[FFmpeg-devel] [PATCH] avcodec: Align AVFrame memory to page size for access via Apple Metal

[Iskandar Safarov]

---
 libavcodec/get_buffer.c | 52 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/libavcodec/get_buffer.c b/libavcodec/get_buffer.c
index a04fd878de..b18af3be4a 100644
--- a/libavcodec/get_buffer.c
+++ b/libavcodec/get_buffer.c
@@ -33,6 +33,11 @@
 #include "avcodec.h"
 #include "internal.h"
 
+#if __APPLE__
+#import <mach/mach_init.h>
+#import <mach/vm_map.h>
+#endif
+
 typedef struct FramePool {
     /**
      * Pools for each data plane. For audio all the planes have the same size,
@@ -81,6 +86,51 @@ static AVBufferRef *frame_pool_alloc(void)
     return buf;
 }
 
+#if __APPLE__
+/* 
+    When compiling for Apple platform the frame buffer data pointers need to be
+    page-aligned for cases when in-place GPU processing may be required
+    https://developer.apple.com/documentation/metal/mtldevice/1433382-newbufferwithbytesnocopy
+ */
+#define POOL_BUFFER_ALLOCZ aapl_buffer_allocz
+
+static void aapl_buffer_free(void *opaque, uint8_t *data)
+{
+    vm_deallocate((vm_map_t) mach_task_self(), (vm_address_t)data, (size_t)opaque);
+}
+
+static AVBufferRef *aapl_buffer_alloc(size_t size)
+{
+    AVBufferRef *ret = NULL;
+    uint8_t    *data = NULL;
+
+    kern_return_t   err;
+    err = vm_allocate(  (vm_map_t) mach_task_self(),
+        (vm_address_t*) &data, size, VM_FLAGS_ANYWHERE);
+    if (err != KERN_SUCCESS || !data)
+        return NULL;
+
+    ret = av_buffer_create(data, size, aapl_buffer_free, (void*)size, 0);
+    if (!ret)
+        free(data);
+
+    return ret;
+}
+
+static AVBufferRef *aapl_buffer_allocz(size_t size)
+{
+    AVBufferRef *ret = aapl_buffer_alloc(size);
+    if (!ret)
+        return NULL;
+
+    memset(ret->data, 0, size);
+    return ret;
+}
+
+#else
+#define POOL_BUFFER_ALLOCZ av_buffer_allocz
+#endif
+
 static int update_frame_pool(AVCodecContext *avctx, AVFrame *frame)
 {
     FramePool *pool = avctx->internal->pool ?
@@ -155,7 +205,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
                 pool->pools[i] = av_buffer_pool_init(size[i] + 16 + STRIDE_ALIGN - 1,
                                                      CONFIG_MEMORY_POISONING ?
                                                         NULL :
-                                                        av_buffer_allocz);
+                                                        POOL_BUFFER_ALLOCZ);
                 if (!pool->pools[i]) {
                     ret = AVERROR(ENOMEM);
                     goto fail;
-- 
2.39.2 (Apple Git-143)