memcpy(out->data + prev_size, ctx->par_out->extradata, extra_size);
AV_WB32(out->data + prev_size + extra_size, 1);
bytestream2_get_buffer(&gb, out->data + prev_size + 4 + extra_size, nalu_size);
memcpy(out->data + prev_size, ctx->par_out->extradata, extra_size);
AV_WB32(out->data + prev_size + extra_size, 1);
bytestream2_get_buffer(&gb, out->data + prev_size + 4 + extra_size, nalu_size);