diff --git a/doc/APIchanges b/doc/APIchanges
index 9367a5fc417855fa2f7c355754215b7106586d3b..335c1634793e1dcc16fd103d99a9056c7146dbc1 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -13,6 +13,9 @@ libavutil: 2015-08-28
API changes, most recent first:
+2017-03-xx - xxxxxxx - lavu 55.34.0 - hwcontext.h
+ Add av_hwdevice_ctx_create_derived().
+
2017-02-10 - xxxxxxx - lavu 55.33.0 - spherical.h
Add AV_SPHERICAL_EQUIRECTANGULAR_TILE, av_spherical_tile_bounds(),
and projection-specific properties (bound_left, bound_top, bound_right,
diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
index 608da6872761faf75128b9ff01ae984fbe069162..252dd32e38355069a3043cbc5aee0d32e00b8522 100644
--- a/libavutil/hwcontext.c
+++ b/libavutil/hwcontext.c
@@ -65,6 +65,8 @@ static void hwdevice_ctx_free(void *opaque, uint8_t *data)
if (ctx->free)
ctx->free(ctx);
+ av_buffer_unref(&ctx->internal->source_device);
+
av_freep(&ctx->hwctx);
av_freep(&ctx->internal->priv);
av_freep(&ctx->internal);
@@ -535,6 +537,69 @@ fail:
return ret;
}
+int av_hwdevice_ctx_create_derived(AVBufferRef **dst_ref_ptr,
+ enum AVHWDeviceType type,
+ AVBufferRef *src_ref, int flags)
+{
+ AVBufferRef *dst_ref = NULL, *tmp_ref;
+ AVHWDeviceContext *dst_ctx, *tmp_ctx;
+ int ret = 0;
+
+ tmp_ref = src_ref;
+ while (tmp_ref) {
+ tmp_ctx = (AVHWDeviceContext*)tmp_ref->data;
+ if (tmp_ctx->type == type) {
+ dst_ref = av_buffer_ref(tmp_ref);
+ if (!dst_ref) {
+ ret = AVERROR(ENOMEM);
+ goto fail;
+ }
+ goto done;
+ }
+ tmp_ref = tmp_ctx->internal->source_device;
+ }
+
+ dst_ref = av_hwdevice_ctx_alloc(type);
+ if (!dst_ref) {
+ ret = AVERROR(ENOMEM);
+ goto fail;
+ }
+ dst_ctx = (AVHWDeviceContext*)dst_ref->data;
+
+ tmp_ref = src_ref;
+ while (tmp_ref) {
+ tmp_ctx = (AVHWDeviceContext*)tmp_ref->data;
+ if (dst_ctx->internal->hw_type->device_derive) {
+ ret = dst_ctx->internal->hw_type->device_derive(dst_ctx,
+ tmp_ctx,
+ flags);
+ if (ret == 0) {
+ dst_ctx->internal->source_device = av_buffer_ref(src_ref);
+ if (!dst_ctx->internal->source_device) {
+ ret = AVERROR(ENOMEM);
+ goto fail;
+ }
+ goto done;
+ }
+ if (ret != AVERROR(ENOSYS))
+ goto fail;
+ }
+ tmp_ref = tmp_ctx->internal->source_device;
+ }
+
+ ret = AVERROR(ENOSYS);
+ goto fail;
+
+done:
+ *dst_ref_ptr = dst_ref;
+ return 0;
+
+fail:
+ av_buffer_unref(&dst_ref);
+ *dst_ref_ptr = NULL;
+ return ret;
+}
+
static void ff_hwframe_unmap(void *opaque, uint8_t *data)
{
HWMapDescriptor *hwmap = (HWMapDescriptor*)data;
diff --git a/libavutil/hwcontext.h b/libavutil/hwcontext.h
index 037ca64224d2355e9aec2219cdcd34149c81aaaf..49c7a21c1e748a0890a639316b9a6d0fb2fac06a 100644
--- a/libavutil/hwcontext.h
+++ b/libavutil/hwcontext.h
@@ -268,6 +268,32 @@ int av_hwdevice_ctx_init(AVBufferRef *ref);
int av_hwdevice_ctx_create(AVBufferRef **device_ctx, enum AVHWDeviceType type,
const char *device, AVDictionary *opts, int flags);
+/**
+ * Create a new device of the specified type from an existing device.
+ *
+ * If the source device is a device of the target type or was originally
+ * derived from such a device (possibly through one or more intermediate
+ * devices of other types), then this will return a reference to the
+ * existing device of the same type as is requested.
+ *
+ * Otherwise, it will attempt to derive a new device from the given source
+ * device. If direct derivation to the new type is not implemented, it will
+ * attempt the same derivation from each ancestor of the source device in
+ * turn looking for an implemented derivation method.
+ *
+ * @param dst_ctx On success, a reference to the newly-created
+ * AVHWDeviceContext.
+ * @param type The type of the new device to create.
+ * @param src_ctx A reference to an existing AVHWDeviceContext which will be
+ * used to create the new device.
+ * @param flags Currently unused; should be set to zero.
+ * @return Zero on success, a negative AVERROR code on failure.
+ */
+int av_hwdevice_ctx_create_derived(AVBufferRef **dst_ctx,
+ enum AVHWDeviceType type,
+ AVBufferRef *src_ctx, int flags);
+
+
/**
* Allocate an AVHWFramesContext tied to a given device context.
*
diff --git a/libavutil/hwcontext_internal.h b/libavutil/hwcontext_internal.h
index 11e3a68e4cf7020a10a3c8ab87ca04574bb4bca8..66f54142e8ef6be84f80179033e82f476f728f47 100644
--- a/libavutil/hwcontext_internal.h
+++ b/libavutil/hwcontext_internal.h
@@ -66,6 +66,8 @@ typedef struct HWContextType {
int (*device_create)(AVHWDeviceContext *ctx, const char *device,
AVDictionary *opts, int flags);
+ int (*device_derive)(AVHWDeviceContext *dst_ctx,
+ AVHWDeviceContext *src_ctx, int flags);
int (*device_init)(AVHWDeviceContext *ctx);
void (*device_uninit)(AVHWDeviceContext *ctx);
@@ -95,6 +97,12 @@ typedef struct HWContextType {
struct AVHWDeviceInternal {
const HWContextType *hw_type;
void *priv;
+
+ /**
+ * For a derived device, a reference to the original device
+ * context it was derived from.
+ */
+ AVBufferRef *source_device;
};
struct AVHWFramesInternal {
diff --git a/libavutil/version.h b/libavutil/version.h
index 0f2b684fa8fc439d00dc2c9ef196746933eced85..7c0e852498cb22c6e920d7bf1ac19beeb495dadc 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -54,7 +54,7 @@
*/
#define LIBAVUTIL_VERSION_MAJOR 55
-#define LIBAVUTIL_VERSION_MINOR 33
+#define LIBAVUTIL_VERSION_MINOR 34
#define LIBAVUTIL_VERSION_MICRO 0
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \