proc av_tx_init(ctx: ptr ptr AVTXContext; tx: ptr av_tx_fn; type: AVTXType;
                inv, len: cint; scale: pointer; flags: uint64): cint {.importc,
    cdecl, ...raises: [], tags: [], forbids: [].}

proc av_tx_uninit(ctx: ptr ptr AVTXContext) {.importc, cdecl, ...raises: [],
    tags: [], forbids: [].}