- * This field should be set before avcodec_open2() is called and is
- * afterwards owned and managed by libavcodec.
+ * If the default get_buffer2() is used with a hwaccel pixel
+ * format, then this AVHWFramesContext will be used for
+ * allocating the frame buffers.
+ *
+ * - encoding: For hardware encoders configured to use a hwaccel pixel
+ * format, this field should be set by the caller to a reference
+ * to the AVHWFramesContext describing input frames.
+ * AVHWFramesContext.format must be equal to
+ * AVCodecContext.pix_fmt.
+ *
+ * This field should be set before avcodec_open2() is called.