lavu: add a framework for handling hwaccel frames

6 files changed, 832 insertions, 0 deletions

diff --git a/libavutil/Makefile b/libavutil/Makefile
index 17bd57e8b7..2c0b7b54aa 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -23,6 +23,7 @@ HEADERS = adler32.h                                                     \
           file.h                                                        \
           frame.h                                                       \
           hmac.h                                                        \
+          hwcontext.h                                                   \
           imgutils.h                                                    \
           intfloat.h                                                    \
           intreadwrite.h                                                \
@@ -78,6 +79,7 @@ OBJS = adler32.o                                                        \
        float_dsp.o                                                      \
        frame.o                                                          \
        hmac.o                                                           \
+       hwcontext.o                                                      \
        imgutils.o                                                       \
        intmath.o                                                        \
        lfg.o                                                            \
diff --git a/libavutil/frame.c b/libavutil/frame.c
index 15276fee49..542215a16b 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -251,6 +251,14 @@ int av_frame_ref(AVFrame *dst, const AVFrame *src)
         }
     }
 
+    if (src->hw_frames_ctx) {
+        dst->hw_frames_ctx = av_buffer_ref(src->hw_frames_ctx);
+        if (!dst->hw_frames_ctx) {
+            ret = AVERROR(ENOMEM);
+            goto fail;
+        }
+    }
+
     /* duplicate extended data */
     if (src->extended_data != src->data) {
         int ch = av_get_channel_layout_nb_channels(src->channel_layout);
@@ -303,6 +311,9 @@ void av_frame_unref(AVFrame *frame)
     for (i = 0; i < frame->nb_extended_buf; i++)
         av_buffer_unref(&frame->extended_buf[i]);
     av_freep(&frame->extended_buf);
+
+    av_buffer_unref(&frame->hw_frames_ctx);
+
     get_frame_defaults(frame);
 }
 
diff --git a/libavutil/frame.h b/libavutil/frame.h
index c723cb02c3..5398b89ba1 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -354,6 +354,12 @@ typedef struct AVFrame {
     enum AVColorSpace colorspace;
 
     enum AVChromaLocation chroma_location;
+
+    /**
+     * For hwaccel-format frames, this should be a reference to the
+     * AVHWFramesContext describing the frame.
+     */
+    AVBufferRef *hw_frames_ctx;
 } AVFrame;
 
 /**
diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
new file mode 100644
index 0000000000..bec8f61e0e
--- /dev/null
+++ b/libavutil/hwcontext.c
@@ -0,0 +1,396 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include "buffer.h"
+#include "common.h"
+#include "hwcontext.h"
+#include "hwcontext_internal.h"
+#include "imgutils.h"
+#include "log.h"
+#include "mem.h"
+#include "pixdesc.h"
+#include "pixfmt.h"
+
+static const HWContextType *hw_table[] = {
+    NULL,
+};
+
+static const AVClass hwdevice_ctx_class = {
+    .class_name = "AVHWDeviceContext",
+    .item_name  = av_default_item_name,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static void hwdevice_ctx_free(void *opaque, uint8_t *data)
+{
+    AVHWDeviceContext *ctx = (AVHWDeviceContext*)data;
+
+    /* uninit might still want access the hw context and the user
+     * free() callback might destroy it, so uninit has to be called first */
+    if (ctx->internal->hw_type->device_uninit)
+        ctx->internal->hw_type->device_uninit(ctx);
+
+    if (ctx->free)
+        ctx->free(ctx);
+
+    av_freep(&ctx->hwctx);
+    av_freep(&ctx->internal->priv);
+    av_freep(&ctx->internal);
+    av_freep(&ctx);
+}
+
+AVBufferRef *av_hwdevice_ctx_alloc(enum AVHWDeviceType type)
+{
+    AVHWDeviceContext *ctx;
+    AVBufferRef *buf;
+    const HWContextType *hw_type = NULL;
+    int i;
+
+    for (i = 0; hw_table[i]; i++) {
+        if (hw_table[i]->type == type) {
+            hw_type = hw_table[i];
+            break;
+        }
+    }
+    if (!hw_type)
+        return NULL;
+
+    ctx = av_mallocz(sizeof(*ctx));
+    if (!ctx)
+        return NULL;
+
+    ctx->internal = av_mallocz(sizeof(*ctx->internal));
+    if (!ctx->internal)
+        goto fail;
+
+    if (hw_type->device_priv_size) {
+        ctx->internal->priv = av_mallocz(hw_type->device_priv_size);
+        if (!ctx->internal->priv)
+            goto fail;
+    }
+
+    if (hw_type->device_hwctx_size) {
+        ctx->hwctx = av_mallocz(hw_type->device_hwctx_size);
+        if (!ctx->hwctx)
+            goto fail;
+    }
+
+    buf = av_buffer_create((uint8_t*)ctx, sizeof(*ctx),
+                           hwdevice_ctx_free, NULL,
+                           AV_BUFFER_FLAG_READONLY);
+    if (!buf)
+        goto fail;
+
+    ctx->type     = type;
+    ctx->av_class = &hwdevice_ctx_class;
+
+    ctx->internal->hw_type = hw_type;
+
+    return buf;
+
+fail:
+    if (ctx->internal)
+        av_freep(&ctx->internal->priv);
+    av_freep(&ctx->internal);
+    av_freep(&ctx->hwctx);
+    av_freep(&ctx);
+    return NULL;
+}
+
+int av_hwdevice_ctx_init(AVBufferRef *ref)
+{
+    AVHWDeviceContext *ctx = (AVHWDeviceContext*)ref->data;
+    int ret;
+
+    if (ctx->internal->hw_type->device_init) {
+        ret = ctx->internal->hw_type->device_init(ctx);
+        if (ret < 0)
+            goto fail;
+    }
+
+    return 0;
+fail:
+    if (ctx->internal->hw_type->device_uninit)
+        ctx->internal->hw_type->device_uninit(ctx);
+    return ret;
+}
+
+static const AVClass hwframe_ctx_class = {
+    .class_name = "AVHWFramesContext",
+    .item_name  = av_default_item_name,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static void hwframe_ctx_free(void *opaque, uint8_t *data)
+{
+    AVHWFramesContext *ctx = (AVHWFramesContext*)data;
+
+    if (ctx->internal->pool_internal)
+        av_buffer_pool_uninit(&ctx->internal->pool_internal);
+
+    if (ctx->internal->hw_type->frames_uninit)
+        ctx->internal->hw_type->frames_uninit(ctx);
+
+    if (ctx->free)
+        ctx->free(ctx);
+
+    av_buffer_unref(&ctx->device_ref);
+
+    av_freep(&ctx->hwctx);
+    av_freep(&ctx->internal->priv);
+    av_freep(&ctx->internal);
+    av_freep(&ctx);
+}
+
+AVBufferRef *av_hwframe_ctx_alloc(AVBufferRef *device_ref_in)
+{
+    AVHWDeviceContext *device_ctx = (AVHWDeviceContext*)device_ref_in->data;
+    const HWContextType  *hw_type = device_ctx->internal->hw_type;
+    AVHWFramesContext *ctx;
+    AVBufferRef *buf, *device_ref = NULL;;
+
+    ctx = av_mallocz(sizeof(*ctx));
+    if (!ctx)
+        return NULL;
+
+    ctx->internal = av_mallocz(sizeof(*ctx->internal));
+    if (!ctx->internal)
+        goto fail;
+
+    if (hw_type->frames_priv_size) {
+        ctx->internal->priv = av_mallocz(hw_type->frames_priv_size);
+        if (!ctx->internal->priv)
+            goto fail;
+    }
+
+    if (hw_type->frames_hwctx_size) {
+        ctx->hwctx = av_mallocz(hw_type->frames_hwctx_size);
+        if (!ctx->hwctx)
+            goto fail;
+    }
+
+    device_ref = av_buffer_ref(device_ref_in);
+    if (!device_ref)
+        goto fail;
+
+    buf = av_buffer_create((uint8_t*)ctx, sizeof(*ctx),
+                           hwframe_ctx_free, NULL,
+                           AV_BUFFER_FLAG_READONLY);
+    if (!buf)
+        goto fail;
+
+    ctx->av_class   = &hwframe_ctx_class;
+    ctx->device_ref = device_ref;
+    ctx->device_ctx = device_ctx;
+    ctx->format     = AV_PIX_FMT_NONE;
+
+    ctx->internal->hw_type = hw_type;
+
+    return buf;
+
+fail:
+    if (device_ref)
+        av_buffer_unref(&device_ref);
+    if (ctx->internal)
+        av_freep(&ctx->internal->priv);
+    av_freep(&ctx->internal);
+    av_freep(&ctx->hwctx);
+    av_freep(&ctx);
+    return NULL;
+}
+
+static int hwframe_pool_prealloc(AVBufferRef *ref)
+{
+    AVHWFramesContext *ctx = (AVHWFramesContext*)ref->data;
+    AVFrame **frames;
+    int i, ret = 0;
+
+    frames = av_mallocz_array(ctx->initial_pool_size, sizeof(*frames));
+    if (!frames)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < ctx->initial_pool_size; i++) {
+        frames[i] = av_frame_alloc();
+        if (!frames[i])
+            goto fail;
+
+        ret = av_hwframe_get_buffer(ref, frames[i], 0);
+        if (ret < 0)
+            goto fail;
+    }
+
+fail:
+    for (i = 0; i < ctx->initial_pool_size; i++)
+        av_frame_free(&frames[i]);
+    av_freep(&frames);
+
+    return ret;
+}
+
+int av_hwframe_ctx_init(AVBufferRef *ref)
+{
+    AVHWFramesContext *ctx = (AVHWFramesContext*)ref->data;
+    const enum AVPixelFormat *pix_fmt;
+    int ret;
+
+    /* validate the pixel format */
+    for (pix_fmt = ctx->internal->hw_type->pix_fmts; *pix_fmt != AV_PIX_FMT_NONE; pix_fmt++) {
+        if (*pix_fmt == ctx->format)
+            break;
+    }
+    if (*pix_fmt == AV_PIX_FMT_NONE) {
+        av_log(ctx, AV_LOG_ERROR,
+               "The hardware pixel format '%s' is not supported by the device type '%s'\n",
+               av_get_pix_fmt_name(ctx->format), ctx->internal->hw_type->name);
+        return AVERROR(ENOSYS);
+    }
+
+    /* validate the dimensions */
+    ret = av_image_check_size(ctx->width, ctx->height, 0, ctx);
+    if (ret < 0)
+        return ret;
+
+    /* format-specific init */
+    if (ctx->internal->hw_type->frames_init) {
+        ret = ctx->internal->hw_type->frames_init(ctx);
+        if (ret < 0)
+            goto fail;
+    }
+
+    if (ctx->internal->pool_internal && !ctx->pool)
+        ctx->pool = ctx->internal->pool_internal;
+
+    /* preallocate the frames in the pool, if requested */
+    if (ctx->initial_pool_size > 0) {
+        ret = hwframe_pool_prealloc(ref);
+        if (ret < 0)
+            goto fail;
+    }
+
+    return 0;
+fail:
+    if (ctx->internal->hw_type->frames_uninit)
+        ctx->internal->hw_type->frames_uninit(ctx);
+    return ret;
+}
+
+int av_hwframe_transfer_get_formats(AVBufferRef *hwframe_ref,
+                                    enum AVHWFrameTransferDirection dir,
+                                    enum AVPixelFormat **formats, int flags)
+{
+    AVHWFramesContext *ctx = (AVHWFramesContext*)hwframe_ref->data;
+
+    if (!ctx->internal->hw_type->transfer_get_formats)
+        return AVERROR(ENOSYS);
+
+    return ctx->internal->hw_type->transfer_get_formats(ctx, dir, formats);
+}
+
+static int transfer_data_alloc(AVFrame *dst, const AVFrame *src, int flags)
+{
+    AVFrame *frame_tmp;
+    int ret = 0;
+
+    frame_tmp = av_frame_alloc();
+    if (!frame_tmp)
+        return AVERROR(ENOMEM);
+
+    /* if the format is set, use that
+     * otherwise pick the first supported one */
+    if (dst->format >= 0) {
+        frame_tmp->format = dst->format;
+    } else {
+        enum AVPixelFormat *formats;
+
+        ret = av_hwframe_transfer_get_formats(src->hw_frames_ctx,
+                                              AV_HWFRAME_TRANSFER_DIRECTION_FROM,
+                                              &formats, 0);
+        if (ret < 0)
+            goto fail;
+        frame_tmp->format = formats[0];
+        av_freep(&formats);
+    }
+    frame_tmp->width  = src->width;
+    frame_tmp->height = src->height;
+
+    ret = av_frame_get_buffer(frame_tmp, 32);
+    if (ret < 0)
+        goto fail;
+
+    ret = av_hwframe_transfer_data(frame_tmp, src, flags);
+    if (ret < 0)
+        goto fail;
+
+    av_frame_move_ref(dst, frame_tmp);
+
+fail:
+    av_frame_free(&frame_tmp);
+    return ret;
+}
+
+int av_hwframe_transfer_data(AVFrame *dst, const AVFrame *src, int flags)
+{
+    AVHWFramesContext *ctx;
+    int ret;
+
+    if (!dst->buf[0])
+        return transfer_data_alloc(dst, src, flags);
+
+    if (src->hw_frames_ctx) {
+        ctx = (AVHWFramesContext*)src->hw_frames_ctx->data;
+
+        ret = ctx->internal->hw_type->transfer_data_from(ctx, dst, src);
+        if (ret < 0)
+            return ret;
+    } else if (dst->hw_frames_ctx) {
+        ctx = (AVHWFramesContext*)dst->hw_frames_ctx->data;
+
+        ret = ctx->internal->hw_type->transfer_data_to(ctx, dst, src);
+        if (ret < 0)
+            return ret;
+    } else
+        return AVERROR(ENOSYS);
+
+    return 0;
+}
+
+int av_hwframe_get_buffer(AVBufferRef *hwframe_ref, AVFrame *frame, int flags)
+{
+    AVHWFramesContext *ctx = (AVHWFramesContext*)hwframe_ref->data;
+    int ret;
+
+    if (!ctx->internal->hw_type->frames_get_buffer)
+        return AVERROR(ENOSYS);
+
+    if (!ctx->pool)
+        return AVERROR(EINVAL);
+
+    frame->hw_frames_ctx = av_buffer_ref(hwframe_ref);
+    if (!frame->hw_frames_ctx)
+        return AVERROR(ENOMEM);
+
+    ret = ctx->internal->hw_type->frames_get_buffer(ctx, frame);
+    if (ret < 0) {
+        av_buffer_unref(&frame->hw_frames_ctx);
+        return ret;
+    }
+
+    return 0;
+}
diff --git a/libavutil/hwcontext.h b/libavutil/hwcontext.h
new file mode 100644
index 0000000000..b30a20a42c
--- /dev/null
+++ b/libavutil/hwcontext.h
@@ -0,0 +1,328 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_HWCONTEXT_H
+#define AVUTIL_HWCONTEXT_H
+
+#include "buffer.h"
+#include "frame.h"
+#include "log.h"
+#include "pixfmt.h"
+
+enum AVHWDeviceType {
+    AV_HWDEVICE_TYPE_VDPAU,
+};
+
+typedef struct AVHWDeviceInternal AVHWDeviceInternal;
+
+/**
+ * This struct aggregates all the (hardware/vendor-specific) "high-level" state,
+ * i.e. state that is not tied to a concrete processing configuration.
+ * E.g., in an API that supports hardware-accelerated encoding and decoding,
+ * this struct will (if possible) wrap the state that is common to both encoding
+ * and decoding and from which specific instances of encoders or decoders can be
+ * derived.
+ *
+ * This struct is reference-counted with the AVBuffer mechanism. The
+ * av_hwdevice_ctx_alloc() constructor yields a reference, whose data field
+ * points to the actual AVHWDeviceContext. Further objects derived from
+ * AVHWDeviceContext (such as AVHWFramesContext, describing a frame pool with
+ * specific properties) will hold an internal reference to it. After all the
+ * references are released, the AVHWDeviceContext itself will be freed,
+ * optionally invoking a user-specified callback for uninitializing the hardware
+ * state.
+ */
+typedef struct AVHWDeviceContext {
+    /**
+     * A class for logging. Set by av_hwdevice_ctx_alloc().
+     */
+    const AVClass *av_class;
+
+    /**
+     * Private data used internally by libavutil. Must not be accessed in any
+     * way by the caller.
+     */
+    AVHWDeviceInternal *internal;
+
+    /**
+     * This field identifies the underlying API used for hardware access.
+     *
+     * This field is set when this struct is allocated and never changed
+     * afterwards.
+     */
+    enum AVHWDeviceType type;
+
+    /**
+     * The format-specific data, allocated and freed by libavutil along with
+     * this context.
+     *
+     * Should be cast by the user to the format-specific context defined in the
+     * corresponding header (hwcontext_*.h) and filled as described in the
+     * documentation before calling av_hwdevice_ctx_init().
+     *
+     * After calling av_hwdevice_ctx_init() this struct should not be modified
+     * by the caller.
+     */
+    void *hwctx;
+
+    /**
+     * This field may be set by the caller before calling av_hwdevice_ctx_init().
+     *
+     * If non-NULL, this callback will be called when the last reference to
+     * this context is unreferenced, immediately before it is freed.
+     *
+     * @note when other objects (e.g an AVHWFramesContext) are derived from this
+     *       struct, this callback will be invoked after all such child objects
+     *       are fully uninitialized and their respective destructors invoked.
+     */
+    void (*free)(struct AVHWDeviceContext *ctx);
+
+    /**
+     * Arbitrary user data, to be used e.g. by the free() callback.
+     */
+    void *user_opaque;
+} AVHWDeviceContext;
+
+typedef struct AVHWFramesInternal AVHWFramesInternal;
+
+/**
+ * This struct describes a set or pool of "hardware" frames (i.e. those with
+ * data not located in normal system memory). All the frames in the pool are
+ * assumed to be allocated in the same way and interchangeable.
+ *
+ * This struct is reference-counted with the AVBuffer mechanism and tied to a
+ * given AVHWDeviceContext instance. The av_hwframe_ctx_alloc() constructor
+ * yields a reference, whose data field points to the actual AVHWFramesContext
+ * struct.
+ */
+typedef struct AVHWFramesContext {
+    /**
+     * A class for logging.
+     */
+    const AVClass *av_class;
+
+    /**
+     * Private data used internally by libavutil. Must not be accessed in any
+     * way by the caller.
+     */
+    AVHWFramesInternal *internal;
+
+    /**
+     * A reference to the parent AVHWDeviceContext. This reference is owned and
+     * managed by the enclosing AVHWFramesContext, but the caller may derive
+     * additional references from it.
+     */
+    AVBufferRef *device_ref;
+
+    /**
+     * The parent AVHWDeviceContext. This is simply a pointer to
+     * device_ref->data provided for convenience.
+     *
+     * Set by libavutil in av_hwframe_ctx_init().
+     */
+    AVHWDeviceContext *device_ctx;
+
+    /**
+     * The format-specific data, allocated and freed automatically along with
+     * this context.
+     *
+     * Should be cast by the user to the format-specific context defined in the
+     * corresponding header (hwframe_*.h) and filled as described in the
+     * documentation before calling av_hwframe_ctx_init().
+     *
+     * After any frames using this context are created, the contents of this
+     * struct should not be modified by the caller.
+     */
+    void *hwctx;
+
+    /**
+     * This field may be set by the caller before calling av_hwframe_ctx_init().
+     *
+     * If non-NULL, this callback will be called when the last reference to
+     * this context is unreferenced, immediately before it is freed.
+     */
+    void (*free)(struct AVHWFramesContext *ctx);
+
+    /**
+     * Arbitrary user data, to be used e.g. by the free() callback.
+     */
+    void *user_opaque;
+
+    /**
+     * A pool from which the frames are allocated by av_hwframe_get_buffer().
+     * This field may be set by the caller before calling av_hwframe_ctx_init().
+     * The buffers returned by calling av_buffer_pool_get() on this pool must
+     * have the properties described in the documentation in the correponding hw
+     * type's header (hwcontext_*.h). The pool will be freed strictly before
+     * this struct's free() callback is invoked.
+     *
+     * This field may be NULL, then libavutil will attempt to allocate a pool
+     * internally. Note that certain device types enforce pools allocated at
+     * fixed size (frame count), which cannot be extended dynamically. In such a
+     * case, initial_pool_size must be set appropriately.
+     */
+    AVBufferPool *pool;
+
+    /**
+     * Initial size of the frame pool. If a device type does not support
+     * dynamically resizing the pool, then this is also the maximum pool size.
+     *
+     * May be set by the caller before calling av_hwframe_ctx_init(). Must be
+     * set if pool is NULL and the device type does not support dynamic pools.
+     */
+    int initial_pool_size;
+
+    /**
+     * The pixel format identifying the underlying HW surface type.
+     *
+     * Must be a hwaccel format, i.e. the corresponding descriptor must have the
+     * AV_PIX_FMT_FLAG_HWACCEL flag set.
+     *
+     * Must be set by the user before calling av_hwframe_ctx_init().
+     */
+    enum AVPixelFormat format;
+
+    /**
+     * The pixel format identifying the actual data layout of the hardware
+     * frames.
+     *
+     * Must be set by the caller before calling av_hwframe_ctx_init().
+     *
+     * @note when the underlying API does not provide the exact data layout, but
+     * only the colorspace/bit depth, this field should be set to the fully
+     * planar version of that format (e.g. for 8-bit 420 YUV it should be
+     * AV_PIX_FMT_YUV420P, not AV_PIX_FMT_NV12 or anything else).
+     */
+    enum AVPixelFormat sw_format;
+
+    /**
+     * The allocated dimensions of the frames in this pool.
+     *
+     * Must be set by the user before calling av_hwframe_ctx_init().
+     */
+    int width, height;
+} AVHWFramesContext;
+
+/**
+ * Allocate an AVHWDeviceContext for a given pixel format.
+ *
+ * @param format a hwaccel pixel format (AV_PIX_FMT_FLAG_HWACCEL must be set
+ *               on the corresponding format descriptor)
+ * @return a reference to the newly created AVHWDeviceContext on success or NULL
+ *         on failure.
+ */
+AVBufferRef *av_hwdevice_ctx_alloc(enum AVHWDeviceType type);
+
+/**
+ * Finalize the device context before use. This function must be called after
+ * the context is filled with all the required information and before it is
+ * used in any way.
+ *
+ * @param ref a reference to the AVHWDeviceContext
+ * @return 0 on success, a negative AVERROR code on failure
+ */
+int av_hwdevice_ctx_init(AVBufferRef *ref);
+
+/**
+ * Allocate an AVHWFramesContext tied to a given device context.
+ *
+ * @param device_ctx a reference to a AVHWDeviceContext. This function will make
+ *                   a new reference for internal use, the one passed to the
+ *                   function remains owned by the caller.
+ * @return a reference to the newly created AVHWFramesContext on success or NULL
+ *         on failure.
+ */
+AVBufferRef *av_hwframe_ctx_alloc(AVBufferRef *device_ctx);
+
+/**
+ * Finalize the context before use. This function must be called after the
+ * context is filled with all the required information and before it is attached
+ * to any frames.
+ *
+ * @param ref a reference to the AVHWFramesContext
+ * @return 0 on success, a negative AVERROR code on failure
+ */
+int av_hwframe_ctx_init(AVBufferRef *ref);
+
+/**
+ * Allocate a new frame attached to the given AVHWFramesContext.
+ *
+ * @param hwframe_ctx a reference to an AVHWFramesContext
+ * @param frame an empty (freshly allocated or unreffed) frame to be filled with
+ *              newly allocated buffers.
+ * @param flags currently unused, should be set to zero
+ * @return 0 on success, a negative AVERROR code on failure
+ */
+int av_hwframe_get_buffer(AVBufferRef *hwframe_ctx, AVFrame *frame, int flags);
+
+/**
+ * Copy data to or from a hw surface. At least one of dst/src must have an
+ * AVHWFramesContext attached.
+ *
+ * If src has an AVHWFramesContext attached, then the format of dst (if set)
+ * must use one of the formats returned by av_hwframe_transfer_get_formats(src,
+ * AV_HWFRAME_TRANSFER_DIRECTION_FROM).
+ * If dst has an AVHWFramesContext attached, then the format of src must use one
+ * of the formats returned by av_hwframe_transfer_get_formats(dst,
+ * AV_HWFRAME_TRANSFER_DIRECTION_TO)
+ *
+ * dst may be "clean" (i.e. with data/buf pointers unset), in which case the
+ * data buffers will be allocated by this function using av_frame_get_buffer().
+ * If dst->format is set, then this format will be used, otherwise (when
+ * dst->format is AV_PIX_FMT_NONE) the first acceptable format will be chosen.
+ *
+ * @param dst the destination frame. dst is not touched on failure.
+ * @param src the source frame.
+ * @param flags currently unused, should be set to zero
+ * @return 0 on success, a negative AVERROR error code on failure.
+ */
+int av_hwframe_transfer_data(AVFrame *dst, const AVFrame *src, int flags);
+
+enum AVHWFrameTransferDirection {
+    /**
+     * Transfer the data from the queried hw frame.
+     */
+    AV_HWFRAME_TRANSFER_DIRECTION_FROM,
+
+    /**
+     * Transfer the data to the queried hw frame.
+     */
+    AV_HWFRAME_TRANSFER_DIRECTION_TO,
+};
+
+/**
+ * Get a list of possible source or target formats usable in
+ * av_hwframe_transfer_data().
+ *
+ * @param hwframe_ctx the frame context to obtain the information for
+ * @param dir the direction of the transfer
+ * @param formats the pointer to the output format list will be written here.
+ *                The list is terminated with AV_PIX_FMT_NONE and must be freed
+ *                by the caller when no longer needed using av_free().
+ *                If this function returns successfully, the format list will
+ *                have at least one item (not counting the terminator).
+ *                On failure, the contents of this pointer are unspecified.
+ * @param flags currently unused, should be set to zero
+ * @return 0 on success, a negative AVERROR code on failure.
+ */
+int av_hwframe_transfer_get_formats(AVBufferRef *hwframe_ctx,
+                                    enum AVHWFrameTransferDirection dir,
+                                    enum AVPixelFormat **formats, int flags);
+
+
+#endif /* AVUTIL_HWCONTEXT_H */
diff --git a/libavutil/hwcontext_internal.h b/libavutil/hwcontext_internal.h
new file mode 100644
index 0000000000..acc775ccc5
--- /dev/null
+++ b/libavutil/hwcontext_internal.h
@@ -0,0 +1,89 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_HWCONTEXT_INTERNAL_H
+#define AVUTIL_HWCONTEXT_INTERNAL_H
+
+#include <stddef.h>
+
+#include "buffer.h"
+#include "hwcontext.h"
+#include "frame.h"
+#include "pixfmt.h"
+
+typedef struct HWContextType {
+    enum AVHWDeviceType type;
+    const char         *name;
+
+    /**
+     * An array of pixel formats supported by the AVHWFramesContext instances
+     * Terminated by AV_PIX_FMT_NONE.
+     */
+    const enum AVPixelFormat *pix_fmts;
+
+    /**
+     * size of the public hardware-specific context,
+     * i.e. AVHWDeviceContext.hwctx
+     */
+    size_t             device_hwctx_size;
+    /**
+     * size of the private data, i.e.
+     * AVHWDeviceInternal.priv
+     */
+    size_t             device_priv_size;
+
+    /**
+     * size of the public frame pool hardware-specific context,
+     * i.e. AVHWFramesContext.hwctx
+     */
+    size_t             frames_hwctx_size;
+    /**
+     * size of the private data, i.e.
+     * AVHWFramesInternal.priv
+     */
+    size_t             frames_priv_size;
+
+    int              (*device_init)(AVHWDeviceContext *ctx);
+    void             (*device_uninit)(AVHWDeviceContext *ctx);
+
+    int              (*frames_init)(AVHWFramesContext *ctx);
+    void             (*frames_uninit)(AVHWFramesContext *ctx);
+
+    int              (*frames_get_buffer)(AVHWFramesContext *ctx, AVFrame *frame);
+    int              (*transfer_get_formats)(AVHWFramesContext *ctx,
+                                             enum AVHWFrameTransferDirection dir,
+                                             enum AVPixelFormat **formats);
+    int              (*transfer_data_to)(AVHWFramesContext *ctx, AVFrame *dst,
+                                         const AVFrame *src);
+    int              (*transfer_data_from)(AVHWFramesContext *ctx, AVFrame *dst,
+                                           const AVFrame *src);
+} HWContextType;
+
+struct AVHWDeviceInternal {
+    const HWContextType *hw_type;
+    void                *priv;
+};
+
+struct AVHWFramesInternal {
+    const HWContextType *hw_type;
+    void                *priv;
+
+    AVBufferPool *pool_internal;
+};
+
+#endif /* AVUTIL_HWCONTEXT_INTERNAL_H */