx, AVFrame *frame)
 {
+    AVCUDAFramesContext *frctx = ctx->hwctx;
     int aligned_width;
     int width_in_bytes = ctx->width;
 
@@ -171,7 +172,11 @@ static int cuda_get_buffer(AVHWFramesContext *ctx, AVFrame *frame)
     }
     aligned_width = FFALIGN(width_in_bytes, CUDA_FRAME_ALIGNMENT);
 
-    frame->buf[0] = av_buffer_pool_get(ctx->pool);
+    if (frctx->flags & AV_CUDA_HWFRAMES_DUMMY_MODE)
+        frame->buf[0] = av_buffer_create(NULL, 0, NULL, NULL, 0);
+    else
+        frame->buf[0] = av_buffer_pool_get(ctx->pool);
+
     if (!frame->buf[0])
         return AVERROR(ENOMEM);
 
@@ -210,6 +215,10 @@ static int cuda_get_buffer(AVHWFramesContext *ctx, AVFrame *frame)
     frame->width  = ctx->width;
     frame->height = ctx->height;
 
+    // they're pointing to invalid memory, dangerous to leave set
+    if (frctx->flags & AV_CUDA_HWFRAMES_DUMMY_MODE)
+        frame->data[0] = frame->data[1] = frame->data[2] = NULL;
+
     return 0;
 }
 
@@ -402,6 +411,7 @@ const HWContextType ff_hwcontext_type_cuda = {
     .name                 = "CUDA",
 
     .device_hwctx_size    = sizeof(AVCUDADeviceContext),
+    .frames_hwctx_size    = sizeof(AVCUDAFramesContext),
     .frames_priv_size     = sizeof(CUDAFramesContext),
 
     .device_create        = cuda_device_create,
diff --git a/libavutil/hwcontext_cuda.h b/libavutil/hwcontext_cuda.h
index 12dae8449e..19accbd9be 100644
--- a/libavutil/hwcontext_cuda.h
+++ b/libavutil/hwcontext_cuda.h
@@ -45,7 +45,27 @@ typedef struct AVCUDADeviceContext {
 } AVCUDADeviceContext;
 
 /**
- * AVHWFramesContext.hwctx is currently not used
+ * This struct is allocated as AVHWFramesContext.hwctx
  */
+typedef struct AVCUDAFramesContext {
+    /**
+     * Special implementation-specific flags.
+     *
+     * May be set by the user before calling av_hwframe_ctx_init().
+     */
+    int flags;
+} AVCUDAFramesContext;
+
+/**
+ * No actual allocation will happen, but otherwise behaves like normal.
+ *
+ * This is to be used if a AVHWFramesContext is required, but the actual
+ * allocation is happening outside of it.
+ *
+ * The resulting AVFrames will be identical to normal frames, except for
+ * their data[] pointers being NULL and the AVBufferRef in buf[0] being
+ * set but containing no notable allocation of memory.
+ */
+#define AV_CUDA_HWFRAMES_DUMMY_MODE (1 << 0)
 
 #endif /* AVUTIL_HWCONTEXT_CUDA_H */
diff --git a/libavutil/version.h b/libavutil/version.h
index 5185454d9b..84409b1d69 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  56
-#define LIBAVUTIL_VERSION_MINOR  18
+#define LIBAVUTIL_VERSION_MINOR  19
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
-- 
2.17.0