+ /**
+ * A reference to the AVHWDeviceContext describing the device which will
+ * be used by a hardware encoder/decoder. The reference is set by the
+ * caller and afterwards owned (and freed) by libavcodec.
+ *
+ * This should be used if either the codec device does not require
+ * hardware frames or any that are used are to be allocated internally by
+ * libavcodec. If the user wishes to supply any of the frames used as
+ * encoder input or decoder output then hw_frames_ctx should be used
+ * instead. When hw_frames_ctx is set in get_format() for a decoder, this
+ * field will be ignored while decoding the associated stream segment, but
+ * may again be used on a following one after another get_format() call.
+ *
+ * For both encoders and decoders this field should be set before
+ * avcodec_open2() is called and must not be written to thereafter.
+ *
+ * Note that some decoders may require this field to be set initially in
+ * order to support hw_frames_ctx at all - in that case, all frames
+ * contexts used must be created on the same device.
+ */
+ AVBufferRef *hw_device_ctx;