/* x264_encoder_invalidate_reference:
 *      An interactive error resilience tool, designed for use in a low-latency one-encoder-few-clients
 *      system.  When the client has packet loss or otherwise incorrectly decodes a frame, the encoder
 *      can be told with this command to "forget" the frame and all frames that depend on it, referencing
 *      only frames that occurred before the loss.  This will force a keyframe if no frames are left to
 *      reference after the aforementioned "forgetting".
 *
 *      It is strongly recommended to use a large i_dpb_size in this case, which allows the encoder to
 *      keep around extra, older frames to fall back on in case more recent frames are all invalidated.
 *      Unlike increasing i_frame_reference, this does not increase the number of frames used for motion
 *      estimation and thus has no speed impact.  It is also recommended to set a very large keyframe
 *      interval, so that keyframes are not used except as necessary for error recovery.
 *
 *      x264_encoder_invalidate_reference is not currently compatible with the use of B-frames or intra
 *      refresh.
 *
 *      In multi-pass encoding, if x264_encoder_invalidate_reference is called differently in each pass,
 *      behavior is undefined.
 *
 *      Should not be called during an x264_encoder_encode, but multiple calls can be made simultaneously.
 *
 *      Returns 0 on success, negative on failure. */
int x264_encoder_invalidate_reference( x264_t *, int64_t pts );