avctx->release_buffer(avctx, &s->last_frame);
if (s->last_frame.data[0]) avctx->release_buffer(avctx, &s->last_frame);
static int xan_decode_end(AVCodecContext *avctx){    XanContext *s = avctx->priv_data;    /* release the last frame */    avctx->release_buffer(avctx, &s->last_frame);    av_free(s->buffer1);    av_free(s->buffer2);    return 0;}