| 
							- /*
 -  * 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[] = {
 - #if CONFIG_CUDA
 -     &ff_hwcontext_type_cuda,
 - #endif
 - #if CONFIG_DXVA2
 -     &ff_hwcontext_type_dxva2,
 - #endif
 - #if CONFIG_LIBMFX
 -     &ff_hwcontext_type_qsv,
 - #endif
 - #if CONFIG_VAAPI
 -     &ff_hwcontext_type_vaapi,
 - #endif
 - #if CONFIG_VDPAU
 -     &ff_hwcontext_type_vdpau,
 - #endif
 -     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->source_frames) {
 -         av_buffer_unref(&ctx->internal->source_frames);
 - 
 -     } else {
 -         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->sw_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;
 - 
 -     if (ctx->internal->source_frames) {
 -         /* A derived frame context is already initialised. */
 -         return 0;
 -     }
 - 
 -     /* 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)
 - {
 -     AVHWFramesContext *ctx = (AVHWFramesContext*)src->hw_frames_ctx->data;
 -     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  = ctx->width;
 -     frame_tmp->height = ctx->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;
 - 
 -     frame_tmp->width  = src->width;
 -     frame_tmp->height = src->height;
 - 
 -     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->source_frames) {
 -         // This is a derived frame context, so we allocate in the source
 -         // and map the frame immediately.
 -         AVFrame *src_frame;
 - 
 -         src_frame = av_frame_alloc();
 -         if (!src_frame)
 -             return AVERROR(ENOMEM);
 - 
 -         ret = av_hwframe_get_buffer(ctx->internal->source_frames,
 -                                     src_frame, 0);
 -         if (ret < 0)
 -             return ret;
 - 
 -         ret = av_hwframe_map(frame, src_frame, 0);
 -         if (ret) {
 -             av_log(ctx, AV_LOG_ERROR, "Failed to map frame into derived "
 -                    "frame context: %d.\n", ret);
 -             av_frame_free(&src_frame);
 -             return ret;
 -         }
 - 
 -         // Free the source frame immediately - the mapped frame still
 -         // contains a reference to it.
 -         av_frame_free(&src_frame);
 - 
 -         return 0;
 -     }
 - 
 -     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;
 - }
 - 
 - void *av_hwdevice_hwconfig_alloc(AVBufferRef *ref)
 - {
 -     AVHWDeviceContext *ctx = (AVHWDeviceContext*)ref->data;
 -     const HWContextType  *hw_type = ctx->internal->hw_type;
 - 
 -     if (hw_type->device_hwconfig_size == 0)
 -         return NULL;
 - 
 -     return av_mallocz(hw_type->device_hwconfig_size);
 - }
 - 
 - AVHWFramesConstraints *av_hwdevice_get_hwframe_constraints(AVBufferRef *ref,
 -                                                            const void *hwconfig)
 - {
 -     AVHWDeviceContext *ctx = (AVHWDeviceContext*)ref->data;
 -     const HWContextType  *hw_type = ctx->internal->hw_type;
 -     AVHWFramesConstraints *constraints;
 - 
 -     if (!hw_type->frames_get_constraints)
 -         return NULL;
 - 
 -     constraints = av_mallocz(sizeof(*constraints));
 -     if (!constraints)
 -         return NULL;
 - 
 -     constraints->min_width = constraints->min_height = 0;
 -     constraints->max_width = constraints->max_height = INT_MAX;
 - 
 -     if (hw_type->frames_get_constraints(ctx, hwconfig, constraints) >= 0) {
 -         return constraints;
 -     } else {
 -         av_hwframe_constraints_free(&constraints);
 -         return NULL;
 -     }
 - }
 - 
 - void av_hwframe_constraints_free(AVHWFramesConstraints **constraints)
 - {
 -     if (*constraints) {
 -         av_freep(&(*constraints)->valid_hw_formats);
 -         av_freep(&(*constraints)->valid_sw_formats);
 -     }
 -     av_freep(constraints);
 - }
 - 
 - int av_hwdevice_ctx_create(AVBufferRef **pdevice_ref, enum AVHWDeviceType type,
 -                            const char *device, AVDictionary *opts, int flags)
 - {
 -     AVBufferRef *device_ref = NULL;
 -     AVHWDeviceContext *device_ctx;
 -     int ret = 0;
 - 
 -     device_ref = av_hwdevice_ctx_alloc(type);
 -     if (!device_ref) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 -     device_ctx = (AVHWDeviceContext*)device_ref->data;
 - 
 -     if (!device_ctx->internal->hw_type->device_create) {
 -         ret = AVERROR(ENOSYS);
 -         goto fail;
 -     }
 - 
 -     ret = device_ctx->internal->hw_type->device_create(device_ctx, device,
 -                                                        opts, flags);
 -     if (ret < 0)
 -         goto fail;
 - 
 -     ret = av_hwdevice_ctx_init(device_ref);
 -     if (ret < 0)
 -         goto fail;
 - 
 -     *pdevice_ref = device_ref;
 -     return 0;
 - fail:
 -     av_buffer_unref(&device_ref);
 -     *pdevice_ref = NULL;
 -     return ret;
 - }
 - 
 - static void ff_hwframe_unmap(void *opaque, uint8_t *data)
 - {
 -     HWMapDescriptor *hwmap = (HWMapDescriptor*)data;
 -     AVHWFramesContext *ctx = opaque;
 - 
 -     if (hwmap->unmap)
 -         hwmap->unmap(ctx, hwmap);
 - 
 -     av_frame_free(&hwmap->source);
 - 
 -     av_buffer_unref(&hwmap->hw_frames_ctx);
 - 
 -     av_free(hwmap);
 - }
 - 
 - int ff_hwframe_map_create(AVBufferRef *hwframe_ref,
 -                           AVFrame *dst, const AVFrame *src,
 -                           void (*unmap)(AVHWFramesContext *ctx,
 -                                         HWMapDescriptor *hwmap),
 -                           void *priv)
 - {
 -     AVHWFramesContext *ctx = (AVHWFramesContext*)hwframe_ref->data;
 -     HWMapDescriptor *hwmap;
 -     int ret;
 - 
 -     hwmap = av_mallocz(sizeof(*hwmap));
 -     if (!hwmap) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 - 
 -     hwmap->source = av_frame_alloc();
 -     if (!hwmap->source) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 -     ret = av_frame_ref(hwmap->source, src);
 -     if (ret < 0)
 -         goto fail;
 - 
 -     hwmap->hw_frames_ctx = av_buffer_ref(hwframe_ref);
 -     if (!hwmap->hw_frames_ctx) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 - 
 -     hwmap->unmap = unmap;
 -     hwmap->priv  = priv;
 - 
 -     dst->buf[0] = av_buffer_create((uint8_t*)hwmap, sizeof(*hwmap),
 -                                    &ff_hwframe_unmap, ctx, 0);
 -     if (!dst->buf[0]) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 - 
 -     return 0;
 - 
 - fail:
 -     if (hwmap) {
 -         av_buffer_unref(&hwmap->hw_frames_ctx);
 -         av_frame_free(&hwmap->source);
 -     }
 -     av_free(hwmap);
 -     return ret;
 - }
 - 
 - int av_hwframe_map(AVFrame *dst, const AVFrame *src, int flags)
 - {
 -     AVHWFramesContext *src_frames, *dst_frames;
 -     HWMapDescriptor *hwmap;
 -     int ret;
 - 
 -     if (src->hw_frames_ctx && dst->hw_frames_ctx) {
 -         src_frames = (AVHWFramesContext*)src->hw_frames_ctx->data;
 -         dst_frames = (AVHWFramesContext*)dst->hw_frames_ctx->data;
 - 
 -         if ((src_frames == dst_frames &&
 -              src->format == dst_frames->sw_format &&
 -              dst->format == dst_frames->format) ||
 -             (src_frames->internal->source_frames &&
 -              src_frames->internal->source_frames->data ==
 -              (uint8_t*)dst_frames)) {
 -             // This is an unmap operation.  We don't need to directly
 -             // do anything here other than fill in the original frame,
 -             // because the real unmap will be invoked when the last
 -             // reference to the mapped frame disappears.
 -             if (!src->buf[0]) {
 -                 av_log(src_frames, AV_LOG_ERROR, "Invalid mapping "
 -                        "found when attempting unmap.\n");
 -                 return AVERROR(EINVAL);
 -             }
 -             hwmap = (HWMapDescriptor*)src->buf[0]->data;
 -             av_frame_unref(dst);
 -             return av_frame_ref(dst, hwmap->source);
 -         }
 -     }
 - 
 -     if (src->hw_frames_ctx) {
 -         src_frames = (AVHWFramesContext*)src->hw_frames_ctx->data;
 - 
 -         if (src_frames->format == src->format &&
 -             src_frames->internal->hw_type->map_from) {
 -             ret = src_frames->internal->hw_type->map_from(src_frames,
 -                                                           dst, src, flags);
 -             if (ret != AVERROR(ENOSYS))
 -                 return ret;
 -         }
 -     }
 - 
 -     if (dst->hw_frames_ctx) {
 -         dst_frames = (AVHWFramesContext*)dst->hw_frames_ctx->data;
 - 
 -         if (dst_frames->format == dst->format &&
 -             dst_frames->internal->hw_type->map_to) {
 -             ret = dst_frames->internal->hw_type->map_to(dst_frames,
 -                                                         dst, src, flags);
 -             if (ret != AVERROR(ENOSYS))
 -                 return ret;
 -         }
 -     }
 - 
 -     return AVERROR(ENOSYS);
 - }
 - 
 - int av_hwframe_ctx_create_derived(AVBufferRef **derived_frame_ctx,
 -                                   enum AVPixelFormat format,
 -                                   AVBufferRef *derived_device_ctx,
 -                                   AVBufferRef *source_frame_ctx,
 -                                   int flags)
 - {
 -     AVBufferRef   *dst_ref = NULL;
 -     AVHWFramesContext *dst = NULL;
 -     AVHWFramesContext *src = (AVHWFramesContext*)source_frame_ctx->data;
 -     int ret;
 - 
 -     if (src->internal->source_frames) {
 -         AVHWFramesContext *src_src =
 -             (AVHWFramesContext*)src->internal->source_frames->data;
 -         AVHWDeviceContext *dst_dev =
 -             (AVHWDeviceContext*)derived_device_ctx->data;
 - 
 -         if (src_src->device_ctx == dst_dev) {
 -             // This is actually an unmapping, so we just return a
 -             // reference to the source frame context.
 -             *derived_frame_ctx =
 -                 av_buffer_ref(src->internal->source_frames);
 -             if (!*derived_frame_ctx) {
 -                 ret = AVERROR(ENOMEM);
 -                 goto fail;
 -             }
 -             return 0;
 -         }
 -     }
 - 
 -     dst_ref = av_hwframe_ctx_alloc(derived_device_ctx);
 -     if (!dst_ref) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 - 
 -     dst = (AVHWFramesContext*)dst_ref->data;
 - 
 -     dst->format    = format;
 -     dst->sw_format = src->sw_format;
 -     dst->width     = src->width;
 -     dst->height    = src->height;
 - 
 -     dst->internal->source_frames = av_buffer_ref(source_frame_ctx);
 -     if (!dst->internal->source_frames) {
 -         ret = AVERROR(ENOMEM);
 -         goto fail;
 -     }
 - 
 -     ret = av_hwframe_ctx_init(dst_ref);
 -     if (ret)
 -         goto fail;
 - 
 -     *derived_frame_ctx = dst_ref;
 -     return 0;
 - 
 - fail:
 -     if (dst)
 -         av_buffer_unref(&dst->internal->source_frames);
 -     av_buffer_unref(&dst_ref);
 -     return ret;
 - }
 
 
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